B8 Gas Exchange and Respiration

Question 1

What is a gas exchange surface?

Answer 1

A gas exchange surface is where oxygen and carbon dioxide are exchanged within the body.

Question 2

What do all gas exchange surfaces have in common? (features)

Answer 2

-Large surface area
-Thin walls
-Good ventilation
-Good blood supply

Question 3

Why is a large surface area important for a gas exchange surface?

Answer 3

A large surface area means a lot of diffusion can occur across the surface. e.g. Lungs and alveoli.

Question 4

Why are thin walls important for a gas exchange surface?

Answer 4

Gas exchange surfaces are often only one cell thick. Diffusion can occur easily over a thin wall. e.g. Alveoli has a 1 cell thick walls which gives a short diffusion distance. Capillaries also have thin walls.

Question 4

Why is ventilation important for gas exchange surfaces?

Answer 4

Good ventilation means good air flow around the gas exchange surface. In the lungs, this is achieved by breathing in and out. This means concentrations gradients for oxygen and carbon dioxide are maintained.

Question 5

What is oxygenated blood?

Answer 5

Oxygenated blood has a larger concentration of oxygen than carbon dioxide and is carried by the left side of the heart. It goes from the lungs to the body.

Question 5

Why is a good blood supply important for a gas exchange surface?

Answer 5

Good blood supply is required for delivery or removal of change gases. This means concentration gradient for oxygen and carbon dioxide are maintained.
e.g. alveoli has a large network of capillaries allowing for a good blood supply to each alveoli. This means concentration gradients for oxygen and carbon dioxide are maintained.

Question 6

What is deoxygenated blood?

Answer 6

Deoxygenated blood has a larger concentration of carbon dioxide than oxygen and is carried by the right side of the heart. It goes from the body to the lungs.

Question 7

Describe the ribs.

Answer 7

The ribs are a bone structure that protects internals organs such as the lungs.

Question 8

Describe the intercostal muscle.

Answer 8

The intercostal muscle are muscles between the ribs which control their movement causing inhalation and exhalation.

Question 9

Describe the diaphragm.

Answer 9

The diaphragm is a sheet of connective tissue and muscle at the bottom of the throat that helps change the volume of the thorax to allow inhalation and exhalation.

Question 10

Describe the trachea.

Answer 10

The trachea is the windpipe that connects the mouth and nose to the lungs.

Question 11

Describe the larynx.

Answer 11

The larynx is also known as the voice box, when air passes across here, we are able to make sounds.

Question 12

Describe the bronchi (pl).

Answer 12

The bronchi are large tubes branching off the trachea with one bronchus for each lung.

Question 13

Describe the bronchioles.

Answer 13

The bronchioles are bronchi split to form smaller tubes connected to alveoli.

Question 14

Describe the alveoli.

Answer 14

The alveoli are tiny air sacs where gas exchange takes place.

Question 15

Why is the air that is breathed in and the air that is breathed out different?

Answer 15

The air that is breathed in and the air that is breathed out has different amounts of gases in it due to exchanges that take place in the alveoli.

Question 16

How is the air we breathe out different?

Answer 16

The air we breathe out contains more water vapour than when we breathe it in. The temperature of exhaled air is higher than inhaled air.

Question 17

What is the composition of inspired air?

Answer 17

Inspired air contains 21% of oxygen (more than expired). It contains 0.04% of carbon dioxide (less than expired). It contains the same amount of nitrogen - 78%.

Question 18

What is the composition of expired air?

Answer 18

It contains 16% of oxygen (less than inspired). It contains 4% of carbon dioxide (more than inspired). It contains the same amount of nitrogen - 78%.

Question 19

How to investigate for the differences in inspired and expired air?

Answer 19

Using limewater.
When we breathe in, the air is drawn through boiling tube A. When we breathe out, the air is blown into boiling tube B. Limewater is clear but turns milky when carbon dioxide is bubbled through.
The limewater in A will remain clear but the limewater in B will turn cloudy/milky. This shows us that the % of carbon dioxide in exhaled air is higher than inhaled air.

Question 19

How to investigate the effects of physical activity on breathing?

Answer 19

Exercise increases the frequency and depth of breathing. This can be investigated by:
-counting breaths taken during one minute at rest and measuring average chest expansion over 5 breaths using a tape measure held around chest.
Then, immediately after exercising, count the breaths taken in one minute and measure the average chest expansion over 5 breaths.
After exercise, the number of breaths per minute and the chest expansion will have increased.

Question 20

What are the effects of physical activity on rate and depth of breathing?

Answer 20

Exercise causes the frequency and depth of breathing to increase. This is because muscles are working harder and aerobically respiring more and they need more oxygen to be delivered to them (and more carbon dioxide removed) to keep up with the energy demand.

Question 21

What happens if the muscles cannot meet the energy demand?

Answer 21

If the muscles cannot meet the energy demand, they will also respire anaerobically which produces lactic acid. After exercise, the lactic acid that has built up in the muscles need to be removed as it lowers the pH of cells and can denature enzymes catalysing cell reactions.

Question 22

How can lactic acid be removed from muscles?

Answer 22

Lactic acid can only be removed by combining it with oxygen - known as repaying the oxygen debt.
This can be tested by seeing how long it takes after exercise for the breathing rate and depth to return to normal - the longer it takes, the more lactic acid produced during exercise and the greater the oxygen debt that needs to be repaid

Question 23

What increases in muscle cells when exercising heavily?

Answer 23

The rate of respiration increases in muscle cells when exercising heavily.
Since carbon dioxide is a product of aerobic respiration, the carbon dioxide levels increase in the muscle cells during exercise.

Question 24

How does carbon dioxide diffuse out of the muscle cells?

Answer 24

Carbon dioxide diffuses out of the muscle cells and into the blood plasma.

Question 25

What protects the breathing system? - from pathogens and particles

Answer 25

-Ciliated epithelial cells.
The passages down to the lungs are lined with ciliated cells. They have cilia which are hair-like projections that beat and push mucus up the passages towards the nose and throat where it can be removed.

Question 26

What is the mucus produced by? What does mucus do?

Answer 26

The mucus is produced by goblet cells.
Mucus traps particles, pathogens like bacteria or viruses, and dust and prevent them from getting into the lungs and damaging the cells there.

Question 27

What can smoking cause?

Answer 27

Smoking can cause chronic obstructive pulmonary disease (COPD), coronary heart disease and increased risks of several types of cancer, including lung cancer.

Question 28

What are the chemical in cigarettes?

Answer 28

-Tar - a carcinogen (substance that causes cancer).
-Nicotine - an addictive substance which also narrows blood vessels.
-Carbon monoxide - reduces the oxygen-causing capacity of the blood.

Question 29

How does nicotine affect the gas exchange system?

Answer 29

-Nicotine narrows blood vessels leading to an increased blood pressure.
-Increases heart rate.
-Both of these can cause blood clots to form in the arteries leading to heart attack or stroke.

Question 30

How does carbon monoxide affect the gas exchange system?

Answer 30

-Carbon monoxide binds irreversibly to haemoglobin, reducing the capacity of blood to carry oxygen.
-puts strain on breathing system as breathing frequency and depth need to increase in order to get the same amount of oxygen into the blood.
-Also puts strain on circulatory system to pump the blood faster around the body and increases the risk of coronary heart disease and strokes.

Question 31

How does tar affect the gas exchange system?

Answer 31

-Tar is a carcinogen and is linked to increased chances of cancerous cells developing in the lungs.
-Also contributes to COPD which is when chronic bronchitis and emphysema occur together.
-Tar causes chronic bronchitis which stimulates goblet cells and mucus glands to enlarge, producing more mucus. This destroys cilia and mucus (containing dirt, bacteria and viruses) and builds up blocking the smallest bronchioles and leading to infections.
A smoker’s cough is the attempt to move the mucus.

Question 32

What is emphysema?

Answer 32

Emphysema is a disease that develops as a result of frequent infection. Phagocytes that enter the lungs release elastase.
This means the alveoli becomes less elastic and cannot stretch so many burst. The breakdown of alveoli reduces the surface area for gas exchange. As it progresses, patients become breathless and wheezy - may need constant supply of oxygen to stay alive.

Question 33

What is elastase?

Answer 33

Elastase is an enzyme that breaks down the elastic fibres in the alveoli.

Question 34

How does increased physical activity cause the breathing area to rise?

Answer 34

Increased physical activity - muscle cells require more oxygen and glucose to work, but they also produce higher amounts of carbon dioxide ;
This means the lungs must obtain more oxygen and exhale more carbon dioxide
So breathing rate rises!

Question 35

What is aerobic respiration?

Answer 35

Aerobic respiration is the chemical reactions in cells that breakdown nutrient molecules to release energy.

Question 36

What are the uses of energy in living organisms?

Answer 36

-Muscle contraction
-Protein synthesis
-Cell division (to make new cells)
-Growth
-Maintaining a constant internal body temperature

Question 37

Where do most of the chemical reactions in aerobic respiration occur?

Answer 37

Respiration occurs in all living cells but most of the chemical reactions in aerobic respiration occur in the mitochondria.

Question 38

What are respiration reactions controlled by?

Answer 38

Respiration reactions are all controlled by enzymes as it is an enzyme-controlled action/process.

Question 39

What is the word equation for aerobic respiration?

Answer 39

Glucose + oxygen => carbon dioxide + water

Question 40

What is the balanced equation for aerobic respiration?

Answer 40

C6H12O6 + 6O2 → 6CO2 + 6H2O

Question 41

What does aerobic respiration require?

Answer 41

Aerobic respiration requires oxygen. It is the complete breakdown of glucose to release a relatively large amount of energy for use in cell processes. It produces carbon dioxide and water.

Question 42

What is anaerobic respiration?

Answer 42

Anaerobic respiration is the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.

Question 43

What does anaerobic respiration not require?

Answer 43

Anaerobic respiration does not require oxygen.

Question 44

Which type of respiration releases less energy?

Answer 44

Anaerobic respiration releases much less energy per glucose molecule than aerobic respiration.

Question 45

What are the two types of anaerobic respiration?

Answer 45

There are two types of anaerobic respiration:
-In muscles during vigorous exercise.
-In yeast cells

Question 46

What is the word equation for anaerobic respiration in muscles during vigorous exercise?

Answer 46

glucose → lactic acid

Question 47

What happens in the muscle cells during vigorous exercise?

Answer 47

Anaerobic respiration mainly takes place in muscle cells during vigorous exercise.
When we exercise vigorously, our muscles have a higher demand for energy than when we are resting or exercising normally. However, our bodies can only deliver so much oxygen to our muscle cells for aerobic respiration. In this instance, as much glucose is broken down with oxygen and some glucose is broken down without it, producing lactic acid instead. There is still energy stored within the bonds of lactic acid molecules that the cell could use; for this reason, less energy is released when glucose is broken down anaerobically.

Question 48

What happens when lactic acid builds up in the muscle cells during vigorous exercise?

Answer 48

Lactic acid builds up in muscle cells and
-lowers the pH of the cells (more acidic).
This could denature the enzymes in cells so it needs to be removed. Cells excrete lactic acid into the blood. When blood passes through the liver, lactic acid is taken up into liver cells where it is oxidised, producing carbon dioxide and water. - lactic acid reacts with oxygen and so aerobic respiration is occurring with lactic acid as nutrient molecule and not glucose.

Question 49

Why do we continue to breathe heavily and our heart rate remains high even after finishing exercise?

Answer 49

We continue to breathe heavily and out heart rate remains high even after finishing exercising because we need to transport the lactic acid from our muscles to the liver and continue getting larger amount of oxygen into the blood to oxidise the lactic acid. This is known as ‘repaying the oxygen debt’.

Question 50

What is the word equation for anaerobic respiration in the microorganism yeast?

Answer 50

glucose => alcohol + carbon dioxide

Question 51

What is the role of anaerobic respiration in yeast during break making?

Answer 51

We take advantage of the products of anaerobic respiration in yeast by using it in bread making. The carbon dioxide produced when yeast breaks down glucose causes the dough to rise.