Lecture 5

Question 1

What does the cytoplasm include?

Answer 1

Cytosol.
Cytoskeleton.
Organelles
Cellular deposits.

Question 2

What is the cytoskeleton?

Answer 2

NETWORK OF PROTEIN FILAMENTS.
Determines the cell shape.
Responsible for movements.

Question 3

What are the three types of cytoskeletal filaments?

Answer 3

Actin filaments- determine shape of the cell

Microtubules- determine movement and position of organelles

Intermediate filaments_ provide mechanical strength and resistaance

Question 4

What are accessory proteins?

Answer 4

They link filaments to other cell components.

Include motor proteins that move organelles along filaments.

Question 5

What are actin filaments? Where are they concentrated?

Answer 5

Also known as microfilaments
5-9nm in diameter
Concentrated in cell Cortex beneath plasma membrane

Question 6

What are the two types of actin?

Answer 6

We had globular 5 nm thick, and one pp change

Filamentous. 7-9 nm thick, two intertwined chains.

Question 7

Describe actin structure

Answer 7

Bundles or network of filaments.

Uniformly oriented g actin.
Two ends, a minus slow growing inert end and a plus positive fast growing end.

Question 8

Actin filament nucleation. Where does it occur?

What phases follow?

Answer 8

Plasma membrane.
Consequently, the highest density of actin filaments in most cells is at the cell periphery.

Phases that follows; elongation and equilibrium phase.

Question 9

Talk about depolymerisation. With actin.

Answer 9

Actin molecule is clam shaped.
Has atp.
Terminal phosphate is hydrolysed and adp is left.
Actin interacts less with adp with neihbours.

Question 10

Examples of actin filaments determining cell shape

Answer 10

Microvilli bundles of actin fil
Lamellipoedia web of actin filaments
Contractile ring contractile bundles of actin filaments with myosin

Question 11

Lamollepedia of fibroblasts

Answer 11

Contain actin filaments
Plus ends are stuck inside the plasma membrane
Important for cell locomotion and chemotaxis

Question 12

What are microtubules made of?

Answer 12

Protein tubilin

One end attached to a centrosome

Question 13

Compare microtubules rigity to actin?

Answer 13

Actin is less rigid.

Question 14

Microtubules

Answer 14

Hollow stiff cylindrical structure
13 parallel protofilaments
Microtubules have distinc structural polarity
Alpha is minus and beta is positive

Question 15

Depolarisation. And polymerisation of microtubules can be influenced by what?

Answer 15

Antimetotic drugs

Colchine wjich binds tightly to tubulin. This causes rapid disappearance of mitotic spindle which kills cell.

Taxol bunds to microtubules and stabilises which arrests division. Anti cancer drugs.

Question 16

Where do microtubules originate?

Answer 16

The water in the centrosome.

Question 17

Centrosome structure

Answer 17

2 centrioles
Centrosome matrix
Astrr

Question 18

Motor proteins. What do they do? MAP

Answer 18

Use the energy of atp hydrolysis to move along a microtubule. KINESIN AND DYNEINS

Question 19

Intermediate filaments. Where are they found?

Answer 19

Meshwork Beneath the nuclear envelope

In the cytoplasm. Epithelial, nerve cells and muscle cells.