Gas Exchange in Humans

Question 1

The larger an organism is….. What does this mean in terms of diffusion

Answer 1

The smaller its surface area to volume ratio. This means that simple diffusion will not be fast enough to supply all its needs and the organism would die.

Question 2

How do larger organisms get past the problem of diffusion being slow? Which system is an example that helps this?

Answer 2

They have specially adapted gas exchange surfaces which increase the effectiveness of gas exchange between the organism and the outside world. Human respiratory system often helps this

Question 3

Definition of gas exchange

Answer 3

The diffusion of oxygen into the blood and the carbon dioxide out of the blood

Question 4

Where does gas exchange take place in humans?

Answer 4

It takes place in the alveoli of the lungs

Question 5

Difference between respiration and breathing

Answer 5

Respiration is the release of energy from glucose using oxygen which produces carbon dioxide as a waste product - it takes place in every living cell.

Breathing is the movement of gases into and out of the lungs. It is the way in which the oxygen needed for respiration enters the body and carbon dioxide leaves the body.

Question 6

Where is the respiratory system located?

Answer 6

It is located in the chest cavity known as the thorax

Question 7

Labelled diagram of respiratory system

Answer 7

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Question 8

Bronchi

Answer 8

The two tubes that the trachea splits into

Question 9

Diaphragm

Answer 9

A muscular sheet at the bottom of the thorax involved in ventilation

Question 10

Trachea

Answer 10

Transmits air from outside to to the lungs

Question 11

What does it mean by rings of cartilage?

Answer 11

It means that it is flexible, but doesn’t collapse when breathing out

Question 12

Alveoli

Answer 12

Air sacs where gas exchange occurs

Question 13

Ribs

Answer 13

Bones that surround the lungs - act as protection and involved in ventilation

Question 14

Bronchioles

Answer 14

The smaller tubes that the bronchi split into

Question 15

Intercostal muscles

Answer 15

The muscles found between the ribs involved in ventilation

Question 16

Pleural membranes

Answer 16

Moist membranes between the inside of the thorax and lungs that provide lubrication to prevent the lungs from ‘sticking.’

Question 17

Diagram of the alveolus to show the adaptations of the alveoli for gas exchange

Answer 17

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Question 18

How is alveoli adapted for gas exchange?

Answer 18

The alveoli has a spherical shape which increases the surface area over which gas exchange can occur so that many gases can pass into the blood stream at once.

The cells lining the alveoli are one cell thick so there is only a short diffusion distance which means that the gases do not have far to travel so that they can be exchanged quickly.

There is a rich network of capillaries surrounding each alveolus. The blood flow maintains a steep concentration gradient for diffusion of gases by continuously delivering excess carbon dioxide to the alveolus and taking away the oxygen to deliver to the respiring cells.

Ventilation also helps to maintain this steep concentration gradient by constantly removing carbon dioxide and delivering oxygen.

They have moist surfaces to allow gases to dissolve so that they can diffuse faster.

Question 19

Practical: investigate breathing in humans including the release of carbon dioxide

Answer 19

Two boiling tubes filled with limewater connected by rubber tubings in which Tube A air enters and Tube B air leaves and in the middle is where your mouth goes.

The limewater changes from a colourless solution to a milky colour when carbon dioxide is bubbled through it.

As the person breathes in, air is drawn through Tube A and bubbles through the limewater. As the concentration of carbon dioxide in inhaled air is low, there is no colour change in the limewater in Tube A.

However, as the person breathes out, exhaled air passes through tube B. This air contains more carbon dioxide than inhaled air so the limewater turns milky.

Question 20

Ventilation definition

Answer 20

The movement of gases into and out of the lungs known as breathing. It involves inhalation and exhalation.

Question 21

What does ventilation require?

Answer 21

It requires pressure changes to occur in the lungs so that the air can be forced in and out of the alveoli

Question 22

How are these pressures brought about? Explain where these are

Answer 22

It is brought about by the movement of two sets of muscles - the diaphragm and the intercostal muscles.

The diaphragm is a sheet of muscle that separates the thorax from the abdomen.

The intercostal muscles lies between the ribs. The external intercostal muscles lie on the outside of the ribcage. The internal intercostal muscles lie on the inside of the ribcage.

Question 23

During gentle breathing, which muscles are involved and what about during exercise and why

Answer 23

During gentle breathing, the diaphragm is involved
During exercise (breathing hard), the intercostal muscles start to work to move the ribs and assist with breathing

Question 24

What evens happen during inhalation? 6 marks

Answer 24

1. The external intercostal muscles contract, making the ribs move upwards and outwards
2. The diaphragm contracts and flattens in shape
3. These changes cause the volume in the thorax to increase
4. This causes the pressure in the thorax to decrease
5. Atmospheric pressure is now higher than the pressure in the thorax
6. This pressure difference causes air to be drawn into the lungs

Question 25

What events happen during exhalation? (7) 7th mark for saying what happens to the intercostal muscles when breathing hard

Answer 25

1. The external intercostal muscles relax allowing the ribs to move back inwards and downwards which also pushes against the lungs. When breathing harms the internal intercostal muscles will contract to help the ribs move back down and in faster. 2. The diaphragm relaxes and returns to its domed shape, pushed up by the liver and the stomach. It pushes up on the lungs from below 3. These changes cause the volume of the thorax to decrease 4. This causes the pressure in the thorax to increase 5. The pressure in the lungs is now greater than atmospheric air 6. This pressure difference causes air to be forced out of the lungs

Question 26

How does air move? From what area to what area?

Answer 26

Air moves from an area of high pressure to an area of low pressure

Question 27

What happens to our muscles when we exercise? How do we do this? What do we need?

Answer 27

When we exercise, our muscles contract. This requires energy. The more movement needed, the more energy they need. They get this energy from respiration so they need a constant supply of oxygen and glucose.

Question 28

What can the muscles do so that we can exercise ?

Answer 28

Muscles can store glucose in the form of glycogen. This can be converted back into glucose for respiration when needed.

Question 29

How is the oxygen supplied in order to exercise?

Answer 29

It is supplied by breathing and transported into the blood to the working muscles

Question 30

Is anaerobic respiration less efficient than aerobic respiration? If so why?

Answer 30

Yes anaerobic is less efficient. This is because the glucose is not completely down into carbon dioxide and water but instead forms another molecule called lactic acid. This means less energy is released. When muscles respire anaerobically, they often get fatigued which means they can't contract efficiently. This is caused by the build up of lactic acid. This lactic acid must be removed by the blood from the muscles and broken down into carbon dioxide and water. This need oxygen. The amount of oxygen needed to do this is the oxygen debt also known as the EPOC. EPOC is the reason why your breathing rate remains high after you have stopped exercising. The fitter you are, the quicker the recovery will be, the soon the lactic acid will be converted into carbon dioxide and water and the sooner you stop panting.

Question 31

What happens to your breathing rate when you exercise and why?

Answer 31

During exercise, you are doing more physical work and so MORE oxygen needs to be given to the muscles by the blood. The more exercise you do, the more your breathing rate will INCREASE as its bringing more oxygen into your lungs so the heart can pump it to the muscles. This means that THE RATE AND DEPTH OF YOUR BREATHING INCREASES which makes sure more oxygen is absorbed into the blood and MORE CO2 is removed. You need more oxygen so you can respire more for respiration - this means the oxygen is used for respiration.

Question 32

What happens to your heart rate when you exercise and why?

Answer 32

When you exercise, your heart rate INCREASES so that MORE blood is pumped to the muscles MORE quickly. This is so it can supply more oxygen for respiration. It also increases because it allows waste products (e.g. carbon dioxide) to be removed. You also need glucose for respiration and so it increases.

Question 33

``` The effect of nicotine (a chemical in tobacco smoke) on humans What is it? What does it specifically affect? What does it increase? What effects does it cause? What can it lead to? ```

Answer 33

Nicotine is a highly addictive drug that affects the central nervous system acting both as a stimulant and a relaxant. As its so addictive, it causes unpleasant withdrawal effects if they do not smoke regularly. Nicotine increases the heart rate and narrows the blood vessels, causing high blood pressure. This can lead to heart disease

Question 34

The effect of tar What is produced to trap dirt and microbes and what moves this? How does this affect you when smoking? What can it lead to? Which disease? Over a long period of time, what can it lead to? Which disease?

Answer 34

Cells in the lining of the respiratory tract produces spicy mucus to trap dirt and microbes. Cells with tiny hair like parts, called cilia, normally move this mucus out of the lungs to the back of the throat where it is swallowed and destroyed by the HCL. The tar forms a black sticky substance in the lungs which coats the cilia making them unable to move to clear the mucus containing dust and micro-organisms. The mucus therefore collects in the lungs and leads to a persistent cough and recurrent infections. This is responsible for the disease bronchitis. Over a long period of time, this continuous coughing damages the alveoli. The walls between adjacent alveoli break down making large individual alveoli with a reduced surface area. This causes a disease called emphysema and the patient can't get enough oxygen for any activity.

Question 35

Carcinogenic Chemicals | What does this cause?

Answer 35

Some chemicals in tar are carcinogenic which means they can cause random mutations to occur. They are a rare change in DNA which can lead to cells starting to divide forming a tumour. This is cancer.

Question 36

``` Carbon monoxide What does it cause? As well as nicotine Haemoglobin? Increase in what? What about when you are pregnant ```

Answer 36

Causes an increase in blood pressure It combines with haemoglobin in red blood cells in preference to oxygen so not enough oxygen can be carried to respiring cells which then die off. Amputation may be necessary. It causes an increase in heart rate to compensate for the reduced oxygen carrying capacity of the blood which can lead to heart disease. It may pass to an unborn baby if a woman smokes while pregnant. This leads to low birth weight babies which can lead to an increased risk of coronary heart disease and heart attack.

Question 37

Chemicals causing cholesterol to be released into the blood What can the cholesterol do? What can be formed? In which two ways can this do?

Answer 37

The cholesterol can attach to the lining of blood vessels that have been irritated by smoke chemicals. This can cause the lining of the blood vessel to become thicker which reduces blood flow and can cause clots to form. If the clot travels to the brain, a stroke may occur. If the clot occurs in the blood vessels supplying the heart, it reduces the amount of oxygen and glucose able to be supplied to the heart muscle which means that the heart muscle does not have enough oxygen for respiration. This leads to death of the heart muscle and a heart attack occurs.

Question 38

Design an experiment to show the effect of exercise

Answer 38

Independent variable - Dependent variable - Control variable -