Muscle Movement

Question 1

Skeletal muscle is antagonistic. What does this mean?

Answer 1

Muscles work in pairs as one contracts and the other relaxes.

Question 2

Describe muscle structure.

Answer 2

Muscle contains fibres.
Fibres divide into myofibrils.

Question 3

What is the cell membrane of a muscle cell called?

Answer 3

Sarcolemma

Question 4

What is the cytoplasm of a muscle cell called?

Answer 4

Sarcoplasm

Question 5

What is the endoplasmic reticulum of a muscle cell called?

Answer 5

Sarcoplasmic reticulum

Question 6

Myofibrils are made of which 2 proteins?

Answer 6

Actin
Myosin

Question 7

What is a sarcomere?

Answer 7

A section of myofibril.

Question 8

What is the Z line?

Answer 8

Where the sarcomere ends.

Question 9

What is the Z line made of?

Answer 9

Actin only

Question 10

What is the M line?

Answer 10

The middle of the sarcomere

Question 11

What is the M line made of?

Answer 11

Myosin only

Question 12

Where is the H zone?

Answer 12

The whole region of muscle fibre containing myosin only.

Question 13

What are I bands?
What is another name for I bands?

Answer 13

Sections of the sacromere containing actin only. Also known as the light band.

Question 14

What are A bands?
What are A bands also known as?

Answer 14

Sections of the sarcomere containing both actin and myosin.
Also known as the dark band.

Question 15

Compare the thickness of actin with myosin.

Answer 15

Actin is thinner, myosin is thicker.

Question 16

What is tropomyosin?

Answer 16

Thin threads wound around actin filaments.

Question 17

State what happens to the H zone, I band, A band and Z lines during muscle contraction.

Answer 17

H zones shorten
I band shortens
A band stays the same
Z lines become closer

Question 18

Name the theory used to describe muscle contraction.

Answer 18

Sliding filament theory.

Question 19

During muscle contraction, action potential causes the release of what ions from the sarcoplasmic reticulum?
These ions are released using which transport process?

Answer 19

Ca2+ Released using active transport

Question 20

During muscle contraction, Ca 2+ released from the sarcoplasmic reticulum diffuses through where?
Where do the ions reach?

Answer 20

Ca 2+ diffuses through the sarcoplasm to the myofibril.

Question 21

During muscle contraction, calcium ions bind to what protein?

Answer 21

Tropomyosin

Question 22

During muscle contraction, binding of Ca 2+ to tropomyosin causes it do what?
What is now exposed by the tropomyosin?

Answer 22

Binding of calcium ions to tropomyosin causes it to move and change shape.
This leads to the myosin binding site on the actin becoming exposed.

Question 23

During muscle contraction, what biomolecule is attached to the myosin heads?

Answer 23

ADP

Question 24

During muscle contraction, how does the actin attach to the myosin?
What biomolecule is required for this process?

Answer 24

Myosin heads attach to binding sites forming a crossbridge. This requires ADP.

Question 25

Describe the movement of actin and myosin during muscle contraction.

Answer 25

Myosin heads pull and slide along actin.

Question 26

During muscle contraction, how is the crossbridge between actin and myosin broken.

Answer 26

Binding of ATP to myosin head causes it to detach from the actin binding site.

Question 27

During muscle contraction, how do the myosin heads return to their original position? (hydrolysis of what substance)

Answer 27

ATP is hydrolysed by ATPase, releasing energy for the myosin heads to return to their original position.

Question 28

During muscle contraction, ATPase is activated by what ions?

Answer 28

Ca 2+

Question 29

After the actin/myosin cross bridge has been broken, what occurs further along the actin?

Answer 29

Myosin reattaches to a different binding site.

Question 30

What are slow twitch muscle fibres adapted to? Give an example of an activity requiring slow twitch fibres.

Answer 30

Sustained muscle contraction (endurance). Eg: long distance running

Question 31

Why do slow twitch fibres contain lots of myoglobin?

Answer 31

To store large amounts of oxygen for aerobic respiration.

Question 32

Why do slow twitch fibres contain lots of mitochondria?

Answer 32

Allows for high rate of respiration.

Question 33

Why do slow twitch fibres contain lots of capillaries? How does this prevent muscle fatigue?

Answer 33

Decrease diffusion pathway and increase surface area, providing a high supply of oxygen and glucose for aerobic respiration. This reduces the need for anaerobic respiration to occur, stopping lactic acid build up and muscle fatigue.

Question 34

What are fast twitch fibres adapted to? Give an example of an activity that would require them.

Answer 34

Adapted for intense, short periods of rapid muscle contraction. For example, sprinting.

Question 35

Why are fast twitch muscles adapted for anaerobic respiration?

Answer 35

To produce ATP and release energy rapidly.

Question 36

Why do fast twitch fibres have low levels of myoglobin?

Answer 36

The muscles typically respire anaerobically so large stores of oxygen are not required.

Question 37

Why do fast twitch muscles contain large amounts of glycogen? Why is this inefficient? Link this to ATP production in glycolysis.

Answer 37

This can be hydrolysed to glucose, which used in glycolysis. Glycolysis only yields 2 ATP, which is inefficient

Question 38

Explain how the rate of anaerobic respiration is increased in fast twitch muscles.

Answer 38

High concentration of enzymes used in anaerobic respiration in the cytoplasm

Question 39

What is the benefit of fast twitch fibres containing large stores of phosphocreatine? Name the process this molecule is involved in.

Answer 39

It can rapidly generate ATP from ATP by providing a phosphate. (phosphorylation)

Question 40

Why do fast twitch muscles become fatigued more quickly?

Answer 40

They store high amounts of lactate.

Question 41

Where is phosphocreatine stored in muscles?

Answer 41

Inside muscle cells.

Question 42

What type of exercise is phosphocreatine used in?

Answer 42

Short bursts of vigorous exercise.