Question

Match the Column I with Column II: Column I A. Peptide, polypeptide protein hormones B. Steroid C. Iodothyronines D. Amino acid derivatives Column II 1\. Epinephrine 2\. \(\mathrm{T}_{3}\) and \(\mathrm{T}_{4}\) (thyroid hormones) 3\. Cortisol, testosterone, estradiol, progesterone, aldosterone 4\. Pituitary hormones, pancreatic hormones, hypothalamic hormone (a) \(\mathrm{A}-1, \mathrm{~B}-2, \mathrm{C}-3, \mathrm{D}-4\) (b) A-4, B-3, C-2, D-1 (c) \(\mathrm{A}-4, \mathrm{~B}-3, \mathrm{C}-1, \mathrm{D}-2\) (d) \(\mathrm{A}-1, \mathrm{~B}-4, \mathrm{C}-3, \mathrm{D}-2\)

Short answer

The correct option is (b) A-4, B-3, C-2, D-1 as peptide, polypeptide protein hormones match with pituitary hormones, pancreatic hormones, hypothalamic hormone, steroid with cortisol, testosterone, estradiol, progesterone, aldosterone, iodothyronines with \(\mathrm{T}_{3}\) and \(\mathrm{T}_{4}\) (thyroid hormones) and amino acid derivatives with epinephrine.

Step-by-step solution

Identify the Type: Peptide, polypeptide protein hormones

Peptide, polypeptide and protein hormones include all hormones derived from amino acids that aren't classified as a single amino acid derivative. They are water-soluble and are unable to pass through the plasma membrane. Some examples of these are the hormones from the pituitary gland, pancreas, and hypothalamus. So, A matches with 4.

Identify the Type: Steroid

Steroid Hormones are derived from cholesterol and are lipid soluble. This quality lets them to pass through cell membranes and get direct access to the DNA within cells. Cortisol, testosterone, estradiol, progesterone, and aldosterone are all examples of steroid hormones. So, B matches with 3.

Identify the Type: Iodothyronines

Iodothyronines are thyroid hormones, containing iodine. Triiodothyronine (T3) and thyroxine (T4) are included in this category. So, C matches with 2.

Identify the Type: Amino acid derivatives

Amino acid derivative hormones are derived from amino acids. Epinephrine is an amino acid derivative hormone. So, D matches with 1.

Key concepts

Hormones Classification

The classification of hormones is an essential concept in understanding the endocrine system. Hormones can be broadly categorized based on their chemical structure and solubility, which determines how they travel in the body and where they have their effects. This classification is crucial because it illustrates how different hormones interact with their target cells.

• Peptide Hormones: These consist of chains of amino acids and are usually water-soluble, which prevents them from crossing cell membranes.
• Steroid Hormones: Derived from cholesterol, these are lipid-soluble, allowing them to easily pass through cell membranes.
• Iodothyronines: Also known as thyroid hormones, these are unique due to their inclusion of iodine in their structure.
• Amino Acid Derivatives: Originating from single amino acids, these hormones have diverse properties.

Peptide and Polypeptide Hormones

Peptide and polypeptide hormones are a critical group within the endocrine system. These hormones are composed of chains of amino acids and range from small molecules like those with just a few amino acids to complex polypeptides. One of their key features is their water solubility, which prevents them from traversing the lipid-rich membranes of cells directly. This means they usually bind to receptors on the surface of the target cells.

Because they cannot enter cells, peptide hormones must initiate changes within the target cells through a secondary messenger system. Some well-known examples include hormones produced by the pituitary gland like growth hormone (GH) and the pancreatic hormone insulin.

These hormones play a pivotal role in regulating many vital processes such as growth, metabolism, and reproduction.

Steroid Hormones

Steroid hormones are an integral part of the endocrine system due to their ability to easily cross cell membranes. This is because they are lipid-soluble, a characteristic that allows them to pass through the lipid bilayer of the plasma membrane effortlessly. Derived from cholesterol, these hormones are known for regulating a wide range of physiological functions. Steroid hormones include sex hormones like testosterone and estradiol, as well as adrenal gland hormones like cortisol and aldosterone.

Mechanism of Action

Steroid hormones typically act by directly influencing gene expression. They enter the cell and bind to specific intracellular receptors, forming a hormone-receptor complex that travels to the nucleus. Once inside the nucleus, this complex can bind to DNA and regulate the transcription of specific genes, thus altering the protein synthesis within the cell.

This fundamental mechanism explains why steroids can have long-lasting effects on cells and tissues, influencing everything from metabolism to immune function.

Amino Acid Derivative Hormones

Amino acid derivative hormones are molecules that are structurally derived from single amino acids. They have unique properties depending on their specific structure and the modifications they undergo. Epinephrine, also known as adrenaline, is one example of an amino acid derivative hormone that plays a critical role in the 'fight or flight' response.

These hormones can be either water-soluble or lipid-soluble and may bind to receptors on the cell surface or within the cell itself, depending on their nature. This offers them a diverse range of functions and mechanisms of action in the body.

Other notable examples include thyroid hormones such as triiodothyronine (T3) and thyroxine (T4), which are iodinated derivatives of the amino acid tyrosine. They are crucial for regulating metabolism and energy balance in the body. Their precise synthesis and release are tightly controlled to maintain homeostasis.