The element that is a component of the vitamin B₁₂ molecule is:
A. Cobalt
B. Iron
C. Magnesium
D. Zinc
Answer: Option A
Solution (By JKExamLibrary)
Vitamin B₁₂ (cobalamin) contains a cobalt ion at the center of its corrin ring. It is the only vitamin that contains a metal. Iron is in heme, zinc in enzymes, magnesium in chlorophyll.
Explanation:
Oxytocin, released from the posterior pituitary, causes contraction of myoepithelial cells in mammary alveoli, forcing milk into ducts (let-down reflex). Prolactin stimulates milk synthesis.
Explanation:
Cuscuta (dodder) is a total stem parasite that wraps around the host plant and absorbs nutrients through haustoria. It lacks chlorophyll and leaves. Mimosa is sensitive plant, Nepenthes is insectivorous, Aloe vera is a succulent. Parasitic plants derive some or all of their nutrition from other living plants. Cuscuta is economically important as a weed.
Explanation:
Vitamin K is required for the gamma-carboxylation of clotting factors II, VII, IX, and X, including prothrombin. Deficiency leads to prolonged clotting time and hemorrhagic disorders.
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