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Why some steroid hormones do not require a membrane receptor?
Some steroid hormones are able to pass directly through cell membranes due to their lipid-soluble nature. Once inside the cell, they bind to intracellular receptors located in the cytoplasm or nucleus. This binding initiates a cascade of cellular responses, ultimately regulating gene expression and affecting various cellular functions.
Where do the hormones move through the body?
....b/c hormones are hydrophobic and therefore do not dissolve in the plasma, they require proteins (ie albumin) to journey through the bloodstream. Once they reach their target cells they easily diffuse through the cell membrane due to their hydrophobicity and bind to their receptor within the cytoplasm. This complex (receptor-hormone complex) then travels to the nucleus of cell to regulate transcription to alter the amount of protein that is made.
How does nitric oxide cross the plasma membrane?
Nitric oxide can diffuse freely across the plasma membrane due to its small size and lipophilic nature. It does not require a specific transporter or receptor for entry into cells.
If hormones travel in the bloodstream why don't all tissues respond to all hormones?
The tissue/cells need a receptor that can interact with that hormone in order to respond to it. This receptor may be on a cell membrane, inside the cell, or even inside the nucleus (in the case of steroid hormones, for example.) Like many organic chemicals in the body, they have structures which result in certain parts of the molecule being presented to cells (active sites). Because cells and tissue have different structures as well, only certain cells will react to the presence of a particular hormone. Many hormones have antagonist hormones that cause an opposite effect. This helps control negative feedback when the target organ's hormone levels are too high.
Why can steroid and thyroid hormones but not amino acid-based hormones move across cell membranes?
Steroid and thyroid hormones are lipid soluble, allowing them to diffuse directly across cell membranes. Amino acid-based hormones are water soluble and require specific receptor-mediated mechanisms to enter cells.
Why is a second messenger not necessary in a steroid hormone?
Steroid hormones act in the transcriptional level in the nucleus of a cell, due to their ability to travel through cell membranes (hydrophillic). Second messengers are necessary for hormones that cannot penetrate cell membranes (peptides).
How does receptor mediated endocytosis differ from receptor mediated facilitated diffusion?
endocytosis is when large substances are taken into the cell(does not require protien carriers or protien channels) .whereas f.diffusion is movement of "hydrophilic" molecules or "ions" in and out of cell through a protein carrier present in the cell membrane.
Does exocytosis require fusion of vesicles with the plasma membrane?
Yes, exocytosis involves the fusion of vesicles with the plasma membrane, releasing the vesicle's contents outside the cell. This process allows cells to secrete molecules such as proteins, neurotransmitters, and hormones.
Which hormone affect only certain cells?
Because they only activate target cells that have special receptors that only work when that specific hormone attaches to it.
What is the difference of g-protein receptor system and tyrosine kinase receptor?
Receptor tyrosine kinases do not require the use of second messengers while G protein-coupled receptors need.
What process does not require energy to move a substance across a membrane?
Osmosis because it is the equalization of pressure.
What can pass through an animals membrane?
Small molecules like oxygen, carbon dioxide, and water can pass through an animal's membrane via simple diffusion. Larger molecules like glucose may require specific transport proteins to facilitate their movement across the membrane.
