MCM 2-5 Signaling I

Question 1

Ligands bind to receptors via what type of interaction?

what effect can this binding have on the receptor?

Answer 1

ligands bind receptors non-covalently which allows for interaction to be reversible

this binding can induce a conformation change in the receptor which can change its activity or affinity for another molecule

Question 2

if the ligand binds a receptor on the outside of the cell….

Answer 2

secondary messengers will carry the message through the cell.

These allow for signal relay and subsequent amplification

Question 3

benefits of secondary messengers?

Answer 3

allow for signal relay and subsequent amplification

amplification of signals allows for

• smaller number of receptors and signal molecules to be needed.
• shorter response time

Question 4

steps leading up to signal transduction

Answer 4

1. ligand receptor binds
2. signal is amplified by secondary messenger
3. amplification causes the signal to be transduced more quickly

the activation of a single receptor can lead to

Question 5

the activation of a single receptor can lead to

Answer 5

formation of MANY secondary messenger molecules —> multiple coordinated responses or a single/amplified response.

Question 6

what will generally cause the signal to be stronger?

Answer 6

greater concentration of signal molecules and greater density of receptors

Question 7

what factors contribute to the exact reactions observed with individual receptors and their ligands?

Answer 7

signal molecule half life and receptor affinity for ligand

short half life means the molecule may need to be synthesized at a faster rate to adequately interact with receptor

if receptor affinity is low, the ligand again may need to be produced more rapidly for sufficient interaction to occur

Question 8

signal molecule concentration is controleld by

Answer 8

how fast molecule is produced and degraded

typically degredation rate is constant, but synthesis rate can vary

Question 9

fast synthesis + fast degredation

Answer 9

strong signal

Question 10

slow synthesis + fast degredation

Answer 10

weak signal

Question 11

degredation speed of hormones

Answer 11

hormones are degraded slowly, signal takes a long time to decrease. hormones are long acting signals

Question 12

if there are more receptors…

Answer 12

there are more spots for ligand to bind and illicit response

Question 13

if a receptor has a higher affinity than another…

Answer 13

it will take less ligand to bind it

Question 14

if a cell is being repeatedly exposed, it will show ______

Answer 14

adaptation via desensitizing receptors, degrading receptors, or regulating receptor synthesis

Question 15

how do nuclear receptors regulate gene expression

Answer 15

nuclear receptors are intracellular receptors that bind steroid hormones

once hormone binds, inhibitor released and the DNA binding domain of the receptor is exposed, allowing for regulation of genes with matching promoter sequences

some genes will require addiitonal parter TF to be activated. Therefor, the partner TF that a cell produces will determine the genes that will be affected by a given signalling pathway.

Question 16

signals may pass from ________, but ussually come from ________. example?

Answer 16

cell to cell directly (gap), but ussually come from outside of the cell, like in the endocrine system.

Question 17

describe the signaling molecules and receptors of endocrine system

Answer 17

very low concentration signals, requiring high affinity receptors

Question 18

describe the signaling molecules and receptors of neurotransmitter systems

Answer 18

very high concentration signals (neurotransmitters), with very low affinity receptors on post-synaptic cells

Question 19

rank the affinity of receptors in the neurotranmitter, paracrine, and endocrine systems

Answer 19

highest affinity - endocrine
medium affinity - paracrine
lowest affinity - neurotransmitters (due to high levels of NT released)

Question 20

steroid hormones must be able to…

Answer 20

diffuse across the membrane

Question 21

affinity

Answer 21

the strength with which a receptor will bind its ligand

Question 22

half-life

Answer 22

the amount of time it takes for the body to halve the amount of a particular signal molecule in circulation

Question 23

adaptation

Answer 23

process of changing a cellular response to a signal of constant concentration (like reducing receptor density/affinity)

Question 24

autocrine

Answer 24

cell secretes signal taken up by receptor on same cell

Question 25

paracrine

Answer 25

cell secretes signal taken up by neighboring cell

Question 26

synaptic

Answer 26

signal processing specific to nerve cells and postsynaptic cells. NT secreted by nerve cell, travels across synaptic cleft, taken up by receptors on post-synaptic cell

high concentration signal, low affinity receptor

Question 27

endocrine

Answer 27

cell secretes signal into blood stream to be distributed systemically.

• very low concentration signal
• very high affinity receptor

Question 28

ligand gated

Answer 28

membrane protein channel that opens in response to binding a ligand. can be on cytosolic or extracellular side of membrane

Question 29

primary response gene

Answer 29

genes activated by intracellular signals from a hormone-occupied receptor. hormone turns these genes on

Question 30

eicosinoid

Answer 30

hydrophobic signal subclass, made by fatty acids that bind surface receptors rather than cytoplasmic proteins

(steroid hormones all work by binding cytoplasmic proteins to be taken into the cell).

Question 31

Describe the similarities and differences between sensory, paracrine, endocrine, and synaptic signaling.

Answer 31

All involve extracellular molecules binding to cellular receptors. Sensory signals originate outside the organism, endocrine originate in one part of the body and move through the bloodstream to another part, paracrine signals travel within a tissue, and synaptic signals only travel across the synaptic cleft.

Question 32

Sensitivity of a cell to ligands can be decreased after prolonged exposure. What is this process called, and what mechanisms may be involved?

Answer 32

This process is called adaptation and it may involve changes in gene expression, receptor turnover, or second messenger systems.

Question 33

Aspirin and other anti-inflammatory drugs block signaling of some members of the ____________ family of signaling molecules. What kind of receptors (cell surface or intracellular) do they bind to?

Answer 33

Aspirin is anti-inflammatory and blocs eicosinoid signaling, which is important in many inflammation responses.

Question 34

Explain the role of heterodimer formation in steroid hormone signaling and its importance for determining the different responses if different tissues to the same hormone.

Answer 34

Heterodimeric transcription factors formed by nuclear receptors allow different cell types to respond differently to the same steroid hormone, because each cell type can express a different partner to make a different heterodimer and potentially elicit different responses.