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AQA A Level Biology > Muscles > Flashcards

Muscles Flashcards

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1
Q

What is cardiac muscle?

A

Contracts without conscious control - only found in the heart

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2
Q

What is smooth muslce?

A

Contracts without conscious control - found in the walls of internal organs e.g. stomach, intestine, blood vessels

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3
Q

What is skeletal muscle?

A

Voluntary muscle, used to move e.g. biceps and triceps

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4
Q

What is skeletal muscle also known as?

A

Striated, Striped, Voluntary muscle

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5
Q

What is skeletal muscle made up of?

A

Long cells - called muscle fibres

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6
Q

What is the cell membrane of the muscle fibre called?

A

Sarcolemma

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7
Q

What are transverse (T) tubules?

A

Where parts of the sarcolemma fold inwards all across the muscle fibre - they stick into the sarcoplasm.

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8
Q

What is the sarcoplasm?

A

The muscle fibres cytoplasm.

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9
Q

What do T tubules help do?

A

They help spread electrical impulses throughout the sarcoplasm. This is so that they reach all parts of the muscle fibre.

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10
Q

What is the sarcoplasmic reticulum?

A

It is a network of internal membranes which run through the sarcoplasm.

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11
Q

What does the sarcoplasmic reticulum do?

A

It stores and releases calcium ions - needed for muscle contraction.

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12
Q

What do muscle fibres have lots of and why?

A

Mitchondria - to provide the ATP needed for muscle contraction.

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13
Q

What are multinucleate?

A

Muscle fibres

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13
Q

Muscle fibres have lots of long cylindrical ORGANELLES… what are they called?

A

Myofibrils

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13
Q

What are myofibrils made up of?

A

proteins

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13
Q

Myofibrils are highly specialised for what?

A

Contraction

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14
Q

What do myofibrils contain?

A

Bundles of thick and thin myofilaments

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15
Q

What do the myofilaments do to make muscles contract?

A

The myofilaments move past each other

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16
Q

What are the thick myofilaments made up of?

A

The protein - myosin

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17
Q

What are the thin myofilaments made up of?

A

The protein - actin

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18
Q

What can you see when looking at a myofibril under an electron microscope?

A

A pattern of alternating dark and light bands.

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19
Q

What do the dark bands show in a myofibril - under an electron microscope?

A

The thick myosin filaments + some overlapping thin actin filaments
These are called A-bands
dArk bands

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20
Q

What do the light bands show in a myofibril - under an electron microscope?

A

Contain only the thin actin filaments
These are called I-bands

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21
Q

What is a myofibril made up of?

A

Many short units called - sarcomeres

22
Q

What marks the end of each sarcomere?

A

Z-line

23
Q

What is the middle of each sarcomere called?

A

M-line

24
Q

What is the H-zone?

A

Near the M-line, but only contains myosin filaments

25
Q

What are the A-bands?

A

thick myosin filaments + some overlapping thin actin filaments

25
Q

What are the I-bands?

A

Contains only the thin actin filaments

25
Q

What changes when the sarcomere is contracting?

A

The I-band gets shorter
The H-zone gets shorter

26
Q

What is the only thing that stays the same when the sacromere contracts?

A

The A-band

27
Q

What is the sliding filament theory?

A

Where actin and myosin filaments slide over one another to make the sacromere contract

28
Q

How does the sliding filament theory result in muscle contraction?

A

The sacromeres contract –> the myofibrils contract –> the muscle fibres contract

29
Q

What happens to the sacromere when it relaxes?

A

It returns back to its original length.

30
Q

What do ligaments connect?

A

Bone to bone

31
Q

What do tendons connect?

A

Skeletal muscle to bone

32
Q

How do a pair of muscles act?

A

In antagonistic pairs against an incompressible skeleton.

33
Q

Describe the role of calcium ions in the contraction of a myofibril:

A

Ca ions diffuse from the sarcoplasmic reticulum into the myofibrils
Ca ions cause the movement of tropomyosin
This movement exposes the binding site on the actin
Myosin heads attach to binding site on actin
An actin-myosin cross-bridge forms

34
Q

DESCRIBE the role of ATP in the contraction of a myofibril:

A

Hydrolysis of ATP (on myosin heads) causes myosin heads to bend
Pulling actin molecules
Attachment of a new ATP molecule to each myosin head causes myosin heads to detach from actin sites.

35
Q

WHAT is the role of ATP in myofibril contraction?

A

Provides energy to move myosin heads
Reaction with ATP breaks actin-myosin bridge and allows binding of myosin to actin.

36
Q

A fall in pH leads to a reduction in the ability of calcium ions to stimulate muscle contraction - how?

A

low pH changes shape of Ca2+ receptors, so fewer Ca2+ bind to tropomyosin, so fewer tropomyosin molecules move away, fewer binding sites on actin revealed, fewer myosin heads can bind and fewer actin-myosin cross bridges form.

37
Q

How is ATP a suitable energy sources for cells to use?

A

It phosphorylates other compounds, making them more reactive
It can be rapidly re-synthesised
Releases energy instaneously
Releases relatviely small amounts of energy
ATP is not lost from cells

38
Q

What are the 3 sources of energy for muscle contraction?

A

Aerobic respiration
Anaerobic respiration
ATP - PCr system

39
Q

What does PCr stand for?

A

Phosphocreatine

40
Q

How does the ATP-PCr system provide energy for muscle contraction?

A

ADP is phosphorylated using a phosphate group from PCr. The system geenrates ATP very quickly.
The system is anaerobic and it’s alactic

41
Q

Where is PCr stored?

A

insides cells

42
Q

When is the ATP-PCr system used?

A

During short bursts of vigorous exercise as PCr runs out very quickly

43
Q

What does alactic meaning?

A

Does not form lactate

44
Q

What does PCr get broken down into?

A

Creatinine

45
Q

Where can creatinine be removed from and to where?

A

From blood via kidneys

46
Q

How does aerobic repiration provide energy for muscle contraction?

A

Most ATP is generated via oxidative phsophorylation (in mitochondria)
Long periods - low intensity

47
Q

How does anaerobic repiration provide energy for muscle contraction?

A

ATP made rapidly by glycolysis. End product is pyruvate –> converted into lactate (by lactate fermentation)
Lactate quickly builds up on muscles causing fatigue - short periods/ high intensity

48
Q

Why is converting pyruvate to lactate essential for the continued production of ATP (during anaerobic respiration)?

A

Regenrates NAD
So that glycolysis can continue

49
Q

What is myoglobin?

A

A single chain protein
It has a high affinity for oxygen and can combine at very low partical pressures

50
Q

What is a slow twitch muscle fibre?

A

Found in muscles that carry out endurance exercise - adapted to carry out aerobic respiration

51
Q

How are slow twitch muscle adapted to aerobic respiration?

A

They are high in myoglobin

52
Q

What colour are slow and fast twitch muscle fibres?

A

Slow - red
Fast - pale

53
Q

What is a fast twitch muscle fibre?

A

contract rapidly/powerfully for short periods. useful for intense exercise + adapted for anaerobic respiration (LOW in myoglobin)

54
Q
A

AQA A Level Biology (23 decks)

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