Question

Give the reactions and the conditions needed for the completion of glucose breakdown in the following.

(i) Yeast cells (ii) Muscle cells of man (iii) Tissue cells of man

Answer 1

Glucose molecules:

1. The primary source of energy in the cells is served by the glucose breakdown.
2. Glucose may break down under aerobic or anaerobic conditions to produce different products.
3. Aerobic breakdown of glucose produces more energy than under anaerobic conditions.

(i) Yeast cells:

1. The glucose molecules break down under anaerobic conditions in the yeast cells.
2. Glucose forms pyruvate, which is educed in the absence of oxygen to form ethanol, carbon dioxide and energy.
3. $\mathrm{Glucose}\to \mathrm{Pyruvate}\stackrel{\mathrm{absence}\mathrm{of}\mathrm{oxygen}}{\to }\mathrm{Ethanol}+{\mathrm{CO}}_2+\mathrm{Energy}$

(ii) Muscle cells of man:

1. Glucose breaks down in muscle cells during contraction to provide energy.
2. Under anaerobic conditions, glucose forms lactic acid and energy.
3. $\mathrm{Glucose}\to \mathrm{Pyruvate}\stackrel{\mathrm{Lack}\mathrm{of}\mathrm{oxygen}}{\to }\mathrm{Lactic}\mathrm{acid}+\mathrm{Energy}$

(iii) Tissue cells of man:

1. Glucose breaks down under aerobic conditions in the tissues.
2. A glucose molecule is formed into pyruvate, which oxidizes to form carbon dioxide and energy.
3. $\mathrm{Glucose}\to \mathrm{Pyruvate}\stackrel{\mathrm{Presence}\mathrm{of}\mathrm{oxygen}}{\to }3{\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}+\mathrm{Energy}$