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As level Biology Revision

My notes for A2 biology

Sean Scully

on 9 February 2015

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Transcript of As level Biology Revision

Biology Revision

water molecule


No electrons between the two hydrogen atoms as they
would force the hydrogen's further around the molecule

Hydrogen atoms always smaller than oxygen atoms

When two water molecules are close together the opposite sides of each molecule attract (similarly to magnets), forming an inter molecular bond

Water is adhesive and sticks to most substances

Water is a solvent and is good at dissolving
most polar and non polar molecules

Water has a high surface tension due to water molecules sticking to each other (cohesion) allowing pond skaters and basilisk lizards to walk on its surface

Water has a high specific heat capacity, so it
takes a lot of energy to increase its temperature

water is both slightly positive and slightly negative, so as a result two water molecules can bond together through an intermolecular bond (also known as a hydrogen bond)
the hydrogens in water are bonded to the oxygen by covalent bonds
proteins are made up of the elements ...
however proteins themselves are polymers...
...made up of amino acids
amino acids look like...
N - C - C


O - H
N-C-C is the back bone of the amino acid
each type of amino
acid has a different R-group and its the r-group that determines the amino acids property's (e.g. whether its hydrophobic or hydrophilic)
this is the Aminile group
this is the carboxile group...
o - h
Deoxyribonucleic acid
D.N.A. has a double helix structure made up of deroxybrose, nitrogen bases and a phosphate group.
DNA has 4 different types of bases that are used to code proteins these bases are....
Adenine always pairs with
thymine and Guanine always
pairs with Cytosine

REMEMBER: Always Take Green Clovers
RNA is a single strand copy of DNA, there are 3 different types of RNA all with different functions
waters structural bonds are organized in
such a way that water just above freezing temperature actual has a higher density than ice, allowing ice to float on water.
how to detect the presence of carbohydrates ,proteins and lipids...
-starch: to detect starch an iodine solution is added to the sample, if the iodine turns from brown to blue/black, starch is present
-Reducing sugars: to detect mono and disaccharides in a substance, the sample is added to a alkaline copper sulfate solution (benidicts solution) and heated to 80+ degrees, if the sugars are present a orange-red precipitate is formed
-non reducing sugars: for sugars that do not react to benidicts solution initially, they must first be boiled in hydrochloric acid to hydrolise any present molecules and then neutralized with a sodium carbonate solution after cooling, then the benidicts test should be performed, if a non-reducing sugar is present the test should now be positive.
- proteins: to detect proteins a biuret agent must be added to the sample as it reacts with the proteins peptide bonds, if proteins are present the solution should turn lilac
-lipids: to detect lipids, a ethanol must be mixed with the sample to break down the lipids, then the resulting mixture must be pored into water, if lipids are present a cloudy white emulsion should form near the waters surface
-messenger RNA (mRNA) is a copy of a single DNA strand
-Ribosomal RNA(rRNA) is the RNA found in Ribosomes
-Transfer RNA (tRNA) carries amino acids to the ribosomes where they are bonded to form polypeptides
nucleic acid has two forms, DNA and RNA,
found in all living organisms they hold the data needed
to buld that organism (like Blueprints)
nucleotides are monomers of nucleic
acid , in other words one phosphate
group, one sugar molecule and one
nitrogen/uracil base joined by covalent

nucleotides join together when a condensation reaction occurs to join the phosphate of one group with the sugar of another, forming the backbone of the acid (see DNA/RNA)
too much nucleic acid in the blood causes gout
DNA Replication
the bases in a DNA chain are held in parallel to each other by two hydrogen bonds
to replicate itself when a cell divides a DNA molecule must first unwind, then the hydrogen bonds are broken down to unzip the DNA, free nucleotides then bond to their counterpart on one of the DNA strands and their sugars/phosphates bond to form a new backbone, this is known as semi conservative replication as one strand of each new DNA molecule is from the origonal

DNA strands are referred to as being anti-parallel as they run in opposite directions to each other
as a result of the base pairing DNA strands are always the same distance apart.
Cell Structure
magnification- the degree to which the size of an image is larger than the object itself (actual size= image size / magnification)
resolution - the degree to which its possible to distinguish between two objects that are close together, the higher the resolution the greater the visible detail
objective lens * eyepiece lens = total magnification
methods of preparing slides:
stains are used to add colour to transparent, thin and some translucent slides so they are visible under a light microscope, the stains work by binding to the sample, this provides contrast to the sample
some biological samples distort when cut into thin sections (which may be required if the initial sample is too thick), to counter this the sample is coated in wax and then sliced into water (e.g. brain samples)

parts of the microscopes: light microscope

-magnification of up to 1500x
-resolution of 200nm
-cheaper than electron microscopes, and smaller so easier to move/use
- eyepiece lens in usually a 10x, objective lenses (max of 4) are usually 4x, 10x ,40x and occasionally a 100x (oil immersion lens)
parts of the microscope: electron microscopes
e.g. of a S.E.M
-both types of electron microscope work by generating a beam of electrons to map out a sample, but the generate the image in different ways, both of them also use magnets to focus the beam, have resolutions of approximately 0.2nm
and are only capable of producing black and white images.however both have different magnifications.

- propels its electron beam through a very thin sample to produce a high detail 2D sample, it has a maximum magnification of 500,000x.
- electrons are "bounced off" the sample to produce a 3D surface model, its maximum magnification is 100,000x
the pictures produces by a electron microscope are called electron micrograph, they are always taken in black and white but are sometimes coloured to allow scientists to distinguish certain features
electron microscopes are very expensive to buy and run and extremely large in comparison to light microscopes. they also require a vacuum to propel the electrons through without disruption, (another expensive feature!), though a scanning electron microscope can still contain live samples due to the
specimen stage being
outside the vacuum, the
T.E.M cannot as it requires
a flat sample
- act as biological catalysts (a substrate) as they don't get used up in a reaction
-hydrophobic globular proteins with a tertiary structure
- the enzyme uses a lock and key model to speed up reactions, each enzyme is specific to a certain molecule (e.g. amylase is specific for glucose) , the active site where the reaction occurs is a tiny part of the enzyme.
-usually found in the cytoplasm or mitochondria
- high degrees of pH denature enzymes as it effects the amino acids bonds warping the active site
- enzymes work best at the ideal (optimal) temperature they are designed for (30 degrees in the human body, though temperature above 40 degrees denature them as high amounts of kinetic energy shake them apart
example of a lock and key model
different enzymes and there products
Lipase: turns fat into fatty acids and glycerol
protease: turns proteins into amino acides
carbohydrase : turns starch into glucose

equation example
protein +
protease/amino acid
protiase +
amino acids
enzyme structure in 1 sentence
enzymes are globular proteins (a tertiary structure of amino acids) composed of amino acids with r-groups that cause it to form this shape, however this structure of r group is also hydrophobic and will break down if it contacts water so the r group is in the interior of the structure whylst the hydrophilic side is exposed. each enzymes active site (the area in which the reaction occurs) is highly specific so is designed to react certain molecules only.
intracellular and extracellular enzymes
intercellular enzymes are enzymes that speed up reactions inside cells whilst extracellular enzymes cause reactions outside the cell.

anabolism is the building of larger molecules from smaller ones, and catabolase is the
mode of action:lock and key
lock and key is when the enzymes active site is specifically designed to fit only a single type of molecule and will only react that type of molecule/s , so the substrates held in place while the reaction occurs
there is another theory that states that the enzyme changes shape when the substrate reacts with the active site this is the induces fit hypothesis
this theory states when the substrate collides with the active site the enzyme changes shape slightly to accommodate it more effectively, they are also pulled together because groups on the substrate and enzyme are oppositely charged. this also slightly distabalises the substrate making the reaction easier. as the resulting substance is a different shape to the substrate, its forced out the enzyme.

Activation Energy
activation energy is the amount of energy required to begin a reaction, enzymes reduce the amount of energy required for the reaction to begin by acting as a catalyst ,this can be represented as a graph (like the one below), this graph dictates the activation energy when enzymes are involved in a reaction is much lower that if the enzymes ar'nt involved
new cells - parent and daughter cells
histone = DNA in a eukariotic cell is wrapped around proteins called histones
chromatin = DNA and histone proteins
before cell division each strand of DNA is copied exactly
centromere- central point that holds together replicated DNA
chromatids - identical sister strands of dna that are connected by a centromere
after copying they are still invisible under a light microscope
before they separate the chromatin becomes supercoiled, meaning that they are now visible, chromatin is 30nm thick, chromosomes are 500nm thick so they can be moved around
factors that effect rate of enzyme reactions:
substrate concentration
as the amount of substrate increases the rate of reaction gradually levels off as the active sites of all the enzymes are filled and they can only process a certain amount of substrate at a time as
the reason for the sharp rise in reaction rate initially is that as more substrate is added the concentration increases causing more collisions between the enzymes and the substrates, speeding up the time it takes for the enzymes to get a new substrate after the last was
Enzyme concentration
eventually the enzymes will process all the available substrate and the graph levels off
too many enzymes for substrate so all substrate is processed quickly
the temperature effects the rate of enzyme reactions because a rise in temperature gives the enzymes and substrates more kinetic energy causing them to collide more often upping the rate of reactions . however too much heat causes the enzyme to gain too much energy, causing the hydrogen bonds holding them together to break and the enzyme to unravel and become denatures
P.H. effects enzyme reaction rates because the ions cluster around the active site and react with the enzymes tertiary structure denaturing it
planning a 12 mark enzyme question
Temperature: temperature increases the rate of reaction up to the enzymes optimum temperature as the increase in kinetic energy increases the chance of collision between the enzymes active site and the substrate molecules ,after which the higher temperatures begin to cause the hydrogen bonds in the enzyme to break down denaturing the enzymes active site and making reactions with substrates impossible
enzyme concentration: an increase in enzyme concentration will increase the rate of reaction
enzyme inhibitors, co-factors, co-enzymes, prophetic groups
enzyme co-factors are any substance that must be present for the reaction to take place
examples of these are:
prosthetic groups
inorganic ion co-factors
prophetic groups: a co-enzyme that forms a permanent part of a enzymes structure, they are also found in some other proteins and are required for the enzyme to carry out its function
co-enzymes: small organic non protein molecules that bind to the enzymes active site just before or at the same time the substrate joins, they normally carry chemical groups between enzymes so reactions occur in sequence or take part in the reaction themselves , however unlike the substrate they are not used up
in some reactions the presence of certain ions increase the reaction rate
enzymes inhibitors enter the allotropic site and disrupts the active site, preventing reactions from occurring
competitive inhibitors are substances with a similar shape to the enzymes that block the active site preventing substrate
snake venom produces inhibitors that block the enzymes in the nervous system preventing them from functioning causing paralysis
is used in the production of gametes, each resulting cell has half the number of chromosomes (Haploid ) and are genetically different from
each other
Stem cells
differentiation-the development and changes seen in cells as they mature to become specialized
erythrocytes-red blood cells
neutrophils- phagocytic white blood cells (they digest bacteria
xylem-a plant cell used to transport water
phloem sieve tubes-
when cell become specialized to carry out a particular role/function
the number of organelles, the cells shape and cell contents may change when this occurs
e.g. red blood cells lack a nucleus
to carry more hemoglobin, and a
more oxygen

transport in plants
xylem and phloem are produced by the dividing of meristem cells such as cambium
meristem tissue cells elongate
walls become reinforced
and waterproofed and lignin
cell contents killed,
ends break down
this creates a long
continuous tube with
wide lumen formed
line up end to end to form
a tube
ends form sieve plates
phloem sieve tubes formed
formation of xylem/phloem
guard cells open when exposed to light and
close when there is an absence of light, where fore only allowing chemicals passage into/out of the leaf from the outside world when the plant is photosynthesizing, they also contain chloroplasts, (an unusual feature considering there location) and a spiral thickening of cellulose on the inner wall
guard cells and the leaf
Tissues Found In Animals
epithelial tissue-layers and linings
connective tissue- support and holding structures together
muscle tissue-contracts to move the body
nervous tissue-converts stimuli to electrical impulses which they then conduct
squamous epithelial tissue - organized in flattened very thin structures, smooth with a flat surface , making it ideal for lining tubes such as blood vessels where fluids can pass over them. its also used to form thin walls such as in alveoli.
ciliated Epithelial tissue- column shaped cells topped with cilia found in the surface of tubes such as airways of lungs and in the oviducts. some of the cells produce mucus
note: mucus is the noun for the substance whilst mucous is the adjective to describe a substance covered in mucus.
cillia wave in a synchronized rhythm and move the mucus
Cillia Epithelial tissue and smoking:
Nicotine - Paralysis cilia
tar - damages cilia and eventually destroys them
different cells and there functions
when two amino acids join the OH and H atoms react to form H2O, the N+C atoms then join as they have room to form a new covalent bond as the water produced splits off from the rest of the structure, this is known as a condensation reaction
two amino acids joined is called a di-peptide, more is called a poly-peptide (think parrots!), multiple polypeptide chains join to form a protein. breaking a peptide bond requires a condensation reaction (add water) to make up for the loss of these atoms in the forming of the chain.
a proteins property's are determined by its sequence of amino acids (also known as its primary structure)(e.g. a protine with many hydrophobic amino acids may be hydrophobic itself and therefor found embedded in a membrane)
protease enzymes also help to break down proteins in both the digestive areas of animals and other areas where protines have to be broken down and re-formed such as in hormone systems or the collagen formation in the skin
secondary structure:
the point when the chain of amino acids folds or coils to form an alpha helix or a beta pleated sheet
tertiary structure :
the final 3 dimensional shape of the protine formed when the alpha helix/beta sheets coil or fold themselves , these final shapes are vital to the functioning of a protine for example a hormone must be the exact shape to fit its hormone receptor of the chain of reactions involving that hormone is broken
globular and fibrous proteins
globular proteins - tend to be rolled up into a ball shaped structure with the hydrophobic proteins on the inside and the hydrophilic proteins on the outside
fibrous proteins- form fibers and have constant repetitive sequences of amino acids usually insoluble in water
quaternary structure: when two polypeptide substructures join to form a working protein, examples of proteins with this structure include haemoglobin and collagen
N - C - C

N - C - C

O - H
peptide bond
haemoglobin and collagen
haemoglobin- has a quaternary structure consisting of 4 polypeptide subunits (two alpha chains and two beta chains), each polypeptide in haemoglobin has a haem group that contains a fe 2+ ion that allows the hemoglobin to join with oxygen. the haem group is responsible for the colour of haemoglobin.
Exchange and Transport
why organisms need exchange systems....
all living cells require substances from outside environments to keep them alive or to help them synthesize other products in the cytoplasm , for example
oxygen for aerobic respiration
glucose as a source of energy
proteins for growth and repair
fats to make membranes and to be a store of energy
minerals to maintain water potential and to help enzyme action
cells also need to be able to remove waste products from metabolic activity in the cytoplasm, these
carbon dioxide
the lungs as an organ of exchange
large surface area greater than skin due to many small alvioli
theirs a thin plasma membrane around cytoplasm readily allowing diffusion of co2 and o2
steep diffusion gradient thanks to blood transport and ventilation movements
no active transport takes place in the lungs as its too slow
the lungs also contains a surfactant to reduce the cohesive forces between water molecules to prevent the collapsing of the alveolus
exchange and transport
Vascular Bundles
transport systems in plants are designed to ensure all areas of the plant get the essential nutrients it needs to survive, transport systems in plants are called vascular tissue, example of transported substances include water, minerals and sugars. water and minerals absorbed in the roots from the soil and are transported up the plant by the xylem . whilst sugars are formed in the leaves and transported down the plant by the phloem.
different vascular bundles are located in different places in different parts of the plant
vascular bundles in the stem are located in the outer edge of the stem, in non-woody plants each bundle is separate whilst in woody plants there separate in saplings but become continuous in the older plants
in dicotyledonous plants there branching veins that get smaller away from the midrib
Tissues in Plants: Xylem
Xylem function
xylem cells are stacked end on end to form tubes, they also transport substances down the potential water gradient. they also transport water and minerals from the roots to the leaves. they also help to support the plants structure
Xylem Structure
xylem tubes have a diameter of 250 micrometers and utilizes dead cells as vessels, they have no microorganells or cytoplasm
tissues in the lungs
the role of cartridge
role of elastic fibers
they dilate the lumen of the airways, then recoil back to there original size when smooth muscles relax
roles of goblet cells and glandular tissue
they secrete mucus to trap tiny partials such pollen from the air
role of ciliated epithelial cells
synchronized wafting of cilia moves mucus to the back of the throat
mucus then swallowed and bactiria killed by stomach acid
cartilage is structural and holds together the shape of the breathing system, it also holds open the trachea and the bronchi preventing there collapse during exhalation, its also highly flexible to allow easy movement and expansion of the oesophagus during swallowing
the role of smooth muscle
contracts to make the lumen of the airway smaller
to restrict the airflow to and from the alvioli , this can be involuntary in the case of an allergic reaction or asthma

unicellular organism= one cell organism
transport in animals
single celled creatures (and a few unicellular) with large surface area/volume ratio use diffusion to transport substances into/out of there cell/s
creatures with more volume than surface area dont do this as they require too much energy
all transport systems are effective (as they produce the desired effect), but in more complex systems there also efficient (saving energy in the process)
single celled organisms use diffusion
fish have a singular circulatory system, mammals have a double circulatory system
efficient transport
exchange surfaces that enable gaseous exchange and of nutrients and waste (alvioli and capillaries)
a fluid or medium to carry around nutrients, oxygen and waste around the body (e.g. plasma)
a pump to create pressure that will push the fluid around the body
tubes and vessels to carry the blood (veins and arteries
two circuits- one to pick up O2 and another to deliver O2 to the tissues
double circulatory system allows for oxygen and nutrients to be delivered more quickly, birds and mammals are very active and endothermic so they need more energy, to release energy they need a good supply of oxygen and nutrients
in fish blood pressure must be low in the gills so the capillaries aren't damaged, blood pressure reduces as blood passes through the capillaries of the gills so blood flows slowly through the rest of the body, oxygen and nutrients are delivered slowly, but fish are not very active and are exothermic so they need less energy, to release energy the cells need a good supply of oxygen and nutrients
endodermis cells actively transport minerals such as nitrates by lowering the water potential in the xylem, causing heightened hydrostatic pressure forcing water up the stem
capillary action- adhesion of water to the sides of the very narrow xylem
transpiration pull-water vapor loss from the leaves pulling water up to replace it
cohesive tension theory
the drawing up of a continuous column of water through the xylem due to waters cohesive propertys and the loss of water from the top of the plant (like a Straw)
leaf structure
the Casparian strip is a band of cell wall material in the endodermis, which is chemically different from the rest of the cell wall. It is used to block the passive flow of materials, such as water and solutes into the stele of a plant (the central part of the roots/stem).
carbon dioxide+water glucose + oxygen
oxygen+glucose water+carbon dioxide
A.S. level
sources release sucrose into the phloem
sinks remove sucrose from the phloem
translocation is an energy requiring process that transports assimilates, especially sucrose, between sources(e.g. leaves) and sinks (e.g. roots and meristems)
1)the process of loading at the source is active as it uses energy in the form of ATP from the mitochondria and transports against the concentration gradient
3)at the source sucrose entering the sieve tubes makes the water potential more negative, water moves into the sieve tube elements via osmosis and hydrostatic pressure increases in the sieve tube element and water moves down the sieve tube from high to low hydrostatic pressure in the sink
2)active bonding at the source ATP used by the companion cells to pump protons out of the cytoplasm into the tissue, generating a diffusion gradient via a co-transporter protein , causing the sucrose to follow the ions back into the sieve into the plasmadesmata
4)at the sink sucrose leaves the sieve tube elements due to the diffusion gradient and makes the water potential less negative , causing the water to move out of the sieve tube elements causing a decrease in hydrostatic pressure
the movement of sucrose along the phloem
water moves from source to sink down the hydrostatic pressure gradient, the flow carries sucrose into the sink. this is also known as mass flow. the water then flows into the xylem and the process resets
you will be assimilated!
Translocation Step by Step
evidence for translocation
reactivity labeled CO2 goes into the plant and the plant uses it to photosynthesize
ringing a tree also helps to confirm the process as the area above the ringed area begins to swell as the sugar collects as the bark which acts as a sink has been removed stopping the translocation
collected substances from aphids, as they absorb nutrients from a plants phloem, also confirms this as they will contain any sugars that the plant has created
to confirm that translocation is an active process
-companion cells contain large numbers of mitochondria showing lots of respiring/ energy consumption
- ATP inhibitors can kill the plant, showing that its stopped the process and that it requires ATP
-the rate of flow is faster that usual showing energy consumption
-temperature and PH dependency showing enzyme activity in the mitochondria
-oxygen dependent showing a respiration reaction
evidence against translocation
- solutes in the phloem all move at different rates
- sucrose moved around the plant at the same speed not dependant on the concentration gradient
-role of the sieve plate is still unknown
tunica externa-outer arterie layer
tunica intima-inner arterie layer
tunica media- middle arterie layer
how an arteries structure helps its function
-elastic tissue to allow stretching
-elastic arteries near heart and elastic recoil along all arteries to even out pressure changes and to help maintain flow
-collagen to provide arterial strength and reinforcement
-endothelium provides a reduction in friction
-narrow lumen to maintain pressure
-tunica media has smooth mucle and elastic tubing
-smooth muscle to maintain pressure and constrict the blood vessles
functions of the blood
- transport (oxygen, sugar, CO2)
- fighting infection (White blood cells, Antibodies)
- heat transferal
- wound repair (platelets)
- maintains diffusion gradient in alvioli
- acts as a PH buffer
-provides pressure and formation of tissue fluid
blood- held in the heart and blood vessels

tissue fluid- bathes the cells of tissues

Lymph-Drains exess tissue fluid into the Lymphatic system
blood tissue fluid and lymph
-tissue fluid is formed at the arteriole
end of the capillary beds
-surrounds the bathed cells
-essential for the efficient exchange
of materials between the blood and
the cells
-constantly drained away from the
cells by lymph vessels
tissue fluid
phospholipids consist of a hydrophilic head, two hydrophobic tails and a phosphate group, due to this structure when they are used to form a membrane the heads will form the exterior of the membrain and the tails the interior. despite the fact that the molecules are not bonded they have a great degree of stability due to it being difficult for the hydrophilic head to enter the are occupied by the hydrophobic tails and the reverse is also true
the fluid mosaic model
the term fluid mosaic model is used to describe the arrangement of different molecular structure arrangements in the cell membrane for example there are stuctures such as glycoprotines and glycolipids, which are ordinary lipid and proteins with a small carbohydrate structure attached
to them. cholesterol can be found within
the membrane itself where it helps to
provide extra stability to the cell. to help
with transport across the membrane there
are a number of channel and carrier
proteins, channel proteins carry
hydrophilic substances and carrier proteins
actively transport substances that are too
large to normally pass through the
membrane, receptor sites are also present
to assist with cell signaling.

the heart
-the coronary artery provides the heart with its own supply of oxygen, a heart attack occurs when these arteries become blocked and the heart cannot get the oxygen supply it needs
-the heart is covered by a tough membrane called the pericardium which contains a pericardium fluid
- atria , thin walled as they pump blood only a short distance to the ventricles, and ventricles have thick walls as they need to pump blood a long distance to ether the lungs or the rest of the body
- remember LORD - left oxygenated right de-oxyginated
-the left atrioventrical valve (or mitrial or bi-cuspid valve) stop a back flow of blood and is formed of two cup shaped flaps , the right atrioventrical valve (or tricuspid) is formed of 3 cup shaped flaps
- tendons (heart strings) attach the valves to the ventricular walls preventing the flaps turning inside out.
-semi lunar valves separate the ventricles from any outgoing tubes
carriage of oxygen
haemoglobin is a globular protein, there are 4 sub-units of haemoglobin in each red blood cell, each subunit has a polypeptide and a haem group, the haem group contains a single Fe2+ ion, causing haemoglobin to have an affinity for oxygen.
Oxygen association and dissociation
haemoglobin readily associated with oxygen at the gaseous exchange surface and dissociates readily at the tissues depending on there oxygen in them.
oxyhaemoglobin dissociation curve
forms an "S" shapedue to difficulty binding with the first Oxygen molecule at low
Partial pressures once it has bonded a confimational change in the haemoglobin
occure allows other oxygen molecules to associate easier, the fourth molecule
also finds it difficult to bind
fetal Haemoglobin
fetal haemoglobin has a higher affinity
to pick up oxygen than an adults
haemoglobin, in order to get oxygen
picked up at the foetal side of the placenta
this also reduces O2 tension which makes
Haemoglobin releases even more O2

the Cardiac cycle
when the pressure underneath the valve
becomes greater than the pressure abouve
it the valve flaps fill with blood causing them
to snap shut, and the tendinous cords work to prevent them inverting
the resting heart rate in humans is 70 Beats
per minute, during each beat the heart fills and
empties, this is the cardiac cycle , the two sides work in sync to co-ordinate the effort
ventricular contraction/systole
the ventricular walls contract, causing ventricular pressure to become higher than arterial pressure , forcing the semi lunar valves open allowing blood to flow into the aorta and pulmonary arterie , the AV valves then snap shut.
this takes approximately 0.3 seconds
filling phase : Diastole
blood flows into the atria nd ventricles so the
heart fills, so the atrioventricular valves are open
, the ventricular walls then relax. the pressure in the arteries is higher thanin the ventricles, so the semi-lunar valves snap shut.
this takes about 0.2 seconds
cardiac cycle graph
filling phase: diastole
blood flow s into the atria and ventricle and the heart fills, valves are open , the ventricular walls then relax and the valves snap shut.
the sinoaltrial node( or pacemaker): starts the heart beat and causes the atria to contract by sending impulses along its walls, it also transmits impulses to the Atroventricular node
atroventricular node: receves electrical impules from the pacemaker and delays the contracting of the ventricals by delaying the retransmttion to the Purkne tissue .
ECG scans
P= atrial systale
QRS= ventricular Systole
heart issues
irregular feat = arrhythmia
beat is not Co-Ordinated= fibrillation (depending on stage of off beat e.g. ventricular fibrillation)
Heart Attack= myocardial infaraction
unspecilised cells capible of forming other types of cells in a process known as differentiation , for example, in animals stem cells in the bone marrow are capable of forming blood cells such as Phagocytes and neutrophiles , and embryonic stem cells are capable of forming any kind of cells. in plants cambium can differentiate into xylem and phloem.
unit 2: food and Health
Balanced Diet and Obesity
balanced diet- a balanced diet is one that contains all the nutrients required for health in appropriate proportions
nutrition - is nourishment - the nutrients and energy needed for health and growth
malnutrition - an unbalanced diet ether too much or too little
obesity - when a person is 20% or more heavier than the recommended weight for there height

mass/g per day
energy in food KJ

food chains and food webs
selective breeding (think Mr Mattinson's pedigree racing cows!!), and improvements
shorter food chains are more efficient as the further you go up the more energy is lost through life processes and heat to the surroundings

-faster growth rate, adding plant food, fertilizers and water
-immunity to diseases/ pests by Genetic modification or selective breeding for resistance
-made to be same size
-insecticides, fungicides, weedkiller and natural defenses to reduce competition .
-improve growth rates (e.g. drugs/ steroids)
-good feed and balanced nutrients
-vaccinations and antibiotics
-reduced movement to "fatten them up", and heaters that stop them using energy
-selective breeding
marker assisted selection- a mechanism used by animal and plant breeders to help select individuals with the desired genotype, the desired gene is linked to a section of DNA that's easy to identify in a young individual
natural selection- animals breed in order to survive and adapt when there is pressure or a threat
artificial selection - aka selective breeding- the process of improving a variety of crop plants or domesticated animals by breeding from selected individuals with desired characteristics

stages of selective
artificial selection
in breeding or line breeding
using chemicals to improve food production
fertilizers-replace elements in soil that are removed by plant growth
herbicides-stop weeds competing with crops for resources

C.H.D and high blood cholesterol
C.H.D = coronary heart disease
obesity related diseases - cancers, cardiovascular disease, type 2 diabetes, gall stones, osteoporosis, hypertension
C.H.D is caused by a build up of fatty substances in the walls of coronary arteries, this is known as atherosclerosis
deposition in the coronary artery walls narrows the size of the lumen which restricts blood flow to the heart muscles and causes oxygen starvation

endothelium of arteries is damaged *
* = this usually due to getting older, carbon monoxide from smoking or high blood pressure due to a high salt intake or again getting older
damage repaired by PHAGOCYTES
(white blood cells)
smooth mucel grows under the damage encouraging...
... fatty substances including cholesterol from LDLS, to be deposited under the endothelium forming an ATHEROMA $
$ = atheroma's also include fibers, dead blood cells and platelets
atheroma breaks through the endothlium, forming a plaque sticking into the lumen
this results in the wall becoming less flexible and reducing in size
controlling risk of C.H.D
risk reduced by -
-Dietary Fibre
-moderate alcohol consumption
-eating oily fish (Omega 3)

Risk increased by -
-excess salt
-saturated fats (usually animal fats)
-cholesterol > 5.2 mmol DM -3
effects of salt on the diet
excess salt in the diet decreases the water potential of the blood
as a result more water is held in the blood and the blood pressure increases
this results in hypertension, meaning that blood pressure and diastolic pressure are held at too high levels
this damages the inner lining of the arteries, one of the earlier steps of atherosclerosis
cholesterol is made in the liver from saturated fats. the ideal concentration of cholesterol in the blood is below 5.2 mmol dm -3, cholesterol is transported in the blood in the form of lipoprotines, there are two types of lipoprotine, high density lipoprotines and density lipoprotines
ways to preserve food
-freezing- puts microorganisms into
a state of hibernation
-drying - lowers water potential of
the food causing the water to be
out of any microorganisms that make
contact with it, drying them out
-airtight storage prevents
microorganisms gaining access to the
food and prevents those already
with access from getting oxygen/
moisture for life processes
e.g. respiration

-irradiating - kills all microorganisms by damaging
- salting- lowers the water potential and prevents microorganisms gaining access to water
-heat treating- denatures enzymes in microorganisms peminantly
-pickling- denatures enzymes in microorganisms
-jam and high sugar foods - inhibits
metabolic processes and lowers
water potential
-vacuum packing- denies microorganisms access to
the food

- when yoghurt is made the lactobacillus uses the lactose sugar to make lactic acid (anaerobic respiration due to airtight container), upping the PH to kill all the bacteria this can also apply to cheese
- in beer yeast uses anerobic fermentation to turn ethanol into ethanol and carbon dioxide which kills them off
-wine uses a similar process exept its the fermenting grapes that produces the ethanol
advantage or



welfare issues

waste products
the protein doesn't have the
taste or texture of regular
this may mean that will not want to eat this in the flavor of traditional meals
pages 158+159
the effects of smoking
the three main chemicals in tobacco smoke
-Carbon Monoxide
the three main lund diseases caused by smoking
- Lung Cancer
-Chronic bronchitis
- Emphysema
how are tumors detected in the lungd?
-Chest X-ray
Tar - short therm effects
settles in airways and alvioli
allergic reaction
glands enlarge
cilia paralyzed or destroyed
increased diffusion distance
smooth mucels contract
smaller Lumen
restricted airflow
more Mucus secreated
mucus not moved
bactiria + viruses that are trapped
blocked bronchioles
tar- long term effects
bactiria laden mucus
smolar coush
(to remove it)
inflamed airways
attracts Leucocytes (white blood cells)
which release enzymes (elastase)
Digests part of lining so
leucocytes can get through
elastic tissue damaged
loss of elasticity
alvioli cant recoil to push air out
bronchioles collapses trapping air
alvioli burst
thicker smooth
muscel layer
reduces lumen
perminantly restricted
damages delicate
replaced by thicker less flexable scar tissue
diseases associated with smoking
chronic bronchitis - the inflammation of the lining of the airways, this is accompanied by damage to the cilia and the overproduction of mucus which settles in the lungs causing irritation and continuous coughing and coughing up of mucus containing bacteria and white blood spells. this also increases risk of lung infection
Emphysema- loss of elasticity in the alvioli, causing them to burst, causing a reduced lung capacity as there is reduced surface area for gaseous exchange, this also causes fatigue and tiredness due to reduced oxidation
Lung cancer - can be recognized by
nicotine and carobon monoxide
effects of nicotine :
-smoker feels more alert due to it mimicing the actions of transmitter substances at the synapses between nerves, this also increases the sensitivity of the nervous system
-raised artiriole blood pressure caused by an adreniline release causimg an increase in the heart and breathing rate and constriction of the artirioles
-reduced blood flow to artirioles due to there constriction
-may cause thrombus due to platelets becoming more sticky and other platelets and blood cells sticking to them forming a clot

effects of carbon monoxide:
-gets into the blood system and combines with red blood cells more easily the oxygen forming carboxyhaemoglobin (a perminant change) , reducing the amount of oxygen carried in the blood, this is noticable when a smoker exersizes
-carbon monoxide also damages the lining of the arteries
carbon monoxide damages the inner lining of the arteries (the endothelium) , a high blood pressure due to age or too much salt in the diet adds to the damage, the damage is repaired by phagocytes encoroging the growth of smooth muscle and the deposition of fatty substances such as cholesterol and Low-density Lipoprotines , this causes a blockage or plaque which sticks out of the lumen of the artery, red blood cells and other blood factors also get stuck on the plaque increasing its size. the smooth mucel reduces the flexibility of the artery and the plaque reduces the amount of blood flow
blood flowing past the plaque cannot flow smoothly increasing the chance of a clot forming (also increased by nicotines effect on platelets, this clot blocks blood flow in the artery, sometimes a peice of the clot will break free and be carried around the circulatory system untill it gets wedged in a smaller artery and then blocks blood flow there
death of brain of brain tissue due to a loss of blood flow to that part of the brain due to ether a blood clot blocking off an arterie in the brain (thrombus) or an artery leading to the brain bursting (hemmoraging)
Pathogenic fungi

Mycosis- A disease caused by a fungi
Superficial Mycosis
 Infection only present on the surface
 E.g Athlete's foot, scalp ringworm
Cutaneous Mycosis
 Infection in the first few layers of skin
 E.g. types of ringworm
Subcutaneous Mycosis
 Under the skin and infects bone and connective tissue
 Usually chronic i.e. long lasting
 E.g. Sporotrichosis created by Sporothrix schenckii
Systemic Mycosis
 Fungal Infection has the ability to reach any part of the body
 Meningitis

Pathogenic Fungi

Decomposition of dead matter
 Returning Nutrients to the soil
 Yeast in bread, beer
 Truffles
 Quorn
Antibiotic penicillin

Examples Of Good Fungi

Antifungal medicine

Skin Infection
Excessive Redness

Signs and Symptoms
Sinus Infection’s
Sinus Pain
Lung Infection

Example 2- Aspergillosis

Invasive Aspergillosis
Damaged is caused to tissue
Usually in lungs but can effect other organs

Broncho-pulmonary Aspergillosis
Allergic respiratory symptoms e.g wheezing and coughing
Fungus is in lungs but hasn’t damaged any tissue

Aspergillus- A common fungus, usually indoors
Weakened immune systems
Lung disease

Example 2- Aspergillosis

Long course,
High dose antifungal.
Via IV

Blood sample
Cerebrospinal fluid test

Signs and Symptoms
Stiff Neck
Nausea and Vomiting
Photophobia (Light sensitivity)
Altered Mental Status

Examples- Fungal Meningitis

Different fungus can cause this disease

Not contagious
Risk increases with weak immune system
Fungus enters the bloodstream and gets into the central nervous system

Rare strain on Meningitis caused by Fungal infection
Systematic- Fungal infection of blood to the spinal cord

Examples- Fungal Meningitis

 Yeast Cell

Eukaryotic cells
Found in almost all climates
Range from unicellular to large multicellular structures
Similar to a plant- Cell wall but no Chlorophyll
It absorbs nutrients from the surroundings to survive

What is A fungi?

hardening of the artery walls making them less flexible due to deposition of minerals such as calcium in the walls epecially of atheroma (this is natural with aging not an affect but as its similar to arterosclerosis therefor i though it best to mention it so they are not confused).
coronary heart desease continued
caused by a partial blockage of the corinary arteries, can then go on to cause an angina or a myocardial infarction
factors that increase the risk of CHD
-exess salt in the diet
-lack of exersize
-high fat intake in the diet (animal fats)
-high stress levels
epidemiological studies help identify....
which countries are at greater risk
which age range of the population may be at greater risk
whick sex may be at greater risk
which lifestyle factors may be at greater risk
the information gained can be used to....
help countries or organisations target further spending
help target reaserch at perticular risk factors to find a cause / cure
help target screening procidures and find those at risk early
help target advice and education at the parts of the population most at risk
predict where a disease may be more prevalent in the future
target geographical areas at risk using preventive measures (e.g. vaccination to help stop diseases spreading
cheack how current campains and preventive measures are working
epidimialogical studies are the comparison of two or more factors in an attempt to find a cause/cure for a problem/ desease in defined popualtions

non-specific immune responses (primary defenses)
mucus membrains- traps pathogrens which are then sneezed out or cillia moves mucus upward to the through where its then swallowed
in females the vagina is slightly acidic to kill microrganisms
anus is regularly cleaned out
scabs/blood clots
skin : uses a layer of dead cells to create a physical barrier, they contain kerotin instead of cytoplasm and are known as kemotinocytes
stomach acid kills any microorganisms swallowed in mucus
ear wax
tear - are antibactirial and contain salt and lysozymes to break down microorganisms
immune responses
(secondary defences)
Phagocytes - are designed to locate and destroy pathogens that enter the body before they reproduce and cause symptoms of a diseases. There are two types of phagocytes:

-Neutrophils: recognizable by it's multilobed nucleus, they are manufactured in the bone marrow and have a short life span and travel in the blood, though they are also capable of passing into the tissue fluid at will where they ingest pathogens, using enzymes called lysins. they also tag pathogens with antibody's which neutralize the toxins produced by the pathogens as well as breaking them down , they also flag up microorganism for the other white blood cells to locate

-Macrophages/monocytes - are larger cells manufactured in the bone marrow, they travel in the blood in the form of monocytes, they tend to settle in bodily organs in particular the lymph nodes, where they release chemicals to attract neutrophiles to the area , these chemicals also make the cpilleries more leaky, causing swelling and more tissue fluid to pass into the lyphatic system toward the waiting macrophages. they like neutrophiles can also ingest pathogens and use antibodys

anti-bodies/ immunoglobulins
antigen : molecules that can stimulate and immune response , there also found on the cell surface membrain of our own cells but they are recognised by are immune system so dont provoke a response
antibodys/immunoglobulins : large protines that have a complimentary shape to a perticular antigens , therefor the body have to create a different antibody for every antigen that they detect
the process where a large antibody binds many pathogens together, the group of pathogens is then too large to enter a host cell
where the antibodys attach to the antigens , blocking the binging sites so the pathogen cannot bind to the host cells
coat the surface of the pathogen in a process called optinisation, increasing the likelyhood of the pathogen being destroyed by phagocytes
memory cells

primary response
secondary response
the bodys initial attempt at combating a pathogen, it takes longer for the body to identify and combat the pathogen and fewer antibodys are reduced
lag time
store the knowlage of which antibodys are requires to combat each pathogen, so when a pathogen infects the body for a second time, the response is quicker and more efficent
the bodys next exposure to a pathogen, response time by the body is quicker and huge numbers of antibodys are produced to more quickly combat the infection.
greatly reduced
reaction time

rapid antibody
antibodys remain in the
body for longer this time
lag time
the time it takes for the body to notice and begin to effectiivly combat the infection

- as its impossible to practically count how many individual organisms are in a specific habitat
-therefor a habitat can be sampled a count of individuals i a small portion of the habitat, then numbers aquired can be used to estimate numbers in the whole of the habitat
how to ensure random sampling
estimate habitat size
choose position of your samples
then ether....
use regular interval sampling
use a random number generator to
get co-ordinates
select map co-ordinates then use hand held GPS system to find the exact spot
sampling plants
percentage cover
but carry out a visual survey also to avoid missing infrequent occuring plants
sampling animals
animals have to be trapped before counting as they move , hide and are hard to find
The specifuc immune system
B cells -plasma cells and B memory cells
T cells- T killer and T help cells
macrophages - phagocytosis and antogen preventing cells
1) infection and reproduction of pathogens
-white blood cells identify forign pathogents
2) macrophages undergo...
-creation of antigen presenting cells
2)infected cells
2) pathogens in bodily fluids
3) clonal selection
finding complimentry antibody
by cloning the correct lymphocyets,
this takes time hence why primary
response is so slow
B cells
plasma cells
B memory cells
T cells
T killer
T memory
T helper
4) Colonal expansion or prelipheration
- cloning begins, cell numbers increase
through mitosis
T Killer and memory cells combat the antigens whilst the t helper cells release cytokines to stimulate the B cells to develop and stimulate Phagocytosis and phagoctes
Roles of T + B cells
T helper Cells
T-helper cells stimulate the B cells during the later stages of the specific immune response so they stimulate phagocytosis by the phagocytes
T-killer Cells
T-killer cells attack and kill infected Body cells
T and B memory cells
remember which antibody are required to tagg and destroy each type of pathogen for the plasma cells
plasma cells
flow around the body manifacturing and releasing antibodys
- species : a group of organisms with similar characteristics, anatomy, physiology,biochemistry and genetics
-habitat : an area in which an organism, organisms , population or community lives
-biodiversity: the variety of life
species ritchness: the number of different species present in the habitat, the more species present the ritcher the sample
species eveness: the measurment of the relative abundunce different specied making up the richness of an area.
mark and recapture
used to help count animals that are too small to count
C1 x C2
c1= animals are captured and marked before release
c2 = second trap collects a second batch of animals

c3 = number of marked indeviduals in the second batch
Simpsons diversity index - as species richness and eveness increase so diversity increases
Simpsons diversity index takes into account both of these
the larger the number the more diverse the habitat

D= 1 [Epsilon(n/N)squared)
this equation is done by diving the number of individuals in that species by the total number of indeviduals, squared and the minus one
natural - exposure to antigen to produce memory cells
artificial - deliberate exposure to an antigen to produce memory cells
passive - antibody's not manufactured by the body (e.g. across the placenta) , only a short term solution as no memory cells are produced
active - immunity through activation of the immune system due to direct exposure to an antigen (e.g. natural and artificial immunity)
herd and ring vaccination

cell communication
cell communication is done by chemicals called cytokines, they can only diffuse short distances and only act on target cells with the correct receptors on them, they trigger secondary messages (chemicals) to be released inside the cell, these secondary messengers can alter gene expression, for example t helper cells tell b cells to differentiate using cytokines
monokines are a type of cytokine released by macrophages, they stimulate b cells to differentiate, they also attract neutrophiles in a process called (chemotaxis)
a type of cytokine released by macrophages,B and T cells, they stimulate the proliferation of B and T cells.
cytokines released by a variey of infected cells in an attempt to slow/inhibit virus reproduction and stimulate T-killer cells
classification, phylogeny and taxonomy
biological classification is the the study of placing living thingsinto groups based on there similaritys
natural classification is the action of placing organisms into groups based on there evolutionary links
classification is an attempt to impose a hierachy on the complex and dynamic variety of life on earth
classification systems have changed and will continue to change as our knowlage of the biology of organisms develop
the study of the principals of classification (e.g. putting species that look similar in the same group
is the study of evolutionary relationships between organisms
why do scientists classify organisms?
to make the study of living things more manageable
to make it easier to identify living organisms
to help us see relationships between species
many species have been reclassified due to phylogeny study's
variations in a species that help the organism to survive
there are 3 kinds of adaptations:
physiological/ biochemical: an adaptation that helps to ensure the correct functioning of cell processes
anatomical: physical adaptations to the structure of an organism that help it to survive
behavioral : aspects of an animals behavior that help it to survive in the conditions its in
a behavioral adaptation for some bird species is to migrate to warmer climates when a climate there in becomes too cold for there food species (e.g. swallows migrate to Africa to find supply's of flying insects when the weather in the UK becomes too cold and there species go into hibernation)
an example of a physiological adaptation is an increase of the metabolic rate of reptiles during the day when the sun is present and its warmer , the rate slows down at night when it becomes cooler again
an example of an anatomical adaptation is the
Xerophytic Plants
most xerophytic plant will ether have a shallow roots spread over a wide area in order to allow them to absorb a lot of water when its available, or deep roots to allow them to tap into underground water sources
they may have a thick fleshy stem to allow
large amounts of water to be stored in case
of drought
the leaves may be reduced in
size in order to reduce water loss through evaporation and transpiration (in the case of cacti these also double up as protective spines)
leaves may also be waxy in order
to ensure water can only be lost through through the stomata
however many of these species are
able to
close there stomata at will when
little water is available, conserving
water and preventing wilting...
...whilst others only open there
stomata at night when its cooler
so theirs less

some xerophytic plants
open there stomata
when water is in short supply
in order to make there leaves wilt
reducing surface area
the system was based on one designed by Carl Linnaeus 250 years ago, his system used 5 taxa but has developed as technology has improved to identify new links (e.g. phylum and family have been added), the modern day taxa now has 8 groups.
taxa: the groups into which biologists identify living organisms
Naming Living Things and Modern Classification
before linnaus species were identified by a common name or a long description, there were a number of issues with identification this way such as different commen names used in different countries, translations from other languages gave different names, some common names were used for different species in different parts of the world and some organisms have different names in different parts of one country. linnaus used Latin for his system of taxa so the system could be universal, so organisms could have the same name eveywhere in the world. the bionomial system of nomenclature was the result, the use of two latin names to identify an organism
the first name used is the genus of the organism and the second is the species name. these are always written in italics and the genus begins with a capital (if hand written they should be underlined instead of italics).
this system helps to identify different species, helps with communication and helps to determine which species are endangered and which are not. before any development takes place a environmental impact assessment is carried out to identify if/ where any rare species present in a habitat.
dichotomous keys
dichotomous (two branching ) keys are a series of simple questions that answer yes or no which are used in order to help identify different organisms.

e.g. Homo sapian
Natural selection and Evolution
continuous variation : variation that shows a complete range with no distinct groups
discontinuous variation : is variation that produces distinct groups
the term variation refers to the differences between individuals
there can be variation between species but also between between individuals within a species.
light microscopes
type of
scanning electron
transmition electron
50,000- 500,000
50-100 NM
viewing the surface of cells and organells - provides in depth 3D images
0.4 -20 NM
0.05 - 1 NM
viewing tissues and cells
detailing organelles and ultra structure
advantages and disadvantages for each microscope type
light microscope
smaller so easier to move and store
cheaper that the alternatives
less magnification and resolution than the larger microscopes
scanning + transmission electron microscopes
higher resolution so more details can be observed
more costly than a light microscope
sample must firstly be dried and therefor dead , potential distorting any observed features
image will be in black or white, colours can be artificial added via a computer (false colour electron micrographs) but this is expensive
Be warned! this song is
additively annoying
but if it helps its worth it
(its also avalible on
start of mitosis
chromosomes shorten and thicken as DNA supercoils
each chromosome becomes visible as two chromatids joined at a centromere
prophase ends when the nuclear membrane breaks down into smaller pieces
centrioles organize fiberous protines into spindles
chromosomes are held on the spindle along the middle of the cell
each chromosone is attached to the spindle on each side of the centromere
chromatids break apart along the centromere and are moved to opposite ends of the cell by the spindle
neuclear envelopes begin to re-form around the chromatids that have reached the two poles of the cell
each new nucleus has the same number of chromasomes as the origonal parent cell
the nuclei are genetically identical to each other
Tissues, Organs and Organ systems
a collection of cells that work together in order to perform a particular function. They may be similar or they may perform different roles, one example of this is cilliated epithelium being made up of the cilliated cells that move mucus over there surface, and the goblet cells which are responsible for producing the mucus
a collection of tissue that work together to perform a common function
Organ system:
two or more organs working together to perform a function vital for life

Cell Co-Operation
to ensure all systems in a multicellular organism operate at maximum efficiency, cell signaling must be used to ensure each cell works with the others in a coordinated fashion, one example of this is the muscles getting more oxygen from the respiratory and circulatory systems and more carbon dioxide removed via these same systems so they can work harder.
cell type
erythrocytes (red blood
lack of nucleus so more room to store haemoglobin
contains haemoglobin to bind with oxygen
biconcave shape to allow for a larger surface are to make gaseous exchange easier
microscopic measurements
there are 1000 mm in one meter

there are 1000 um (micrometers) in one mm

there are 1000 nm (nanometers) in one um
so to convert a measurement from mm to um you must times it by one thousand, and a thousand again to convert from um to nm , to convert back, you divide by a thousand for each stage (see above)
References/ Sources
OCR As biology Textbook
my revision notes As biology textbook (i heavily recommend getting this if you don't have it, here's a link to the amazon page:
My own notes from my lessons and independent study (hence some of the strange ways of remembering things and a few vague bits/spelling mistakes (sorry for those) !)
a thanks to my class mates for there input and advice (not to mention letting me add our group works!)
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