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Cell Biology > Unit 3 > Flashcards

Unit 3 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the two types of signaling molecules?

A

hydrophobic / hydrophilic

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2
Q

What are the two general classes of receptors

A

cell surface and intracellular

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3
Q

What is a gap junction and what type of signaling molecules can pass through it

A

small pore between cells, small signaling molecules only

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4
Q

What is required for a cell to respond to a signal

A

correct receptor and “signaling machinery” inside the cell

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5
Q

Acetylcholine

A

contraction in skeletal muscle cells
relaxation in heart muscle cells
signaling in secretory cells

3 responses from the same signal

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6
Q

Paracrine signaling

A

local signal

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7
Q

Synaptic signaling

A

long range - neurotransmitter signal from axons

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8
Q

Endocrine signaling

A

long range - hormones / blood stream

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9
Q

Autocrine signaling

A

short lived / self signaling

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10
Q

What are the classes of hydrophobic signaling molecules

A

steroids hormones
thyroid hormones
retinoids

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11
Q

Steroids

A

planar structure made from cholesterol

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12
Q

Examples of steroid hormones

A

cortisol (made by adrenal gland on top of kidney)
estradiol (ovary)
testosterone (testis)
vitamin D (made in skin)

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13
Q

Thyroids hormones

A

made from tyrosine

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14
Q

Hsp

A

heat shock protein

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15
Q

What are the domains of intracellular receptors

A

activation domain
ligand binding domain
DNA binding domain

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16
Q

When intracellular receptors are in the cytosol

A

They are bound to an inhibitory complex (chaperone)

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17
Q

What happens when a signaling molecule binds an intracellular receptor

A

molecule binds and displaces HSP
causes a conformational change and exposes DNA binding domain
Goes to nucleus and acts as a transcription factor

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18
Q

What is the first response of intracellular receptors

A

Early Primary Response

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19
Q

What happens in the early primary response?

A

signal binds to receptor
receptor goes to nucleus and acts as transcription factor
Increases transcription / translation of proteins in ~30 minutes
**Makes early response proteins

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20
Q

What is the second response of intracellular receptors

A

Secondary Response

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21
Q

What happens in the secondary response of intracellular receptors?

A

Early response proteins act in a neg. feedback loop turn off transcription of primary response genes.
Early response proteins increase transcription/translation of secondary response proteins.

**Cells can change behaviors

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22
Q

Hydrophilic signaling molecules aka

A

soluble signaling molecules

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23
Q

What are the two types of proteins in relay systems within cells

A

proteins that become phosphorylated

proteins that bind GTP (called G proteins)

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24
Q

Both phosphorylation / dephos and GTP - GDP act to

A

turn signal molecules on and off

Phos = on
GTP = on
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25
Q

G Protein receptors can

A

activate adenyly cyclase
inhibit adenyly cyclase
activate phospholipase C (PLC)

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26
Q

Steps in G protein signaling

A

Receptor becomes activated when it binds the ligand
This receptor then interacts with the G protein
Binding activates the G protein
G protein then activates the next protein

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27
Q

G protein linked cell surface receptor structure

A 
7 pass proteins
N terminus binds ligand
C3 look (3rd cytoplasmic) specifies which G protein interacts
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28
Q

What do GAPs and RGSs do to G proteins?

A

increase rate of GTP hydrolysis and turn G proteins off

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29
Q

Many G proteins regulate ________levels

A

cAMP

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30
Q

cAMP is a

A

secondary messengers

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31
Q

what are the 2 types of heterodimeric G proteins

A

stimulatory G proteins (Gs)

Inhibitory G proteins (Gi)

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32
Q

Which enzyme controls cAMP levels

A

adenylyl cyclase

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33
Q

cAMP cycles to what that is NOT a signaling molecule

A

5’AMP

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34
Q

What is contained on the alpha subunit of a Gs protein

A

nucleotide binding domain and GDP binding pocket

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35
Q

How does adenylyl cyclase make cAMP

A

from ATP

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36
Q

How do Gs proteins work

A

ligand binds and causes conformational change
G protein binds receptor and alpha subunit binds GTP
alpha subunit diffuses away from beta and gamma subunits.
alpha subunit moves through membrane and interacts with second enzyme
ATP becomes cAMP
alpha subunit hydrolyzes GTP back to GDP and associates with beta and gamma subunits
cycle will repeat

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37
Q

How does cholera work like a Gs protein

A

modifies subunit so that it can’t hydrolyze GTP

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38
Q

How does pertussis work like a Gi protein

A

locks the alpha subunit in the GDP phase

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39
Q

True or False: Many different G coupled protein receptors are able to turn on Gs proteins

A

True….means many different ligands can turn on the same receptors.

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40
Q

How do Gi proteins work

A

ligand binds receptor
receptor interacts with Gi protein
alpha subunit will interact with adenylyl cyclase but will inhibit it

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41
Q

How do they know it is the C3 loop of the G protein coupled receptor that makes it specific

A

Use recombinant DNA tech to swap out this sequence and you get a different receptor.

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42
Q

GPCR

A

G protein coupled receptor

43
Q

What rises in the intracellular space when Gs activates adenylyl cyclase?

A

levels of cAMP

44
Q

Kinases

A

phosphorylate proteins

45
Q

PKA

A

protein kinase A

46
Q

When is PKA inactive

A

When all 4 subunits are bound together

47
Q

How is PKA activated

A

cAMP binds regulatory subunit and causes conformational change
This releases the catalytic domain
PKA then phosphorylates other proteins

48
Q

What are some examples of cellular changes caused by PKA

A

glycogen breakdown
alterations in transcription
release of fluid across epithelial cells (membranes)

49
Q

How are receptors involved in signal amplification

A

Each receptor can stimulate many different G proteins

50
Q

How does cAMP activation cause glycogen breakdown in muscle cells?

A

Ligand binds receptor which activates cAMP.
cAMP turns on PKA
PKA phosphorylates phosphorylase kinase (activates it)
This enzyme activates glycogen phosphorylase
This enzyme turns glycogen to glucose 1 phosphate that feeds into respiration cycles.

51
Q

WHY is cAMP generated in times of stress?

What signaling molecule is the ligand?

A

cAMP causes glycogen to break into glucose which then becomes ATP
Adrenaline is the ligand

52
Q

How does PKA (due to cAMP) change gene expression

A

PKA enters nucleus and phosphorylates CREB

CREB (activated) binds P300/CBP to create transcription factors (loosens DNA around histones)

53
Q

What does CREB stand for

A

cAMP response element binding protein

54
Q

How does PKA (due to cAMP) release fluid in epi cells

A

after increase in cAMP and then in PKA…

This signaling creates a gradient that will draw water by osmosis

55
Q

Movement of water across epithelial cells relies on what protein

A

CFTR = cystic fibrosis transmembrane conductance regulator

CFTR = membrane of ABC superfamily of proteins
Uses ATP but NOT a pump because moves things down the concentration gradient

56
Q

What are the main domains of the CFTR protein

A 
MSD = membrane spanning domain 
NBD = nucleotide binding domain
R = regulatory domain *turns CFTR on / off
57
Q

How is CFTR activated by cell signaling

A

PKA turns CFTR on (activates it)

58
Q

CFTR normally

A

Moves Cl- ions from cells into mucus causing water to follow and thin mucus

59
Q

How do mutations stop CFTR from working

A

Most common will delete Phe at 508
Causes misfolded protein
Induces unfolded protein response so receptor is degraded in cytosol
Most of the people with the mutation are missing the receptor all together.

60
Q

If you are heterozygous for a mutation in the CFTR gene it gives you an advantage to survive

A

Cholera. Cholera locks the CFTR in the on position. Lower levels of CFTR means less water loss

61
Q

How does cholera affect CFTR

A

Cholera turns off CFTR because it locks the Gs into the “on” position. So, constantly moving ions and you lose large amounts of water into intestines

62
Q

How does pertussis affect CFTR

A

locks Gi in off position. So, CFTR continues to move ions and therefore water out of cells. Lungs fill with fluid.

63
Q

PLC

A

Phospholipase C

64
Q

IP3 and Ca +2 ions

cAMP

A

are secondary messengers

65
Q

What is the basic pathway of signal transduction through membrane receptors

A

Ligand binds receptor (in membrane)
Receptor interacts with G protein
G protein activates and enzyme
The enzyme activates secondary messengers
Secondary messengers act on target molecules

66
Q

PIP2 is cleaved to create

A

DAG and IP3 secondary messengers

67
Q

What are some ways that Ca+2 levels are kept very low in cells

A

Ca-ATPase
Ca binding proteins
Pumps
Na+/Ca+2 antiporter

68
Q

Why is Ca+2 concentration kept low in cells

A

It is a very powerful signaling molecule

69
Q

Gq linked receptors generate

A

IP3

70
Q

How does the Gq protein work

A

*like Gs
Activated alpha subunit interacts with PLC and activates it
Activated PLC cleaves into DAG and IP3
IP3 goes to the ER and releases Ca+2 ions into cytosol
PKC uses the Ca+2 ions and then goes on to change gene expression (usually)

71
Q

Orail

A

plasma membrane associated Ca+2 channel

72
Q

Stim =

A

stromal interaction molecule

An ER membrane protein that binds Ca+2 ions

73
Q

What happens in ER after IP3 signal

A

ER moves Ca ions to cytosol
Decrease in Ca in ER triggers STIM dimers and conformational change
The STIM dimers interact with Orail

74
Q

What is the G Protein-Ca/IP3 pathway that leads to activation of transcription factors and modulation of gene expression

A

DAG binds to PKC and activates it
PKC phosphorylates MAP kinase and activates it
MAP kinase moves to nucleus and phosphorylates transcription factors
PKC also phosphorylates IK-B and it releases NF-KB
NF-KB moves to nucleus and works as transcription factors

75
Q

Enzyme linked receptors

A

Have catalytic activity and are active when bound to a ligand

76
Q

Receptor tyrosine kinases are

A

an example of enzyme linked receptors

77
Q

What are some examples of receptor tyrosine kinases receptors

A 
NGF (nerve growth factor)
PDGF (platelet derived growth factor)
FGF (fibroblast derived growth factor) 
EGF (epidermal derived growth factor) 
VEGF (vascular endothelial growth factor)
78
Q

What do receptor tyrosine kinases do

A

phosphorylate tyrosines

79
Q

How are receptor tyrosine kinases activated

A

When no ligand bound they are monomers and when a ligand binds they dimerize. This dimerization will activate them.

80
Q

What are the three domains of a RTK

A

extracellular ligand binding domain
transmembrane alpha helix
cytosolic domain with the tyrosine kinase activity

81
Q

After RTKs are dimerized what is the first step

A

Autophosphorylation of multiple tyrosines on the receptor itself.

82
Q

Ras is active / inactive when

A 
active = bound to GTP
inactive  = bound to GDP

Ras is a monomeric G protein

83
Q

GAP =

A

GTPase activating protein

84
Q

Why does RAS need GAP to work

A

its own GTPase activity is very low.

85
Q

The cell cycle is regulated by proteins within the cell at what points

A

in G1 just before S
in G2 just before M
in M just before metaphase

86
Q

heterokaryon

A

has double the amount of DNA

87
Q

MPF

A

mitosis promoting factor (a dimer)

88
Q

CDK

A

cyclin dependent kinase

phosphorylates other proteins

89
Q

WHat causes CDK to become active

A

binding to specific cyclins

different cyclins are made / degraded with every phase of every cell cycle

90
Q

What are the main classes of cell cycle control system

A

G1-S phase CDKs
S phase CDKs
Mitotic CDKs
APC/C activity

91
Q

Proteosomes

A

large protein complexes that degrade proteins that have been ubiquinated

92
Q

Rb

A

retinoblastoma

an inhibitor of E2F transcription factor

Turned off by phosphorylation and releases E2F. This causes transcription of G1 cyclins

93
Q

What can cause retinoblastoma tumors in the eye

A

No function of Rb so E2F is always active and G1 always moves into S because it induces S phase cyclins.

94
Q

Role of Sic 1

A

keeps S phase cyclin-cdk “off” in G1

When sic 1 is phosphorylated and tagged for degradation then DNA replication is initiated by S phase Cyclin-CDK

95
Q

Role of active S phase cyclins

A

phosphorylate proteins in ori rep. complex and cause conformational change.

Proteins fall off and ori remains active

96
Q

What is the role of Mad2 in the spindle assembly checkpoint

A

Mad2 inhibits proteosome that degrades securin if the spindle is not properly formed

97
Q

Chromosome segregation checkpoint

A

If chrs. not at poles, then inhibit cdc14

Cdc14 promotes degradation of mitotic cdks

98
Q

ALL DNA damage checkpoints:

in G1, before S phase entry, During S phase, in G2

A

Use p53

99
Q

IF DNA has not replciated

A

ATM/R activates p53 which activates P2ICIP which inhibits cyclin/cdk dimers and pauses cell cycle

ATR activates CHK 1 which inhibits Cdc25C. (This is the protein that moves cell to M phase)

100
Q

p53

A

is a transcription factor

unstable unless there is DNA damage

101
Q

Unipotent

A

can only form one differentiated cell type

102
Q

Multipotent

A

can form multiple types of differentiated cells

103
Q

Pluripotent

A

can form all of the different cell types

104
Q

Totipotent

A

can form all of the differentiated cell types + specialized tissues

Cell Biology (3 decks)

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