Problem 85 - Objective Biology for NEET

Question

The following are petide hormones except (a) Insulin (b) PTH (c) Thymosin (d) \(\mathrm{T}_{4}\)

Step-by-Step Solution

Answer

\(\mathrm{T}_{4}\) (Thyroxine)

Step 1: Understand Peptide Hormones

Peptide hormones are hormones made up of amino acids, some as few as three (tri-peptides), others as many as 200 (polypeptides). They are secreted by different glands in the body and bind to the receptors on the cell surface to bring about cell signaling.

Step 2: Classification of Given Hormones

(a) Insulin - It is a peptide hormone, secreted by beta cells of the pancreas. (b) PTH (Parathyroid hormone) - It is a peptide hormone, produced by the parathyroid gland. (c) Thymosin - It's also a peptide hormone, produced by the thymus gland. (d) \(\mathrm{T}_{4}\) (Thyroxine) - It is not a peptide hormone, but rather an amino acid-derived hormone, produced by the thyroid gland.

Key Concepts

Amino Acid-Derived Hormones

Hormones are chemical messengers in the body that help regulate physiological activities. Amino acid-derived hormones, also known as biogenic amines, are a unique class. Unlike peptide hormones, which consist of chains of amino acids, these hormones originate from single amino acids. Examples include epinephrine, norepinephrine, and thyroxine. Their chemical structure allows them to easily pass through cell membranes, directly affecting target cells by interacting with their receptors. This interaction triggers various biological responses, making amino acid-derived hormones essential for regulating functions such as metabolism and growth.

Insulin

Insulin is a crucial peptide hormone secreted by the beta cells of the pancreas. It plays a vital role in glucose metabolism, helping cells absorb glucose from the bloodstream to be used for energy. When you eat, insulin is released to lower blood sugar levels by facilitating the uptake of glucose by the body's cells, particularly those in the liver, muscle, and fat tissue. This process helps maintain stable blood sugar levels and is fundamental for energy regulation. Without proper insulin function, conditions like diabetes can arise, leading to severe health issues.

Parathyroid Hormone

Parathyroid hormone (PTH) is another essential peptide hormone, produced by the parathyroid glands located in the neck. Its primary function is to regulate calcium levels in the blood. When calcium levels drop, PTH is released to increase the breakdown of bone tissue, releasing calcium into the bloodstream. Additionally, it helps the kidneys in reabsorbing calcium and increases the activation of vitamin D in the intestine, aiding in more efficient calcium absorption from food. This hormone's regulation is crucial for maintaining the body's calcium balance, necessary for healthy bones and various physiological processes.

Thyroxine

Thyroxine, often abbreviated as T4, is an amino acid-derived hormone produced by the thyroid gland. It plays a pivotal role in metabolism, influencing how the body consumes energy. Thyroxine increases the metabolic rate of cells, thus affecting how fast or slow certain physiological processes occur, such as heart rate and digestion. The hormone is derived from the amino acid tyrosine and includes iodine, which is vital for its synthesis. Proper thyroxine levels are essential for overall energy balance and development. Abnormal levels can result in conditions like hypothyroidism or hyperthyroidism, impacting general health and well-being.