ORTCITIAEE: Muscle contraction

Question 1

Myofibrils contain many thread-like structures called ______ filaments.

Answer 1

Protein

Question 2

What are the two types of protein filaments?

Answer 2

• Thin filaments (actin)
• Thick filaments (myosin)

Question 3

How many actin filaments are wrapped around each other in a thin filament?

Answer 3

2

Question 4

Within a thin filament, wrapped around the actin filaments is another protein chain called _________.

Answer 4

tropomyosin

Question 5

How many myosin filaments are wrapped around each other in a thick filament?

Answer 5

2

Question 6

Thick filaments are made up of a protein called ______.

Answer 6

myosin

Question 7

Thin filaments are made up of a protein called _____.

Answer 7

Actin

Question 8

What does a sarcomere look like?

Answer 8

AT LEAST

1 myosin filament (in the middle)
4 actin filaments (in each corner of the myosin)

Question 9

Myofibrils are made up of many repeating ______.

Answer 9

Sarcomeres

Question 10

What is the middle of a sarcomere called?

Answer 10

M-line

(literally the middle line)

Question 11

What is the middle of 2 sarcomeres OR/AND the middle of an actin filament called?

Answer 11

Z-line

(2 different sarcomeres that are connected by their actin filaments- it is in the middle of their shared actin filaments OR just in the middle of 1 sarcomeres actin filamets- this is confusing look it up)

Question 12

Under a light microscope what are actin filaments described as?

Answer 12

Light bands (I bands)

Question 13

Under a light microscope what are myosin filaments described as?

Answer 13

Dark bands (A bands)

Question 14

Actin filaments can be described as _____/__ bands.

Answer 14

Light/I

Question 15

Myosin filaments can be described as _____/__ bands.

Answer 15

Dark/A

Question 16

The A-band contains overlapping _____ and _____ filaments

Answer 16

Thin
Thick

Question 17

Why is the H-Zone lighter than the A-band?

Answer 17

Only contains thick filaments
No overlapping thick and thin filaments

Question 18

What is the area between 2 M-lines called?

Answer 18

Z-line

Question 19

What causes the movement of actin and myosin?

Answer 19

An action potential that is triggered inside a muscle fibre of a neuromuscular junction.

Question 20

Where do the calcium ions come from?

Answer 20

Action potential inside muscle fibre causes the sarcoplasmic reticulum to release calcium ions into the myofibrils.

Question 21

What do the calcium ions do?

Answer 21

They trigger tropomyosin to change shape and move away from the binding site, so the myosin heads are able to bind to them.

Question 22

Where in the muscle fibre are calcium ions released from?

Answer 22

Sarcoplasmic reticulum

Question 23

Myosin heads have an active site for ____.

Answer 23

ATP

Question 24

A myosin head that is attached to an actin forms a _______ _____.

Answer 24

Actinomyosin crossbridge

Question 25

Myosin heads hydrolyse ATP into ADP + Pi. What do they use this energy for?

Answer 25

Allows the myosin head to take its starting position

Question 26

Myosin heads hydrolyse ATP. This makes them _____.

Answer 26

ATPases

Question 27

What do calcium ions do?

Answer 27

Trigger tropomyosin to move away from the binding site.

Question 28

Explain the sliding filament theory:

Answer 28

- Calcium ions trigger tropomyosin to move away from the binding site. - Myosin head attaches to a binding site on actin to form an actinomyosin cross bridge. - ADP + Pi are released from the myosin head- the power stroke. - ATP binds to the myosin head and the myosin head detaches from actin. - The myosin head hydrolyses ATP, which releases energy and allows for the myosin head to return to its starting position.

Question 29

How does the sliding filament theory actually allow for muscle contraction?

Answer 29

- Actin contracts within sarcomeres. - Many sarcomeres contracting allows for larger muscle contraction.

Question 30

How is the power stroke triggered?

Answer 30

ADP and Pi are released.

Question 31

What happens to the band/zones during muscle contraction?

Answer 31

Z-lines move closer to eachother H-bands contract A-band and M-line stay thesame