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Understand Anaerobic Respiration

Worksheet Overview

QUESTION 1 of 10

Did you know that Usain Bolt is currently the fastest sprinter in the world? He ran 100 metres in a record 9.58 seconds!

 

Image of athletes running

 

In order to do this, Usain Bolt’s muscles need to respire super quick. He needs all that energy to sprint so fast. But his body can’t keep up with these demands - it can’t respire fast enough. This is where anaerobic respiration steps in. 

 

Image of females exercising

 

 

Anaerobic respiration is where glucose breaks down but without oxygen. Energy is released, but not as much as in aerobic respiration. Lactic acid is produced instead of carbon dioxide and water. Lactic acid can cause painful cramps - something we feel in our muscles that stops us from carrying on. To get rid of the lactic acid, the person has to breathe in deeply in order to get a good supply of oxygen. You have to keep breathing hard for a while, after you stop exercising, to get oxygen back into your muscles to convert the painful lactic acid which has built up, into harmless carbon dioxide and water. The amount of oxygen needed to do this is called the oxygen debt.

Anaerobic respiration can be represented by the equation: 

 

glucose → lactic acid + energy


The reactant in anaerobic respiration is glucose. The product is lactic acid. Energy is also released.

Anaerobic respiration occurs in the cytoplasm of the cell, and not the mitochondria, as in aerobic respiration. 

 

Plants can also respire anaerobically. However, they don't produce lactic acid. Glucose is broken down into ethanol and carbon dioxide.

 

Image of plant and animal cell

 

Uses of anaerobic respiration

 

Image of alcohol

 

 

Anaerobic respiration is useful in bread making and alcohol brewing. Yeast will respire anaerobically, releasing alcohol and carbon dioxide. The carbon dioxide helps bread to rise, creating its fluffy texture. This process is also known as fermentation.

 

glucose → alcohol + carbon dioxide

 

Image of bread made with yeast

 

In the following activity, you will investigate anaerobic respiration.

Some plants and microorganisms respire anaerobically.

 

Where can anaerobic respiration be used in industry?

Making paper

Making wine and beer

Making chocolate

Making bread

Glucose is important in respiration.

 

Which of the following statements about glucose are correct?

Glucose is a reactant in the process of respiration

Glucose is a reactant in the process of photosynthesis

Glucose is a product in the process of respiration

Glucose is a product in the process of photosynthesis

Name the reactant involved in both anaerobic and aerobic respiration. 

Glucose

Oxygen

Carbon dioxide

What is the name of X in the equation below? 

 

Image of anaerobic respiration equation

Water

Carbon dioxide

Lactic acid

There are two types of respiration - aerobic and anaerobic.

 

Which type of respiration needs the reactant oxygen?

 

Image of oxygen bubbles

Fill in the blanks below describing anaerobic respiration.  

Yeast respires anaerobically and is used to make beer.

 

Complete the word equation for the reaction that takes place: 


 

...A... → alcohol + ...B...

Column A

Column B

A
Glucose
B
Carbon dioxide

Lizzie is making bread. She adds yeast to her flour and other ingredients before placing it in the oven. Lizzie's bread rises nicely. 

 

How did the bread rise? 

 

Image of bread

Column A

Column B

The yeast respires anaerobically
in the dough causing it to rise
The carbon dioxide gets trapped
releasing carbon dioxide

Karl is at the gym exercising. After a while on the treadmill, he gets a cramp in his legs.

 

Why does this happen?

Karl's leg muscles aren't receiving enough oxygen, so start to respire aerobically

Karl's leg muscles aren't receiving enough oxygen, so start to respire anaerobically

Carbon dioxide is produced which starts building up in the muscles, causing pain

Lactic acid is produced which starts building up in the muscles, causing pain

What do aerobic and anaerobic respiration have in common?

Glucose is a reactant

Oxygen is a reactant

Energy is released

Water is released

  • Question 1

Some plants and microorganisms respire anaerobically.

 

Where can anaerobic respiration be used in industry?

CORRECT ANSWER
Making wine and beer
Making bread
EDDIE SAYS
There were two correct options in this question. Just as in plants, yeast respires anaerobically. Bread making and brewing alcohol are the two most common uses of yeast and the products are carbon dioxide and alcohol. This process is known as fermentation.
  • Question 2

Glucose is important in respiration.

 

Which of the following statements about glucose are correct?

CORRECT ANSWER
Glucose is a reactant in the process of respiration
Glucose is a product in the process of photosynthesis
EDDIE SAYS
Did you get the two correct options? Remember that respiration and photosynthesis are opposite reactions! The reactants of one are the products of the other! Glucose is a reactant in both types of respiration and a product in photosynthesis. We get the glucose we need for respiration from the food we eat. Our food is a source of glucose - originally made by plants during photosynthesis. Without the glucose in food, we wouldn't be able to respire!
  • Question 3

Name the reactant involved in both anaerobic and aerobic respiration. 

CORRECT ANSWER
Glucose
EDDIE SAYS
Did this confuse you a little? Oxygen is a vital reactant in the process of aerobic respiration but it is not present in anaerobic respiration. The correct answer is glucose because it is needed in both types of respiration. It is important to remember though, that the glucose is not broken down completely in anaerobic respiration - this means that the process gives less energy.
  • Question 4

What is the name of X in the equation below? 

 

Image of anaerobic respiration equation

CORRECT ANSWER
Lactic acid
EDDIE SAYS
Did you work out that this is the equation for anaerobic respiration? If it had been for aerobic respiration, there would have been two reactants (glucose and oxygen) and two products - water and carbon dioxide. But we can see that this is anaerobic because there is only one reactant - glucose, not oxygen. There's only one product in anaerobic respiration and that's lactic acid.
  • Question 5

There are two types of respiration - aerobic and anaerobic.

 

Which type of respiration needs the reactant oxygen?

 

Image of oxygen bubbles

CORRECT ANSWER
aerobic
EDDIE SAYS
This is the key difference so try to remember it! Aerobic: uses oxygen Anaerobic: without oxygen
  • Question 6

Fill in the blanks below describing anaerobic respiration.  

CORRECT ANSWER
EDDIE SAYS
This activity is useful for making revision notes. Have a few tries if you didn't get it correct the first time around.
  • Question 7

Yeast respires anaerobically and is used to make beer.

 

Complete the word equation for the reaction that takes place: 


 

...A... → alcohol + ...B...

CORRECT ANSWER

Column A

Column B

A
Glucose
B
Carbon dioxide
EDDIE SAYS
Try not to confuse the anaerobic respiration equation that occurs in the body with the one that occurs in yeast and plants! All types of anaerobic respiration require the same reactant - glucose, but they have different products. In our bodies, the product is lactic acid, but in plants and yeast cells, carbon dioxide is produced as well as ethanol or alcohol.
  • Question 8

Lizzie is making bread. She adds yeast to her flour and other ingredients before placing it in the oven. Lizzie's bread rises nicely. 

 

How did the bread rise? 

 

Image of bread

CORRECT ANSWER

Column A

Column B

The yeast respires anaerobically
releasing carbon dioxide
The carbon dioxide gets trapped
in the dough causing it to rise
EDDIE SAYS
Remember the equation for anaerobic respiration in yeast cells? The products are alcohol or ethanol, plus carbon dioxide. The carbon dioxide here proves to be useful! It helps the bread to rise, keeping it nice and fluffy.
  • Question 9

Karl is at the gym exercising. After a while on the treadmill, he gets a cramp in his legs.

 

Why does this happen?

CORRECT ANSWER
Karl's leg muscles aren't receiving enough oxygen, so start to respire anaerobically
Lactic acid is produced which starts building up in the muscles, causing pain
EDDIE SAYS
There were two answers again here. As Karl continues to exercise, his muscles begin to get low on oxygen, so they start to respire anaerobically. This produces the energy he needs, but also makes lactic acid. Lactic acid will cause pain! Our body won't be able to tolerate a build-up of lactic acid. The only way for the body to deal with this is to breathe deeply in order to break up the lactic acid.
  • Question 10

What do aerobic and anaerobic respiration have in common?

CORRECT ANSWER
Glucose is a reactant
Energy is released
EDDIE SAYS
Energy is pretty much the whole point of respiration! The amount of energy differs, however, depending on the type of respiration that occurs. Aerobic respiration produces much more energy than anaerobic. The other similarity is that they both have glucose as a reactant. This is the only reactant in anaerobic respiration - it doesn't use oxygen. The products are different between the two types of respiration and it is important to get these the right way round! The products of aerobic respiration are carbon dioxide and water, whereas lactic acid is the only product of anaerobic. Complicated isn't it?! Well done for reaching the end of this activity.
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