Cytoskleton

Question 1

3 - make up the cytoskeleton

Answer 1

Actin micro filaments
Intermediate filament
Microtubles

Question 2

Microtubles (overview)

Answer 2

subunit: alpha, beta tubles
growth: + end
Enzyme activity: GTP
Motor protein: Kinesine/Dyneins
Associate proteins: MAPS
Structure: hallow tube
Function: chromosome movement, cytoplasmic streaming (cilia+flagella)

Question 3

Intermediate filaments overview

Answer 3

sub-units; globular proteins 
growth: internal
polarity: none
Enzyme activity: none
Motor proteins: none
Associate proteins: plakins
Structure: Rope like fibers. 
Function: structural support.

Question 4

Actin filaments overview

Answer 4

subunits: actin monomers
growth + ends
polarity: yes 
Enzyme activity: ATP 
Motor protein: myosin
Associated proteins: Actin proteins 
Structure: Thin solid flexible fibers 
Functions: Contractility  motility

Question 5

Structure of microtubles

Answer 5

• alpha and beta tubulin
• ATP GTP and Beta GTP = heterodimers
• 13 alpha micro filaments
• (-) end is stable , grows from the + end

Question 6

Colchicine ?

Answer 6

binds to beta subunits and prevents the addition of elongation of microtubles

Question 7

Function of microtubules

Answer 7

• chromosome movement: spindle fibers form during mitosis are made up of bundles of microtubules,
• cytoplasmic streaming

Question 8

The cell cycle

Answer 8

1. G0
2. G1 phase
3. S-phase
4. G2 phase
5. M phase
6. back into G0 or G1 phase
7. Cytokinesis

Question 9

The G0 phase

Answer 9

cell resting not going through mitosis, functional stage of the cell.

Question 10

G1 phase -

Answer 10

Growth phase, synthesize and prep enzymes and proteins to duplicate it’s chromosome.

Question 11

G2 phase

Answer 11

cell preps and synthesize the enzymes and proteins to undergo mitosis.

Question 12

M phase

Answer 12

mitosis cell separates the duplicated chromosomes and enclose them into two different nuclei.

Question 13

What happens after the M phase?

Answer 13

the cell can go back to G0 phase or G1 phase.

Question 14

Cytokineses

Answer 14

separation of the cytoplasm

Question 15

Steps of Mitosis

Answer 15

PMAT

Question 16

Prophase

Answer 16

a. Duplicated chromosomes condense
b. Nuclear membrane dissociates
c. Centriole duplicates

Question 17

Structure of centrioles

Answer 17

a. Radial spoke proteins
b. B+C = have 10 microfilaments
c. B filaments are attached to the adjacent C microtubules by a nectin-like protein

Question 18

Metaphase:

Answer 18

spindle fibers form (bundles of microtubules) from centrioles and grow out to center of cell where they join to duplicated chromosomes

a. Pericentiolar area - formation site of the spindle fibers via
i. 13 gamma tublin

Question 19

Centrosome

Answer 19

found near the nucleus.

• Made up of 2 centrioles.
• Formation site for mitotic spindle and microtubles.

Question 20

How do fibers attach to the chromosome?

Answer 20

a. Via the centromere – composed of satellite DNA, highly repetitive DNA , no protein coding regions
b. Duplicated chromosome joined at centromere

Question 21

Centrome structure:

Answer 21

Chromosome Inner Protein plate - Interzone proteins  Interplate proteins  spindle fibers.

Question 22

what does Kinesin do during mitosis?

Answer 22

motor proteins that carry alpha and beta sub-units to a spindle fiber to lengthen it.

Question 23

Anaphase:

Answer 23

duplicated chromosomes separate , spindle fibers sorten and single chromosomes pull apart . Dynein motor proteins carries alpha and beta subunits to centrioles

Question 24

Telophase:

Answer 24

a. Single chromosomes reach the centrioles
b. Spindle fibers have been broken down
c. Nuclear membrane reforms
d. One centriole at each nucleus is broken down.

Question 25

Cytokinesis:

Answer 25

separating of cytoplasm after mitosis.

Question 26

Cytokinesis (animal cells)

Answer 26

a. Animal cells – actin microfilaments in cytoplasm between 2 cells i. Actin and its motor protein

Question 27

Cytokinesis (plant cells)

Answer 27

cytokinesis is called cell plate formation i. Golgli complexes in plant cells releases vesicles of membrance and cell wall ii. Vesicles join to form membrane and cell wall fro separation.

Question 28

How are 7. Microtubules responsible for Vesicle movement in the cytoplasm ?

Answer 28

a. Example: in a nerve cell, the movement of nuerotransmiters down the axon i. Anterograde transport : from the body to the end of the axon “forward movement” ii. Retrograde transport: from the end of axon back to the cell body

Question 29

8. MAPS: microtubules associated proteins

Answer 29

microtubules associated proteins

Question 30

kinesin (family of proteins)

Answer 30

i. Kinesin moves molecules in a anterograde transport toward the + end of microtubule. 1. Orginally called CENP-E (centriole protein E)

Question 31

Dymein family protein

Answer 31

Dymein family protein of motor protein moves vesicles in retrograde transport (back toward the (– ) end of microtubule.

Question 32

Melanophores

Answer 32

pigment containing vesicles found in frogs to darken the skin = anterograde transport toward the cell membrane. To lighten the skin retrograde transport of vesicled toward the center the cell.

Question 33

Experiment to demonstrate MAP's #1

Answer 33

EXP #1: Giant squid axon  Isolate cystoplam from squid axon  spread on a microscope slide - add dye containing vesicles  RESULTS: Vesicles moved along the microtubule in the squid cytoplasm.

Question 34

Experiment to demonstrate MAP's #2

Answer 34

i. Added isolated mictotuble  added TAXOL chemical joined microtubule into bundle  add ATP  added vesicles containing dye --> Results: no movement of vesicles along the microtubule.

Question 35

MAPS

Answer 35

d. MAPS are part of the kinesin family of motor protein. 380,000 molecular weight , 4 polypeptides 2 long and 2 short i. Globular head function: ATP hydrolysis , ATP  ADP, Pi + energy ii. Carboxyterminal and short protein bind to vesicles .

Question 36

Kinesin

Answer 36

ATP motor proteins that walk along microtubules anterograde + end.

Question 37

Dynein

Answer 37

ATP motor proteins that walk along microtubules retrograde | - end.

Question 38

Microtubules responsible Cilia and Flagella movement of whole cell

Answer 38

1. Microtubules responsible Cilia and Flagella movement of whole cell a. Sperm have flagella b. Cells line respiratory system have cilia (to remove foreign materials) c. Cilia – short , flagella – long