Download Anaerobic respiration - Pukekohe High School

INTERNAL ANATOMY OF A HORSE.
Biology 1.5
The mammal as a consumer
AS 90929
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Mammals as consumers
Mammals are warm blooded animals that are covered in hair or fur and suckle their young.
Mammals are said to be heterotrophic i.e. they cannot make their own food. This means they
must move to find and obtain food to sustain their metabolism. In order to gain their food the
requirements of MRS C GREN must be met.
Body Systems involved
Identify the body system associated with each of the life functions that support a heterotrophic
way of life.
Life function
Body System
Movement
Skeletal and
muscular
Functions
Muscles and bones work together to
enable locomotion in order to get food
Respiration
Sensitivity
Growth
Circulation
Reproduction
Excretion
Nutrition
Nutrition
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Mammals cannot make their own food -they need to obtain food from other sources.
Food is required for energy, growth and to maintain a healthy body.
There are six main classes of nutrients: Carbohydrates, lipids, proteins, minerals,
vitamins and water.
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1) Carbohydrates:
 They provide a source of energy for respiration; glucose provides immediate energy, starch
provides long-term energy but fibre can not be broken down.
 They are made of the elements carbon, hydrogen and oxygen. These are burned up, for use
during respiration in the cells, releasing energy for body functions.
 These can be divided into 3 groups;
i) Monosaccharides; are the simplest forms of sugar they are made up of single glucose
(monosaccharide unit) and can be absorbed directly into bloodstream. Glucose is found in
energy drinks and honey and in fruit (fructose)
ii)Disaccharides; made up of two saccharide units joined together.e.g sucrose is table sugar.
iii)Polysaccharides; complex carbohydrates made up of many monosaccharide units joined
together.eg. starch found in potatoes, pasta and rice, and fibre found in bran, prunes etc.
N.B Disaccharides and polysaccharides need digesting in the body.
2)
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Proteins
Proteins they are important for growth, cell repair and replacement.
Proteins make up muscle tissue and are the building blocks of all cells.
Enzymes are special proteins that act as enzymes i.e. they speed up chemical reactions
without taking being used up in the reaction (e.g. digestive enzymes).
Some hormones are also proteins e.g. oestrogen and insulin.
Protein contain Carbon, oxygen, hydrogen and nitrogen.
A protein molecule consists of many small units called amino acids, which are arranged in a
specific sequence and combinations. There are 20 different types of amino acids and it is the
order of these amino acids that makes each protein different.
Sources of protein include meat, fish, eggs .
Two different proteins, A and B, are shown below – they are made up of the same amino
acids but arranged in a different order.
A
B
3) Lipids (Fats and oils):
 Lipids include fats (solids) and oils (liquids ) at room temperature.
 Mammals use lipids as a source of energy Gram for gram they provide two and half times
more energy than carbohydrates, but are not broken down as easily.
 Mammals use fat as an outer insulating layer to prevent heat loss from the body.
 Fats form part of cell membranes and are important in nerve tissues.
 Too much fat in the diet can lead to obesity.
 Fats are long chains of fatty acid and glycerol units joined together
 Fats are made up of carbon, hydrogen and oxygen.
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 Sources of fat include dairy products, meat, sources of oil include peanut oil, olive oil.
A lipid molecule;
4) Vitamins and minerals
These are needed in much smaller amounts than carbohydrates, proteins or lipids. Vitamins are
organic substances. Vitamin C from oranges and Vitamin D from the sun. Minerals are inorganic
e.g Iron, calcium etc found in meat and dairy products. They have a very important role in
helping enzymes to work in biochemical processes such as respiration.
5) Water
Makes up 70% of the body and is vital for all the biochemical reactions in the body and is a
solvent for chemicals in our body.
Food Tests
1) Carbohydrate tests
a) Starch test:
 Add a few drops of iodine solution to the sample.
 If the iodine turns a blue black colour, then the substance is a starch.
b) Glucose test
 Add 5 drops of Benedict’s solution to the sample.
 Gently heat the test tube.
 If it turns orange-red then the substance is a sugar.
2) Protein test
 Add a few drops of Biuret solution to the broken up pieces of the food to be tested.
 If it turns purple, the sample is a protein.
3) Lipid test
 For oils, put 1 mL of alcohol in a test tube. Add two drops of the oil and shake. Pour into
another test tube that contains water.
 Fats must first be made into a liquid. Mix the fat with a few drops of alcohol and crush using
a mortar and pestle. Filter the liquid. Treat a few drops of the liquid as for oils.
 If a cloudy white precipitate forms, lipids are present.
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THE DIGESTIVE SYSTEM
When mammals consume food they have to process the food which involves the following
five stages;
1. Ingestion- taking food into the mouth.
2. Digestion- involves the breakdown of food into small particles.
 Physical digestion- this involves chopping the food into smaller pieces using
teeth.
 Chemical digestion- the breakdown of complex foods such as starch, protein
and fats into small particles using enzymes.
3. Absorption- products of digestion are absorbed through the walls of the intestine into
the bloodstream.
4. Assimilation- how the different food particles are distributed by the circulatory system
and are absorbed and used by the target cells. This includes the process of respiration.
5. Egestion- Elimination or getting rid of undigested food as faeces through the anus.
Parts of the Digestive System- how food is processed.
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Overview of path followed by food during the process of digestion:
1) Mouth:
 Digestion begins here. Teeth break up food into smaller pieces.
 Salivary glands release saliva which contains amylase. This
starts to break down the starch before it leaves the mouth.
2) Oesophagus (tube connecting mouth to stomach)
 Food is pushed along by muscle contractions called
peristalsis until it reaches the stomach
small intestine
3) Stomach
 Mixes the food with hydrochloric acid and starts to digest it.
 The enzyme, pepsin, is added to begin protein digestion
4) Duodenum (start of the small intestine)
 Enzymes are added from the pancreas – these digest protein,
fat and starch
 Bile is added – this emulsifies fats to increase surface area
for digestion and to neutralise acidic stomach content
5) Ileum
 Broken down food is absorbed into the bloodstream
 The wall of the intestine has folds, called villi to increase the
surface area for absorption
6) Large intestine:
 Water is removed and waste material is formed into faeces
7) Rectum
 Faeces are stored here until they pass out of the anus.
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Physical digestion
The teeth:
 Digestion begins in the mouth.
 The teeth are designed to cut, tear and crush food into
smaller pieces so that it can be swallowed easily.
 Humans have different types of teeth which perform
different functions:
Parts of a tooth - Label the following diagram of the
tooth and complete the table
Part
Function
Enamel
Dentine
Pulp cavity
Root
Complete the following table:
Type of
Location
Tooth
Incisors
Situated in the
front of the mouth
Canines
Situated next to
the incisors
Molars
Back teeth
Shape
Function
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The number and kind of teeth in mammals depend on what they eat.
Carnivores eg cats and dogs
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Carnivores eat_____________.
They have small, sharp incisors to ___________ and
pull flesh off bones.
 They have large fang-like canines for killing and
________________ flesh.
 Some of their molars are big with sharp ridges for
scraping flesh off bones.
 The teeth in the upper and lower jaw slice past
each other like a pair of scissors.
 The jaw moves mainly _________ and
____________ with little sideways movement.
Herbivores eg sheep , cows, rabbits and horses.
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Herbivores eat __________ material (e.g. leaves,
grass).
They have sharp incisors to _________ and cut off
grass etc.
They do not need well-developed canines –these are
often absent.
The molars are ______________ with ridges and are
used to grind up the plants before swallowing.
The lower jaw is usually large and heavy and mainly
moves from ___________ to ______________.
Omnivores eg Pig and humans.
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Humans are _________________. Omnivores eat both
meat and plants.
 Their teeth are suited to eating most kinds of foods.
 They have a mixture of sharp tearing teeth and flat
grinding teeth.
 The lower jaw moves up and down. It can also move a
little from side to side.
Chemical digestion
Digestive system or Alimentary canal
The human alimentary canal is a 9 metre long tube that begins in the mouth and ends at the
anus and is adapted along its length, specialising in the processing of food.
Digestion is the breakdown of food into particles small enough to be absorbed in the blood.
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Two kinds of digestion occur in the body:
1. physical digestion – food is physically broken into __________ particles by the teeth.
These smaller food particles now have a large surface area available for enzymes to work
on.
2. chemical digestion – these smaller food particles are broken down into even smaller
particles by substances called enzymes.
Enzymes are biological catalysts. This simply means that they are substances that speed
up the rate of reaction that occur in the cells of living organisms. Without enzymes these
reactions would occur so slowly that the cell could not survive.
Hundred of chemical reactions can occur in a single living cell. Enzymes speed up these
reactions, and they can also regulate them. Each chemical reaction is controlled by
specific enzymes. A reaction will only occur if the appropriate enzyme is present. This
helps prevent chemical chaos in the cell, and also explains why cells function in different
ways. A muscle cell contains different enzymes from a cell in your intestine that produces
enzymes.
As well as the enzymes that are present inside cells (intracellular) and control cell
metabolism (all reactions that occur within cell), others are secreted and function outside
the cell (extracellular). Digestive enzymes that break down food in an animal’s gut fall
into this category.
Most enzymes are named by adding “ase” to the name of the substance they act on. The
enzyme maltase acts on maltose, lipase on lipids and so on
How enzymes work
Enzymes can break down and build
up molecules. Enzymes have an
active site which joins up with certain
molecules (called the substrate
molecules) and causes them to react.
This is called the lock and key model;
the shape of the enzyme acts rather
like a key that can open and close a
lock. Just as the shape of the key
determines which lock it will open, the
shape of the enzyme’s active site
determines which substrate molecules
can latch onto it and therefore the
reaction it can speed up. Enzymes are not altered or destroyed, just like a key can be used
repeatedly in the same lock.
Factors affecting enzyme action
Enzymes are proteins, and like all proteins are affected by heat. Heating an enzyme changes
the shape of the molecule so that its active site is lost and it cannot join with the correct
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substrate molecules (the key no longer fits the lock). Enzymes altered by heat are said to be
denatured. Most human enzymes would be denatured at about 45C, which is why it can be
fatal if your body temperature rises more than a few degrees.
Enzymes can also be affected by acidity and alkalinity (pH). For most enzymes, neutral
conditions provide the optimum pH, but digestive enzymes in the stomach require acidic
conditions while those in the small intestine need an slightly alkaline pH.
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DIGESTIVE ENZYMES
Digestive enzymes can be divided into groups according to the type of food they digest :
Enzymes break down large food molecules step wise into smaller ones
Carbohydrases (e.g amylase) breakdown complex carbohydrates (eg Starch) into
disaccharide and then finally monosaccharides
Lipases break down lipids into simpler fatty acids and glycerol
Proteases (e.g. pepsin) breakdown proteins to polypeptides and finally into amino acids
Digestion in the mouth;
While chewing occurs, salivary glands produce saliva. Saliva (neutral pH) moistens the food
and contains the enzyme amylase. This breaks down starch into sugars.
The tongue helps to shape the food into a ball called a bolus and physically helps to push it to
the back of the mouth where it is swallowed.
The bolus moves down the oesophagus by regular muscular contractions known as peristalsis.
Peristalsis occurs throughout the rest of the alimentary canal.
Digestion in the stomach;
The stomach is an organ which has sphincter muscles situated at both ends to regulate the
entry and exit of food passing through. These also help to store the food in the stomach (up to 2
hrs) while chemical digestion occurs. This involves a gastric juice containing the enzyme
pepsin, which along with hydrochloric acid (HCl) begins the process of the breakdown of
proteins. The acid is necessary to create a low pH as pepsin works most efficiently at pH 1-2.
The stomach itself is protected from being digested by a thick layer of mucus. The low pH also
kills off bacteria in food. Food is moved into the duodenum as a soupy liquid called chyme.
Digestion in the small intestine;
In the duodenum (which is the first part of the small intestine) food is mixed with bile. Bile is a
yellowy-green liquid which is made in the liver and stored in the gall bladder and enters the
duodenum via the bile duct. Bile is alkaline which helps to neutralise the acidic contents of the
stomach and also emulsifies lipids, which means that they are broken down into minute
droplets. This increases their surface area so now the enzyme lipase can breakdown lipids to
fatty acids and glycerol more efficiently.
The pancreas produces pancreatic juice which is transported to the duodenum via the
pancreatic duct. Pancreatic juice contains the enzymes lipase, trypsin (a type of protease)
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which continues breakdown of proteins and amylase which continues digestion of starch.
Pancreatic juice is also alkaline (pH 8.0) because it contains sodium bicarbonate. This provides
the right environment for the pancreatic enzymes to be effective as well as helping to neutralise
the acidic contents from the stomach.
The ileum (second part of the small intestine) also produces proteases for final protein
digestion, lipase and other carbohydrate digesting enzymes. These enzymes digest food
completely into small enough particles to be absorbed through the wall of the small intestine.
NB. Digestion involves the breakdown of large food molecules to small easily absorbed
particles:
 complex carbohydrates are broken down to monosaccharides
 proteins are broken down to amino acids
 lipids are broken down to fatty acids and glycerol.
Function of the large intestine (colon)
The substances that cannot be digested pass into the large intestine. Bacteria present in the
colon make vitamin K. Importantly, water and salts are absorbed through the wall of the large
intestine (and into the blood stream – recycled), and faeces move to the rectum where it is
stored until evacuation through the anus, This is known as egestion.
Absorption of digested food:
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Food eaten by mammals is made mainly of large molecules.
Digestive enzymes (throughout the alimentary canal) break these large nutrient molecules
into smaller molecules which can then be absorbed (this means they are taken into the
blood through diffusion).
This occurs through the walls of the small intestine.
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Absorption of digested nutrients occurs in the small intestine or ileum.
The inner wall of the ileum is covered with millions of small finger-shaped structures called
villi. Villi themselves have folds called micro-villi. Villi are especially adapted by being;.
o greatly folded which significantly increases the surface area available for
absorption of nutrients.
o thin walled so that the digested nutrients can be diffused efficiently. eg glucose
and amino acids move from a high concentration in the intestines to a low
concentration in the bloodstream across the semi-permeable membrane (the villi
walls)
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Each villus contains a capillary network to transport the absorbed nutrients in the blood
stream. Amino acids, glucose and certain vitamins and minerals diffuse into the blood
stream.
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Each villus has a central lacteal (part of the lymphatic system) which transport fatty acids,
glycerol and fat soluble vitamins separate from the blood.
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Activity: Model gut demonstration
The model gut demonstrates digestion and movement of nutrients through the wall of the small
intestine.
What does the dialysis tubing represent?
Test the contents of the beakers for starch and glucose and record your results.
Food test
Starch
Glucose
Time
Initial
After 30 min
Initial
After 30 min
Beaker 1
Beaker 2
Explain these results:
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
Assimilation:
This is the process where cells take in and make use of digested nutrients.
The digested nutrients having entered the blood via the capillary networks in the villi are
transported by the hepatic portal vein to the liver for further processing. The liver then releases
them to the body at a rate which depends on current needs. The liver therefore acts as a sorting
house and ensures the consistent delivery of nutrients to body cells.
The liver is the largest gland in the body and has a huge range of functions:
1. The liver keeps the amount of glucose in the blood at a fairly constant level by
converting excess glucose into glycogen (‘animal starch’) or fat ( which can be stored
under the skin). This conversion is done by insulin (a hormone produced by the
pancreas). Insulin also enables the uptake of glucose into body cells for cellular
respiration.
A lack of insulin therefore leads to high glucose levels in the blood which causes a
condition known as diabetes.
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2. The liver removes excess amino acids from the body by converting them to urea. This
process is called deamination and prevents the build up of toxic ammonia. The less
harmful urea is then excreted from the kidneys as a component of urine.
3. The liver stores vitamins and minerals eg vitamin A, D and Iron.
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Herbivore and Carnivore digestive systems
All mammals that are carnivores and omnivores have an alimentary canal that is basically the
same as humans. However, herbivores have a gut that is longer and especially adapted to
cope with their type of diet which, being plant material is made up largely of cellulose (the cell
walls of plants) and is difficult to digest.
As humans, we are unable to digest cellulose because we do not produce a cellulose digesting
enzyme. However, cellulose makes up the fibre in our diet and plays an important role in
assisting the action of peristalsis, so food is pushed through the gut efficiently and prevents
constipation.
Herbivores do not produce this type of enzyme either. However they do have special bacteria
living their gut which can digest cellulose breaking it down to glucose. The cellulose digesting
bacteria are found in specialised parts of the herbivores gut. In many herbivores like rabbits, the
caecum and appendix are found at the end of the digestive system, and are enlarged to house
bacteria. In other herbivores, such as cows and sheep, the bacteria are found largely in the four
chambered stomach, which is therefore larger (longer) while the caecum is very small.
The diagram below compares the gut of a human, rabbit and cow.
Even so cellulose is still difficult to digest and herbivores have a very long alimentary canal to
give more time for digestion and provide more surface area for absorption. Despite this rabbits
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will eat their own faeces thus sending food twice through the gut to give it even more digestion
time and cows regurgitate and re-chew the cud to further breaks down the tough plant fibres.
Depending on whether the animal is a carnivore, herbivore or omnivore the gut length can vary.
This is further shown in the diagrams below.
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THE CIRCULATORY SYSTEM
The mammalian circulatory system involves the heart and blood vessels (arteries, veins and
capillaries). Humans and all other mammals have a closed, double circulatory system of blood
flow.
1. Pulmonary circulatory system - carries blood from the heart to the lungs (where gas
exchange takes place) and back to the heart (in the pulmonary vein)
2. Systemic circulatory system - carries blood from the heart. The aorta is the main artery
which branches into smaller arteries taking blood to the all parts of the body (except the
lungs). Veins bring blood back to the heart.
Between the arteries and veins are anetwork of tiny blood vessels called capillaries which have
walls one cell thick. It is through the walls of these capillaries that interchange of substances
occurs directly with the body cell,
The heart
The heart is a muscular pump which maintains a flow of blood around the body. It is made up of
two separate pumps. One pumps blood to the lungs, the other pumps blood to the body.
Label the diagram below with the following labels
Right atrium, vena cava, bicuspid valves, aorta, pulmonary artery, tricuspid valve, pulmonary
veins, left atrium, semilunar valve, septum, right ventricle, left ventricle
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Arteries
Arteries are thick-walled vessels which carry blood
away from the heart, The major arteries are the
pulmonary artery taking blood to the lungs, and the
aorta taking blood to the rest of the body.
The walls of arteries have many fibres in them which
give these vessels elastic properties to enable them
to cope with the pressure of the blood passing
through. Each time a quantity of blood is pumped by
the heart, the walls of the arteries expand a little,
contacting back to normal as the “pulse” of blood
passes. These pulses of blood correspond to each
beat of the heart and be felt in places where arteries
are close to the surface of the skin such as the wrist
or neck.
Capillaries
From the arteries, blood flows into capillary networks
which have vessels with walls one cell thick. There
are capillary networks throughout the body with no
body cell very far from a capillary. There are so many
of them that if a piece of muscle the size of the letter
‘o’ on this page were cut, it would sever several
thousand capillaries.
It is in the capillaries that nutrients, oxygen and other
materials diffuse from the blood, through the wall of
the capillary and into the surrounding cells. Similarly,
waste materials (urea and water) and gases diffuse
from cells, through the capillary wall, into the blood
stream and are taken away to be processed or
removed from the body.
Veins
After passing through capillary networks blood
passes into thin-walled vessels called. At this point
the pressure of blood flowing in the vessel is low, and
it flows back to the heart rather than being pumped.
Veins have many valves in them which prevent blood
flowing backwards or sinking to the lowest part in the
body. Blood is helped back to the heart by the action
of muscles that surround them. The muscles have the
effect of squeezing the blood in the right direction as
they contract and relax during normal body
movements
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Respiratory system
Respiration releases energy for use in life processes. There are two types of respiration,
aerobic (uses oxygen) and anaerobic (does not use oxygen). Respiration can produce useful
products that have uses in a range of industries.
Aerobic respiration
Respiration is not the same thing as breathing. Breathing is more properly called ventilation.
Instead, respiration is a chemical process in which energy is released from food substances,
such as glucose - a sugar.
Aerobic respiration needs oxygen to work. The oxygen and glucose needed are carried to the
muscles by the blood system.
The word and chemical equations for aerobic respiration are:
glucose + oxygen → carbon dioxide + water (+ energy)
C6H12O6 + 6O2 → 6CO2 + 6H2O
The energy released by respiration is used to make large molecules from smaller ones. In
plants, for example, sugars, nitrates and other nutrients are converted into amino acids. Amino
acids can then join together to make proteins. The energy is also used:
 To allow muscles to contract in animals
 To maintain a constant body temperature in birds and mammals
Anaerobic respiration
Anaerobic respiration is a type of respiration that does not use oxygen. It is used when there is
not enough oxygen for aerobic respiration, but energy is still needed to survive.
a) In animals
If we carry out vigorous exercise our heart and lungs would not be able to get sufficient oxygen
to our muscles in order for them to respire. In this case our muscles carry out anaerobic
respiration. The word equation is:
glucose → lactic acid (+ energy released)
This type of respiration may be used when, for example, an animal is being chased by a
predator. It is not as efficient as aerobic respiration as it produces less energy since the glucose
is only partially broken down. If the lactic acid produced builds up in the body it stops the
muscles working and can cause cramp.
b) In plants
Anaerobic respiration also takes place in plants and some microbial cells in the presence of little
or no oxygen. Examples of this include the roots of plants in waterlogged soils and bacteria in
puncture wounds.
Anaerobic respiration in plant cells and some microorganisms (such as yeast) produces ethanol
and carbon dioxide, as opposed to lactic acid. It can be summarised by the following equation:
glucose → ethanol + carbon dioxide (+ energy released)
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When the above reaction occurs in yeast cells it is referred to as fermentation. It is used in the
baking of bread and the brewing of alcohol.
Gaseous exchange:
 This is the process by which the body obtains ____________ and gets rid of
______________________________.

In humans, gas exchange takes place in the ___________________ .
Breathing:
 This is the mechanical process by which air is moved in and out of the gas exchange
system.
Gaseous exchange
Involves the diffusion of gases from regions of high
concentration to regions of low concentration.
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Gas exchange occurs in the alveoli. Each alveolus is covered
by a network of capillaries.
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Gas exchange occurs because the concentration of oxygen in
the air in the alveoli is higher than in the blood. So oxygen
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from the alveoli diffuses into the blood. Carbon dioxide concentration in the blood is higher
than in the alveoli so carbon dioxide diffuses from the blood to the __________.
The alveoli are specially adapted for the efficient exchange of gases:
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The walls of the capillaries and alveoli are very thin so gases diffuse rapidly over a short
distance.
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The inside walls of the alveoli are moist so oxygen can dissolve before diffusing through the
cell membrane.
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The alveoli have a very large surface area – (if the alveoli were cut open and spread out
they would cover an entire tennis court) this maximise the process of gaseous exchange
lungs
oxygen + haemoglobin
oxyhaemoglobin
tissues
It is important to note that gases are exchanged
at the alveoli AS WELL as in the body cells.
Oxygenated blood is pumped by the heart to the
cells where it will diffuse into the cells and be
used for respiration. Carbon dioxide which is
produced as a waste product (and other waste
products such as urea) will diffuse from the cells
into the blood. These waste products are
excreted at organs such as lungs.
Energy
In mammals every cell needs a regular supply of energy in order to survive and remain active.
This energy is needed to carry out a variety of living processes: Energy is needed to
 power chemical processes such as manufacturing proteins,
 build up cell structures,
 move chemicals through membranes and around cells
 keeps body temperatures up
 bring about the contraction of muscles
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Cellular Respiration is a process that takes place in all body cells and involves the chemical
breakdown of glucose in the presence of oxygen, to release energy for all life processes.
Respiration is a very complex process, controlled be enzymes, that breaks down the complex
molecules one step at a time releasing energy in small amounts at each stage.
glucose + oxygen
C6H12O6 +
6O2
carbon dioxide + water + energy
6CO2
+ 6H2O
 Glucose – the product of digestion; is absorbed into the blood steam via the villi (in the
small intestine) and is transported by the blood to all body cells
 Oxygen – enters the blood via the alveoli and is transported by the blood to all the body
cells
 Both the glucose and oxygen enter the capillary beds which are in close proximity to
the body cells. In the blood, oxygen and glucose are in high concentration so will
diffuse into the body cells where oxygen and glucose are in low concentration.
 Waste products of cellular respiration e.g carbon dioxide and water will diffuse into
capillaries and be removed for excretion.
On diagram below annotate to show substances entering and leaving the body cells from
the blood in the capillaries
Respiration in the Cell.
Glucose diffuses into the cytoplasm of the cell and is converted into pyruvic acid
This pyruvic acid now enters the mitochondria. Mitochondria are tiny oval shaped organelles
(in the cytoplasm), and are often referred to as the ‘powerhouses’ of the cell because it is here
that the process of respiration occurs. The inner wall of each mitochondrion is folded. These
folds or cristae greatly increase the surface area on which the chemical reactions for respiration
can occur.
Mitochondria are more common in cells which require extra energy such as muscle cells
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The energy released by glucose during respiration cannot be used directly by the body. The
energy is used to create molecules of a chemical called adenosine triphosphate or ATP.
ATP is a temporary store of energy which can be released whenever required for a wide variety
of jobs, such as contraction of muscles (movement) or the manufacture of complex chemicals
etc.
ATP is formed during respiration from a related substance adenosine diphosphate or ADP.
ADP consists of adenosine plus 2 phosphate groups bonded to it. Energy released during
respiration is used to bond a third phosphate group to ADP molecules making ATP. These are
energy rich bonds which are easily broken and this happens whenever energy is required.
(works a bit like rechargeable batteries)
ADP + energy + P
ATP
Advantages of ATP-ADP system.
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ATP takes up some of the energy which would otherwise be lost as heat during the
breakdown of respiratory enzymes. This increases the efficiency of respiration.
Energy can be released from ATP the instant it is required.e.g during strenuous exercise,
when muscles contract.
ATP delivers energy in precisely controlled amounts.
Energy rich bonds can be transferred from ATP to other substances without loss of
energy. This is important in the manufacture of complex chemicals from simpler ones.
REVIEW - DIGESTION.
Fill in the gaps to summarize the process of digestion.

Digestion begins with the process of __________________ i.e. taking food in.

Food is chewed in the mouth and mixed with _____________ from the salivary glands.

Saliva contains an enzyme called ______________ which begins the breakdown of
__________________.
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The food is then swallowed and is moved down the ________________ by muscular
contractions called ____________________.

The stomach acts as a temporary storage for food. Here enzymes (with the help of
hydrochloric acid) begin the breakdown of _________________. Muscular contractions in
the stomach turn the food into a thick fluid.

Small amounts of this pass into the ___________________ which is the first part of the
small intestine.

Bile, which is made in the ______________ and is stored in the __________ __________ ,
is released into the duodenum where it helps another enzyme break down lipids.

Food passes through the small intestine and is broken down (digested) by other enzymes
into ______________ particles.

These particles have to be _________ through the small intestines and into the
___________ ______________. To increase this area for absorption, the lining of the
intestines is covered by tiny finger-like projections called ___________.

Each villus contains blood vessels into which the absorbed __________ particles pass.

The blood containing these ______________ nutrients are carried to the __________ which
_____________ and ______________ the food.

Water is absorbed through the __________________ _________________.

Waste food is ______________ as ________________ through the ___________.
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