CNC Fundamentals of Nutrition Science 5

Question 1

Which vitamin is synthesized in the skin upon exposure to ultraviolet B (UVB) radiation and functions as a prohormone regulating calcium absorption?

Accepted Answer

Vitamin D

Answer

UVB radiation converts 7-dehydrocholesterol in the skin to vitamin D3 (cholecalciferol), which is then activated in the liver and kidneys to regulate intestinal calcium absorption.

Question 2

The essential amino acid that serves as a precursor to serotonin and melatonin synthesis is:

Accepted Answer

Tryptophan

Answer

Tryptophan is hydroxylated to 5-hydroxytryptophan (5-HTP) and then decarboxylated to serotonin, which can further be converted to melatonin in the pineal gland.

Question 3

In the context of energy balance, what term describes the energy expenditure associated with non-exercise physical activity such as fidgeting, posture, and daily movement?

Accepted Answer

NEAT (Non-Exercise Activity Thermogenesis)

Answer

NEAT encompasses all energy spent on physical activity that is not structured exercise, and can vary by up to 2,000 kcal/day between sedentary and active individuals.

Question 4

Which mineral is required for the synthesis of thyroid hormones T3 and T4, and its deficiency results in goiter?

Accepted Answer

Iodine

Answer

Iodine is incorporated into thyroxine (T4) and triiodothyronine (T3) by the thyroid gland; deficiency causes the gland to enlarge (goiter) in an effort to trap more iodine.

Question 5

The concept of 'nitrogen balance' is used to assess protein metabolism. A negative nitrogen balance indicates that:

Accepted Answer

Protein breakdown exceeds protein synthesis

Answer

Negative nitrogen balance occurs when nitrogen excretion (via urine, feces, skin) exceeds nitrogen intake, indicating net protein catabolism greater than anabolism.

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CNC Fundamentals of Nutrition Science 5