Cell Signaling and Signal Transduction- Exam 1

Question 1

Cell theory

Answer 1

1. living organisms are made of cells
2. cells are the building blocks of life
3. all existing cells come from pre-existing cells

Question 2

Signal input for cells

Answer 2

physical environment and other cells

Question 3

Signal output from cells

Answer 3

extracellular matrix and signals to other cells

Question 4

What do signal transduction pathways do?

Answer 4

regulate transcription factor and other cytosolic metabolic pathways directly

Question 5

Types of signaling

Answer 5

1. direct

2. indirect

Question 6

Direct signaling

Answer 6

signals pass through gap junctions which are made of six connexin proteins, this way small molecules can pass through without crossing plasms membranes. Example: calcium in glial cells

Question 7

Autocrine signaling

Answer 7

the target cell is also the secreting cell

Question 8

paracrine signaling

Answer 8

Signal released from a cell has an effect on neighboring cells.

Question 9

hormonal signaling

Answer 9

a type of long-distance signaling where an endocrine excretes hormones in a blood vessel to travel to a target cell

Question 10

synaptic signaling

Answer 10

a nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell

Question 11

On and off

Answer 11

Phosphorylation ( on Ser. Thr. Tyr): kinases, phosphatases

G-proteins: GTP binding (activation), GTP hydrolysis (inactivation), arrestins (bind to G-protein)

Question 12

Three stages of cell signaling

Answer 12

1. Reception
2. Transduction
3. Response

Question 13

Reception

Answer 13

1. cytoplasmic receptors

2. transmembrane receptors

Question 14

cytoplasmic receptors

Answer 14

signal molecules are hydrophobic and can permeate the plasma membrane, ideal for steroids such as estrogen, testosterone, and cortisol

Question 15

transmembrane receptors

Answer 15

transmembrane proteins with extracellular binding domains that have large hydrophilic ligand binding to them and they do NOT cross the plasma membrane

1. GPCRs
2. Enzyme-linked receptors
3. ligand-gated ion channels

Question 16

GPCRs

Answer 16

• very common
• a frequent target for drug design (because it has amplification properties?)
• seven transmembrane helices
• three subunits: alpha, beta, gamma
• termination: initially GTP hydrolysis, then GRK/arrestins

Question 17

Enzyme-linked receptors

Answer 17

• receptor tyrosine kinase
• only one TM segment
• ligand binding=dimerization\
• trans-autophosphorylation on tyrosine residues( what does this mean bruh?)
• termination by receptor internalization
• ligand-mediated(ligand dimer), receptor-mediated(receptor dimer)

Question 18

ligand-gated ion channels

Answer 18

-IP3 and Ryanodine receptor (in neuro bio lecture)

Question 19

Transduction

Answer 19

Second messengers (example: cyclic AMP)

-the first messenger is the extracellular ligand, the second messenger is its intracellular surrogate

Question 20

Caffeine

Answer 20

Caffeine inhibits cAMP phosphodiesterase

Question 21

glucose example

Answer 21

glucose: released from liver cells, regulated by glucagon and/or epinephrine

GPCR
effector protein: adenylyl cyclase
protein kinase A
cytoplasmic and nuclear responses

Question 22

calcium example

Answer 22

calcium allows for buffering and hotspots and waves (e.g. glial cells)

larger concentration outside, in mitochondria, and in ER than in cytosol so when calcium is pumped into those regions an ATP powered pump is required.

Question 23

activation of calcium fluxes example

Answer 23

GPCRs or RTKs
effector protein: phospholipase C
Protein kinase C
second messengers:
calcium, IP3, DAG

Question 24

PIP2, DAG, IP3

Answer 24

PIP2= phosphatidyl inositol phosphate
DAG= diacylgylcerol
IP3= inositol triphosphate

Question 25

calmodulin example

Answer 25

in addition to protein kinase C, sometimes calcium uses CaM to affect the downstream activity of enzymes CaM undergoes a conformational change by binding to four calcium ions

Question 26

calcium-induced calcium release in animals

Answer 26

what happens in brain glial cells calcium ions can be used to release more calcium ions from the endoplasmic reticulum including from the sarcoplasmic reticulum of muscle cells

Question 27

CICR in plants

Answer 27

when too much water is released, the hormone abscisic acid is released, this triggers the influx of calcium ions into the vacuole which causes an outflux of the calcium ions from the vacuole which then causes water to follow out of the vacuole leading to a lower turgor pressure causing the guard cells to close the pore thereby inhibiting the loss of water

Question 28

amplification

Answer 28

cascade/amplification fo cAMP or PKA is when one ligand molecule triggers the production of infinitely more molecules downstream causing a much larger response example: one molecule of epinephrine or glucagon can lead to the production fo 100,000 molecules of glucagon

Question 29

example of amplification

Answer 29

``` RTK Ras/MAPk pathway Ras: a single subunit G-protein Ras stimulates cell division Ras is mutated in about 30% of cancers such that it cannot hydrolyze GTP to GDP which leads to continuous cell division leading to cancer due to lack of cell division termination ```

Question 30

blood vessel dilation

Answer 30

1. ACh receptor 2. Calcium flux activates nitric oxide synthase 3. nitric oxide synthase produces nitric oxide nitric oxide activates guanylyl cyclase which leads to the production of cGMP 4. cGMP leads to the relaxation of blood vessels causing the blood to flow

Question 31

Viagra

Answer 31

Viagra inhibits cGMP phosphodiesterase

Question 32

Response

Answer 32

cytoplasmic and nuclear responses

Question 33

CRE and CREB

Answer 33

``` CRE= cAMP response element CREB= CRE binding element ```

Question 34

CREB activation in the liver

Answer 34

leads to the transcription and translation of genes involved in gluconeogenesis

Question 35

specificity of responses

Answer 35

divergence: one molecule leads to two responses crosstalk: respond to different signals and interact example of crosstalk: PKA activates CREB phosphorylation but inhibits MAPk pathway that can also modulate CREB phosphorylation

Question 36

termination of cAMP

Answer 36

cAMP phosphodiesterase

Question 37

termination of cGMP

Answer 37

cGMP phosphodiesterase

Question 38

termination of protein-p

Answer 38

phosphatase

Question 39

termination of calcium ions

Answer 39

reuptake back into the endoplasmic reticulum or sarcoplasmic reticulum in the case of muscle cells

Question 40

cholera

Answer 40

toxin modifies G protein so that it cannot hydrolyze GTP leading to an inability to terminate the transduction pathway leading to constant high levels of cAMP which means that the patient experiences acute diarrhea, dehydration, and vomiting