Quality Control

• Enzymology of Fatty Acid Desaturation in Mammals:
• Mammalian hepatocytes possess $\Delta^9$, $\Delta^6$, and $\Delta^5$ acyl-CoA desaturases, which can introduce double bonds between an existing double bond and the carboxyl terminal.
• Mammals completely lack $\Delta^{12}$ and $\Delta^{15}$ fatty acid desaturases:
• They cannot introduce a double bond beyond Carbon atom 9 (counted from the carboxyl terminal towards the methyl end).
• Consequently, Linoleic acid ($18:2\Delta^{9,12}$) and $\alpha$-Linolenic acid ($18:3\Delta^{9,12,15}$) cannot be synthesized de novo and are obligate dietary essential fatty acids.
• nalysis:
• (Carbon atom 9): Correct.

Correct option: (1) Carbon atom 9

• CNCPS Protein Partitioning:
• Fraction A: Non-Protein Nitrogen (NPN), instantly degraded in the rumen ($A = \text{Soluble Protein} - \text{True Soluble Protein}$).
• Fraction B1: Rapidly degraded true protein (buffer soluble, TCA precipitable).
• Fraction B2: Moderately degraded protein ($B2 = \text{Total Protein} - A - B1 - B3 - C$).
• Fraction B3: Slowly degraded protein associated with plant cell walls:

(Neutral Detergent Insoluble Protein minus Acid Detergent Insoluble Protein).

• Fraction C: Completely indigestible protein ($C = \text{ADIP}$).
• nalysis:
• (NDIP - ADIP): Correct definition of Fraction B3.

Correct option: (4) NDIP -ADIP

• Principles of Animal Bioenergetics:
• Heat of combustion of hydrogen is $\approx 34.2\text{ kcal/g}$, whereas carbon is $\approx 7.8\text{ kcal/g}$—over 4 times higher (True).
• Wide variations in the efficiency of utilizing Metabolizable Energy (ME) for different physiological functions ($k_m, k_l, k_g$) stem from differences in Heat Increment (HI) (True).
• Net Energy (NE) determination requires total animal calorimetry or comparative slaughter, making it significantly more difficult and expensive than ME determination (Statement C is False).
• Respiratory Quotients (RQ) below $0.70$ are observed during prolonged starvation due to ketogenesis and gluconeogenesis (True).
• Gross energy of combustible methane ($CH_4$) gas is $\approx 9.45 - 9.5\text{ kcal/L}$ ($13.3\text{ kcal/g}$) (True).
• nalysis:
• Statements (A), (B), (D), and (E) are true. Hence, Option 3 is correct.