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Biology IGCSE

For students taking the Cambridge International Examinations IGCSE (0610)

nikisha m

on 13 May 2015

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Transcript of Biology IGCSE


Cell Wall
Cell Membrane
Cell Organelles:
made of cellulose
criss-cross fibres
large molecules pass
fully permeable
protect & support cell
found in plant cells
cell surface membrane/ plasma membrane
thin layer of protein & fat
controls what goes in & out
partially permeable
found in plant & animals cells
clear jelly
70% water
dissolved substances (proteins)
metabolic reactions
animal & plant cells
space surrounded by a membrane
contains a solution
plants:solution of sugars & other substances called cell sap
animals:solution of food or water
green pigment called chlorophyll
chlorophyll absorbs sunlight
sunlight energy is used to make food by photosynthesis
contains starch grains, made by photosynthesis
found in plant cells
stores gentic information
make right proteins
info kept on chromosomes
chromosomes made of DNA
chromosomes are long & thin
chromosomes only seen during cell division (become short & thick
controls cell activities
found in plant & animal cells
cell wall
cell membrane
structures within a cell
Key Terms:



organ system:
a structure within a cell
a group of cells with similar structrues working together to perform a shared function
a structure made up of a group of tissues working together to perform specific functions
a group of organs with related functions, working together to perform body functions

In and Out of Cells
atoms, molecules & ions are always moving
the higher the remperature, the faster they move
when they move freely (gas state), particles tend to spread out as evenly as they can
Diffusion in Plants
Diffusion in Plants
Diffusion in Animals
the net movement of molecules from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement
gas exchange of carbon dioxide
carbon dioxide diffuses from the air (higher concentration) into the leaves (lower concentration) through the stomata, down the concentration gradient.
gas exchange of oxygen
oxygen diffuses from the leaf (higher concentration) into the air (lower concentration) through the stomata, down the concentration gradient.
gas exchange of carbon dioxide
gas exchange of oxygen
carbon dioxide diffuses from the lungs (higher concentration) to the air (lower concentration), along the concentration gradient.
oxygen diffuses from the air (higher concentration) to the lungs (lower concentration),along the concentration gradient.
scent diffuses from the flowers (higher concentration) diffuses into the air (lower concentration) along the concentration gradient.
in Animal Cells
in Animal Cells
in Plant Cells
in Plant Cells
the diffusion of water molecules from a region of their higher concentration (dilute solution) to a region of their lower concentration (concentrated solution), through a partially permeable membrane.
water potential
the diffusion of water molecules from a high water potential to a low water potential down the water potential gradient
Animal cell in (Dilute) Pure water:
Water molecules diffuse into the animal cell from a region of their higher concentration (dilute solution) [outside the cell] to a region of their lower concentration (concentrated solution) [inside the cell] through the partially permeable membrane.
Animal cell in Concentrated solution
Water molecules diffuse out of the animal cell from a region of their higher concentration (dilute solution) [inside the cell] to a region of their lower concentration (concentrated solution) [outside the cell] throught the partially permeable membrane.
Plant cell in (dilute) pure water
Water molecules diffuse into the plant cell's cytoplasm and vacuole from a region of their higher concentration (dilute solution) [outside the cell] to a region of their lower concentration (concentrated solution) [inside the cell] through the partially permeable membrane.
The plant cell swells and becomes tugid.
Turgid: tight and firm. like a blown-up tyre
-keeps leaves firm & plant stay upright
Doesn't burst because it has a strong cell wall that resists the pressure and presses back on the contents
The animal cells bursts.
The animal cell shrinks.
Water molecules diffuse into the plant cell's cytoplasm and vacuole from a region of their higher concentration (dilute solution) [outside the cell] to a region of their lower concentration (concentrated solution) [inside the cell] through the partially permeable membrane.
Plant cell in concentrated solution
Plant cell becomes flaccid & may plasmolyse
flaccid: floppy, loses firmness & wilts
plasmolyse: cytolpasm shrinks and pulls the cell membrane away from the cell wall
(kills a plant cell because cell membrane is damaged)
Active Transport
the movement of ions in or out of a cell through the cell membrane, from a region of their lower concentration to a region of their higher concentration against a concentration gradient, using energy released during respiration
*energy is used to produce the shape change in the carrier protein
the glucose molecules enter the carrier proteins of root hair cells
The carrier protein changes shape. The energy needed for it to do this is procided by respiration in the cell.
The change of shape of the carrier protein pushes the glucose molecule into the cell.
The carrier protein changes shape again, in order to move the next glucose molecule.
Active Trasport
of Glucose in Root Hair
Chemicals of Life
80% of our body is made up of water
cytoplasm contains substances dissolved in water
spaces between cells are filled with a watery liquid
Metabolic Reactions
Waste products
Keep Cool
chemical reactions that take place inside a living organism.
can only take place if reacting chemicals are dissolved in water
if cell dry out, reactions stop, and the organism dies
plasma (liquid part of blood) must contain a lot of water
so substances (e.g. glucose) can dissolve in it
dissolved substances are transported around the body
kidneys remove urea (waste product) from the body
urea is dissolved in water to form urine
when we are hot
sweat glands in the skin release sweat
sweat ismostly water
water in sweat evaporates to cool us down
is a simple sugar
come mostly from plant-based foods
Starch is a polysaccharide
Living organisms
get energy from carbohydrates
Sucrose is a complex sugar
C6H12O6 (6 carbon atoms,12 hyrdrogen atoms,6 oxygen atoms)
simple sugars:
very small
soluble in water
taste sweet
e.g. sucrose (sugar in hot drinks & breakfast cereal)
e.g. maltose (malt sugar)
soluble in water
taste sweet
e.g. cellulose of plant cell walls
e.g. starch
do not taste sweet
1g of carb releases 17KJ of energy
energy released by respiration
in Animals
transported around the body
human plasma contains dissolved glucose,
transported to all cells
cells use it to release energy needed to carry out the process of life
do not store starch
store carbs in form of glycogen
small quantities of glucose is stored in the liver and muscles
in Plants
respiration, to provide energy
transport sucrose not glucose
celles change sucrose to glucose when needed
store carbohydrates as starch
quick & easy to change glucose to starch,
starch to glucose
large quantities stored in seeds/tubers
plants make their own carbs by photosynthesis
animals get carbs from the food they eat
animals store very little carb in their body, so meat & fish hardly contain carbs
carbon (C)
hydrogen (H)
oxygen (O)

3 types:
monosaccharides-simple sugar
disaccharides-complex sugar
A.K.A. lipids
carbon (C)
hydrogen (H)
oxygen (O)
made of fatty acids and gylcerol
used in a cell to release energy
Apidose tissue
layers of fats/oils underneath the skin to release energy when needed
helps to keep heat inside the body (insulation)
stores oils in seeds
oils provide a good store of energy for germination
Good storage products
carbon (C)
hydrogen (H)
oxygen (O)
nitrogen (N)
small amounts of sulfur (S)
made of amino acids (20 kinds)
e.g. haemaglobin (soluble) -blood
e.g. keratin (insoluble) -hair
Growth & Repair
used for making new cells
new cells needed for growing & repairing damaged tissues
found in cell membranes & cytoplasms
used to make antibodies to fight bacteria & viruses
enzymes are proteins
Alimentary Canal
Plant Germination
substrate & product
Glucose & Fructose
Amino acids
Fatty acids
& glycerol
enzymes fasten the reaction of breaking down large molecules into smaller one during digestion
different enzyme for each kind of food
e.g. amylase digests starch to maltose
e.g. protease digests proteins to amino acids
seeds contain starch
amylase is activated when the seed soaks up water
amylase breaks down starch to maltose
maltose (soluble) is transported to embryo in the seed
maltose is used by embryo for growth,glucose (cellulose) and cell wall for new cells
speeds up the breakdown of a substance
works inside cells of living organisms
e.g. liver (potato) cells:
breaks down hydrogen peroxide (dangerous substance)
hydrogen peroxide is produced in many chemical reactions
catalyst: a substance that speeds up a chemical reaction and is not changed by the reaction
enzymes: proteins that function as biological catalysts
Each enzyme has an active site into which its substrate fits exactly.
The substrate molecule slots into the active
The substrate is split into smaller molecules. The enzyme is unaltered & is ready to accept another part of the substrate.
Lock & Key
active site: the part of an enzyme molecule which its substrate fits
Enzymes are specific
Enzymes are made inactive by high temperature
Enzymes work best at a particular temperature
Enzymes work best at a particular pH
Enzymes are Catalysts
All enzymes are proteins
some enzymes digest proteins
protein molecules are damaged by heat
enzymes in the human body work best at 37 degrees Celcius
Some enzymes work best in acidic conditions, others work best in alkaline conditions
They are not changed in the chemical reactions which they control. They can be used over and over again, so a small amount of enzyme can change a lot of substrate into a lot of product.
Each kind of enzyme will only catalyse one kind of chemical reaction.
denatures enzymes
Chemical reactions take place faster
have more kinetic energy
move faster
more likely to bump into the substrate
damaged by high temperatures
human enzymes denature from 40+ degrees
enzymes loses it shape so substrate doesn't fit
enzymes is denatured & cannot catalyse
denatured: when an enzyme changes shape so the substrate no longer fits into it
optimum temperature: the temperature at which an enzyme works fastest
pH affects enzymes
pH of a solution affects the shape of an enzyme
most enzymes are their correct shape at pH 7
if the solution is too acidic/alkaline the enzymes lose their shape and denature
optimum pH: the pH at which an enzyme works fastest
optimum pH can be not neutral
e.g. protease in stomach has optimum pH 2, because there is hydrochloric acid present so it needs to be able to work well in acidic conditions.
Making use
of Enzymes
washing powders
food industry
detergents: helps greasy dirt mix with water to be washed away
protease: breaks down haemoglobin (red protein in blood) into a colourless substance which can dissolve and easily be washed away.
lipases: catalyse the break down of fats to fatty acids & glycerol to remove greasy stains.
pectinase is used for fruit extraction and make the cloudy juice clear by breaking down pectin in fruits to make it easier to squeeze the juice out
high-protein baby foods contain proteases to break down proteins into polypeptides & amino acids making it easier for babies to absorb the food.
Sugar Extraction
starch-containg materials (potatoe/grain) are crushed with water
added to amylase
amylase digests starch to maltose making a syrup
sugar found in fruits
tastes sweet, less sugar
substitute for glucose/sucrose
sugar from plants is usually glucose/sucrose
isomerase converts glucose to fructose
How it's made?
makes Penicillin
needs to grow & reproduce
supply of oxygen (bubbles-air)
supply of nutrients
suitable pH
suitable temperature
culture medium
steam/cold water (control temperature)
so enzymes of the microorganism work well
antibiotic penicillin is made from fungus
antibiotic: kills bacteria without harming human cells (fight bacterial infections)
the penicillium is grown in a large fermenter tank
supplied with a culture medium containing carbohydrates & amino acids
fungus secretes penicillin
small amounts of sugar are added
stirred with nutrients to mix oxygen into it and roll the fungus into pellets
culture is filtered
liquid istreated to collect the penicillin which it contains
Plant Nutrition
nutrition: taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth & tissue repair, absorbing & assimilating them
substances that have been made by living organisms,
or whose molecules contain, carbon, hydrogen and oxygen
substances that have not been made by living organisms
Animals & fungi cannot make their own food. They feed on organic substances
(originally made by plants).
Green plants make their own food by converting inorganic substances (carbon dioxide, water & minerals-from air & soil) into complex materials (carbohydrates, lipids, proteins & vitamins).
Importance of
the fundamental process by which plants manufacture carbohydrates from raw materials using energy from light
'photo' means light
'synthesis' means manufacture
green pigment in chloroplasts
absorbs light energy from sun
releases energy to make carbon dioxide react with water (with enzymes in chloroplasts)
glucose is made
light energy (sun) converted into chemical energy (glucose)
carbon dioxide + water glucose + oxygen
6CO + 6H O C H O + 6O
of a
Basic structure
Upper Epidermis
Mesophyll Layer
Lower Epidermis
lamina: broad, flat part
petiole: a leaf stalk (joining lamina to rest of the plant)
vascular bundles: a vein in a plant,
containing xylem vessels and phloem tubes
veins: made of vascular bundles
tissue on the upper part of the leaf made up of a layer of epidermal cells
epidermal cells do not contain chloroplasts
protect the inner layers of cells
secretes the cuticle: waxy substance
cuticle: stops water evaporating from the leaf
palisade layer:
spongy layer:
middle layers of leaf containing
cells with chloroplasts
the upper mesophyll
layer, made up of rectangular palisade cells, containing many chloroplasts
the lower mesophyll layer, made up of cells with chloroplast (photosynthesise), with many air spaces between them
present in the mesophyll layer
xylem vessels:
phloem tubes:
long, hollow tubes, made
up of dead, empty cells with lignified walls, which transport water in plants & helps to support them
long tubes made up of living cells with perforated end walls, which transport sucrose & other substances
tissue in the lower part of the leaf, containing a layer of epidermal cells
contains stomata: gaps between guard cells
guard cells: two sausage-shaped cells, between which there is a stoma; guard cells can change shape to open & close the stoma
Carbon dioxide
Stored as Starch
Make Proteins & other organic substances
Changed to sucrose for transport
Starch Test
Concentration of carbon dioxide
Light Intensity
Control Conditions
from the air-0.04% carbon dioxide
mesophyll cells need carbon dioxide
enters leaf through stomata, by diffusion
travels through the air spaces connected to the mesophyll cells
goes into the chloroplasts
from the soil
absorbed by root hair cells
carried to leaf through xylem vessels
travels to the mesophyll cells, by osmosis
goes to chloroplasts
absorbed by chlorophyll
needed by mesophyll cells
thin leaves-penetration of light
transparent epidermal cells with no chloroplasts-reach all cells
released from glucose
obtained for all cells by respiration
some glucose from repiration is broken down to release energy
glucose turned into starch & stored
glucose-not a good storage molecule bcoz it's
reactive: get involved in chemical reactions when not wanted
soluble:dissolves in water>lost from cell
soluble:once dissolved it increases concentration of solution>cause damage
make carbohydrate sucrose, cellulose, fats & oils
makes proteins:
nitrate ions absorbed through soil through root hairs by diffusion & active transport
nitrate ions combine with glucose to form amino acids
amino acids string together to make proteins
makes chlorophyll:
magesium ions absorbed from soils through root hairs by diffusion & active transport
glucose is reactive so it's converted to sucrose to be transported
sucrose molecules are small, soluble & less reactive than glucose
sucrose molecules dissolve in sap of phloem vessels to be distributed
can be turned back into glucose, to be broken down & release energy
can be turned into starch & stored
can be used to make other substances needed for growth
control plant: given everything it needs including the substance being tested for
experimental plant: given everything it needs except the substance being tested for

treated in the same way
any differences in the end is due to substance being tested for
at the end of investigation, they're tested for starch
not sure if plant is photosynthesising if they contain starch (could've been made before investigation)
left plant in dark cupboard for 24 hours
no light so can't photosynthesis
uses up starch store
test leaf for starch before investigation
iodine solution tests starch
blue-black colour indicates presence of starch
not turn black instantly-contains choloplasts
iodine cannot get through the cell membrane to react with starch
Remove Green Colour
boiled-break down cell membranes
dipped in alcohol-remove chlorophyll
the more carbon dioxide a plant is given, the faster it can photosynthesise, until a point when max is reached

0-0.04%: carbon dioxide is a limiting factor
plant is limited on how fast it can photosynthesis because not enough carbon dioxide
when plant is given more carbon dioxide, it photosynthesises faster
0.04-0.20: carbon dioxide is not a limiting factor
even if the plant is given more carbon dioxide, it cannot photosynthesise any faster,because it already has as much carbon dioxide it can use
limiting factor: something present in the environment in such short supply that it restricts life processes
in dark-cannot photosynthesis at all
in dim light=photosynthesis slowly
as light intensity increases, the rate of photosynthesis will increase, until the plant is photosynthesising at max speed

A-B: light is a limiting factor
Plant is limited on how fast it can photosynthesis because not enough light
when plant is given more ligh, it photosynthesises faster
B-C: light is not a limiting factor
even if the plant is given more light, it cannot photosynthesise any faster, because it already
has as much light it can use
chemical reactions of photosynthesis can only take place very slowly at low temperatures
plants can photosynthesise faster on warm days
if stomata is closed, photosynthsis cannot take place-carbon dioxide cannot diffuse into leaf
stomata close when it's very hot & sunny to prevent water loss
photosythesis slows down on hot days
if crops are grown in glasshouses, then it's possible to control the conditions so that they are photosynthesising as fast as possible

e.g. cold places: tomatoes are grown in heated glasshouses at optimum levels to encourage them to grow fast, strongly & produce large yield of fruit that ripens quickly

can control light, temperature
& carbon dioxide
important to all living organisms
basic reaction bringing energy of Sun into ecosystems
flow of energy in ecosystems is one-way
constant need for energy source> constant need for photosynthesis
maintains constant global level of oxygen and carbon dioxide
oxygen is used for respiration
carbon dioxide (respiration & conbusting fuels) helps stop rising levels of carbon dioxide in the atmosphere
Animal Nutrition
Animals need food:
the food an animal eats every day is its diet
animals get food from other organisms
of Nutrition
Balanced Diet
& Minerals
Saturated Fat
of Food
food is needed
for energy
if you miss out on any of the nutrition, your body will not function well
a diet which contains all 7 nutrition in the correct amount & proportion
energy comes from food animals eat
the amount og energy you need depends on your age, gender &
helps to keep the alimentary
canal working properly
assists to keep the digestive system in a good working order
to function
helps to prevent constipation
vitamins:organic substances, found in citrus fruits, butter, etc
minerals: inorganic substances found in bread, red meat, dairy
both needed in small amounts
not enough=deficiency disease
fat found in animal foods
found in dairy, red meat, eggs
contains cholesterol
coronary heart disease
blood clots
heart attacks
not enough food
due to droughts,natural calamities
unbalanced diet
due to lack of protein
e.g. kwashiokor
being very fat
due to unbalanced diet
due to lack of exercise
consuming more energy
than used up
heart disease
strokes, diabetes
Used as Food
Agriculture produces
most of our food
Food Supplies
Food Production
many people die due to an inadequate diet
food is distributed unequally on our planet
some food prices rise too high, so many people can't afford it
famines & droughts make it impossible for crops to die. animals die
human population multiples, so the land cannot provide enough food
war raging prevents people from working to harvest
increase in quantity of food produced
more crops to be grown
more animals to be kept
development of modern agricultural machinery
development of chemical fertilisers, pesticides & herbicides
selective breeding
provide a good source of protein in places of food shortages
can be grown cheaply & waste less energy
1st attempt: Germany:yeast cultured with molasses (food source) to produce a protein supplement
Single Cell Protein (SCP):food made from these microorganisms protoctists & bacteria)
e.g. microprotein made by fussarium (fungus) with carbohydrates & ammonium nitrate (food source) forming mycelium, which is harvested, treated (remove RNA), dried & shaped.
myrcroprotein has a high protein content,very little fat, no cholesterol, lot of fibre & fibrous texture like meat
milk from cattle is used to make yoghurt
lactobacillus (bacterium) + milk + lactase (sugar from milk as energy source)
lactic acid ---> lactic acid + energy
lactic acid lowers the milk pH to form curds & whey
a culture is added to the bacterium for a few hours
heated to 70 degrees Celcium to kill other microorganisms
cooled, then added to L.bulgaricus
something that is added to the food other than nutrition
each permitted food additive is given an E number to show that it has been tested & passed as safe
Tartrazine (orange food colouring) causes behavioural problems for kids
food colouring doesn't improve food in any way
some are good for us e.g. ascorbic acid-
preservative-vitamin C
Not all foods
need digesting
Types of
Digestion makes
nutrients easier to absorb
simple sugars
small molecules are absorbed just as they are
Mechanical Digestion:
Chemical Digestion:
breakdown of large pieces of food into smaller ones, increasing the surface area
done by teeth in the mouth
done my contraction of muscles in the stomach wall
breakdown of large molecules of food into smaller ones
done by specific enzymes
the alimentary canal is a long tube running from one end of the body to another
5 processes:
ingestion: taking substances into the body through the mouth
digestion: breakdown of large, insoluble food molecules into small, water-soluble molecules by chemical & mechanic processes
absorption: movement of digested molecules through the walls of the intestine into the blood/lymph
egestion: passing out of undigested food
(faeces) through anus
of Fats
2. bile salts break down large fat drops into smaller ones
1. broken into small pieces by teeth
3. lipase breaks down fats into fatty acids & glycerol
1. broken into small pieces by teeth
2. water in digestive juices dissolves some carbohydrates into smaller pieces
3. amylase: breaks down starch to maltose
4. maltase: breaks down maltose into glucose
1. broken into small pieces by teeth
2. water in digestive juices dissolves some proteins into small pieces
3. proteases: break down proteins into polypeptides
4. peptidases: break down polypeptides into amino acids
of Teeth
Types of Teeth
2 Sets of Teeth
Gum Disease
Tooth Decay
Tooth Decay & Gum Disease
Fluoride is
Added to Drinking Water
Digestions in humans:
help with ingestion & mechanical digestion
bite off pieces of food
chop, crush or grind them into smaller pieces
creates a large surface area for the enzymes
incisors: chisel-shaped, for biting off pieces of food
canines: more pointed, similar function as incisors (tear)
premolars: wide surfaces, for grinding food
molars: wide surfaces, for chewing food
First set:
milk teeth/ deciduous teeth
grow from 5 to 24-30 months
set of 20 teeth
fall out at age 7
Second set:
permanent teeth
fully grown at age 17
set of 32 teeth
sticky film over the teeth
formed by bacteria in the mouth & other substances in the saliva
if it is left, it hardens to form tartar, which cannot be removed by brushing
plaque builds up around the edges of the teeth & gum
bacterium may work down around the roots
the tooth is loosened & may fall out
particles of sugar get trapped in the teeth
bacteria feed on the sugar to form acids
acids erode the enamel & dentine
as the infection spreads through the pulp cavity, it forms an abscess at the root of the tooth & decay sets in
helps to reduce the incidence of tooth decay
repairs any damage done to teeth
forms a hard mineral around the tooth enamel
too much, makes the teeth go black
cheap & effective way to maintain teeth
lessen sugar intake
use a fluoride toothpaste regularly
brush teeth regularly & thoroughly
visit the dentist regularly
Digestion in the Alimentary Canal
The Alminetary Canal is a Muscular Tube
In the Mouth, Food is Mixed with Saliva
The Oesophagus Carries Food to the Stomach
Stomach Stores Food & Digests Proteins
The Small Intestine is Very Long
Pancreatic Juice Flows into the Duodenum
long tube from mouth to anus
peristalsis: muscles contract & relax in the walls
sphincter muscles: c;pose canal to keep food in one part
mucus: made in goblet cells, for food to slide easily
ingestion takes place here
teeth create a large surface area of food
saliva is made in salivary glands
saliva contains enzymes:
water: dissolve nutrients
mucus: bind food into bolus & lubricate
amylase: digest starch to maltose
2 tubes:
trachea/windpipe: carry air to lungs
oesophagus: carry food to stomach
epiglottis: stops food from entering trachea
sphincter: muscle relaxes to let food pass into the stomach
stomach walls churn food to mix with enzymes & mucus to form chime
pepsin degests proteins into polypeptides
rennin causes milk, that young mammals get from their mother, to clot
hydrochloric acid kills bacteria
between the stomach & colon
5m long
beginning part: duodenum
end part: ileum
pancreatic juice is made in the pancreas
enters the duodenum through the pancreatic duct
pancreatic juice contains enzymes:
amylase: breaks down starch to maltose
trypsin (protease): breaks down proteins into polypeptides
lipase: breaks down fats (lipids) to fatty acids & glycerol
Most Absorbed Food Goes to the Liver
The Colon Absorbs Water
Digested Food is Absorbed in the Small Intestine
Digestion is Completed in the Small Intestine
Bile Helps Digest Fat
bile is made in the liver
stored in the gall bladder
flows into the duodenum through the bile duct
emulsification: (bile salts) breaking dow large drops of fats into tiny droplets, so they mix easily with water
Bile contains bile pigments made by the liver when it breaks down haemaglobin in old red blood cells (excreted as faeces as they're unneeded by the body)
inner walls of the intestine have villi
cells covering the villi make enzymes
maltase: breaks down maltose to glucose
sucrase: breaks down sucrose to glucose & fructose
lactase: breaks down lactose to glucose & galactose
these enzymes are carbohydrases & proteases, so they break down polypeptides into amino acids
lipase: breaks down fat (lipids) to fatty acids & glycerol
absorption takes place here
lacteal absorbs digested fats by diffusion into the lymph
blood capillaries absorb amino acids, water, sugar, fats, vitamins & minerals by diffusion & active transport into the blood
undigested food travels past the caecum & appendix
colon absorbs water & salt
large intestine: colon & rectum
ingestible foods (fibre, roughage), bacteria & some dead canal cells form the faeces
faeces are passed out through the anus, in egestion
the nutrients are taken to the liver in the hepatic portal vein & processed
the liver converts some of the excess glucose in the blood into glycogen & stores it
our bodies can't store amino acids & proteins, so the liver converts them into other substances that we can use/store in the body by removing the nitrogen during deamination (into ammonia & carbohydrates)
urea: the nitrogen-containing parts is transported to the kidneys & excreted (also through sweat)
cells in the liver break down toxins y converting them into harmless substances to be transported into the blood & excreted
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