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 $>1$ ?
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.
$\mathrm{F}_0-\mathrm{F}_1$ particles present in the inner mitochondrial membrane are involved in the synthesis of ATP (Adenosine Triphosphate), the energy currency of the cell.
(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.
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
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
The product of aerobic glycolysis in skeletal muscles is pyruvic acid while in anaerobic fermentation in yeast ethanol and $\mathrm{CO}_2$ are produced.
