Cell Bio Final Exam

Front 1

What attaches sister chromatids to spindles?

Back 1

Kinetochores

Front 2

What transition are G1 cyclins responsible for?

Back 2

G1 --> S

Front 3

What transition are mitotic cyclins responsible for?

Back 3

G2 --> M

Front 4

Association of mitotic cyclins with a cdk forms what?

Back 4

MPF = M-phase-promotion factor or maturation promoting factor

Front 5

When does mitotic spindle form?

Back 5

Prophase

Front 6

How many replication origins do bacterial and eukaryotic chromosomes have?

Back 6

Bacterial = 1

Eukaryotic = Many

Front 7

Which lasts longer? M phase or interphase?

Back 7

Interphase

Front 8

G1 is period at end of ____ to the beginning of ___

Back 8

1. Mitosis

2. DNA Replication

Front 9

G2 is period between end of ___ and beginning of ___

Back 9

1. DNA replication

2. Mitosis

Front 10

Cyclins, in general, do 2 things:

Back 10

1. Activate CDK

2. Determine specificity of CDK

Front 11

1. G1 cyclin levels remain steady until ___

2. G1/S cyclin form in ___ phase and remain steady until ___

3. S cyclin form in ___ phase and remains steady until ___

4. M cyclin form in ___ phase and remain steady until ___

Back 11

1. End of G1

2. Form in G1 phase, steady until end of G1

3. Form in G1 phase, steady until beginning of M phase

4. G2 phase, steady until end of metaphase

Front 12

5 ways to control activity of proteins involved in cell cycle regulation:

Back 12

1. Protein synthesis

2. Phosphorylation (ex: activ/inactivation of M-CDK)

3. CDK inhibitors (p21 inhibits S-CDK)

4. Subcellular localization of cyclins or of regulatory proteins (CDC25 phosphatase)

5. Protein degradation (APC or SCF)

Front 13

What is another name for active M-Cdk?

Back 13

MPF

Front 14

Explain the formation of MPF (or active M-Cdk)

Back 14

CDK binds to M-Cyclin --> Phosphorylation by CAK on T loop's active site --> simultaneous phosphorylation by Wee1 to inactive site --> Build up of inactive M-Cdk to tipping point --> CDC25 dephosphorylates inactive site and creates active M-Cdk --> Active M-Cdk can help phosphorylate CDC25 to increase its affinity for inactive M-Cdk --> Active M-Cdk inhibits Wee1 --> Further dephosph. of inactive site --> Mitosis can occur

Front 15

Explain the transition from G1 to S phase

Back 15

Active RB protein bound to inactive E2F protein --> Active G1-Cdk stimulates the phosphorylation of RB --> RB unbinds and E2F is activated --> E2F stimulates transcription of S-phase genes --> G1/S and S cyclin synthesized --> S-Cdk formed --> DNA replication

The positive feedback aspects:
- Transcription of S-phase genes stimulates E2F activation

- Synthesis of G1/S and S cyclin stimulate more deactivation of RB

- Activated S-Cdk stimulates further deactivation of RB

Front 16

G2 has 2 specific cyclin

T or F?

Back 16

False

G2 has no specific cyclin, but S cyclin is present until beginning of mitosis

Front 17

Why is destroying cyclin important in the cell cycle?

Back 17

1. It is irreversible

2. Sets up the next phase

Front 18

How is M cyclin destroyed?

Back 18

Ubiquitination and degradation by proteasome

This is accomplished by use of active APC, an E3 ubiquitin ligase complex

Inactive APC is bound by CDC20 --> This, along with E1 and E2 + ubiquitin = ubiquitination of M cyclin --> destruction

This leads to anaphase

Front 19

What does APC stand for?

Back 19

Anaphase promoting complex

Front 20

1. What does CKI stand for? What does it do?

How is CKI inactivated?

Back 20

1. Cyclin/Kinase Inhibitors

They inhibit Cdk-Cyclin complexes by binding to the tops

2. It is first phosphorylated by a kinase --> This allows active SCF (An E3) to function with E1, E2, and ubiquitin --> CKI ubiquitinated and sent for destruction

Front 21

What phase is the pre-RC formed in?

Can they be reused after used once?

Back 21

G1

No

Front 22

Describe the initation of DNA replication using ORCs

Back 22

ORC is always bound to ORC DNA

--> CDC6 and MCM (helicase) bound to ORC to form Pre-RC

--> Once S-Cdk triggers S phase, it phosphorylated CDC6 --> destroyed by ubiquitination

--> Preinitation complex binds to Pre-RC


--> ORC is phosphoylated to inhibit further CDC6 binding --> replication occurs --> transition to G2 phase

Front 23

1. What are cohesins?

2. When are they loaded?

3. General structure

Back 23

1. Protein ring that aligns sister chromatids during replication (S-phase). They are bound until after condensation and will be destroyed before anaphase (They move to allow condensin to work)

2. Loaded during S phase

3. Two SMC molecules: Helical structure with a tail (hinge) and the head (ATPase domain)

Front 24

1. What is the function of condensin?

2. When are they activated?

3. General structure

Back 24

1. They condense chromosomes

2. Activated by phosphorylation of M-cdk

3. Antiparallel coiled coil with tail (hinge) and head (ATP binding site)
- Similar to cohesin structure

Front 25

Events of prophase

Back 25

1. Condensation of chromosomes (from two chromatids)

2. Formation of mitotic spindle

3. Breakdown of nuclear envelope by MPF activity (CDK kinase phosphorylates lamins)

Front 26

Events of pro-metaphase

Back 26

1. Chromosomes moved by microtubules to center of cell (connect at kinetochore) by growth of microtubules

Front 27

Events of metaphase

Back 27

1. Chromosomes aligned at center

2. Microtubules organized into astral, kinetochore, and polar microtubules

3. Metaphase checkpoint (MAD2)

Front 28

Events of anaphase

Back 28

1. APC/C activity

2. Sister chromatids split from one another

3. Chromatids separate and move toward opposite poles

4. Anaphase A and B

Front 29

Events of telophase

Back 29

1. Nuclear envelopes and nuclei reassemble

2. Decondensation of chromosomes

3. Cytoplasm partitioned into two cells

Front 30

Events of cytokinesis (End of telophase)

Back 30

1. Actin-myosin ring forms between opposite poles

2. Contraction to separate cells

Front 31

What determines the placement of the actin-myosin ring in cytokinesis?

Back 31

The astral microtubules

Front 32

When do the centrioles of the centrosome duplicate?

Back 32

During S-phase

Front 33

Which motors are present at the kinetochore?

Back 33

Dynein and KRP

Front 34

What role does chromokinesin serve?

Back 34

Moves chromosomes by their arms to middle of cell

It is + end directed (toward middle)

Front 35

The - ends of astral microtubules are not bound directly to the plasma membrane.

T or F?

Back 35

True. They are bound to the plasma membrane through a dynein intermediate that pulls toward the - end of the microtubules (toward the centrosome)

Front 36

Spindle and kinetochore microtubules are capped at - ends.

T or F?

Back 36

False. They are uncapped and will depolymerize while the + end polymerizes.

Results in treadmilling

Front 37

Explain the metaphase-anaphase transition.

Explain difference between Anaphase A and B.

Back 37

Inactive APC/C --> binding to CDC20

--> active APC/C destroys M cyclin and securin

--> destruction of securin leads to activation of protease called Separase

--> Separase cleaves cohesins, allowing chromatid separation

Anaphase A: shortening of kinetochore microtubules to pull chromosomes toward poles. Contributing to this effect is the depolymerization of + ends of kinetochore MTs and Dyneins

Anaphase B: Overlapping microtubules push poles further apart as they elongate. Also, the dyneins at the astral microtubules pull the poles.

Front 38

Besides chromokinesin, what keeps chromosomes at metaphase plate?

Back 38

Motor proteins on the kinetochore itself

Front 39

1. What factors would cause a halt of the cell cycle at the G2 checkpoint?

2. How does G2 checkpoint work?

Back 39

1. Cell is not big enough, DNA damage, replication issues

2. If there is DNA damage or replication is incomplete, CDC25 is exported from the nucleus to cytoplasm. This keeps M-Cdk from becoming active and halts the cycle. Once the issue is resolved, CDC25 is sent back in.

Front 40

Explain how the G1 checkpoint works

Back 40

In normal circumstances with no DNA damage, p53 is bound to Mdm2. It has a very short life and is degraded quickly

In the case of damage:
p53 is phosphorylated and freed from Mdm2

--> p53, as a transcription factor, binds to the regulatory region of CKI gene

--> CKI gene transcribed --> translated

--> CKI formed and binds to G1/S-Cdk and S-Cdk to inhibit their functioning

--> Cell cycle arrest

Front 41

Explain how the Metaphase checkpoint works

Back 41

MAD2 exists on kinetochores

--> As the kinetochores are bound by MTs from opposite poles, they lose MAD2

--> If a kinetochore has not been bound at both sides, MAD2 acts as a flag to prevent progression to Anaphase

--> This results from the checkpoint preventing the degradation of M-cyclin and the cleavage of cohesin

In other words, the checkpoint relies on tension applied to the kinetochore

Front 42

Name the two classes of receptors discussed in class

Back 42

1. G-protein coupled receptors (GPCRs)

2. Enzyme-coupled receptors

Front 43

The trimeric G proteins are anchored by what?

Back 43

Lipids

Front 44

What acts as a GEF for the G protein?

What acts as GAP?

Back 44

Receptor

Effectors (target proteins) and RGS (Regulator of G-protein signaling

Front 45

How does G protein associate with the receptor? What is required?

Back 45

A ligand must bind to the receptor --> this causes a conformational change to allow binding to G protein

Front 46

What are three effectors of the G protein we discussed?

Back 46

Phospholipase

Adenylyl cyclase

Ion channels

Front 47

What does cAMP activate?

Back 47

Kinases, particularly PKA (protein kinase A)

Front 48

What happens when adrenaline builds up?

Back 48

1. Glycogen is broken down into glucose (liver)

2. Genes coding for glucose are turned on

Front 49

What are the two general functions we discussed with regards to G proteins?

Back 49

1. Regulate production of cAMP

2. Act in inositol phospholipid pathway by activating phospholipase C-B

Front 50

Process of turning on genes for coding glucose with G proteins?

Back 50

Signal molecule to receptor

--> G- alpha exchanges GDP to GTP --> Adenylyl cyclase activated

--> ATP converted to cAMP by Adenylyl cyclase

--> PKA activated by binding to regulatory subunit and releasing PKA

--> PKA passes through nucleopore --> activates CREB

--> CREB binds with CBP to cAMP response element (CRE) on DNA --> Gene transcription

Front 51

Explain the process of GPCR (G protein coupled receptor)

Back 51

GPCR activated by ligand

--> Active GPCR stimulated GRK (G-protein receptor kinase) to phosphorylate receptor at multiple sites (NEEDS ATP)

--> Arrestin binds to phosphorylated GPCR to prevent interaction with G proteins

--> Arrestin acts as adaptor for clathrin-coated pits to form --> Endocytosis

Front 52

Explain the phospholipase pathway with G proteins

Back 52

Signal molecule activates GCPR --> G alpha activated --> Phospholipase C- B activated

--> PCB cleaves PIP2 to DAG (diacylglycerol) and IP3 --> IP3 opens gate on ER to release Ca++

--> DAG and Ca++ act together to activate protein kinase C

Front 53

Besides in the phospholipase pathways, where is Ca++ used? Explain this use

Back 53

CamKII regulation (Cam Kinase II)

CamKII inactive --> Calmodulin activated by Ca++ and changes conformation

Calmodulin binds to CamKII --> CamKII activated --> Autophosphorylation of CamKII --> FULL ACTIVATION

Calmodulin and Ca++ dissociate --> Phosphorylated CamKII remains active for use

Phosphotase can return CamKII to inactive form

Front 54

Ligand binding causes Receptor Tyrosine Kinases (RTKs) to dimerize

T or F?

Back 54

True. They exist as two parts and only come together when the ligand binds

Front 55

RTKs monomers require separate kinases to become phosphorylated.

True or false?

Back 55

False. They phosphorylate each other

Front 56

Name the kinase that generates memory in cells with regard to stimulation?

Back 56

CamKII

Front 57

Name the 4 binding domains that are seen on RTKs and their binding sites

Back 57

1. PH --> phosphorylated inositol phospholipid

2. PTB and SH2 --> phosphotyrosine

3. SH3 --> Proline-rich motif

Front 58

How are PLC gamma and PLC beta different and similar?

Back 58

They both have the same enzymatic activity (Cleave PIP2 to IP3 and DAG) --> PKC signaling

PLC - G acts with RTKs, while PLC - B acts with GPCRs

Front 59

What does PI3 Kinase do? Explain pathway

Back 59

RTK activated --> PI3 Kinase binds in active state --> Adds phosphate to 3 position on PIP2

--> New PIP3 bound by PKB -- PKB phosphorylated and activated

--> PKB dissociates in active form --> Acts in inhibiting apoptosis

Front 60

Which cells of epidermis divide?

Back 60

Only those in the basal layer. The rest specialize and die

Front 61

What is the state that non-dividing, long-lived cells exist in?

Back 61

Go or Quiescence

Front 62

What is a mitogen?

What is a growth factor?

Can a growth factor act as a mitogen?

Back 62

1. Mitogens are molecules that send signals into cell to drive the cell cycle

2. Growth factors promote the growth of a cell by signaling for nutrient uptake

3. Yes, some

Front 63

Which pathway do mitogens mostly stimulate?

Back 63

The RAS/MAP Kinase signaling pathway

Front 64

There are CKIs for a limited number of cyclins.

What are they?

Back 64

G1, G1/S, and S cyclin.

There is no CKI for M cyclin

Front 65

What is the big regulator of the cell cycle?

Back 65

Myc. It triggers the beginning of the cell cycle

Front 66

What is the big regulator for cell growth?

Back 66

mTOR

Front 67

Explain how Myc is synthesized.

Explain has Myc acts.

Back 67

1. Mitogen binds to receptor --> Grb2 adapter protein --> RasGEF --> Activated Ras protein --> MAP Kinase-Kinase-Kinase --> MAP Kinase-Kinase --> MAP Kinase --> Myc transcription factor synthesized

2. Myc acts as a transcription factor. It leads to heightened G1 cyclin and SCF synthesis, which leads to G1-Cdk formation, Rb phosphorylation, and G1/S-Cdk activation.

It also leads increased E2F synthesis.

All this together aids in S phase activation

Front 68

Explain how mTOR is syntheiszed.

Explain how mTOR leads to cell growth

Back 68

1. Growth factor binds to receptor --> PIP2 interacts with activated PI3 kinase --> PIP3 formed --> PKB (Akt) activated and phosphorylated --> mTOR activated

2. mTOR uses amino acids to change gene regulation and increase ribosome synthesis to promote the growth of the cell

Front 69

What is caspase?

How is a caspase cascade formed?

Back 69

Protein that acts in apoptosis by cleaving proteins (such as cystolic and lamin proteins)

Procaspase cleaved at pro domain to turn into caspase --> caspase can cleave one another --> more and more cleave one another to produce effect

Front 70

Explain the extrinsic apoptopic pathway

Explain the intrinsic apoptopic pathways

Back 70

1. Ligand of killer lymphocyte binds to receptor on cell --> procaspase and adapter proteins recruited at receptors --> procaspase cleave one another --> cascade --> apoptosis

2. Injured mitochondria --> cytochrome c escapes and binds to adapter proteins --> recruit procaspase --> cleavage --> cascade

Front 71

In the absence of proliferation signals, what type of signal determines the fate of the cell?

What is the result?

Back 71

Survival signals

Absence = Apoptosis

Presence = Go, Quiescence

Front 72

Explain how survival signals lead to quiescence

Back 72

Survival signal binds to receptor on cell --> PI3 activated --> PI3 changes PIP2 to PIP3

--> PIP3 binds and activates PKB (Akt) --> mTOR and then dissociation of PKB

--> Dissociated PKB phosphorylated Bad --> Bad dissociates from Apoptosis inhibitory protein --> Inhibition of apoptosis