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10
Explain the term 'energy currency'. Which substance acts as energy currency in plants and animals?
Explanation

The term energy currency refers to that molecule which provides energy for cellular activities, whenever required. ATP is termed as energy currency because the energy is present in the form of high energy bonds of ATP. Other energy yielding molecules are GTP, CTP, UTP, etc.

The conversion of ATP to ADP yields about $7.3 \mathrm{kcal} / \mathrm{mol}$ of energy. This is the energy source in a variety of biological processes occurring in both plants and animals.

Justification for the term 'energy currency' for ATP can be given as

(i) Store small packets of energy as soon as it is available thus, minimising its wastage.

(ii) Can make energy available to a distant location in cell away from where the site it is produced.

(iii) Can carry out heavy work/activity by continuosly supplying large amount of energy through its accumulation at one place.

11

Different substrates get oxidised during respiration. How does Respiratory Quotient (RQ) indicate which type of substrate, i.e., carbohydrate, fat or protein is getting oxidised?

$$\text { R.Q. }=\frac{A}{B}$$

What do $A$ and $B$ stand for?

What type of substrates have R.Q. of $1,<1$ or $>1$ ?

Explanation

The ratio of $\mathrm{CO}_2$ evolved and consumption of $\mathrm{O}_2$ in respiration is called the Respiratory Quotient (RQ) or respiratory ratio.

$$\text { R.Q. }=\frac{A}{B}=\frac{\text { Volume of } \mathrm{CO}_2 \text { evolved }}{\text { Volume of } \mathrm{O}_2 \text { consumed }}$$

Substrates like carbohydrates have $\mathrm{RQ}=1$ during, aerobic respiration.

Proteins and fats have RQ of $<1$ and it occurs during germination of seeds.

Substrates like organic acids have RQ of $>1$ under aerobic conditions.

12
$F_0-F_1$ particles participate in the synthesis of ............. .
Explanation

$\mathrm{F}_0-\mathrm{F}_1$ particles present in the inner mitochondrial membrane are involved in the synthesis of ATP (Adenosine Triphosphate), the energy currency of the cell.

13
When does anaerobic respiration occur in man and yeast?
Explanation

(a) In animals anaerobic respiration occurs in the situation of deficiency of oxygen during heavy exercise when pyruvic acid is reduced to lactic acid by the enzyme lactate dehydrogenase.

(b) In yeast, the incomplete oxidation of glucose occurs under anaerobic conditions, where pyruvic acid is converted to $\mathrm{CO}_2$ and ethanol by the action of enzyme pyruvic acid decarboxylase and alcohol dehydrogenase.

14

Which of the following will release more energy on oxidation? Arrange them in ascending order.

(a) 1 gm of fat

(b) 1 gm of protein

(c) 1 gm of glucose

(d) 0.5 gm of protein +0.5 gm glucose

Explanation

The ascending order of substrate that will release more energy on oxidation will be as follows

1 gm protein $<0.5 \mathrm{gm}$ In protein $<1 \mathrm{gm}$ glucose $<1 \mathrm{gm}$ fat +0.5 gm glucose