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PSU Freshman > BIOL230W Exam 3 > Flashcards

BIOL230W Exam 3 Flashcards

1
Q

Describe the general process of signaling (including signals, receptors, second messengers and final target/effector)

A

Ligand is the chemical signal. The receptor senses the signal, thus a physical change occurs and is typically an integral protein. The effector typically uses secondary messengers to alter proteins by pathway.

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2
Q

Define protein conformation changes and how conformation changes result in changes in function

A

Protein shape determines function (ligand binding to receptor)

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3
Q

What protein components make up a GPCR? (G-Protein Coupled Receptor)

A

Integral membrane protein
Extracellular ligand-binding domain
Intracellular G-protein coupled domain
G-proteins (associated proteins)

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4
Q

3 subunits of G-proteins

A

Alpha, beta, gamma (classified as heteromeric G-protein)

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5
Q

RTK (receptor tyrosine kinase)

A

Tyrosine kinase domain of protein is activated and phosphorylates tyrosines
Once activated, the RTK can phosphorylate other proteins

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6
Q

What protein is phosphorylated first after RTK activation?

A

RTK

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7
Q

What type of ligand binds to intracellular receptors?

A

non-polar

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8
Q

Second messenger definition

A

Intracellular signaling molecules released by the cell in response to extracellular signaling molecules
(Chemicals that relay the signal from the membrane to the cytoplasm)

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9
Q

Effector definition

A

Proteins that are altered in the signal pathway

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10
Q

What type of membrane proteins are receptors for extracellular signals that are impermeable to the membrane?

A

Integral membrane proteins

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11
Q

Describe the role of G-proteins in signaling

A

relay the signals from GPCRs which function as GEFs for G-proteins

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12
Q

What enzyme is activated to produce cAMP

A

Adenyl cyclase

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13
Q

What is one possible effector (target) activated by cAMP?

A

Protein kinase A

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14
Q

Secondary messengers are NOT

A

proteins

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15
Q

How is cAMP synthesized in a cell

A

After ligand binding, activated alpha G-protein stimulates enzyme adenyl cyclase. Uses ATP to make cAMP. cAMP targets effectors

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16
Q

What enzyme is produced to produce IP3 and DAG?

A

Phospholipase C (PLC)

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17
Q

Function of PLC

A

Phospholipase C cleaves the fatty acid chains of a phospholipid in membrane

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18
Q

Compare and contrast kinases and phosphatases

A

Kinases can activate or inactivate a protein and add a phosphate to a protein which alters protein structure. Phosphatase only removes a phosphate.

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19
Q

What type of macromolecule are effectors?

A

Protein whose function is changed in the pathway

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20
Q

G0

A

Cells that have stopped dividing

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21
Q

G1

A

Cells increase in size and phase contains a mechanism to ensure that everything is ready for DNA synthesis

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22
Q

G2

A

contains a mechanism that ensures the cell is ready to enter the M phase

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23
Q

S

A

DNA replication occurs

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24
Q

M

A

Cell growth stops at this stage and cellular energy is focused on the orderly division into two daughter cells

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25
Stages included in interphase
G1, S, G2
26
What is the relationship between a microtubule and alpha/beat tubulin dimers?
A microtubule is a polymer of many alpha, beta tubulin dimers
27
During polymerization, the tubulin dimers are n the ____-bound state
GTP
28
The microtubule end with alpha-exposed subunits is the ___ end, while the microtubule with the beta-exposed subunits is the ___ end
minus, plus
29
Microtubule nucleation
Event that initiations polymerization of tubulin dimers to the polymer form (microtubules)
30
Prophase
Replicated chromosomes are condensed, centrosomes nucleate microtubules by the nucleus
31
Prometaphase
Nuclear envelope breaks down. Spindle microtubules begin interacting with kinetochores
32
Metaphase
Pushing and pulling action of kinetochore microtubules cause chromosomes to line up towards middle of cell
33
Anaphase
Sister chromatids separate
34
Telophase
Nuclear envelope reforms, DNA relaxes to euchromatin
35
Major role of centromere
Area of the chromosome where sister chromatids are joined
36
Kinetochore
A complex of proteins that serve as the point of attachment for spindle microtubules during mitosis
37
Function of cohesion
Attach sister chromatids together via cohesion protein
38
Compared to G1, how much DNA is in the nucleus of a cell in G2?
Double
39
Microtubules form a
hollow tube structure
40
How might the lack of GTP affect the stability of a microtubule?
MTs can grow (polymerize) or shrink, typically from the + end. Cycle of growing and shrinking= dynamic instability
41
Tubulin monomer is what type of protein
G-protein because it binds to GTP and GDP
42
Microtubule monomer
a/b tubulin dimers
43
microtubules polarity
+ and -
44
Connecting bond microtubules
Hydrogen
45
Polymerizing agent microtubules
Self-polymerize
46
What organelle nucleates microtubule polymers?
Centrosomes (2 centrioles and associated proteins, centrosome duplicates during S phase, migrate to poles of cell through prometaphase)
47
What cellular event allows microtubules to invade the nuclear space during prometaphase?
Bind to kinetochores to stabilize microtubules (no longer depolymerize)
48
Centromeres are present during
All phases
49
Kinetochores are present during
Forms during prophase (M)
50
what does the + end of mitotic microtubules attach to?
Kinetochore
51
3 types of mitotic microtubules
Kinetochore, polar, astral
52
How does the dynamic instability of the microtubule relate to the attachment of microtubules to chromosomes?
attached by hydrogen bond
53
Steps of spindle formation first two steps
Prophase (centrosomes migrate to opposite poles, growth of + end) Prometaphase (nuclear membrane dissolves and attachment of chromosomes to microtubules at kinetochore)
54
Steps of spindle formation last two steps
Metaphase (Chromosomes balanced by microtubules forces at midline) Anaphase (Separation and migration of sister chromatids to opposite poles)
55
What provides the force to position the chromosomes at the center of the cell at metaphase?
Motor proteins bind to MT and create force by "walking" on the polymers Kinesin "walks" along a microtubule track
56
CDK
Cyclin-dependent kinase
57
What molecule is required to activate CDK?
cyclin
58
What biochemical function does an activated CDK perform?
Phosphorylation
59
___levels remain constant while ____ levels can fluctuate depending on cell cycle stage
CDK/cyclin
60
Which of the following is an important function of checkpoints in the cell cycle?
Ensure DNA is undamaged before replication, cell has enough raw materials to fully replicate, check to see if time is right, check to ensure spindle has formed and chromosomes are aligned correctly
61
G1/S checkpoint
Before DNA replication
62
G2/M checkpoint
Before entry to mitosis
63
metaphase checkpoint
between metaphase and anaphase
64
Function of APC
Triggers the transition from metaphase to anaphase by degrading specific proteins
65
Relation between separase, cohesion, and chromatids?
Separase degrades cohesin that normally holds the chromatids together. it allows the chromatids to separate
66
What DNA structure does C-myc (a protein) bind in DNA?
enhancer regions
67
What result does C-myc have on transcription?
Increases transcription
68
Expression of myc can alter the chromatin structure in a nucleus
true
69
proto-oncogene vs oncogene
Proto-oncogene CAN cause cancer Oncogene WILL cause cancer
70
How does an oncogene cause cancer?
Results in uncontrolled cell growth
71
G1
Cell size grows, mRNA and protein synthesized for DNA synthesis
72
S
Replicated cell, also DNA repair activity occurs
73
G2
Preparation for mitosis; rapid cell growth and protein synthesis (double check for errors)
74
Mitosis
Cell division, result is two identical cells
75
G1->S checkpoint
3 damage checkpoints occur to ensure proper growth and synthesis of DNA Damaged DNA result in expression of ATM/R protein
76
G2->M checkpoint
Prevents cell from entering mitosis when DNA is damaged
77
Metaphase checkpoint
Ensures a bipolar spindle formed and all chromosomes are aligned before anaphase
78
How does cyclin concentration compare to CDK?
CDK concentration remains constant as cyclin concentration varies during the cell cycle
79
When is cyclin levels the highest
M phase
80
How are CDKs uninhibited
Cyclin unbinds and cyclin degraded by proteasome
81
Active cyclin
CDK complexes phosphorylation additional target proteins to promote cell cycle progression until cyclin is degraded
82
myc function
Triggers mitosis- gain function
83
p53 function
Stops mitosis- inhibit function
84
What happens if both p53 and myc do not work?
Both alleles removes suppression and uncontrollable division may occur
85
When kinase activity outcompetes p-protein activity, the cell cycle will (proceed/inhibit)
Proceed
86
When p-protein activity outcompetes kinase activity, the cell cycle will (proceed/inhibit)
Inhibit
87
What enzyme directly degrades cohesin?
Separase
88
Cohesin function
Holds sister chromatids together.
89
Separase must be regulated to prevent
inappropriate separation of sister chromatids
90
Describe the role APC in the metaphase to anaphase transition?
Anaphase-promoting complex activator Separase. Inactive APC is activated by a protein called cdc20. Cdc20 is the point of regulation for the metaphase checkpoint to prevent early release of sister chromatids
91
When is the metaphase checkpoint signal on vs off?
Turned on when there are unattached kinetochores Turned off when all are attached
92
If the metaphase checkpoint signal is on, how is anaphase affected
Will not occur
93
Inhibition of cdc20 causes inhibition of
APC
94
What is the metaphase checkpoint signal?
To check if chromosomes are correctly attached to kinetochore/spindles
95
Anueploidy
Wrong number of chromosomes in a cell
96
Chromosome missegregation occurs if proteins involved with the signal are
Mutated
97

PSU Freshman (12 decks)

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