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91 Cards in this Set

  • Front
  • Back

4 Functions of Cytoskeleton


Organizes Organelles

Interact Mechanically with the Environment

Carry Out Coordinated Movements

Subunit of Intermediate Filaments

heterogenous family of fibrous proteins

Subunit of Microtubules

Dimer of alpha and beta tubulin

Subunit of microfilaments


Rate MT, MF, and IF from smallest to largest


Often connect to the plasma membrane at desmosomes

Cytoplasmic IFs

Nuclear lamins that assemble into a mesh that supports the nuclear envelope

Nuclear IFs

Defects in nuclear lamin can cause...


4 Protein filaments that make up IFs and where they're found

Keratin filaments: epithelial cells

Vimentin: connective tissue

Neurofilaments: nerve cells

Nuclear lamins: all animal cells

FIbrous proteins bind together and twist to form...

Intermediate filaments

In intermediate filaments, the monomer consists of...

an alpha helical central rod domain

Do IFs have polarity?


What stabilizes IFs and connects them to other parts of the cytoskeleton?


What are the 3 roles of MTs in the cell?

Cell organization/intracellular transport

Spindle assembly

Structural support of cilia and flagella

MTs have polarity. Which end is the plus end and minus end?

Beta: plus

Alpha: minus

Where are MTs nucleated from?

Gamma-tubulin complexes in centrosomes

Dynamic instability occurs in MTs when

they grow and shrink rapidly

Beta tubulin is a


Growing MTs have a

GTP cap

Conformation of GDP tubulin favors


MT dynamics are controlled by what 2 things?

GTP caps

Microtubule associated proteins (MAPS)

What does the drug taxol do?

disrupts spindle assembly

binds and stabilizes MTs

What do the drugs Colchinine and Vinblastine do?

Bind subunits and prevent MT assembly

Disrupts spindle assembly

2 Motor proteins for MTs and which direction they move:

Dynein: minus end

Kinesin: plus end

Kinesin and Dynein movement is due to

conformational changes powered by ATP hydrolysis

Motor proteins arrange what two organelles

Golgi and Er

_____ coordinates cilia and flagella movement

Ciliary dynein

4 Roles of actin


Contractile bundles

Protrusions needed for cell movement

Cytokinetic contractile ring

MFs are composed of globular ___proteins aligned with 2 twisted _______



Explain MFs polarity

Actin is more likely to be added to the plus end.

Actin is an


Actin-ATP is added to both ends but faster growth at the

plus end

Treadmilling occurs in


What does the drug Phalloidin do?

binds and stabilizes filaments

What does Cytochalasin do?

Caps filament plus ends, prevents polymerization

What does Latrunculin do?

Binds actin monomers and prevents polymerization

Some MFs are nucleated by

actin nucleating proteins


Branched actin network


unbranched actin network

Lamellipodia are nucleated by

ARP complexes

Growth of unbranched filaments in Fillopodia are promoted by



Bind to the extracellular proteins and internal MFs

Internal contraction of the cell is mediated by

Myosin II

Rho promotes

contractile bundles

Rac promotes


Cdc42 promotes


Muscle cells contain ______ which are chains of repeating _____ units

Myofibrils; sarcomere

specialized region of the Er that holds CA2+

Sarcoplasmic reticulum

What does tropomyosin do?

covers MFs and prevents myosin from binding (resting muscle cell)

4 phases of the cell cycle and what happens in each:

1. G1 phase (gap): cell growth

2. S phase (synthesis): DNA replication

3. G2 phase (gap): cell growth

4. M phase: mitosis and cytokinesis

CDK role in cell division

kinase that activates cellular machinery

* constant amount, but cyclical activation

What activates CDK?


How are cyclin concentrations regulated? 2 ways and how

Transcription: increase in cyclins

Proteolysis: decrease in cyclins

What promotes cyclin transcription for entry into S phase?


by activating G1-Cdk and G1/S-Cdks which inactivateRetinoblastoma (Rb) proteins.

What is the difference between G0 and G1?

In G0, the cell-cycle control system is partlydismantled, so that some of the Cdks and cyclins arenot present. Cells paused in G1, by contrast, stillcontain all the components of the cell-cycle controlsystem. Whereas the latter cells can rapidly progressthrough the cycle when conditions are right, G0cellsneed to synthesize the missing cell-cycle controlproteins so as to re-enter the cycle, which usuallytakes 8 hours or more

What cells dismantle the cell cycle control system completely

muscle and nerve cells

What cell is usually in G0 but can revert back to G1 if needed?

Liver cells


extracellular signal that stimulate cell division by the production of thecyclins.

The Retinoblastoma protein

blocks cellsfrom entering the cell cycle by inhibiting cyclintrascription


Inactivation of G1/Sand S-Cdks during G1and S for DNA repair.

What happens if there is DNA damage?

Activation of p53, Production of p2, Inhibition of cyclin-Cdkcomplexes DNA damage can arrest thecell cycle in G1

Centrosome cycle is triggered by_____in G1

G1/S Cdk and S-Cdk

What are the 4 steps in the initiation of replication (S phase)

look at the slides

Sister chromatids are held together by

cohesin rings

When chromosomesare copied during S phase, they are called

sister chromatids

Activation of M CDK by ___ leads to entry into M phase


What 2 things must be duplicated before the cell can enter mitosis

centrosome and DNA

What two things happen during prophase

mitotic spindle begins to form

chromosomes condense

Phosphorylation by M CDK triggers formation of _____complexes that condense chromasomes


In prophase, motorproteins and MAPs __ __ __formingthe mitotic spindle.

Crosslink interpolar microtubules

2 Things that happen in prometaphase

Nuclear envelope disappears

MTs attach to kinetochores

How is the nuclear envelope broken down

phosphorylation of the nuclear pore proteins and lamins

What happens during metaphase?

Chromosomes line up on the metaphase plate.

Aurora Kinase B

detects tension and promoteskinetochore microtubule stability

What 3 things happen in anaphase?

Chromatids separate

Kinetochore MTs get shorter

Spindle poles move apart

Anaphase begins with

the breakageof the cohesin linkages that hold sisterchromatids together (by enzyme separase)

Securin is an inhibitory protein for


Active APC leads to

ubiquitylation and destruction of securin

What happens in Anaphase A and B

Kinetochore MTs shorten in AA

Sliding force of interpolar MTs push poles apart in AB

What 4 things happen during telophase?

Chromosomes arrive at opposite ends of cell

Contractile ring starts to form

Nuclear envelope is reassembled

Chromosomes decondense

The contractile ring is made of

actin and myosin filaments

Contractile ring assembly is mediated by



In plant cells, the interpolar MTs that form the cell walls

Programmed cell death


Apoptosis is mediated by what family of proteases


What family of proteins promotes AND inhibits apoptosis


Promote apoptosis by releasing cytochrome c from the mitochondria

Bax and Bak

Inhibits apoptosis by inhibiting Bax and Bak


Promotes apoptosis by inhibiting Bcl2


2 examples of mitogens

Platelet-derived growth factors – promoteswound repair–

Hepatocyte growth factor – promotes liver celldivision

inhibits growth and proliferation of myoblasts