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Biology IB - SL core

Some core biology notes for the IB diploma. If you like these notes then please become a fan of IB notes on facebook for more similar styled notes.

IB Notes

on 17 May 2011

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Transcript of Biology IB - SL core

Biology standard level core
IB Outline the cell theory. All living organisms are made of one or more cells
Cells are the smallest unit of life
All cells come from pre-existing cells Discuss the evidence for the cell theory. All organisms are made of one or more cells: Microscopic observations of cork, plants and animals Cells are the smallest unit of life: No living entity has yet been found that does not conist of at least one cell All cells come from pre-existing cells: Sterilizing chicken broth by boiling showed that life did not reappear without first getting in contact with pre-existing life State that unicellular organisms carry out all the functions of life. Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit. Objects are in 3-D and up to: ________________________________________________ I I I I I I Cells Organelles Bacteria Viruses Membranes Molecules 100 μm 10 μm 1 μm 100 nm 10 nm 1 nm 1 μm = 0.001 mm
1 nm = 0.000001 mm Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification. Magnification = size of image ________________ size of specimen Size of image = diameter of microscope's field of vision
Size of specimen = can often be calculated in the field ________________ I ________________ ________________ _________ ______ M S Explain the importance of the surface area to volume ratio as a factor limiting cell size. Page 14
Pearson Baccalaureate HL book State that multicellular organisms show emergent properties. Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others. State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways. Outline one therapeutic use of stem cells. Blood stem cells can replace damaged bone marrow of leukemia patients. Possible future therapeutic use of stem cells include:
Replacing brain cells lost due to Parkinson's or Alzheimer's disease
Stem cell implant in pancreas to help certain diabetes patients Start End 2.1 Cell theory Draw and label a diagram of the ultrastructure of Escherichia coli (E. coli) as an example of a prokaryote. Annotate the diagram with the functions of each named structure. Cell wall: Maintainance of shape
Protection of cell
Made of peptidoglycan Plasma membrane: Control of movements in and out of cell
Role in binary fission (division of prokaryotic cells) Nucleoid: Contains the DNA of the cell in a single, long, continuous, circular thread
Involved in cell control and reproduction Ribosomes: Sites of protein synthesis
Numerous in cells with high protein production Pili: Help with attachment
Join bacterial cells in preparation for sexual reproduction . . . . . . Identify structures in electron micrographs of E. coli. State that prokaryotic cells divide by binary fission. DNA is copied
Daughter chromosomes become attached to different regions of the plasma membrane
Cell divides into two genetically identical cells 2.2 Prokaryotic cells Draw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell. Annotate the diagram with the functions of each named structure. Cell membrane: Controls what goes into and out of the cell Nucleus: Contains the cell's DNA Nucleolus: Ribosome production Nuclear envelope: Allows communication between nucleus and the rest of the cell through nuclear pores Mitochondria: Production of ATP (the cell's energyhouse)
More of them in high energy-consuming cells Have own DNA
Can reproduce independently of the cell
Have own ribosomes (70s) vs. Chloroplasts: Only present in plant cells
Absorption of light for photosynthesis Have own DNA
Can reproduce independently of the cell
Have own ribosomes (70s) Golgi complex/apparatus: Ribosomes: Size: 80s (compared to 70s in prokaryotic cells)
Can be attached on the (rough) ER or free in cytoplasm
Site of protein synthesis Packaging, modification and distribution of materials synthesized in the cell Endoplasmic reticulum (ER): Rough ER: Has ribosomes on surface
Site of proteins synthesis Smooth ER: Site of important enzymes that for instance:
Produce sex hormones
Removes toxic drugs in liver
Store calcium ions needed for contraction in mucle cells
Transport lipid-based compounds
Aid the liver in releasing glucose into bloodstream when needed Lysosomes: Arise from golgi apparatus
Contain enzymes that catalyze the breakdown of proteins, nucleic acids, lipids and carbohydrates
Recycling of old or damaged organelles
May break down materials introduced to cell by phagocytosis The region within the cell membrane
The region of all organelles
The fluid portion of the cytoplasm is called the cytosol Cytoplasm: Vacuoles: Storage organelles usually sent from the golgi apparatus
Fill up a large space in most plant cells
Can store several different substances such as potential food, metabolic wastes and water
Allow cells to have higher surface area to volume ratio, even when larger Centrosomes: Present in all eukaryotic cells
Consists centrioles (except for higher plant cells)
Important for cell division ______________ ______________ 2.5 Cell division Outline the stages in the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis. State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue. State that interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts. Drscribe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase, telophase) Explain how mitosis produces two genetically identical nuclei. State that growth, embyonic development, tissue repair and asexual reproduction involves mitosis. G1: The smallest the cell will ever be
Mostly growing of cell S: Also called synthesis phase
Replication of DNA G2: Increase in organelles
DNA begins to condense
Microtubules may begin to form Mitosis: Cytokinesis: See in later learning outcome Division of cell
In animal cells there is a pinching inwards of the plasma membrane to form cleavage furrows
Plant cells form cell plate that occurs midway between the two poles and moves outward toward the sides of the cell Prophase: Nucleoli disappear and nuclear envelope disintegrates
Chromatin starts condensing to form visible chromosomes
Spindles start forming
Centrosomes start moving towards opposite poles
Kinetochores of chromosomes attach to spindles Metaphase: Chromosomes move towards the cell's center; the metaphase plate
Centrosomes are at opposite poles Anaphase: Chromosomes split and move towards opposite poles due to shortening of spindles
Centrosomes move towards poles first (form a 'v', like in picture) Telophase: Nuclear envelope starts forming around the two identical sets of chromosomes
Nucleoli reappear
Spindles disappear
Chromosomes start elongating to form chromatin
Cell elongates as preparation for cytokinesis Meiosis I: Nuclear envelope disintegrates
The homologous chromosomes line up across the cell's equator Chromosomes become visible due to supercoiling
Homologous chromosomes attract each other in pairs - one from fater and one from moter
Crossing over occurs
Spindles start forming Telophase II: Anaphase I: Metaphase I: Prophase I: Sometimes chromosomes start elongating again
Usually new nuclear envelopes form
Spindles disappear
Many plants do not have this phase Spindles attach to the chromosomes
Chromosomes move towards opposite poles due to shortening of spindles (no splitting occurs, only seperation of the homologous chromosomes) Meiosis II: DNA strands unwind
Nuclear envelopes form around all sets of haploid cells
Preparation for cytokinesis Metaphase II: Telophase II: Random orientation causes chromosomes to align randomly at the cells' equators
Nuclear envelope disintegrates
Spindles at the poles attach to centromeres Prophase II: Centromeres split into chromosomes into two chromatids
Spindles pull chromatids towards poles
Random orientation causes chromatids to move randomly to either pole
In animal cells, membranes pinch off in the middle while plant cells form new cell plates to demarcate the four cells Anaphase II: Chromosomes condense
Spindles start forming A cell in telophase I: State that the most frequently occurring chemical elements in living things are carbon, hydrogen, oxygen and nitrogen. State that a variety of other elements are needed by living organisms, including, sulfur, calcium, irons, phosphorus and sodium. State on role for each of these elements: (sulfur, calcium, irons, phosphorus and sodium). Sulfur Calcium Phosphorus Sodium Irons Role in animals For simplification and to more easily remember, only the role of these elements in animals are considered. Component of bones and co-factor in some enzymes Phosphategroups in ATP In haemoglobin and cytochromes Role in sending nerve-impulses and membrane function In some amino acids _______ _______________ _______________ _______________ _______________ _______________ _______________ Outline thermal, cohesive and solvent properties of water. Explain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport medium. Draw and label water molecules to show their polarity and hydrogen bond formation ____ ____ + - H H O ------- 'Split-second' hydrogen bond H O ____ ____ + H Direction of movement Direction of movement - Thermal: High specific heat:

High heat of vaporization: Can absorb or give off a lot of heat without greatly changing temperature Absorbs a lot of heat when evaporating thus useful for cooling mechanisms. Cohesive: Water's ability to form polar covalent bonds between negative and positive ends. Solvent: Great solvent for polar molecules, making it a perfect medium for 'aqueous solutions' (fluids that mostly contain water such as cytoplasm, stroma) and for transport. Identify structures in electron micrographs of liver cells. State three differences between plant and animal cells Plant cells

Animal cells Chloroplasts Vacuole Cell wall Yes

No Yes

No Yes

No or small ____________________________ _______ _______ Outline two roles of extracellular components. Allows cell-to-cell interaction that can:
Alter gene expression
Bring about co-ordination of cell action

Thought to be involved in directing stem cells to differentiate. Compare prokaryotic and eukaryotic cells. Prokaryotic Eukaryotic _______ DNA in rimg without protein
No nucleus
DNA free in cytoplasm
Ribosomes of size 70s
No compartmentalization
No mitochondria present
Size less than 10 micrometers DNA with proteins as chromosomes
Nucleus present
DNA kept in nucleus
Ribosomes of size 80s
Compartmentalization to form organelles
Mitochondria present
Size more than 10 micrometers 2.3 Eukaryotic cells 3.1 Chemical elements and water 3.2 Carbohydrates, lipids and proteins Distinguish between organic and inorganic compounds. Identify amino acids, glucose, ribose and fatty acids from diagrams showing their structure. List three examples each of monosaccharides, disaccharides and polysaccharides. State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants. Outline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides and polysaccharides; between fatty acids, glycerol and triglycerides; and between amino acids and polypeptides. State three functions of lipids. Compare the use of carbohydrates and lipids in energy storage. Organic compounds always contain carbon
Carbon molecules are not always organic Glucose: 6-carbon
monosaccharide Ribose: 5-carbon
monosaccharide Amino acid: The common structure of an amino acid. The R-group represents the molecule that differs between amino acids. Fatty acid: Differ in the amount of the total number of carbons and by the presence and location of any double bonds between carbons. OH-C-(CH ) -CH 17 2 3 O _ _ is the same as: Monosaccharide Disaccharide Polysaccharide Fructose
Galactose Sucrose
Maltose Cellulose
Glycogen ______________________ ______________________ ______________________ ______________________ ___________________ ___________________ ___________________ Outline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate. State the names of the four bases in DNA. Outline how DNA nucleotides are linked together by covalent bonds into a single strand. Explain how a DNA double helix is formed using a complementary base pairing and hydrogen bonds. Draw and label a simple diagram of the molecular structure of DNA. 3.3 DNA structure 3.4 DNA replication Explain DNA replication in terms of unwinding the double helix and separation of the strands by helicase, followed by formation of the new complementary strands by DNA polymerase. Explain the significance of complementary base pairing in the conservation of the base sequence of DNA. State that DNA replication is semiconservative. Glucose
Glycogen In animals: A substance found in milk 1. Energy storage
2. Insulation
3. Phospholipids in cell membranes A mass of lipids can store twice as much energy as the same mass of carbohydrates. Chemical fuel for cell respiration Stores glucose in liver and muscles In plants: Fructose

Cellulose What makes fruits sweet Often transported from leaves to other parts of the plant Component of plants' cell walls Hydrolysis: Reactant: Product: Water Smaller compound Condensation: Bigger compound + water Catalyzing enzyme Examples of hydrolysis (reverse arrow for condensation reactions): Lactose + water Glucose + galactose Disaccharide 2 monosaccharides Starch + (many) water (many) glucose Polysaccharide Many monosaccharides Triglyceride + 3 water Glycerol + 3 fatty acids Triglyceride lipid Glycerol and fatty acids Protein + (many) water (Many) amino acids Polypeptide (protein) Amino acids ____________ _________ _________ ____________ ____________ Adenine Guanine ____________ ____________ _________ _________ ____________ ____________ Thymine ____________ _________ _________ ____________ ____________ _________ ____________ Cytosine ____________ _________ ____ ____ ____ ____ Deoxyribose sugar Deoxyribose sugar Deoxyribose sugar Deoxyribose sugar ______________ P _____________ P ______________ _____________ ------ ------ ------ ------ ------ 3 hydrogen bonds Only 2 hydrogen bonds Phosphate Base Guanine and adenine bigger than thymine and cytosine
Thus the complementary base pairing (as seen in picture above) is the only way to create a consistent distance from one strand to another Flagellum: Longer than pili
Allows the cell to move . . 2.4 Membranes Draw and label a diagram to show the structure of a membrane. Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain the structure of the cell membranes. The hydrophobic and hydrophilic regions cause phospholipids to always align as a bilayer in the presence of water.
What maintains the overall structure of the membrane is the tendency water has to form hydrogen bonds. List the functions of membrane proteins. Integral protein: Penetrates cell membrane
Control the entry and removal of specific molecules in cell Glycoproteins: Recognition of like cells and involved in immune responses Define diffusion and osmosis. Diffusion: A passive transport
Particles move from high concentration to low concentration
Move along concentration gradient
Aim to create equilibrium
Usually involves a membrane in organisms (Facilitated diffusion): Involves carrier proteins that combine with substance to aid its movement. > > Osmosis: Movement of water along concentration gradient
Passive transport through partially permeable membrane
The concentration gradient is due to a difference in solute concentration on either side of membrane
Water move from hypo-osmotic solutions to hyperosmotic solutions
Iso-osmotic solutions is when equilibrium has been reached > Hypo-osmotic solution Hyperosmotic solution Explain passive transport across membranes by simple and facilitated diffusion. Go through the slideshow (or look around freely). Not all assessment statements have been covered but then a page number is usually given to indicate the page at which the information can be found on. Page numbers (and information) refer to the Pearson biology book.
Enjoy and good luck with studying (and in the exams of course!) Explain the role of protein pumps and ATP in active transport across membranes. ATP is required for active transport
Particles do not move along concentration gradient (1). 3 sodium ions (Na ) attaches to a open protein in the phospholipid bilayer. + (1)-(2). The attachment causes phosphorylation by ATP (ATP attaches to the protein) (3). Phosphorylation causes a change in the protein's shape, expelling the sodium ions to the exterior (out of the cell) (3)-(4). 2 extracellular potassium ions bind to the protein, causing the release of the phosphate group. (4). Loss of the phosphate group restores the original shape of the protein, thus releasing the potassium ions into the cell. The description of active transport below is only to show the role of protein pumps and ATP but according to the assessment statements, it is not necessary to know the exact process. Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatur and plasma membrane. Describe how the fluidity of the membrane allows it to change shape, break and re-form during endo- and exocytosis. Proteins produced by ribosomes of the rough ER enters the lumen (the 'inside') of the ER.
Proteins exit the ER and enter cis side; a vesicle is involved.
Proteins move through Golgi apparatus while it is being modified and exits on the trans side in a vesicle.
The vesicle with the modified proteins moves and fuses with the plasma membrane; results in secretion from cell. What allows membrane to break:

What allows membrane to re-form: 'Loose' connections between the fatty acids tails The properties of the hydrophilic and hydrophobic regions cause them to form a stable bilayer in an aqueous environment. For comparison of meiosis and mitosis: Notice how one polymerase moves in the same direction as the helicase while the other one moves in the opposite direction. 1. Process: Enzyme involved: Unwinding of double-stranded DNA 2. Breaking of hydrogen bonds between complementary base pairs to form two single strands 3. Helicase Free nucleotides from the nucleoplasm locate on an opened strand at one end so that a second one can join. 4. For a second nucleotide to be able to join, a covalent bond has to be formed to adjoin the two nucleotides DNA polymerase 5. Steps 1-4 are true for the opposite strand but in the opposite direction 5. The bond between the tRNA and the amino acid is broken since the amino acid is stuck to the second amino acid. The first tRNA flots away in the cytoplasm and reloads with another amino acid of the same kind.
6. The ribosome moves one triplet codon further 'down' so that a new tRNA can attach to the second one.
7. Steps 3-6 are repeated until the whole gene has been translated.
8. The last triplet codon signals 'stop' and then the complete polypeptide breaks away from the final tRNA and becomes free in the cytoplasm. Compare the structure of RNA and DNA. 3.5 Transcription and translation Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase. Describe the genetic code in terms of codons composed of triplets of bases. Explain the process of translation, leading to polypeptide formation. Discuss the relationship between one gene and one polypeptide. 3.6 Enzymes Define 'enzyme' and 'active site'. Explain enzyme-substrate specificity. Explain the effects of temperature, pH and substrate concentration on enzyme activity. Define denaturation. Explain the use of lactase in the producion of lactose-free milk. RNA DNA Single stranded
RNA nucleotides have 4 nitrogenous bases:
Adenine, uracil, guanine, cytosine
Contains 5 carbon-sugar: ribose Double stranded
DNA nucleotides have 4 nitrogenous bases:
Adenine, thymine, cytosine, guanine
Contains a 5 carbon-sugar: deoxyribose _____________________________________ _____________________________________ _____________________________________ _____________________________________ ___________________ Much like DNA replication (you might want to go back in the slideshow to review it). Helicase Enzyme involved: RNA polymerase 3. For a second nucleotide to be able to join, a covalent bond has to be formed to adjoin the two nucleotides Process: Breaking of hydrogen bonds between complementary base pairs to form two single strands 4. 2. Only one strand is replicated (recall that RNA is single stranded). Uracil pairs with adenine (thymine does not exist in RNA). Free RNA nucleotides from the nucleoplasm locate on an opened strand at one end so that a second one can join. 1. Unwinding of a single gene (not entire DNA molecule) This produces an mRNA molecule that is complementary to the one gene of DNA that was transcribed. 3 bases need to code for 1 of the 20 amino acids.
Any set of 3 bases that code for an amino acid is called a triplet.
A triplet found in an mRNA molecule is called a codon (or codon triplet). Ribosome Triplet anticodons Hydrogen bonds Triplet codon Previous peptide bonds created 1. mRNA locates a ribosome and aligns with it to fit the first two codon triplets (the picture shows the middle of the process where the ribosome fits two later codon triplets).
2. A tRNA (transfer RNA) complementary to the first codon triplet of the mRNA floats in. Each tRNA carries an amino acid and thus the first one is brought into the translation process. (Recall that this amino acid was originally determined by the DNA that transcribed the mRNA)
3. A second tRNA flots in (complementary to the second triplet codon) and brings another amino acid.
4. An enzyme catalyses a condensation reaction between the two amino acids held in place by the tRNA's in the ribosomes. This results in them covalently bonding with a peptide bond. It was believed that every gene could code for just one polypeptide.
However not that simple; one gene may lead to a single mRNA which might be modified in several ways, causing the production of a different polypeptide. Enzyme: Long chains
of amino acids
that have taken on specific 3D shapes. Shape may seem random but is in fact designed to match a specific molecule known as a substrate. Active site: Area in which to fit substrate almost like a glove that fits a hand. Optimum temperature Increasing enzyme activity Enzymes start denaturing Most enzymes have optimum pH around 7 (neutral) Some enzymes (e.g. pepsin in stomach) prefer an acidic environment. Neutral Acidic Basic Every molecule is working as fast as possible ______ Increasing substrate concentration thus more collisions When an enzyme (and hence also the active site) loses its specific 3D shape due to intramolecular bonds being stressed and broken.
Can be either permanent or temporary. Effect of temperature on enzyme activity Effect of pH on enzyme activity Some people cannot digest lactose, a sugar found in milk, due to lack of lactase in the digestive tract. This can cause bacterial colonies in the intestines leading to e.g. cramps and diarrhoea.
If milk is treated with lactase before consumption, the nutrients of the milk won't be affected but the person will be able to digest the the lactose. 6.1 Digestion Explain why digestion of large food molecules is essential. Because the molecules are too large to pass any cell membrane; by making them small enough, they can pass and be digested. Explain the need for enzymes in digestion. Enzymes lower the activation energy for reactions. This energy usually comes in the form of heat. Enzymes make digestion possible at a temperature low enough and safe for humans (if enzymes were not present, we would need a far higher body temperature for digestion to occur) State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase. Source



Optimum pH Salivary amylase Pepsin (protease) Pancreatic lipase Salivary glands Amylose (starch) Maltose and glucose Neutral (pH 7) Stomach cells Proteins (polypeptides) Amino acids Acidic (pH 3) Pancreas cells Lipids Glycerol and fatty acids Neutral (pH 7) Draw and label a diagram of the digestive system. You do not need to memorize salivary glands. Rectum Outline the function of the stomach, small intestine and large intestine. Stomach: Mixing of food with gastric juices by a churning motion created by the muscular walls of the stomach. The juices are:
Pepsin - needs an acidic environment to break down proteins.
Hydrochloric acids - breaks down and degrades food. Creates the acidic environment needed for pepsin.
Mucus - protects the stomach wall from the hydrochloric acids. Small intestine: Large intestine: Water absorption happens last to keep the food in a fluid environment.
Contains naturally occurring bacteria, like E. coli which synthesize vitamin K for humans while we provide them with a warm, nutritious environment.
Any food undigested by us or the bacteria is eliminated from the body. Distinguish between absorption and assimilation. Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion. Villus significantly increases the surface area for absorption.
All villi contain a lacteal (for absorption of fatty acids) and a capillary bed (for absorption of pretty much all other molecules). All absorbed molecules are taken into a wide variety of body cells by the circulatory system. 6.2 The transport system Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves, and the route of blood through the heart. Look it up in the book (page 156 in HL Pearson). It was impossible to find a picture that matched all of IB's requirements...
Make sure you know where to find:
The right and left atrium
The right and left ventricle
The right and left semilunar valve
The right and left atrioventricular valve
The aorta
The pulmonary artery
Superior and inferior vena cava State that the coronary arteries supply heart muscle with oxygen and nutrients. Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves. A red blood cell (RBC) that has just come from the body goes through (in order):

Right atrium
Atrioventricular valve
Right ventricle
Right semilunar valve
Pulmonary artery
Capillary bed

Left atrium
Atrioventricular valve
Left ventricle
Left semilunar valve
Capillary bed (Pulmonary circulation) (Systematic circulation) NOTE! As you can see, veins and arteries can not be categorized as oxygenated or deoxygenated. Veins carry blood from capillary beds to the heart . Arteries carry blood from the heart to the . capillary beds What happens in the right atrium? Blood starts flowing through the semilunar valve (the right one of course) to the ventricle (right again). The atrium contracts to force any remaining blood into the ventricle. What happens in the right ventricle? Once a certain amount of blood has accumulated in the ventricle, it contracts causing:
The atrioventricular valve to close to prevent backflow.
Increase in blood pressure in the ventricle and so the semilunar valve opens up to the pulmonary artery.
Blood leaves the heart through the pulmonary artery due to the pressure. What happens in the capillary bed? Pick up of oxygen and give off of carbon dioxide. Blood starts flowing through the semilunar valve (the left one this time) to the ventricle (left one). The atrium contracts to force any remaining blood into the ventricle. What happens in the left atrium? What happens in the left ventricle? Once a certain amount of blood has accumulated in the ventricle, it contracts causing:
The atrioventricular valve to close to prevent backflow.
Increase in blood pressure in the ventricle and so the semilunar valve opens up to the aorta.
Blood leaves the heart through the aorta due to the pressure. What happens in the capillary bed? Pick up of carbon dioxide and give off of oxygen. Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and adrenaline. Myogenic muscle contratcion: Muscle tissue that contracts and relaxes without nervous system control. Medulla: Adrenaline: Pacemaker: Area in the brainstem that chemically senses increases in carbon dioxide. A hormone that, when released into the bloodstream, causes the heart to beat more frequently than when at resting rate. Control of heartbeat: Tissue in the wall of the right atrium known as sinoatrial node (SA node) and acts as a pacemaker. The SA node (pacemaker) sends out an 'electrical' signal initiating contraction in both atria. The AV node gets the signal from the SA node and sends out another 'electrical' signal in about 0.1 seconds. This goes to the ventricles, causing them to contract. AV node: Another mass of tissue in the walls of the right atrium. In times of exercise: During exercise there is an increase in the demand for oxygen and need to get rid of carbon dioxide. The medulla reacts to the increased carbon dioxide and sends a message through the cranial nerve (cardiac nerve) to increase heartbeat to an appropriate level. The SA node receives the signal and increases the frequency of the signals.
When carbon dioxide levels decrease again, the medulla sends another message through the cranial nerve (this time the vagus nerve). When received by the SA node, the SA node takes control over the heart beat again and 'calms down'. Explain the relationship between the structure and function of arteries, capillaries and veins. Arteries: Have smooth muscle layer so that the automatic nervous system can change the inside diameter of the blood vessels. This helps regulate blood pressure.
Are thick walled to be able to 'take' the pressure from the ventricles of the heart. Capillaries: Are 1 cell thick to enable chemical exchanges. Veins: Are thin walled since most pressure is lost in the capillary beds.
Have internal valves to prevent the slowly-moving blood to backflow
Have a large diameter to account for the slowness of veins compared to arteries. State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets. State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat. 6.3 Defence against infectious disease Define pathogen. Any living organism/virus that can cause a disease. Y Y Y Y Y Y Y Y Y Explain why antibiotics are effective against bactera but not against viruses. Antibiotics can inhibit:
Protein synthesis
Cell wall production
They make use of the differences between eukaryotic and prokaryotic cells; they only attack prokaryotic cells.

Antibiotics are not effective against viruses because they make use of our cells (which are eukaryotic) and hide in them while antibiotics only attach prokaryotic cells. Outline the role of skin and mucous membranes in defence against pathogens. Skin The outer layer (epidermis) is mostly made of dead cells, thus as long as it stays intact, it prevents pathogens from getting intrance to our living tissues. Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissues. Macrophage is one type of leucocyte. It can identify cells as part of the 'self' or 'not-self' based on proteins that make up the surface of all cells and pathogens (referred to as antigens on pathogens). If something is recognized as an antigen ('not-self'), the macrophage engulfs it, much like an amoeba swallows food, in a process called .
Phagocytes contain many lysosomes that can digest what has been engulfed.
This response is referred to as non-specific.
Macrophaes can change their shapes and thus they are often found engulfing pathogens outside blood vessels. phagocytosis ______ SEM of phagocytosis Distinguish between antigens and antibodies. Antigens: The 'not-self' proteins on the surface of a pathogen which can be recognized by leucocytes. Antibodies: Protein molecules the body produces to fight specific antigens. Many pathogens have more than one antigen on their surface and thus triggers the production of several antibodies. [ [ [ [ Explain antibody production. An antigen is identified (e.g. a cold virus).
A B lymphocyte that can produce an antibody that can bind to that specific antigen is identified.
The B lymphocyte and several other identical ones clone themselves repeatedly by mitosis to quickly increase their population (since B lymphocytes only produce a small amount of antibodies).
The new 'army' begins antibody production.
The antibodies are released and circulate in the bloodstream until they find the antigen match (the proteins of the pathogens to which they can attach).
Antibodies help eliminate the pathogen using various methods.
Some of the cloned B lymphocytes remain in the bloodstream to give immunity to a second attack by the same pathogen. These are called memory cells. __________ Outline the effects of HIV on the immune system. Viruses can only make use of specific cells that match their own proteins.
HIV (human immunodeficiency virus) attacks the so called helper-T cells, which communicate what cells need to clone themselves for antibody production (recall from previous learning outcome). HIV infects helper-T cell. Usually it takes many years from an infection until AIDS symptoms develop. Helper-T cells eventually start dying. The absence of helper-T cells prevents communication in bloodstream. Antibody production decreases until it stops. AIDS symptoms start appearing; the body does not fight off pathogens like before. Might eventually take the life of a person. Discuss the cause, transmission and social implications of AIDS. Cause: The human immunodeficiency virus... Transmission: By body fluids (thus often via exchange of body fluids during sexual intercourse or by the use of uncleaned needles). Social implications: It was believed that HIV could only affect homosexuals and drug abusers but it is now known to be able to affect anyone.
Social implications of being diagnozed with AIDS may cause discrimination negatively affecting e.g.:
Getting ensurances
Getting a job
Getting an education
Etc. HIV might get transmitted. An interesting picture that you don't have to memorize but which is pretty much what it is like. Mucous Sticky substance that traps incoming pathogens and prevents them from our infecting cells.
Example of their locations:
Trachea - a tube that carries air to/from lungs
Nasal passage - tubes allowing air to enter the nose and then the trachea
Urethra - tube carrying urine from bladder to outside
Vagina - female reproductive tract leading from uterus and out Secretion of more juices to continue digestion. These include:
Bile from the liver and gall bladder
Trypsin (a protease), amylase, lipase and bicarbonate from the pancreas.
Production of small enough molecules to be absorbed by villi (and then either a capillary bed or lacteal).
Absorption: using the molecule for energy (e.g. glucose)
Assimilation: using the molecule to build bigger molecules.
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