what are the names and functions of three cell membrane protiens?

Question

pleas explain this in simple words


thanks

Answer 1

Here are three examples of the many many receptors in membranes.

1. Voltage-gated Na+ channels: these are proteins that detect voltage changes that are caused by membrane potential fluctuations. When the voltage across a membrane reaches a certain level (called a threshold potential), it causes a conformational change in the ion channel, thus opening the "voltage gate". This allows strong influx of sodium traveling down its concentration and charge gradient.

2. T-cell receptor: In order to develop adaptive immune function, T-cells must be presented with antigen in order to recognize something foreign (with the assistance of MHC proteins of course). The antigen is presented to T-Cell receptors embedded in membranes that recognize the given antigen, thus activating the T-cell.

3. Adrenergic receptor: An adrenergic receptor recognizes epinephrine in circulation. Epinephrine is synthesized by the adrenal gland during sympathetic stimulation, and is then released into circulation where it binds to adrenergic receptors. This binding to the adrenergic receptor activates a G-protein system, where a bound GDP is replaced by GTP on this G-protein molecule. This change causes the G protein to dimerize into subunits, including the G-alpha subunit. The G-alpha subunit then activates a protein called adenylyl cyclase which converts ATP into cAMP. cAMP then acts on transciption factors, upregulating (or down regulating) some gene product associated with the sympathetic nervous system (by epinephrine). For example, epinephrine acts on hepatocytes to upregulate gluconeogenesis enzymes and thus upregulate glucose secretion into plasma.

Answer 2

There are many proteins in the cell membrane. I guess you asking the general names of the proteins. There are : protein channels, carrier proteins, transmembrane proteins. These three are the most important ones.
Protein channels: they allow the molecules to diffuse from one side to another with their concentration gradient and this diffusion is called facilitated diffusion. It does not require any energy. Ex: glucose channels
Carrier proteins: Carry the molecules from one side to another side of the membrane, generally against concentration gradient. Therefore, it expends energy in the form of ATP: active transport. Ex: Na+/K+ pump
Transmembrane proteins: Appear only on one side of the membrane, usually on the extracellular side. Carbohydrate molecules are attached to these proteins and aid in there recognition of th type of cell.
Hope that helps!