ks4 biology

© Boardworks Ltd 20041 of 57

Respiration

KS4 Biology


Contents

Respiration

Waste products

Aerobic respiration

Anaerobic respiration

What is respiration?

An energy-making process


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

The answer is ENERGY making.



Ingredients to make energy

The energy-making process depends on the breathing system and the digestive system.

This will produce energy in the form of heat but only if it is supplied with 2 main ingredients.

FUEL OXYGEN

Imagine a fire...


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.

+and the fuelfuel (in the form of digested food) comes courtesy of the digestive system.

2

the oxygenoxygen is supplied by the

breathing system

Our fuel


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.

these substances eventually arrive at the body cells

food oxygen

breathing system

digestive system

BLOODBLOOD

Our pipelines to the cells


Every living cell needs to respire

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 NR E S P I R A T I O N

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

oxygen

blood

food++

capillary

muscle cell


Contents

Respiration

Aerobic respiration




Waste products


Waste products

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.

This is exactly what happens!

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.


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

After a short while, the lime water becomes cloudy.

Test One

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

lime water

straw

What’s the waste?


Identification of the first waste product

If a gas is bubbles through lime water and the liquid becomes cloudy, the gas is identified as….

This is the first of our waste products of respiration.

carbon dioxide (CO2)


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.

Seeing your breath

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.

WATERCARBON DIOXIDE

++ ++ ENERGYFOOD (GLUCOSE)

OXYGEN++

from digestive system

from breathing system

USEFUL!waste product exhaled

waste product exhaled

The equation for respiration


Contents

Respiration

Waste products

Aerobic respiration





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 restingresting

low energy requirements

When is energy needed?


A busy day!

sometimes you are activeactive

high energy requirements


Food and fuel flexibility

Your body requires different amounts of 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


Throughout the day…

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 is not the daily activities of an average human, but this scenario will help us understand the process of respiration in more depth.

1. sleeping

2. running a marathon


SLEEPING

When we sleep, our body is at rest.

There is a 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 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.

Sleeping


Contents

Respiration

Waste products




Aerobic respiration


Aerobic respiration

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

When the body…

We say it is performing AEROBIC respiration.

OO22

has plenty of oxygenis able to completely digest foodcan 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.

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.

Glucose + Oxygen Carbon Dioxide + Water + Energy

Equation for aerobic respiration


Exercise: before - during - after

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?

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.

duringduringbeforebefore afterafter

Remember the runners?


Energy demands

Oxygen available

Form of respiration

What’s happening?

beforelow high aerobic

during

high low / none aerobic

(but slowing)

afterdropping none / low

??

Physical activity dictates energy demands


??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.

Running out of the good stuff


No energy would lead the body to stop working!

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.

But how?

Oxygen levels at zero


With aerobic respiration, the cells supply of oxygen and food is relatively constant.

oxygen

food

cellblood

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!

Oxygen shortage at the cellular level


Contents

Respiration

Waste products

Aerobic respiration





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

But it is not aerobic respiration because there is nono oxygen present. (aero- means of air)

Therefore we call it ANAEROBICANAEROBIC 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.



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.

Hitting the wall


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.

So, what is the problem with anaerobic respiration?

What’s wrong with anaerobic respiration?


Glucose Lactic Acid + (some) Energy

This waste product is known as 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 periods of time.

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

The anaerobic equation


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.

Why is lactic acid so harmful?


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

We want the energy that anaerobic

respiration produces

YES NO

So the answer is for anaerobic respiration to be a ‘gap-fill’ during periods of very low / no oxygen availability.

But we don’t want the lactic acid waste

product

Striking the right balance


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.

Oxygen debt


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.

Paying it off


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.

Doing the sums


Dealing with the lactic acid build-up

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...


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

Aerobic respiration (complete breakdown of food)

Anaerobic respiration (incomplete breakdown of food)

Aerobic respiration is performed when oxygen is present.

Anaerobic respiration is performed when oxygen is absent.

glucose + oxygen carbon dioxide + water + lactic acid + little energy

Respiration summary


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

Respiration…do I really need oxygen?


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

Respiration…do I really need 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

Why would the body be short of oxygen?


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

Why would the body be short of oxygen?


The acid test

fatigued

oxygen

muscle

contracting

anaerobicaerobic

broken

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 __________.


Multiple choice questions

Multiple choice section


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 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.


12. 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”.

ks4 biology

Documents