RESPIRATION KEY STAGE 4

RESPIRATION

KEY STAGE 4

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

something that we need constantly and without it our bodies would die.

The answer is ENERGY making.ENERGY

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 heat

FUELFUEL OXYGENOXYGEN

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 Oxygen supplied by the

breathing system

2

+

And the fuel (in the fuel form of digested food) comes courtesy

of the digestive system

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 Digestive

system

BLOOD BLOOD

These substances

eventually arrive at the

body cells

Therefore, the raw materials for the energy making process eventually arrive at the body cells.

This energy making process is known as...

R E S P I R A T I O N R E S P I R A T I O N

Each living cells is supplied with food and oxygen in order to generate energy.

Oxygen Blood

+

+

capillary

muscle cell

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!!

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.

Test One Blow gently

through a straw into a test tube filled with lime water.

lime water straw

Before you start exhaling, the lime water is a clear liquid

After a short while, the lime water becomes cloudy.

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 first

waste waste products

products

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.

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) OXYGEN CARBON WATER

DIOXIDE

+ + + + + +

from digestive

system

from breathing

system USEFUL!USEFUL!

waste product exhaled waste

product exhaled

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 resting

Sometimes you are

active active

Low energy requirements

High energy requirements

Your body requires different amounts of energy energy at different times.

Therefore...

The process of

respiration must be able to ‘speed up’ and ‘slow

down’

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 The blood will have

to flow at different speeds according to

demand Our rate of breathing will

change

This is exactly what happens

Let’s take two extreme examples human activity and see how the process of respiration change...

It seems that the process of respiration changes during the course of the day.

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.

1. 1.

2. 2.

marathon

SLEEPING

What happens to the process of respiration when the body is performing these different activities. Let’s deal with each one in

turn.

When we sleep, our body is at rest. There is a low low demand for energy.

Low energy demand

Blood flow does not have to be

rapid Low

demand for food and

oxygen

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.

When the body is performing respiration in such as way, it is given a special name.

When the body…

We say it is performing AEROBIC respiration. AEROBIC

O O

• has plenty of oxygen

• is able to completely digest food

• can supply the cells with the oxygen and food that they need

So our original equation for the process of respiration is actually the equation for aerobic respiration.aerobic

Glucose + Oxygen Carbon Dioxide + Water + Energy

This is an efficient process...

Enough energy is made to supply the whole

body

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.

Of course, the amount of energy we produce will drop if the level of oxygen drops.

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.

during during before

before afterafter

before before

after after during during

Energy Demands

Oxygen available

Form or respiration

Low High Aerobic

High Low /

None

Aerobic (but slowing)

Dropping None /

Low ??

What’s happening?

? ?

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.

No energy would lead to stop working!

This would mean that the body would stop working whenever it became short of

oxygen.

The problem is that we often do

exercise and our bodies continue

working.

What must be happening when our oxygen levels

drop to zero?

?

? ?

?

? ?

The body must be able to keep working through short

periods of low/no oxygen.

?

?

?

HOW? HOW?

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 Food

cell blood

When this supply is cut off, the cell is left with excess

food and lacks energy.

It solves this problem by making energy from just

the food alone!

Now because it is releasing energy from food, it is still performing respiration.

But...

Therefore we call it

ANAEROBIC ANAEROBIC

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.

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.

Glucose Lactic Acid + (some) Energy This waste product is known as LACTIC ACID.LACTIC ACID.

Therefore the equation for Anaerobic respiration is…

from the digestive

system

waste product

not as much energy as with

aerobic respiration

You will notice that this reaction is only an option for short

short periods of time.

This is because the waste product is harmful and not enough energy is made to satisfy the

body.

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 fatigued

experience cramp.

If you want to consider the full impact of damage caused by the presence of Lactic Acid, just remember that the

heart

heart is made of muscle cells!

This leaves us with a

problem... If we want to do exercise

We want the energy that anaerobic

respiration produces

But we don’t want the Lactic Acid

waste product

YES NO

So the answer is for anaerobic respiration to be a ‘gap-fill’

during periods of very low / no oxygen availability.

In other words….

time oxygen

levels

rest

exercise

exercise

stops Aerobic

Anaerobic

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.

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. lactic acid

As soon as this begins, the body starts building an

oxygen debt

oxygen debt. This is

equivalent to the amount of oxygen it would have used

if aerobic respiration had continued.

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...

before before exercise exercise

after after exercise exercise

Glucose

Lactic Acid

+

little energy

at rest at rest

again again

Glucose

+

Oxygen

Carbon Dioxide

+

water

+

Lots of energy

Glucose

+

Oxygen

Carbon Dioxide

+

water

+

Lots of energy

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.

Glucose + Oxygen Carbon Dioxide + Water + Energy

Lactic Acid + Little Energy oxidised

Aerobic respiration

Aerobic respiration (complete breakdown of food)

Anaerobic Anaerobic respiration respiration

(incomplete breakdown of

food)

Aerobic respiration is performed when oxygen is present Anaerobic respiration is performed when oxygen is absent

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.

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

What is energy used for?

We can consider each one in turn.

To allow muscles to contract and relax.

11

In order for muscles to have an effect, they must move something in the body.

Often this tends to be a bone.

By moving the bone, they create a lever which lever does some work.

bone

muscle

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

Muscle contracted energy

To build up large molecules from smaller ones.

2 2

In order for the human body to stay healthy, it must obtain nutrients from the 7 food groups. These are:

Fats

Proteins

Minerals

Vitamins Carbohydrates

Water Fibre

A balanced diet should contain elements from all 7 groups.balanced diet

Once we have digested the food from our diet, we release many useful substances.

DIET DIET

digestion

Useful raw materials

The body uses the energy from respiration to turn these raw materials into

useful substances.

ENERGY

Respiration

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

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.

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

new protein (old) respiration

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.

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.

33

This constant temperature is 37^oC.

The reason why our bodies must remain at 37^oC 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...

37^oC hotterhotter colder

colder

Enzymes working well

and body is fine.

Enzymes working slowly and the body is suffering.

Enzymes damaged and body can

become ill.

The temperature of the body is controlled by a region of the brain.

As bloodblood flows around the body, it

also visits this

‘thermo-regulatory’

‘thermo-regulatory’

centre in the brain.

REST OF BODY

The brain senses the bodies temperature by

sensing the

temperature of blood.

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?

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.

outer wall blood

artery

These muscle cells contract and relax using energy from respiration.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.

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

Direction of blood flow

skin

Blood vessels

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.

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 respiration these muscle cells.

Brain Brain

BB LL OO OO DD

makes the blood flow to the surface of

the skin

> 37^oC

this vessel widens

this vessel constricts

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.

The heat within the blood escapes to the cool air and the result is that the body’s temperature drops.

blood skin

HEAT HEAT HEAT air

Remember, respiration produces the energy that is needed by the muscle cells within the walls of the blood vessels.

4 4

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.

High

Concentration

Low

Concentration

The particles would move from left to right.

This particle could be an oxygen molecule that is moving from the alveolus to the blood capillaries within the lungs.

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 speed up the process of diffusion.

High Concentration

Low

Concentration

Active

transport gives this process an

extra ‘push’.

This completes our study of the breathing system and the processes of aerobic and anaerobic respiration.

Respiration….do I really need oxygen?

Work through the following tasks, filling the missing words or crossing out the wrong words where necessary.

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) A

Aerobic Respiration

_______ + ______ _______ _______ + ______ + ______

B

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.

C

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…

1. HEAVY / LIGHT exercise for LONG / SHORT periods of time.

2. HEAVY / LIGHT exercise for LONG / SHORT periods of time.

D

Anaerobic Respiration

_______ + ______ _______ _______ + ______

waste product useful E

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.

F

fatigued

oxygen

muscle contracting

anaerobic aerobic

broken

Use the words below to answer the next section.

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.

This is poisonous. It can build up in _________ cells and stop them

___________ and relaxing. We say the cell is tired or __________.

Lactic Acid

Multiple choice Questions

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

2. Aerobic respiration is a type of respiration that uses up…

A oxygen.

B energy.

C carbon dioxide.

D water.

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

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

5. Which of the following is a useful product of aerobic respiration?

A oxygen B energy

C carbon dioxide D glucose

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

7. Animals perform anaerobic respiration when the body is short of…

A energy.

B carbon dioxide.

C food.

D oxygen.

8. The main waste product from the process of anaerobic respiration is…

A lactic acid.

B carbon dioxide.

C urea.

D water.

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.

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.

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

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.

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 ^.

14. If muscle cells are deprived of oxygen then aerobic respiration will…

A stop.

B speed up.

C slows down.

D remains constant.

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”.