Which of the following reagents is useful to prepare soluble... | Agrigyan

In milk, phospholipids (phosphatidylcholine, phosphatidylethanolamine, sphingomyelin) are concentrated almost entirely in the Milk Fat Globule Membrane (MFGM). During butter churning, the mechanical impact ruptures the fat globule membranes, and the polar membrane fragments are preferentially washed into the aqueous serum phase. Consequently, buttermilk contains the highest proportion of phospholipids (about $0.15\%$ to $0.20\%$ on a whole liquid basis, and up to $1.5\%$ to $2.0\%$ on a total lipid basis), far exceeding cream, butter, or anhydrous butter oil.

Option analysis:

• Cream: Lower phospholipid proportion relative to total lipids ($0.3\%$ to $0.4\%$).
• Butter: Most phospholipids are lost in the buttermilk during churning ($0.15\%$ to $0.2\%$).
• Butter oil: Minimal, as phospholipid-rich curd is separated during clarifying.
• Butter milk: Correct. Contains the maximum concentration of MFGM-derived polar phospholipids.

Ethylene ($C_2H_4$) is the natural gaseous phytohormone responsible for triggering fruit ripening. Under FSSAI regulations (Food Safety and Standards Act), the artificial ripening of fruits using harmful, toxic calcium carbide (acetylene gas) is strictly banned, whereas the controlled exposure to ethylene gas (up to a concentration of $100\text{ ppm}$) is legally permitted and recognized as safe for ripening bananas, mangoes, and other climacteric fruits.

Option analysis:

• Auxin: Incorrect. Plant growth hormone involved in cell elongation and apical dominance.
• Cytokinin: Incorrect. Hormone promoting cell division and delaying senescence.
• Papain: Incorrect. A proteolytic enzyme extracted from papaya latex.
• Ethylene: Correct. Legally permitted phytohormone for fruit ripening.

In the mammary secretory epithelial cell, lactose biosynthesis follows the pathway:
Blood Glucose -> Glucose-6-phosphate -> Glucose-1-phosphate -> UDP-Glucose -> UDP-Galactose (catalyzed by UDP-galactose 4-epimerase).
In the Golgi apparatus, Lactose Synthase (galactosyltransferase complexed with alpha-lactalbumin) transfers the galactose moiety from UDP-galactose directly to free unphosphorylated D-glucose, yielding free Lactose and UDP:
$\text{UDP-Galactose} + \text{D-Glucose} \rightarrow \text{Lactose} + \text{UDP}$.
Lactose-6-phosphate is never produced during mammalian lactose biosynthesis (it is an intermediate in bacterial lactose transport via the PEP-PTS system in lactic acid bacteria).

Option analysis:

• Lactose-6-phosphate: Correct (not an intermediate in mammary lactose biosynthesis).
• UDP-Galactose: Incorrect (key donor substrate intermediate).
• Glucose-1-phosphate: Incorrect (precursor in pathway).
• UDP-Glucose: Incorrect (precursor in pathway).