Respiration in Humans

Question 1

adaptation of lungs for gas exchange

Answer 1

• numerous alveoli in lungs provide a large SA
• wall of alveolus is one cell thick, providing short diffusion distance for gases, ensuring a faster rate of diffusion
• a thin film of moisture covers the surface of alveolus that allows oxygen to dissolve in it
• walls of alveoli are richly supplied with blood caps - flow of blood maintains the conc grad of gases

Question 2

oxygen & CO2 conc gradients between alveolar air & blood are maintained by:

Answer 2

• continuous blood flow through blood caps
• movement of air in & out of alveoli, caused by breathing

Question 3

describe the removal of carbon dioxide from the lungs, including the role of the carbonic anhydrase
enzyme

Answer 3

1. Tissue cells produce a large amnt of CO2 as a result of aerobic respiration
2. As blood passes through these tissues via blood caps, CO2 diffuses into the blood & enters the RBCs
3. CO2 then reacts w/ water in RBCs to form carbonic acid. This reaction is catalysed by enzyme carbnic anhydrase which is present in RBCs
4. Carbonic acid is then converted into hydrogencarbonate ions which diffuse out of the RBCs. Most of CO2 is carried as hydrogencarbonate ions in the blood plasma. A small amnt of CO2 s also carried & dissolved in RBCs
5. In lung, hydrogencarbonate ions diffuse back into RBCs where they are converted into carbonic acid, and then into water & CO2.
6. CO2 then diffuses out of blood caps and into alveoli, where it is expelled when you breathe out.

Question 4

functions of ciliated cells

Answer 4

• have cilia (hair-like structures)
• cilia sweep dust-trapped mucus up trachea

Question 5

Inspiration

Answer 5

1. Diaphragm muscle contracts & flattens
2. Ext intecorstal muscles contract while int intercostal muscles relax
3. Ribs move upwards & outwards
4. Sternum moves up and forward
5. Vol of thoracic cavity increases
6. Lungs expand & air pressure inside them decreases as vol increases
7. Atmospheric pressure now higher than pressure w/n lungs which forces atmospheric air into lungs

Question 6

Expiration

Answer 6

1. Diaphragm muscle relaxes & arches upwards
2. Ext intecorstal muscles relax while int intercostal muscles contract
3. Ribs move downwards & inwards
4. Sternum moves down and in og position
5. Vol of thoracic cavity decreases
6. Lungs are compressed & air pressure inside them increases as vol decreases
7. Pressure w/n lungs now higher than atmospheric air which forces air out of lungs into exterior environment

Question 7

Effects of tobacco smoke

Answer 7

Nicotine:
- Addictive drug that causes the release of the hormone adrenaline > Increases heartbeat rate and blood pressure.
- Makes blood clot easily > Increases risk of blood clots in the arteries, which leads to increased risk of coronary heart disease.

CO:
- Combines with haemoglobin to form carboxyhemoglobin > Reduces ability of blood to carry oxygen.
- Increases the rate of fatty deposits on the inner arterial wall, which leads to increased risk of coronary heart disease > Narrows the lumen of arteries and leads to increase in blood pressure.

Tar:
- Causes uncontrolled cell division > Increases risk of cancer in lungs.
- Paralyses cilia lining the air passages > Dust particles trapped in the mucus lining the air passages cannot be removed, increasing risks of chronic bronchitis and emphysema.

Irritants (hydrogen cyanide, acrolein etc):
- Paralyse cilia lining the air passages > Dust particles trapped in the mucus lining the air passages cannot be removed, increasing risks of chronic bronchitis and emphysema.

Question 8

define and state the equation, in words and symbols, for aerobic respiration in humans

Answer 8

Aerobic respiration is the breakdown of food subs (molecules) in the presence of oxygen w/ the release of a large amnt of energy. Carbon dioxide & water are released as waste products.
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
glucose + oxygen → carbon dioxide + water + large amount of energy

Question 9

define and state the equation, in words only, for anaerobic respiration in humans

Answer 9

Anaerobic respiration is the breakdown of food subs (molecules) in the absence of oxygen. It released less energy than aerobic respiration.
glucose →lactic acid + SAE

Question 10

describe the effect of lactic acid in muscles during exercise