B8.1 : Gas exchange, breathing, smoking, passage of oxygen

Question 1

Gas exchange

Answer 1

1. Respiration uses oxygen to “burn” (oxidise) food and so release the energy that cells need to stay alive
2. Living organisms must be able to take oxygen from the air and get rid of carbon dioxide to the air
3. Swapping oxygen for carbon dioxide in this way is called gas exchange
4. Gas exchange takes place through a gas exchange surface, also known as a respiratory surface
5. Multicellular organisms (with more than one cell) cannot just rely on diffusion. Their cells are too far from the external environment, and so they need a transport system with specialised surfaces to exchange molecules.

Question 2

Gas exchange surface

Answer 2

1. Also known as a respiratory surface
2. Exchange surfaces are surfaces that are adapted to maximise the efficiency of gas and solute (a substance dissolved in a liquid) exchange across them.
3. e.g. alveoli

Question 3

Respiration equation

Answer 3

Glucose + Oxygen –> energy + carbon dioxide + water

Question 4

Components of a gas exchange system in humans

Answer 4

1. A respiratory surface
2. Set of tubes
3. Blood supply
4. A ventilation system

Question 5

A respiratory surface

Answer 5

membranes lining the alveoli (air sacs) in the lungs

Question 6

Set of tubes (gas exchange)

Answer 6

1. a set of tubes to allow air from the outside to reach the respiratory surface.
2. This set of tubes has many branches and is sometimes called the bronchial tree

Question 7

Blood supply (gas exchange)

Answer 7

1. A blood supply (carried by the pulmonary artery and pulmonary vein) to carry dissolved gases to and from the respiratory surface

Question 8

Ventilation system

Answer 8

1. intercostal muscles and the diaphragm

2. it keeps a good flow of air over the respiratory surface

Question 9

Exchange surfaces adaptations

Answer 9

1. Kept clear
2. Near a blood supply
3. Thin membrane
4. Well ventilated
5. Large surface area

Question 10

Kept clear (exchange surface)

Answer 10

1. Any particles of dust for example will block an exchange surface and reduce the rate of exchange.
2. Goblet cells and cilia cells line the airways to prevent this.
3. Goblet cells produce sticky mucus that traps particles and cilia cells waft the mucus up and out of the airway.

Question 11

Near a blood supply (exchange surface)

Answer 11

1. Where substances are exchanged through blood in animals, exchange surfaces are densely packed with blood vessels
2. These blood vessels replenish the blood supply to maintain a high concentration gradient by bringing in new blood as diffusion starts to even out the concentrations.
3. There are many capillaries around the alveoli.

Question 12

Thin membrane (exchange surface)

Answer 12

1. A thin membrane reduces the diffusion distance.

2. Alveoli are one cell thick.

Question 13

Well ventilated (exchange surface)

Answer 13

In animals, if a gas is exchanged, the surface is ventilated (through breathing) to maintain a high concentration gradient and increase the rate of exchange.

Question 14

Large surface area (exchange surface)

Answer 14

1. A large surface area allows more of a substance to diffuse at the same time.
2. Alveoli create a large surface area for gas exchange in the lungs.

Question 15

Passage of air in the lungs

Answer 15

1. Deoxygenated blood arrives at the lungs from the heart via the pulmonary artery.
2. The lungs oxygenate (supply oxygen to) the blood before it returns to the heart through the pulmonary vein.

Question 16

Passage of oxygen into the blood

Answer 16

1. Air is breathed into the lungs through the trachea (windpipe).
2. The trachea divides into two tubes called the bronchi.
3. The bronchi divide to form bronchioles.
4. The bronchioles divide until they end up in tiny air sacs called alveoli.
5. There are millions of alveoli.
6. They are surrounded by a network of capillaries, allowing for oxygen and carbon dioxide to be exchanged between the blood in the capillaries and the air in the lungs.

Question 17

Alveoli

Answer 17

1. The alveoli are tiny air sacs in the lungs.
2. They are surrounded by a network of capillaries, allowing for oxygen and carbon dioxide to be exchanged between the blood in the capillaries and the air in the lungs.
3. The surface is moist, thin, and has an enormous area

Question 18

Larynx

Answer 18

1. voice box
2. air passes through hear during breathing
3. When breathing out, the vocal cords can be made to vibrate
4. The sounds produced to make up our speech

Question 19

Trachea

Answer 19

1. windpipe
2. tube that carries air towards the lungs
3. C-shaped rings of cartilage prevent the trachea from collapsing during in halation

Question 20

Bronchus

Answer 20

1. first branch from the trachea

2. there is one bronchus to each lung

Question 21

Bronchiole

Answer 21

final, very fine branch leading into the alveoli

Question 22

Breathing

Answer 22

1. Breathing is the set of muscular movements that gives respiratory surface a constant supply of fresh air
2. This means there is always a concentration gradient between the blood and the air in the alveoli for both oxygen and carbon dioxide
3. The diaphragm contracts and the rib cage move up and out to bring air into the lungs.
4. The diaphragm relaxes and the rib cage moves in and down to force air out of the lungs.

Question 23

Breathing in

Answer 23

1. Called inspiration
2. The diaphragm contracts and becomes flattened.
3. The internal intercostal muscles relax and the external intercostal muscles contract, moving the ribcage up and out.
4. The thorax volume increases, forcing air into the lungs because of decreased internal pressure.

Question 24

Breathing out

Answer 24

1. Called expiration
2. The diaphragm relaxes and becomes dome-shaped.
3. The internal intercostal muscles contract and the external intercostal muscles relax, moving the ribcage downwards and in.
4. The thorax volume decreases, increasing internal pressure.
5. Air is forced out of the lungs.

Question 25

Breath composition

Answer 25

1. The air that is breathed in is different to the air breathed out.
2. The amount of carbon dioxide in our breath can be tested using a solution called lime water.

Question 26

Difference in breath composition

Answer 26

1. Some of the oxygen that is breathed in is used up in respiration, and the carbon dioxide produced in respiration is breathed out.
2. So air that is breathed out contains less oxygen but more carbon dioxide than air breathed in.
3. The air that is breathed out also has more water vapour in it because the airways are moist inside.

Question 27

Investigating carbon dioxide in the breath

Answer 27

1. Lime water is a clear solution that turns cloudy when carbon dioxide dissolves in it.
2. An experiment where air that has passed through lime water is breathed in (so the carbon dioxide in the air is not breathed in) and exhaled air passes through lime water and turns it cloudy shows that more carbon dioxide is breathed out.

Question 28

Exercise and breathing

Answer 28

Exercise increases the rate of respiration in muscle cells. This causes both the rate and depth of breathing to increase.

Question 29

Breathing’s response to exercise

Answer 29

1. The increased rate of respiration in cells creates a higher concentration of carbon dioxide (a waste product of respiration) in the blood.
2. The brain detects this and causes breathing to become deeper and faster.
3. This means more carbon dioxide can be breathed out at a quicker rate (and more oxygen is also breathed in).

Question 30

Investigating breathing

Answer 30

1. The rate and volume (or depth) of someone’s breathing can be tested using a piece of equipment called a spirometer.
2. The closer together the waves shown by the spirometer, the faster the breathing rate.
3. The higher the waves, the deeper the breaths.

Question 31

Risks of smoking

Answer 31

1. Smoking is inhaling the smoke from burning tabacco (and paper)
2. This smoke can harm the lungs because it is hot, it has a drying effect, and it contains many harmful chemicals
3. The heat and dryness irritate the lungs, but the dangers of smoking come from the chemicals
4. There are over 1000 known chemicals in tabacco smoke including tar, carbon monoxide, sulphur dioxide, nicotine etc

Question 32

How Smoking affects the lungs

Answer 32

1. Alveoli are small, delicate air sacs that are found within the lungs
2. When we inhale, air enters into the body and travels through passageways to reach the lungs and the alveoli
3. Over time when you smoke, toxins from inhaled cigarette smoke will break the thin walls of the alveoli.
4. The alveoli have thin walls in order to allow for faster diffusion of gases
5. When the walls of the alveoli start to break down, there are larger and less efficient air sacs. The sacs also begin to lose their bounce which makes it harder to bring in oxygen and expel carbon dioxide.
6. The gases can eventually get trapped in the lungs in a process called emphysema

Question 33

Why is it difficult to give up smoking

Answer 33

1. In physical addiction, the body cannot function properly in the absence of the chemical because it has partly replaced a natural body chemical
2. In psychological addiction, the addicted person links smoking with comfort or lack of stress. When they feel stressed they may automatically reach for a cigarette

Question 34

Nicotine

Answer 34

1. Nicotine is the chemical in cigarettes that causes addiction
2. It is also a stimulant which makes the heart beat faster and at the same time makes blood vessels narrow
3. Nicotine increases heart rate and blood pressure and it is carcinogenic – causes cancer. It is used in some insecticides because it is poisonous. It is addictive.

Question 35

Tar

Answer 35

1. Tar in cigarettes causes lung cancer which is an uncontrolled division of cells
2. Tar is also an irritant which makes coughing more likely which can lead to physical damage to the lungs and makes the effects of emphysema even worse
3. Tar is a carcinogen also and it damages the cilia causing bronchitis.

Question 36

Bronchitis

Answer 36

1. When smoking, cilia are destroyed which means that mucus accumulates in the respiratory tubes
2. Dust and microbes, trapped in the mucus, slide down towards the lungs making the person coughThe coughing inflames the lining of the bronchi, causing bronchitis
3. Bacteria is also trapped din the mucus and the bacteria breed which can develop bacterial lung infections

Question 37

Tabacco

Answer 37

1. Burning tobacco releases carbon monoxide which is poisonous – it stops haemoglobin transporting oxygen.

Question 38

Smoking and the heart

Answer 38

1. Muscles in the heart need a steady supply of oxygen-rich blood to work efficiently.
2. Smoking reduces the amount of oxygen the blood can carry by up to 30%.
3. Over time, smoking damages the heart by overworking it and this disease is called coronary heart disease (CHD).
4. Even light smokers have a higher risk of CHD than non-smokers.

Question 39

Strokes

Answer 39

1. Smokers are much more likely to have a stroke than non-smokers.
2. People who smoke more than 20 cigarettes a day are four times more likely to suffer a stroke than a non-smoker.

Question 40

Asthma

Answer 40

1. Bronchioles when smoking fill with mucus and muscles fail to dilate properly.