RECEPTORS: LEARN THIS

Question 1

Describe regulated intramembrane proteolysis

Answer 1

This is the breakdown of proteins using a metalloproteinase. When the signal molecule binds tacid can enter th eo the receptor, the intramembrane protein is broken down and this translocated into the nucleus to bind to the DNA to alter gene transcription

Question 2

Describe Eiscanoid receptors

Answer 2

When the signal molecule binds to the receptor, this activate phospholipase A2 which breaks down phospholipids of the cell membrane into arachnadonic acid. This acid can enter the cyclooxygenase pathway to produce prostaglandins increase vascular actions and to help with uterine contractions for childbirth

Question 3

Describe the Gs (Gi) protein coupled receptor

Answer 3

The name refers to the response of the second messenger not of the whole cell. In the membrane there is a G-protein coupled receptor and there is a G protein possible associated with it and this consists of three subunits (α, β, gamma). The g-protein are definitely associated with the signal molecule binds, When it binds, the GDP on the α subunit is replaced by GTP which allows this subunit to dissociate. The α subunit can activate adenylyl cyclase which converts ATP to cyclic AMP which acts as a second messenger and has effects in the cell. One of these is that it activates protein kinase A which can phosphorylate CREB which acts as a transcription factor to increase the production of genes

Question 4

Describe the Gq protein coupled receptor

Answer 4

In the membrane there is a G-protein coupled receptor and there is a G protein possible associated with it and this consists of three subunits (α, β, gamma). The g-protein are definitely associated with the signal molecule binds, When it binds, the GDP on the α subunit is replaced by GTP which allows this subunit to dissociate. The α subunit activates phospholipase C which forms the products IP3 and DAG. IP3 leaves the membrane and travels to the endoplasmic reticulum to cause the opening of Ca2+ channels which allows Ca2+ to leave the ER to cause Ca2+ dependent processes. The IP3 activates protein kinase C which activates proteins by phosphorylating them

Question 5

What does IP3 stand for?

Answer 5

inositol triphosphate

Question 6

What does DAG stand for?

Answer 6

diacylglycerol

Question 7

Describe enzymes linked receptors

Answer 7

There is a 2 subunit receptor within the membrane and when the signal molecule binds, it stabilises the intracellular portion of the receptor to become an active catalytic domain. This can then activate enzymes and other proteins inside the cell

Question 8

Give an example of an enzyme linked receptor

Answer 8

a tyrosine kinase associated receptor

Question 9

Describe tyrosine kinase associated receptors

Answer 9

These are examples of an enzyme linked receptor. These have a tyrosine kinase attached to them (eg JAK kinase) which phosphorylates tyrosine within proteins to activate the proteins

Question 10

Describe receptor tyrosine kinases

Answer 10

These are receptors which have tyrosine kinase as an integral part of the receptor. This tyrosine kinase phosphorylates tyrosine within proteins to activate the proteins

Question 11

Describe metabotropic receptors

Answer 11

An example of metabotropic receptors are G-protein coupled receptors. This is when there is a receptor within the membrane and an associated G-protein consisting of 3 subunits (α, β and gamma). It is unclear whether the receptor and the G-protein are associated without the signal molecule being bound but as soon as the signal molecule binds, the two are definitely associated. The GDP bound to the α subunit breaks off and is replaced by GTP which allows the disassociation of the α subunit from the complex. The α subunit can go on to do other things such as causing the opening of an ion channel

Question 12

Describe ionotropic receptors

Answer 12

These are receptors which have an ion channel as an integral part of the receptor. When the signal molecule binds, there is a confirmation change which opens the ion channel and allows ions to flow in across the membrane

Question 13

Describe the glutamate receptor

Answer 13

I think this is an example of an ionotropic receptor. There are 3 transmembrane domains and 4 subunits and different combinations of the subunits will cause different properties to the receptor. . This is an excitatory receptor because when it opens, Na+ or Ca2+ ions can enter

Question 14

What are the 3 different examples of glutamate receptors?

Answer 14

Kianate
NMDA
AMPA

Question 15

Describe the cys-loop receptor

Answer 15

I think this is an example of an ionotropic receptor. There are 4 transmembrane domains and 5 subunits and different combinations of the subunits will cause different properties to the receptor. . This can be an excitatory receptor if Na+ or Ca2+ ions enter, inhibitory if Cl- enter or K+ leaves

Question 16

What are the five different types of cys-loop receptor?

Answer 16

GABA, serotonin, glycine, ACh, purines

Question 17

What is the name of the ACh cys-loop receptor?

Answer 17

nicotinic receptor

Question 18

What is the name of the serotonin cys-loop receptor

Answer 18

5-HT3

Question 19

What is the name of the purine cys-loop receptor?

Answer 19

P2X receptor

Question 20

Describe the way that NO is synthesised and released

Answer 20

Arginine is converted to citruline via the enzyme nitric oxide synthase and NO is a biproduct of this reaction. NO diffuses into the postsynaptic cell to act on soluble guanylyl cyclase which converts GTP to cyclic GMP

Question 21

Describe thyroid signalling

Answer 21

T3 and T4 diffuse into the cell because they are both lipophilic. T4 is often converted to T3 inside the cell. They travel into the nucleus and bind to the thyroid hormone receptor to make a complex with three parts: the hormone, the receptor and a cofactor to the receptor called retinoid X receptor. This complex binds to the DNA and acts as a transcription factor to increase the production of genes involved in metabolism

Question 22

What is another name for T3?

Answer 22

tri-iodothyronine

Question 23

what is another name for T4?

Answer 23

thyroxine

Question 24

Describe steroid receptors

Answer 24

Because steroids are lipophilic, they can diffuse into the cell. Steroids bind to either cytoplasmic receptors or nuclear receptors. If they bind to cytoplasmic receptors, they translocate into the nucleus and bind to DNA to alter gene transcription