CBSE Class 10 Biology Life Processes Notes Set 12

Respiration

Respiration oxidises food in the cell to release energy, which is stored as ATP. Breathing is the physical exchange of air, while respiration is the biochemical release of energy in all cells with the help of enzymes.

1. Glycolysis: glucose (6 C) to two pyruvate (3 C) in the cytoplasm, common to both types.
2. Yeast ferments pyruvate to ethanol and carbon dioxide. Lime water turns milky with the CO2.
3. In muscles during hard exercise pyruvate becomes lactic acid, which causes cramps.
4. Germinating seeds with KOH in the flask show that seeds release CO2: water rises in the tube as KOH absorbs the gas.

Gaseous Exchange in Plants and Animals

1. Plants exchange gases by diffusion through stomata, lenticels and root hairs. In the day the CO2 of respiration is used in photosynthesis, at night CO2 is released.
2. Waterlogged soil lacks oxygen, so roots respire anaerobically and the plant may die.
3. Fish take dissolved oxygen through gills. Water has less than 1 percent oxygen against 21 percent in air, so aquatic animals breathe faster.
4. Earthworm uses skin, insects use tracheae, frog, reptiles, birds and mammals use lungs.

Human Respiratory System

Air passes through nostrils, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and finally the alveoli. C shaped cartilage rings keep the trachea open. Alveoli have a total area of about 80 square metres, thin walls and many capillaries, so they are the site of gas exchange.

1. Oxygen diffuses into blood and joins haemoglobin in red blood cells to form oxyhaemoglobin.
2. Carbon dioxide is more soluble in water than oxygen, so most of it is carried dissolved in plasma.
3. Inhalation: diaphragm contracts and flattens, ribs move up and out, chest volume rises and air enters. Exhalation is the reverse.
4. Smoking destroys cilia of the air passage, so dust and germs reach the lungs and can cause infection and cancer.
5. Diffusion alone cannot supply oxygen to the cells of a large animal, so a respiratory pigment and a transport system are needed.