Test: Mechanism of Hormone Action (October 6) - NEET MCQ

Steroid hormones, being hydrophobic molecules, diffuse freely into all cells and act within the cell. Steroid hormones enter the cytoplasm of a target cell and bind with specific receptor proteins (mobile). Hormone-receptor complex then diffuses into nucleus and activates specific genes to form a new protein. This protein carries out the specific response for a particular steroid hormone.

Hormones recognise target organs by the presence of specific receptor molecules on the plasma membrane of target organs, if these receptor molecules are removed then a hormone will be unable to give any response.

FSH  is a proteinaceous hormone. It does not enter its target cells, thus, it never reaches to cytoplasm. Instead, it binds to the receptor present on the cell membrane and activates a membrane bound enzyme that causes conversion of ATP to cAMP. This then alters the activities of enzymes in the cytoplasm.

Estrogen and testosterone being steroid hormones are soluble in lipids, therefore they can cross the plasma membrane and bind to the cytoplasmic receptors to trigger their action.

Cortisol and testosterone are steroid hormones and are easily soluble in lipids. They regulate gene expression by the interaction of hormone receptor complex with the genome. So, these easily pass through the cell membrane of the target cell and bind to a receptor inside it.

Hormone receptors are proteinaceous in nature. These receptors are located on or inside the cells. It is where a hormone binds on a cell. The binding of the hormone signals the cells to perform their tasks.

Receptors are the structures of the cell to which hormones bind and form hormone-receptor complex. They do not disintegrate. Receptors are specific for each hormone. Intracellular receptors are present in the cytoplasm.

Glucagon is a peptide hormone. It is synthesized and secreted by the alpha cells of the pancreas. The function of glucagon is to break glycogen into glucose. This raises the blood sugar level.

Hypothalamic hormones are peptides. They are secreted by the hypothalamus. Peptides, steroids, iodothyronines and amino acid derivatives are the different categories of hormones.

Adrenaline or epinephrine is derived from amino acids. It is secreted by the outer cortex of the pair of adrenal glands. It is the emergency hormone secreted during a fight or flight response.