1. Compare and contrast steroid and non-steroid hormones. Specifically address h

ID: 3505392 • Letter: 1

Question

1. Compare and contrast steroid and non-steroid hormones. Specifically address how each category is carried in the blood and how each interacts with the cellular membrane of target cells. Why do these two categories of steroid interact with plasma membranes in different ways?

2. Provide a brief (no longer than three sentence) description of how cortisol is released and elicits a response within a target cell.

3. Provide a brief (no longer than three sentence) description of how antidiuretic hormone is released and elicits a response within a target cell.

Explanation / Answer

Steroid Hormones

Non Steroid Hormones

Steroid hormones bind to a receptor that will activate or inhibit a gene that activates a protein. This protein will then induce the metabolic change.

Binding of non-steroid hormones to receptors activates signal enzymes or membrane transport systems. These systems activate a second messenger that have chemicals that react with the hormone.

The receptors can be present intracellularly in cytoplasm or on cell membrane

The receptors are membrane bound.

Steroid hormones are derived from cholesterol and can easily diffuse through cell membrane.

These hormones are not lipid soluble. They cannot diffuse easily through the cell. They can be peptide or amino acid derived. They are synthesized as prehormones, which can be cleaved to prohormones in endoplasmic reticulum and cleaved in storage vesicles to form active hormones.

Steroid hormones are transported to the different tissues bound to plasma proteins via blood circulation.

They are transported via blood circulation without binding to carrier proteins. They diffuse through the interstitial tissues at target site.

Steroid hormones have a steran nucleus and are made up of 4 carbon rings.

They are mostly amino acid or protein derived and lack steran nucleus. Size ranges from 3-200 amino acids

Examples: Cortisol, aldosterone, oestrogen, progesterone, testosterone

Example: LH, FSH, ACTH, TSH, growth hormone, parathyroid hormone, insulin

They bind to receptors in cell membrane or cytoplasm and are internalized. The hormone receptor complex enter the nucleus where it binds to hormone receptor element on gene on DNA. This activates transcription of these genes and increased proteins synthesis.

They bind to specific cell membrane receptors and activate second messenger systems such as cAMP, G proteins, PIP system, calmodulin, tyrosine kinase. As a result, cellular response is induced.

Comparison: Both hormones have specific receptors to which they bind. Both are secreted by endocrine glands.

Steroid are derived from cholesterol and are fat soluble. Hence, they can easily diffuse through the hydrophobic core of the plasma membrane and enter the cytoplasm. Here, they bind to cytoplasmic receptors. Some steroid hormones can also bind to receptors in plasma membrane and the hormone receptor complex can be internalized into cytoplasm.

On the other hand, non steroid hormones lack the steran nucleus and are water soluble. Hence, they cannot pass through the hydrophobic core of plasma membrane. Therefore, they can only bind to receptors in cell surface.

2. Cortisol, a glucocortocid hormones involved in stress response, is secreted by the adrenal gland into blood in response to adrenocorticotrophic hormone produced by the pituitary. Cortisol released from its transcortin bound state in blood diffuses into the target cell and enters the cytoplasm. In the cytoplasm, cortisol binds to a specific receptor and the cortisol- receptor complex enter the nucleus, where it bind DNA and activates or inhibits the transcription of target genes.

3. Antidiuretic hormone or vasopressin, a nine amino acid hormone, is produced by the supraoptic and paraventricular nuclei of hypothalamus, and transported to the posterior pituitary via neurophyseal capillaries. It is stored in hypothalamic neurons and released via secretory vesicles, in blood circulation in response to changes in plasma osmolarity sensed by hypothalamic osmoreceptors. ADH binds to the distal convoluted tubules and collecting ducts of the kidneys and increases the transcription and incorporation of aquaporin -2, a water transport protein in plasma membrane, resulting in absorption of water from urine to cause increase plasma osmolarity.