2.38 Understand the role of diffusion in gas exchange.
Diffusion: The net movement of molecules from a region of high concentration to a region of lower concentration down a concentration gradient.
- In the circulatory system oxygen enters the blood and carbon dioxide leaves the blood via gaseous exchange.
- Gasses move across the walls of alveoli to an area of lower density than they are in:
- Oxygen moves into the blood as there is a low density of oxygen in the blood;
- Carbon dioxide moves into the lungs as it is an area of lower density.
- Oxygen moves into the blood as there is a low density of oxygen in the blood;
Flowering Plants
2.39 Understand gas exchange (of carbon dioxide and oxygen) in relation to respiration and photosynthesis,
2.41 Explain how the structure of the leaf is adapted for gas exchange.
Specific Adaptations:
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General Adaptations:
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2.42 Describe the role of stomata in gas exchange.
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Humans
2.44 Describe the structure of the thorax.
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2.45 Understand the role of the intercostal muscles and the diaphragm in
ventilation.
Inhaling (breathing in)
These things increase the space inside the lungs, letting the air in. |
Exhaling (breathing out)
These things reduce the space inside the lungs, pushing the air out. |
2.46 Explain how alveoli are adapted for gas exchange by diffusion between air
in the lungs and blood in capillaries.
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2.47 Understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease.
Biology of tobacco smoke:
Diseases caused by smoking:
- Nicotine:
- Makes the heart beat faster and narrows the arterioles, which increases blood pressure;
- It increases the stickiness of blood platelets, leading to blood not being able to clot.
- Tar
- Irritates the lining of the airways and stimulates them to produce more mucus.
- This accumulates as the cilia (tiny hair which keep the lungs clean) are damaged.
- Can eventually lead to throat cancer.
- Carbon monoxide
- Particles are absorbed by haemoglobin in red blood cells.
- It combines permanently with the haemoglobin so reduced the volume of oxygen which blood can carry,
- This leads to the heart having to beat faster, to pump enough oxygen around the body.
- Smoking during pregnancy can lead to birth defects, as not enough oxygen can reach the foetus.
Diseases caused by smoking:
- Chronic bronchitis and emphysema
- Tobacco smoke irritates the lining of the airways,
- Mucus cells produce more mucus in response,
- The cilia are damaged so cannot remove mucus and dust,
- Leading to accumulation of mucus, dust and bacteria,
- This stimulates the body's immune and eventually leads to the alveoli bursting as there is so much pressure put on them.
- Lung cancer
- The carcinogens in tar promote changes in the DNA of cells lining the airways,
- These changes can lead to mutations, and tumours,
- These tumours if not discovered may grow to occupy a large area of the lung and block the airway.
- Heart disease
- Tobacco smoke increases the chances that fat will deposit in the walls of arteries,
- This leads to blocked arteries,
- These blocked arteries put excess pressure on the heart muscle as it has to beat faster to move more blood around the body,
- Increasing the risk, and eventually leading to a heart attack.
2.48 Describe experiments to investigate the effect of exercise on breathing in humans.
- Select a group of people to test. Eg. twenty 16 year old males, non smoking.
- Measure their breaths per 10 seconds when stationary.
- Then measure after one minute of running at 7 km/h
- Then after two minutes etc.
- You will find a linear relationship as described below.
- During exercise cells respire more quickly (to provide more energy for movement)
- This means oxygen has to be delivered more quickly and carbon dioxide taken away more quickly.
- As a result of this the lung muscles contract and relax more rapidly and the heart beats faster.