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Y13 A2 Biology > Muscle contraction > Flashcards

Muscle contraction Flashcards

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1
Q

What is the structure of a myosin filament?

A

They have globular heads that are hinged, they can move back and forth. Each myosin head has a binding site for actin and a binding site for ATP

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2
Q

What is the structure of an actin filament?

A

They have binding sites for myosin heads (actin-myosin binding sites).

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3
Q

What protein is found between actin filaments?

A

Tropomyosin

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4
Q

What is the purpose of tropomyosin?

A

Helps myofilaments move past each other

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5
Q

What is the myosin-actin binding site like in a resting muscle?

A

Blocked by tropomyosin which means that the myofibrils cant slide past each other because the myosin heads cant bind to the actin filaments

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6
Q

What happens to the sarcolemma when an action potential arrives?

A

It becomes depolarised

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7
Q

What happens once the sarcolemma has become depolarised?

A

Depolarisation spreads down the T-Tubules in the sarcoplasmic reticulum

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8
Q

When the T-Tubules become depolarised, what happens?

A

The sarcoplasmic reticulum releases stored calcium ions into the sarcoplasm and this influx causes muscle contraction

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9
Q

What role do Ca2+ ions have in muscle contraction?

A

They attach to tropomyosin which causes the protein to change shape, pulling it out of the actin-myosin binding site on the actin filament

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10
Q

What is the actin-myosin cross bridge?

A

The bond formed when a myosin head binds to an actin filament

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11
Q

What do Ca2+ ions activate?

A

ATP hydrolase

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12
Q

What does ATP hydrolase do?

A

Hydrolyses ATP into ADP and Pi to provide the energy needed for the muscle contraction

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13
Q

What does the energy released from the ATP being hydrolysed also do?

A

Causes the myosin head to bend which pulls the actin filament along in a kind of rowing action

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14
Q

How is the actin-myosin cross bridge broken?

A

Another ATP molecule provides the energy to break the actin-myosin cross bridge so the myosin head detaches from the actin filament after its moved

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15
Q

What does the myosin head do once the actin-myosin cross bridge is broken?

A

Returns to its starting position and reattaches to a different binding site further along the actin filament

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16
Q

What rate do actin-myosin cross bridges form and break?

A

Very rapidly

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17
Q

What happens when the muscle stops being stimulated?

A

Calcium ions leave their binding sites and are moved by active transport back into the sarcoplasmic reticulum.
This causes the tropomyosin molecules to move back so they block the actin-myosin binding sites again

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18
Q

What happens to the sarcomere and actin filaments when the muscles aren’t contracted?

A

The sarcomere lengthens as the actin filaments slide back to their relaxed position

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19
Q

What three ways is the ATP generated for muscle contraction?

A

1) Aerobic respiration
2) Anaerobic respiration
3) ATP-Phosphocreatine system

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20
Q

How is ATP generated in aerobic respiration?

A

Mostly generated in oxidative phosphorylation in the cell’s mitochondria

21
Q

When is using aerobic respiration good?

A

Long period of low intensity exercise

22
Q

How is ATP generated in anaerobic respiration?

A

it is generated rapidly in glycolysis, the end product in glycolysis is pyruvate

23
Q

What is the issue with anaerobic respiration?

A

When pyruvate is converted to lactate by lactate fermentation, lactate can build up in the muscles and cause muscle fatigue

24
Q

When is using anaerobic respiration good?

A

Short periods of hard exercise

25
Q

What is the equation for the production of ATP using the ATP-phosphocreatine system?

A

ADP + PCr -> ATP + Cr (creatine)

26
Q

Where is PCr stored?

A

In cells

27
Q

When is PCr used?

A

Short bursts of vigorous exercise

28
Q

What are the features of the ATP-PCr system?

A

Anaerobic

Alactic

29
Q

What does some of the creatine get broken down into?

A

Creatinine

30
Q

How is creatinine removed from the body?

A

Via the kidneys

31
Q

In what type of people are creatinine levels high in?

A

People who exercise regularly and those with a high muscle mass

32
Q

What does high creatinine levels indicate?

A

Kidney damage

33
Q

How does the ATP-PCr system generate ATP?

A

ADP becomes phosphorylated into ATP and the phosphate comes from the PCr

34
Q

Do slow twitch muscle fibres contract slowly or quickly?

A

Slowly

35
Q

How long can slow twitch muscle fibres work for?

A

Long periods of time without getting tired

36
Q

What are slow twitch muscle fibres good for?

A

Endurance activities

37
Q

Where are high proportions of slow twitch muscle fibres found?

A

In the muscles for posture eg. back and calves

38
Q

What type of respiration is used in slow twitch muscle fibres?

A

Slowly through aerobic respiration

39
Q

What do slow twitch muscle fibres have?

A

Lots of mitochondria and blood vessels to supply the muscle with oxygen

40
Q

Where are the mitochondria in slow twitch muscle fibres found and why?

A

The edge of muscle fibres

Short diffusion pathway for oxygen from the blood vessels to the mitochondria

41
Q

What is myoglobin?

A

Red-coloured protein that stores oxygen

42
Q

Do slow twitch fibres or fast twitch fibres have lots of myoglobin?

A

Slow twitch muscle fibres

43
Q

Do fast twitch muscle fibres contract fast or slow?

A

Very fast

44
Q

How long can fast twitch muscle fibres contract for?

A

Short periods of time as they get tired really quickly

45
Q

What are fast twitch muscle fibres good for?

A

Short bursts of speed and power

46
Q

Where are high amounts of fast twitch muscle fibres found?

A

In muscles that you use for fast movement, such as legs, arms and eyes

47
Q

How is energy released in fast twitch muscle fibres?

A

Quickly through anaerobic respiration

48
Q

What do fast twitch muscle fibres have stores of? Why?

A

PCr

So energy can be generated very quickly when needed

49
Q

What do fast twitch muscle fibres not have a lot of?

A

Mitochondria
Blood vessels
Myoglobin

Y13 A2 Biology (45 decks)

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