Explain respiration, including its equation, and the transport functions of blood.

a) Define

• i) What is respiration? Respiration is the biochemical process in which living cells obtain energy by breaking down organic substances, such as glucose, typically in the presence of oxygen.

• ii) Write down an equation that summarizes aerobic respiration.

  $$\boxed{\text{C}_6\text{H}_{12}\text{O}_6 \text{(glucose)} + 6\text{O}_2 \text{(oxygen)} \to 6\text{CO}_2 \text{(carbon dioxide)} + 6\text{H}_2\text{O} \text{(water)} + \text{Energy (ATP)}}$$

b) Explain how oxygen from the atmosphere enters the blood stream.

Oxygen from the atmosphere enters the lungs during inhalation and reaches the alveoli. The walls of the alveoli are very thin and surrounded by a dense network of capillaries. Due to the partial pressure gradient, oxygen diffuses from the high concentration in the alveolar air across the alveolar and capillary walls into the blood plasma, and then into red blood cells where it binds to hemoglobin.

c) State three (3) transport functions of blood.

1. Transport of oxygen from the lungs to the body tissues.
2. Transport of carbon dioxide from the body tissues to the lungs for exhalation.
3. Transport of nutrients (e.g., glucose, amino acids, fatty acids) from the digestive system to the body cells.
4. Transport of hormones from endocrine glands to target organs.
5. Transport of waste products (e.g., urea) from cells to excretory organs like the kidneys.