Transcript No Slide Title

KEY STAGE 4
RESPIRATION
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So far, we have considered both the structure of the
breathing system and how it is adapted for breathing
in and out.
BUT...
We have not talked about why the body needs
to breathe.
If you remember, we know that we breathe constantly
throughout life. Also, we know that if we stopped
breathing we would eventually die.
So, breathing in Oxygen (O2) must be linked to
something that we need constantly and without it our
bodies would die.
The answer is ENERGY making.
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The energy making process depends on the
breathing system and the digestive system.
Imagine a fire...
This will produce energy in the form of heat but only if
it is supplied with 2 main ingredients.
FUEL
OXYGEN
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Well, the bodies energy making reaction needs similar things to
the energy making process of fire.
Like the fire, the body needs Oxygen and a Fuel.
The Oxygen is
supplied by the
breathing
system
+
And the fuel (in the
form of digested
food) comes courtesy
of the digestive
system
2
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If we now think back over the journey of oxygen and digested food through
the human body, we will realise that they both end up in the same place.
Food
Oxygen
Breathing
system
These
substances
eventually
arrive at the
body cells
Digestive
system
BLOOD
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Therefore, the raw materials for the energy making
process eventually arrive at the body cells.
This energy making process is known as...
RESPIRATION
Each living cells is supplied with food and oxygen in
order to generate energy.
capillary
Blood
Oxygen
+
Food
muscle cell
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No chemical reaction is 100% efficient.
Therefore, as well as producing the useful energy,
respiration also produces waste products.
These waste products
must be removed
from the body
If the process of breathing in is used to
obtain the O2 for respiration, it would
make sense for the body to use the
process of breathing out to remove
these waste products of this reaction.
This is exactly what happens!!
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If we study the composition of the air that is breathed
out, we will identify the waste products of respiration.
Two tests help us identify these waste products.
Before you start
exhaling, the lime
water is a clear liquid
Test One
Blow gently
through a straw
into a test tube
filled with lime
water.
straw
After a short while,
the lime water
becomes cloudy.
lime water
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If a gas is bubbles through lime water and the liquid
becomes cloudy, the gas is identified as….
Carbon Dioxide (CO2)
This is the first of our waste
products of respiration.
Test Two
On a freezing
cold day, watch
what happens
when you
breathe out.
The air you breathe
out is visible because
the mystery waste
product condenses
back into a liquid.
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This waste product is water vapour and so our final waste
product of the process of respiration is...
Water
Using this information, we can now write out the full
equation for respiration
FOOD
(GLUCOSE)
from
digestive
system
+
OXYGEN
CARBON
DIOXIDE
from
breathing
system
waste
product
exhaled
+
WATER
waste
product
exhaled
+
ENERGY
USEFUL!
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However, to call this reaction just ‘respiration’ is
not quite correct.
Let us try to understand why…..
Think about what you
do in an average day
Sometimes
you are
resting
Low energy
requirements
Sometimes
you are
active
High energy
requirements
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Your body requires different amounts of energy
at different times.
This is exactly
what happens
Our rate of
breathing will
change
The blood will have
to flow at different
speeds according to
demand
The process of
respiration must be able
to ‘speed up’ and ‘slow
down’
Therefore...
This will mean
that we need
different amounts
of food to feed the
reaction
It will also mean that
we need different
amounts of oxygen
to feed the reaction
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It seems that the process of respiration changes
during the course of the day.
Let’s take two extreme examples human activity and
see how the process of respiration change...
1.
Sleeping
2.
Running a
marathon
This may not represent the daily activities of an average
human, but this scenario will help us understand this
process of respiration in more depth.
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What happens to the process of respiration when the body is
performing these different activities. Let’s deal with each one in
turn.
SLEEPING
When we sleep, our body is at rest. There is a low
demand for energy.
Low
energy
demand
Low
demand for
food and
oxygen
Blood flow
does not
have to be
rapid
The breathing
rate remains
normal
In other words, the body has plenty of time to inhale the oxygen that it
needs. It also has time to completely digest the food to release the
important chemicals (e.g glucose). The blood can efficiently transport
these substances to the cells without increasing its rate of flow.
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When the body is performing respiration in
such as way, it is given a special name.
When the body…
O2
• has plenty of oxygen
• is able to completely digest food
• can supply the cells with the oxygen
and food that they need
We say it is performing AEROBIC respiration.
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So our original equation for the process of respiration is
actually the equation for aerobic respiration.
Glucose + Oxygen
Carbon Dioxide + Water + Energy
This is an efficient process...
Our bodies perform aerobic
respiration for much of the day.
In fact, as long as the supply of
Oxygen remains high enough,
we will continue to perform
aerobic respiration.
Enough energy is made
to supply the whole
body
Of course, the amount of energy we produce will drop if the
level of oxygen drops.
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So, now we know that there is a form of respiration which is
performed when there is a supply of oxygen to the body.
But, what happens in situation 2?
remember the runners?
Are they performing aerobic respiration?
Well, in order to answer that question, we have to think
about what their bodies are doing during the race.
before
during
after
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What’s happening?
before
Energy
Demands
Oxygen
available
Low
High
Aerobic
Low /
Aerobic
(but
slowing)
High
during
after
None
Dropping
None /
Low
Form or
respiration
?
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?
How can the body perform aerobic
respiration in this situation?
Aerobic respiration requires oxygen but when you have
been running a race or doing strenuous exercise, you
cannot inhale enough oxygen for this reaction.
Glucose + Oxygen
Carbon Dioxide + Water + Energy
This process fails!
But, if this process fails when the oxygen levels drop, the
body would be left with absolutely no energy.
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No energy would lead to stop working!
?
The problem is that
we often do
exercise and our
bodies continue
working.
?
What must be
happening when
our oxygen levels
drop to zero?
?
?
?
?
?
This would mean that the
body would stop working
whenever it became short of
oxygen.
?
The body must be able to
keep working through short
periods of low/no oxygen.
?
HOW?
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Well, it is quite a remarkable process….let’s examine it.
With aerobic respiration, the cells supply
of oxygen and food is relatively constant
Oxygen
When this supply
is cut off, the cell
is left with excess
food and lacks
energy.
Food
blood
cell
It solves this problem by
making energy from just
the food alone!
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Now because it is releasing energy from food, it is still
performing respiration.
But... It is not aerobic respiration because there is no
oxygen present. (aero- means of air)
Therefore we call it ANAEROBIC respiration
The energy being made by breaking down the food
without oxygen.
This seems a better process! To be able to make energy
without needing oxygen would be very beneficial.
However, there is a problem.
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Remember the last time you ran a race, carried a heavy
weight or swam under water for too long and ran short of
breath.
It probably felt uncomfortable.
Well, if anaerobic respiration was as efficient as it
sounds, this lack of comfort would not happen.
So, what is the problem with anaerobic respiration?
When the cell breaks down the food to release the
energy, it also makes a potentially harmful waste
product. The breakdown of the food is also incomplete.
It is not an efficient process.
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This waste product is known as LACTIC ACID.
Therefore the equation for Anaerobic respiration is…
Glucose
from the
digestive
system
Lactic Acid + (some) Energy
waste
product
not as much
energy as with
aerobic
respiration
You will notice that this reaction is only an option for
short periods of time.
This is because the waste product is harmful
and not enough energy is made to satisfy the
body.
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Why is Lactic Acid so harmful?
Well, this chemical can stop muscles within the body, from
contracting and relaxing.
The Lactic acid soaks the
muscle cells and prevents the
muscle cell from doing its job.
Relaxation
Contraction
If the muscles in your body stop contracting and relaxing
they are said to be fatigued. They eventually seize and you
experience cramp.
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If you want to consider the full impact of damage caused
by the presence of Lactic Acid, just remember that the
heart is made of muscle cells!
This leaves us with a
problem...
If we want to do exercise
YES
We want the energy
that anaerobic
respiration
produces
NO
But we don’t want
the Lactic Acid
waste product
So the answer is for anaerobic respiration to be a ‘gap-fill’
during periods of very low / no oxygen availability.
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In other words….
rest
exercise
stops
Aerobic
Anaerobic
oxygen
levels
exercise
time
Anaerobic respiration keeps our bodies going until we
can breathe in more oxygen again.
Whilst we are performing anaerobic respiration, our
bodies are building up a ‘debt’ of oxygen.
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This is rather like owing the bank some money. Once
you get some money, you have to pay off that debt.
We can think of that debt as being the presence of lactic
acid in the body.
When our bodies
convert from aerobic
to anaerobic
respiration, we start
making lactic acid.
As soon as this begins, the
body starts building an
oxygen debt. This is
equivalent to the amount of
oxygen it would have used
if aerobic respiration had
continued.
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This oxygen debt will have to be repaid when the exercise stops.
Oxygen will be used to break down the lactic acid that is present in
the body. The oxygen ‘oxidises’ the lactic acid.
In fact, the lactic acid is
oxidised into carbon
dioxide and water.
In this way, the process of aerobic
respiration can be converted into
The process of anaerobic respiration
which can then turn back into...
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Glucose
Glucose
Glucose
+
+
Oxygen
Oxygen
Carbon Dioxide
Carbon Dioxide
+
Lactic Acid
water
+
water
+
+
+
Lots of
energy
little
energy
Lots of
energy
before
exercise
after
exercise
at rest
again
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So, in summary, the body has the ability to produce energy,
despite changes in the supply of oxygen.
Here are the two forms of respiration.
Aerobic respiration (complete breakdown of food)
Glucose + Oxygen
Carbon Dioxide + Water + Energy
oxidised
Anaerobic
respiration
Lactic Acid + Little Energy
(incomplete
breakdown of
food)
Aerobic respiration is performed when oxygen is present
Anaerobic respiration is performed when oxygen is absent
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Now that we know how the energy is made, we
need to consider what it is used for?
Remember, cellular respiration
occurs all over the body.
Energy
Therefore this energy is used for the many processes
that sustain life.
Amongst all these, there are a few important uses that we
can examine.
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What is energy used for?
1
To allow muscles to contract
2
To build up large molecules from
smaller ones
3
To help maintain a steady body
temperature
4
To power the active transport of
substances within the body
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We can consider each one in turn.
1
To allow muscles to contract and relax.
In order for muscles to have an effect, they must move
something in the body.
Often this tends to be a bone.
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By moving the bone, they create a lever which
does some work.
muscle
bone
Using energy generated within the muscle, it contracts
and alters the position of the bones. In doing so, work
can be done e.g. something can be lifted.
Muscle
relaxed
energy
Muscle
contracted
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2
To build up large molecules
from smaller ones.
In order for the human body to stay healthy, it must obtain
nutrients from the 7 food groups. These are:
Fats
Proteins
Minerals
Vitamins
Water
Fibre
Carbohydrates
A balanced diet should contain elements from all 7 groups.
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Once we have digested the food from our diet, we
release many useful substances.
DIET
Respiration
digestion
Useful raw
materials
ENERGY
The body uses the energy
from respiration to turn these
raw materials into useful
substances.
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A simple example of this use of energy can be seen
when the body builds new proteins from amino acids.
Step 1
Proteins are eaten as part of
our food (e.g. protein in eggs)
Step 2
These proteins are made of amino
acid chains. The order of the amino
acids is specific to the protein.
amino acids
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Step 3
This protein may not be the one that the body requires.
Therefore, the digestive system uses protease enzymes to
break up the amino acid chain.
Step 4
This process of digestion releases the
individual amino acids.
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Step 5
Now that the raw materials are free, the body then uses
the energy from respiration to assemble them into new
proteins.
A new protein will have a different order of amino acids.
Energy
respiration
new protein
(old)
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Step 6
This new protein, and others like it, will now be used in
different ways by the body.
The energy from respiration has made this possible.
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3
To help maintain a steady body temperature.
The conditions outside our body are constantly changing.
One minute they can be hot, the next cold.
Despite this, our bodies must be kept at a constant
temperature.
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This constant temperature is 37oC.
The reason why our bodies must remain at 37oC is
because this is the temperature at which enzymes
work most effectively.
You may remember that enzymes are chemicals that control
many of the chemical reactions within our bodies.
Therefore...
colder
37oC
hotter
Enzymes working
slowly and the
body is suffering.
Enzymes
working well
and body is
fine.
Enzymes damaged
and body can
become ill.
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The temperature of the body is
controlled by a region of the brain.
As blood flows
around the body, it
also visits this
‘thermo-regulatory’
centre in the brain.
The brain senses the
bodies temperature by
sensing the
temperature of blood.
REST
OF
BODY
Once it knows what the body temperature is, it can act
accordingly.
In order to understand what happens, think about what
your body does when it is hot or cold outside. How do you
react?
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On a hot day…
You sweat.
Blood is pumped to the
surface of your skin.
If we consider the second of these effects, we can see
where the energy from respiration is used.
Remember that blood flows through vessels which
are lined with muscle cells.
blood
artery
outer wall
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These muscle cells contract and relax
using energy from respiration.
The contraction and relaxation of these muscles can affect the
blood flow through the vessel.
E.g. if the muscle runs
in a circular direction
around the vessel,
when it contracts, it
could constrict the
blood flow
If a blood vessel is constricted in this way, blood flow is reduced and
this in turn, will affect the direction of blood flow through the body.
The opposite is also true. If the muscles relax, the blood vessel
could become wider and the blood flow increases.
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Now, if we consider the blood vessels within the skin, we see
how the contraction and relaxation of blood vessel muscles
affects the flow of blood.
surface of the skin
skin
Blood
vessels
Direction of
blood flow
We can see that blood can flow in different directions within the
skin. When the brain senses that the body is too hot, it takes steps
to redirect the blood flow to the skin surface.
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The brain can cause the contraction and relaxation of
muscles within the walls of these blood vessels. Energy
from respiration is used to power the contraction of
these muscle cells.
Brain
B
L
O
O
D
> 37oC
makes the
blood flow to
the surface of
the skin
this vessel
widens
this vessel constricts
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When the blood flows to the surface, it comes into close contact with
the air surrounding the body. This air is much cooler than the
temperature of the blood.
HEAT
HEAT
HEAT
air
skin
blood
The heat within the blood escapes to the cool air and the result is that
the body’s temperature drops.
Remember, respiration produces the energy that is needed by
the muscle cells within the walls of the blood vessels.
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4 To power the active transport of substances within
the body.
This is our final use of the energy generated during
respiration.
In order to understand how active transport works, we
must firstly consider the concept of diffusion.
Diffusion is the movement of a substance from an area of
high concentration to an area of low concentration.
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The particles would
move from left to right.
High
Concentration
Low
Concentration
This particle
could be an oxygen molecule that is
moving from the alveolus to the blood capillaries within
the lungs.
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The diffusion of oxygen into the blood will eventually
mean that the body cells can perform respiration.
But what if the supply of oxygen (or another molecule)
was not fast enough?
This is when active transport comes into play.
Active transport requires energy.
This energy comes from respiration.
Active transport uses energy to speed
up the process of diffusion.
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Active
transport gives
this process an
extra ‘push’.
High
Concentration
Low
Concentration
This completes our study of the breathing system and the
processes of aerobic and anaerobic respiration.
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Respiration….do I really need oxygen?
Work through the following tasks, filling the missing words
or crossing out the wrong words where necessary.
A
The body can perform two types of respiration.
These are:
1. ____________ respiration (performed in plenty of O2)
2. ____________ respiration (performed in little or no O2)
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B
Aerobic Respiration
_______ + ______
_______ _______ + ______ + ______
C
Aerobic respiration is performed when the supply of
oxygen to the cells is HIGH / LOW. It is the COMPLETE /
INCOMPLETE breakdown of food and so is very
INEFFICIENT / EFFICIENT. It is a method of respiration
that produces LOTS / LITTLE energy for the body. If the
body does not get enough oxygen to the cells it CAN /
CAN’T perform aerobic respiration. Instead it has to
perform __________ respiration for a LONG / SHORT
period of time.
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Why would the body be short of oxygen?
Two common reasons for the body being short of energy
would be if a human was performing…
D
1. HEAVY / LIGHT exercise for LONG / SHORT periods of
time.
2. HEAVY / LIGHT exercise for LONG / SHORT periods of
time.
E
Anaerobic Respiration
_______ + ______
_______ _______ + ______
waste product
useful
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F
Anaerobic respiration is performed when the supply
of oxygen of the cells is HIGH / LOW.
It is the COMPLETE / INCOMPLETE break down of
food and so is very INEFFICENT / EFFICIENT.
It is a method of respiration that produces LOTS /
LITTLE energy for the body.
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Use the words below to answer the next section.
fatigued
aerobic
oxygen
muscle
contracting
anaerobic
broken
Lactic Acid
This is poisonous. It can build up in
_________ cells and stop them
___________ and relaxing. We say
the cell is tired or __________.
If we then relax and breathe again the body recovers. The
supply of ___________ increases and the lactic acid is
___________ down. The body can now stop performing
___________ respiration and go back to performing
__________ respiration.
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Multiple choice Questions
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1. Which of the following is a definition of
respiration?
A breathing
B the release of energy from food
C obtaining oxygen and releasing carbon dioxide
D exchanging gases
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2. Aerobic respiration is a type of respiration that
uses up…
A oxygen.
B energy.
C carbon dioxide.
D water.
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3. Which of the following are the raw materials for
the process of aerobic respiration?
A carbon dioxide, water and glucose
B glucose and carbon dioxide
C oxygen, water and energy
D oxygen and glucose
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4. Which of the following are the waste products of
aerobic respiration?
A oxygen and carbon dioxide
B glucose and energy
C carbon dioxide and water
D oxygen, water and energy
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5. Which of the following is a useful product of
aerobic respiration?
A oxygen
B energy
C carbon dioxide
D glucose
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6. Which of the following is an accurate equation for this
process of aerobic respiration?
A Glucose + Carbon Dioxide  Water + Energy + Oxygen
B Oxygen + Carbon Dioxide  Glucose + Sugar + Energy
C Water + Energy + Sugar  Carbon Dioxide + Oxygen
D Glucose + Oxygen  Carbon Dioxide + Water + Energy
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7. Animals perform anaerobic respiration when the
body is short of…
A energy.
B carbon dioxide.
C food.
D oxygen.
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8. The main waste product from the process of
anaerobic respiration is…
A lactic acid.
B carbon dioxide.
C urea.
D water.
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9. Which of the following statements accurately
describes one use of the energy released during
respiration?
A The breakdown of protein into muscle from which
amino acids are made.
B The building of amino acids from proteins.
C The building of protein from amino acids, with these
proteins then being used to make muscle.
D The building of carbohydrates from fatty acids to
make organs.
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10. One further use of the energy that is
generated by respiration is in…
A the lowering of the body temperature on a cold
day.
B the raising of the body temperature on a hot
day.
C allowing the body temperature to change to
match the air temperature.
D maintaining a steady body temperature despite
changes in the air temperature.
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11. What is the term used to describe the
inefficient contraction of muscles that can occur
during anaerobic respiration?
A tiredness
B exhaustion
C fatigue
D hyperventilation
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12. What causes the inefficient contraction of
muscle that can occur during anaerobic
respiration?
A The complete breakdown of glucose (releasing more
energy than aerobic respiration) and the build up of
lactic acid.
B The incomplete breakdown of glucose (releasing
less energy than aerobic respiration) and the build
up of lactic acid.
C The incomplete breakdown of glucose (releasing
more energy than aerobic respiration) and the
breakdown of lactic acid.
D The complete breakdown of glucose (releasing
more energy than aerobic respiration) and the
breakdown of lactic acid.
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13. If muscle cells become short of oxygen then
the rate of aerobic respiration…
A stops.
B speeds up.
C slow down.
D remain constant .
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14. If muscle cells are deprived of oxygen then
aerobic respiration will…
A stop.
B speed up.
C slows down.
D remains constant.
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15. David Beckham has just come off the pitch at
Old Trafford after a tiring game. He is breathing
heavily in order to…
A carry out a series of chemical reactions that result
in the complete oxidation of lactic acid to carbon
dioxide and water.
B slow down anaerobic respiration.
C speed up anaerobic respiration.
D increase the “oxygen debt”.
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