Which of the following is the primary function of the Smooth Endoplasmic Reticulum (SER)?
A. Lipid synthesis and detoxification
B. ATP production
C. Protein synthesis
D. Protein modification
Answer: Option A
Solution (By JKExamLibrary)
The Smooth Endoplasmic Reticulum (SER) lacks ribosomes on its surface and is primarily involved in the synthesis of lipids, including sterols and phospholipids. In liver cells, SER also plays a crucial role in the detoxification of poisons and drugs. Rough ER, which has ribosomes, is responsible for protein synthesis.
Explanation:
Vitamin E (tocopherol) is a lipid-soluble antioxidant that scavenges free radicals and prevents lipid peroxidation of cell membranes. Vitamin C is water-soluble antioxidant, A is for vision, K for clotting.
Explanation:
Photolysis of water occurs at the manganese cluster of photosystem II, releasing electrons, protons, and oxygen. The electrons replace those lost by P680. Photosystem I reduces NADP⁺. Cytochrome b6f transports electrons between the two photosystems. Thus, water splitting is a hallmark of PSII.
Explanation:
Nitrification is a two-step process in the nitrogen cycle where ammonia is oxidized to nitrates. First, ammonia (NH3) is converted to nitrites (NO2-) by bacteria like Nitrosomonas. Then, nitrites are converted to nitrates (NO3-) by bacteria like Nitrobacter. Nitrates are the primary form of nitrogen absorbed by plants. Denitrification is the reverse process, converting nitrates back to nitrogen gas.
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