Cell Signaling Quiz One

Question 1

Three parts of a signaling pathway

Answer 1

Reception, transduction and response

Question 2

Reception

Answer 2

Receptor binds signal

Question 3

Transduction

Answer 3

Passing of message

Question 4

Response

Answer 4

Some action taken by the cell

Question 5

Sites of response in signaling pathways?

Answer 5

Nucleus, vesicles, cytoplasm, other bits of endomembrane system, PM, cytoskeleton

Question 6

Different outcomes of signal molecules depend on different cell types.

Answer 6

Signaling molecule may activate multiple pathways
May act in concentration dependent manner
No signal: cell does X
Some signal: cell does Y
Lots of signal: cell does Z

Question 7

What is the key to signaling?

Answer 7

Change
Change in concentration of intracellular signaling molecule (Ca2+, BMP, cAMP, cGMP, IP3, etc…)
Change in protein activity (activation/deactivation or increase/decrease in activity)

Question 8

How do we get change in protein activity?

Answer 8

Conformational change and location

Question 9

Examples in change in conformation of proteins?

Answer 9

Accessibility of active site
Dissociation from binding partner
Formation of higher-order complex
exposure of other regulating element
Degradation sequence exposure (leads to protein destruction)

Question 10

Examples of change in protein activity location?

Answer 10

Nuclear import/export (nucleus vs. cytoplasm)
Membrane-bound vs. cytoplasmic

Question 11

What is the key to signaling working properly?

Answer 11

Specificity
Signaling molecule binds receptor (right molecule binds the right receptor)
Transduction is specific
Outcome is specific

Question 12

Characteristics of a signaling molecule?

Answer 12

Small (permeability and diffuses easily)
Lifespan requirements
Must be able to be released quickly (Can accomplish this with either 1. Synthesize, sequester, and release or 2. rapid synthesis
Therefore it is not a protein since transcription takes time.
Therefore is ither an ion or a molecule created by a catalytic reaction

Question 13

How does the PKC and CaM-KII pathway get activated at the right time when they both need Ca2+ to work. How do they not activate one another when Ca2+ is present?

Answer 13

Scientists are not sure however:
Specific pathways have different molecules in specific areas of the cytoplasm
Therefore cytoarchitecture may play a role in this activity
Perhaps cytoplasm is compartmentalized

Question 14

Signal molecules

Answer 14

Extracellular binders
Intracellular binders

Question 15

Hormones

Answer 15

Part of the endocrine system
water soluble
small, hydrophilic, cannot cross PM

Question 16

Histamine

Answer 16

mast cells, promotes blood vessel dilation
has a negative charge since it has an N2 on it

Question 17

Epenephrine

Answer 17

Adrenal medulla
Rapid response when more energy is required
Has places for positive and negative charges

Question 18

peptide hormones

Answer 18

vascular system
water soluble
vacuoles and secretory vesicles (get sent out and to exit cell space
Release is usually initiated by a Ca2+ spike (fastest way to do anything at all in signaling)

Question 19

Insulin and glucagon

Answer 19

Insulin:
Most common peptide hormone
peptide synthesized as a pre-protein called proinsulin
Undergoes proteolytic cleavage to mature into insulin (It attaches to receptors on pancreas for the uptake of glucose)
A chain (22 A.A.)
B chain (30 A.A.)

Question 20

Insulin function

Answer 20

Uptake of glucose
Lipid synthesis
Protein synthesis
Proliferation

Question 21

Glucagon

Answer 21

Glycogen breakdown
Lipid hydrolysis
Increase in glycolysis
Increase in respiratory rates

Question 22

Lipophilic Molecules

Answer 22

Some bind extracellular receptors
DONT cross PM (prostaglandins)
Arachidonic acid derivatives (20 carbons with 5 carbon ring)
9 classes
Some can pass the PM: Steroid hormones, thyroid hormones, retinoids

Question 23

What is cholesterol derived from?

Answer 23

Steroids

Question 24

Plant hormone

Answer 24

Auxin

Question 25

Cytokines

Answer 25

Paracrine or autocrine signaling Over 80 types Generally released by immune cells <10KDa --> ~70KDa Most are 15-40 KDa

Question 26

Interferons

Answer 26

Viral infections NK cells make IF-gamma

Question 27

Interleukins

Answer 27

IL-1 --> IL-38 Maturation process Synthesized in pre=protein state Are cleaved post translation

Question 28

TNFs

Answer 28

Tumor necrosis factor Monocytes and macrophages Involved in cell survival and cell death Proliferation and differentiation

Question 29

TNF-alpha and TNF-beta

Answer 29

Bind same receptor TNF-beta brings in additional protein to form a trimer to cause a different signal than TNF-alpha

Question 30

CSFs

Answer 30

Colony stimulating factors Development of bone marrow Induces development of leukocytes Athenian cells, fibroblasts, etc... Uptake of CSFs in response to infection

Question 31

Chemokines

Answer 31

~45 types Structurally related Not functionally related

Question 32

Growth factors

Answer 32

Proliferation/differentiation Over 50 types of GFs 14+ families of receptor

Question 33

PDGF

Answer 33

Platelet derived growth factor AA, AB, BB attached to PDGF

Question 34

Most studied growth factor of all?

Answer 34

EGF

Question 35

EGF

Answer 35

Contain cysteine rich domain 6 cysteines in it held together by disulfide bridges Therefore very stable structure hydrophobic regions on surface of EGF molecules

Question 36

FGF

Answer 36

Mammals: GFG-a, FGF-b, FGF3-19 Humans DO NOT have FGF-15 Also key for locomotion

Question 37

Neurotransmitters

Answer 37

Small molecules: GABA (acetylcholine) dopamine signal across synapse (20nm) Neuropeptides: Beta-endorphin (vasopressor) Some other small molecules e.g., ATP

Question 38

GPCR

Answer 38

G-protein coupled receptor gamma and alpha are membrane bound alpha holds a guanine nucleotide Signal molecule binds GPCR which causes conformational change Shift in loop causes nucleotide change in G-alpha Leads to dissociation of G-alpha from G-beta/gamma 800-1,000 types

Question 39

Three subfamilies of GPCR

Answer 39

A, B and C B downstream uses cAMP

Question 40

Ion channels (Gated ion channels)

Answer 40

Acetylcholine receptor: 6 subunits 2 alpha subunits 1 beta subunit 1 gamma subunit 1 delta subunit Glutamate receptor: four subunits, many possible combos Ligand binds alpha 18 genes with splice variants

Question 41

Enzyme-linked receptors

Answer 41

Enzyme linked or enzyme associated with them many dimerize to activate N-terminus is always extracellular Only one TM domain

Question 42

Binding between signal + receptor

Answer 42

Reversible reaction L+R --> LR <--

Question 43

Kd

Answer 43

Dissociation constant State at which receptors are 1/2 bound and 1/2 unbound Low Kd = high affinity L --> R High Kd = low affinity L --> R

Question 44

Kd equation

Answer 44

Kd= ([R] [L])/[RL]

Question 45

Do we want a high Kd?

Answer 45

Depends! Consider: 1. Signal molecule concentration 2. number of signal receptors on the cell