Biochemistry of Cellular Receptors

Question 1

For each signaling system, give its messenger
nervous system
endocrine system
immune system

Answer 1

NT; hormones; cytokines

Question 2

The Eicosanoids: Prostaglandins, thromboxjnes and leukotrienes control cellular functions in response to what?

Answer 2

injury

Question 3

Almost every cell in the body produces Eicosanoids. True or false?

Answer 3

true

Question 4

Eicosanoids affect what cells?

Answer 4

the cells that produce them or their neighboring cells

Question 5

What are growth factors

Answer 5

polypeptides that function through stimulation of cellular proliferation e.g EGF, FGF

Question 6

Define signal transduction

Answer 6

chemical messenger binds to receptor, signal it’s carrying must be converted into an intracellular response

Question 7

Tyrosine kinase receptors are an example of what type of receptor

Answer 7

enzyme-linked receptor

Question 8

Jak-Stat receptors are what type of receptor

Answer 8

cytokine receptor

Question 9

In regards to the ion-channel receptor: Nicotinic acetylcholine receptor, ___ is the NT at neuromuscular junctions

Answer 9

acetylcholine

Question 10

Nicotinic acetylcholine receptor are found where?

Answer 10

plasma membrane of muscle cells

Question 11

As acetylcholine binds to the receptor, describe what happens

Answer 11

conformation change opens the narrow portion of the channel (the gate), allowing Na+ to diffuse in and K+ to diffuse out.

Question 12

Tyrosine Kinase receptors generally exist in the ____ as ___ with a single membrane-spanning helix

Answer 12

membrane; monomers

Question 13

In regards to the tyrosine kinase receptor, one molecule of ___ generally binds two molecules of the receptor and promotes their ___

Answer 13

GF; dimerization

Question 14

In regards to the tyrosine kinase receptor, once the receptor dimer has formed, the intracellular tyrosine kinase domains of the receptor ___ each other on certain tyrosine residues

Answer 14

phosphorylate

Question 15

In regards to the tyrosine kinase receptor, the phosphotyrosine residues form specific binding sites for what?

Answer 15

signal transducer proteins

Question 16

Serine-Threonine kinase receptors are used by proteins in what superfamily?

Answer 16

transforming growth factor (TGF)

Question 17

Serine-threonine kinase receptors associate with proteins from the sad family which are ___ ___ transcription actors

Answer 17

gene specific

Question 18

The superfamily of TGF is involved in what?

Answer 18

tissue repair, immune regulation, and cell proliferation

Question 19

The Jak-STAT receptor is used by cytokines to regulate what?

Answer 19

proliferation of certain cells

Question 20

True or false? The Jak-STAT receptor has no intrinsic kinase activity, but it binds the tyrosine kinase Jak

Answer 20

true

Question 21

STAT is phosphorylated by Jak which causes what?

Answer 21

STAT’s dimerize and move to nucleus where they activate transcription

Question 22

____ is the guanosine analogue of ATP and is involved in G-protein coupled receptors

Answer 22

GTP

Question 23

Small G-protiens related to the ___ oncogene are involved in vesicle transport in cells, interactions between the cytoskeleton and cell membrane and cell growth

Answer 23

ras

Question 24

All the heterotrimeric G protein-coupled receptors are proteins that span the cell membrane ___ times

Answer 24

7

Question 25

When the signal reaches a G-protein, the protein exchanges GDP for ___

Answer 25

GTP

Question 26

The resting state of a G-coupled receptor is achieved when GTPase converts GTP to ___

Answer 26

GDP

Question 27

Messengers that use intracellular receptors must be ___ molecules that are able to diffuse through the plasma membrane

Answer 27

hydrophobic

Question 28

Lipophilic hormones that use intracellular gene-specific transcription factors include the ____ hormones, ___ hormone, ____ acid and vitamin ___

Answer 28

steroid; thyroid; retinoic; D

Question 29

In regards to lipophilic hormone receptors, cytosolic (subclass-1) receptors are in the cytosol bound to ___ ___ proteins

Answer 29

heat shock

Question 30

When a hormone binds to a cytosolic receptor, the heat shock protein is displaced. What happens now?

Answer 30

hormone-receptor complex moves to nucleus and alters transcription

Question 31

Sex steroids generally fall into the category of ___ receptors

Answer 31

cytosolic

Question 32

These receptors are a type lipophilic hormone receptors found within the nucleus, not bound to hsps.

Answer 32

Nuclear (subclass-2) receptors

Question 33

Binding of the hormones to nuclear receptors induces a conformation change (activation). What happens next? Give some examples

Answer 33

transcription is altered; thyroid hormone, retinoids, vitamin-D

Question 34

Define down-regulation

Answer 34

when a hormone or NT is present in excess, the number of active receptors generally decreases

Question 35

Define up-regulation

Answer 35

in the presence of a deficiency of the chemical messenger, there is an increase in the number of active receptors

Question 36

Define internalization

Answer 36

in the case of receptors in the membrane, ligands bind to their receptors, and the ligand-receptor complexes move laterally in the membrane to coated pits, where they are taken into the cell by endocytosis

Question 37

This is a type of down regulation in which receptors are chemically modified in ways to make them less responsive

Answer 37

desensitization

Question 38

Ligands that bind to receptors and cause a maximal response are often termed full ____

Answer 38

agonists

Question 39

Ligands that evoke a sub maximal response, even when filling all the receptors are termed ___ ___

Answer 39

partial agonists

Question 40

Define antagonist

Answer 40

some ligands bind to receptors with high affinity, yet elicit no response ex: tamoxifen

Question 41

The affinity of a ligand to the receptor is measured using ___

Answer 41

RRA (radio receptor assay)

Question 42

____ analysis will give the affinity of a ligand

Answer 42

scatchard

Question 43

A disease in which antibodies produced attack thyroid stimulating hormone receptors is called what?

Answer 43

grave’s disease

Question 44

A disease in which antibodies attack nicotinic acetylcholine receptors is called what?

Answer 44

myasthenia gravis

Question 45

What are the symptoms of myasthenia gravis?

Answer 45

muscle weakness, fatigue