Lecture 6

Question 1

What are the two main mechanisms for generating movement?

Answer 1

Assembly and dissemble of microfilaments and microtubules.

2nd mechanism requires motor proteins.

Question 2

Whatvare the two main motor systems in cellular movement?

Answer 2

Actin myosin

Tubulun dynein/kinesin

Question 3

Actin myosin movements. Yeah

Answer 3

Motor proteins:

• muscle contraction
• cytokinesis

Not on MP
cell migration

Question 4

What is myosin 2?

Answer 4

Based on actin motor proteins.
IT IS ALSO CALLED SKELETAL MUSCLE MYOSINE
FOR MUSCLE CONTRACTION

Two heavy chains and two copies of each of two light chains.

Question 5

Structure of heavy chain of MYOSIN TWO

Answer 5

It has; N DOMAIN with a head. The light chains are close to this head.
A long amino acid sequence that forms an extended cooled coil and mediates heavy chain dimerisation

Question 6

In muscle contraction what are myofibrils? Talk about dark and light bands

Answer 6

Myofibrils have small contractile units called sarcomeres.

Dark bands A bands are myosin and light bands are I bands and are actin.

Question 7

How does myosin move along?

Answer 7

By atp generation,
Provide allosteric changes to myosin.

Short lived attached state
Atp bonding releases head
Cocked state. Head is displaced
Weak binding to new site.

Question 8

How is contraction regulated?

Answer 8

There is depolarisation which causes an influx of calcium ions.

These affect troponin and troponyosij which leave the actin myosin binding site. With every myosin, one actin g molecule moves.

Question 9

Movement of organelles

Answer 9

Via microtubules and motor proteins.

Kinesins or dyneins.
Away from centrosome is k. Towards centrosome is dyneins

Question 10

Position of organelles. Microtubules and motor proteins

Answer 10

Normal position is determined by receptor proteins on cytosolic surface of membrane.

Membrane of endoplasmic reticulum binds kinesin

Golgi located near centrosome binding dynein

Question 11

Movement of cilia or flagellum

Answer 11

By bending of its core which is called axenome.

Axenome is composed of microtubules and associated proteins.

Microtubules are arranged in a distinctive pattern. 9 special doublet microtubules are arranges in a ring around a pair of single microtubules.

Question 12

What do flagella and cilia grow from?

Answer 12

Basal bodies

They have 9 groups of three microtubules. In triplets.

Each doublet microtubules of axenome grows from two microtubules in triplet microtubules.

Question 13

Accessory protein when moving cilia.

Answer 13

Ciliary dynein

Interacts with microtubules to generate a sliding force.
Moving of dynein heads will bend the cilium