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A Level Biology Paper 2 > Muscles > Flashcards

Muscles Flashcards

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1
Q

How are sarcomeres positioned

A

Run adjacent to eachother

Along length of myofibril

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2
Q

Example of an antagonistic pair

A

Bicep

Tricep

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3
Q

What is dystophin

A

Prevents membrane damage when muscle contracts

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4
Q

What is duchenne muscular dystrophy

A

A genetic mutation, X linked recessive disease
Causes dystrophin to be extremely short
Usually lacking dystroglycan binding end
So every time muscle contracts small rips appear in membrane
Allowing for diffusion of molecules
Calcium diffuses in and activates enzymes called proteases that break down proteins
Instead of breaking old and non functional proteins they also break down new functional proteins
Creatine kinase leaks out of myocyte and into blood and can be uses to identify DMD
Meaning less energy storage occurs

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5
Q

What type of neurone stimulates muscle contraction

A

Motor neurone

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6
Q

What is the power stroke

A

The myosin head changes angle and bends to pull the actin filament a short distance over itself

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7
Q

What is the recovery stroke

A

When ATP is hydrolysed into ADP and Pi by ATP hydrolase

And the energy released re cocks the myosin head

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8
Q

Advantages of using aerobic respiration instead if anaerobic to provide ATP in a long distance race

A

Waste product carbon dioxide is easily removed from body during aerobic respiration
Aerobic respiration releases/produces more ATP
Lactate will not accumulate in the body so avoids cramps

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9
Q

Why does converting pyruvate into Lactate allow the continued production of ATP by anaerobic respiration

A

Regenerates NAD
Glycolysis continues
ATP can be produced via substrate level phosphorylation

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10
Q

Why can’t cross bridges between actin and myosin be broken after death

A

No respiration after death

ATP required to break cross bridges

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11
Q

What happens to the length of the I band and A band when sarcomeres contract

A

Neither change in length

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12
Q

3 types of muscle

A

Smooth; contracts without conscious control, in walls of internal organs like stomach and intestines

Cardiac; contracts without conscious control, myogenic, only found in the heart

Skeletal; striated muscle used in locomotion like biceps and triceps and work in antagonistic pairs

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13
Q

What are antagonistic pairs

A

Pair of muscles
As one contracts the other relaxes
Since muscles can only pull

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14
Q

How are skeletal muscles attached to bone

A

Tendons

Fibrous proteins

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15
Q

Key structures of the skeletal muscle

A 
Bone
Tendon
Muscle:
Sarcolemma
Sarcoplasm 
Myofibril
Myofilament
Actin and myosin
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16
Q

How are muscle cells specialised

A

Long thin cells

Several nuclei

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17
Q

Sarcolemma

A

Each muscle fibre is surrounded by this thin cell membrane

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18
Q

Epimysium

A

Protective layer surrounding muscles that protects from friction against other muscles and bones
Continues at the end of the muscle go form tendons along with other connective tissue that connects muscle to bone

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19
Q

Endomysium

A

Fibrous connective layer of tissue covering each muscle fibre
Insulates each fibre

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20
Q

What can be found on the Sarcolemma

A

Acetylcholine receptors

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21
Q

Sarcoplasm

A

Contains a large number of mitochondria, organelles, nuclei, sarcoplasmic reticulum

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22
Q

Myofibrils

A

Run parallel to each other along the length of muscle cells
Surrounded by sarcoplasmic reticulum
Made of myofillaments that are divided into thick (myosin) and thin (actin) myofilaments

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23
Q

What are sarcomeres

A

Run adjacent to eachother along the length of the myofibril

Contractile units made of mypfilaments actin and myosin

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24
Q

Sarcoplasmic reticulum

A

Stores and releases calcium ions for muscle contraction

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25
Q

Striated

A

Under light microscopes dark bands are visible across the muscle fibre

Under electron microscopes dark bands are visible across each myofibril
Each darcomere had a distinctive banding pattern due to the presence or absence of thick and thin filaments

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26
Q

What is the result of the sliding filament theory

A 
Sarcomere shortens
Z lines closer
Actin pulled over myosin
Increased overlap means appears darker
Filaments the same size
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27
Q

Explain a relaxed myofibril

A

Tropomyosin covers the binding site on actin filament which myosin attaches to

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28
Q

Explain the sliding filament theory

A

Muscle fibre excited by a motor neurone
Ca²+ released from sarcoplasmic reticulum
Into sarcoplasm
Ca²+ diffuses and binds to troponin
Conformational change in shape
Causes tropomyosin to move
Exposing myosin heads binding sites on actin filament
Myosin head binds and forms a cross bridge
Nods and bends to pull actin filament over itself in the power stroke
ADP and Pi released from myosin head
New ATP binds and breaks the cross bridge
Myosin separates from actin
ATP hydrolysed to ADP and Pi by ATP hydrolase
Energy released re-cocks the myosin head in recovery stroke
Process repeats to pull actin over myosin a bit more each time
Shortening of sarcomere

FINISH

29
Q

Explain Ca²+ in muscles

A

Actively transported back into the sarcoplasmic reticulum
Activate ATP hydrolase
Bind to troponin and cause a conformational change in shape to tropomyosin to uncover the myosin head binding site

30
Q

Why can producing less ATP mean people aren’t able to maintain strong muscle contractions during exercise

A

ATP is needed for attachment and cross bridges between actin and myosin
Power stroke in which myosin head bends to pull actin over it from ATP hydrolysis
Dectachment of myosin heads when new ATP binds
Myosin heads move back to original position in recovery stroke

31
Q

Describe the role of tropomyosin and myosin in myofibril contractions

A

Tropomyosin:
Moves out of the way when calcium ions bind to troponin
Allowing myosin head to bind and form cross bridge

Myosin:
Myosin head inds to actin and performs power stroke to pull actin over itself
Myosin head detaches and resets in recovery stroke
Uses ATP

32
Q

Why do mitochondria in muscles contain many cristae

A

Large face area for the electron transport stem/oxidative phosphorylation
Provides ATP needed for muscle contraction

33
Q

Why does increased cardiac output give an advantage in exercise

A

In exercise more energy released/more respiration/more oxygen for aerobic respiration
Higher cardiac output means more oxygen supplied to muscles
Increased glucose supply to muscles
Increased carbon dioxide removed and more lactate removed
Increases heat removal for cooling

34
Q

Importance of ATP hydrolase in muscle contraction

A

Hydrolyses ATP yielding energy

Used to break cross bridges

35
Q

What are the advantages of using aerobic rather than anaerobic respiration to provide ATP for long distance races

A

Aerobic respiration releases more energy/produces more ATP
Little/no lactate produced so doesn’t accumulate
Avoiding cramps and muscle fatigue
CO2 removed easily from the body by breathing

36
Q

A muscle fibre contracts when it is stimulated by a motor neurone

How does transmission occur across the synapse between the motor neurone and a muscle fibre

A

Calcium ion channel proteins open
Calcium ions enter neurone by facilitated diffusion
Vesicles move towards and fuse with presynaptic membrane
Release the neurotransmitter via exocytosis
Neurotransmitter diffuses across the synaptic cleft
Binding to receptor on post synaptic membrane
Sodium ion channels open and sodium ions enter

37
Q

Why do cross bridges between actin and myosin remain firmly bound after death and lead to rigor mortis

A

Respiration stops
No more ATP produced
ATP needed to break the actin and myosin cross bridges

38
Q

Describe the role of phosphocreatine

A

Provides a phosphate
Phosphorylating ADP
To produce ATP

39
Q

Describe fast twitch muscle fibres

A

Used for rapid and brief and powerful contractions
Phosphocreatine used up rapidly during contraction to make ATP
Anaerobic respiration involved
ATP used to reform phosphocreatine
Lots of phosphocreatine in fast muscle fibres

40
Q

Describe the role of calcium ions in the contraction of a sarcomere

A

Binds to binding site on troponin and causes tropomyosin to move
Exposing myosin head binding sites on actin
Allowing myosin head to bind to actin and form a crossbridge
Activates ATP hydrolase to hydrolyse ATP and provide energy needed for power stroke

41
Q

Use of ATP other than in power stroke and recovery stroke

A

Active transport of calcium ions back into the sarcoplasmic reticulum

42
Q

A muscle fibre can only store enough ATP to sustain muscle contraction for how long

A

3 to 4 seconds

43
Q

How long does regeneration of ATP by anaerobic respiration take

A

10 seconds
This is too long in fight or flight instances
Even longer if aerobic

44
Q

Is phosphocreatine a source of ATP

A

No
Source of Pi
Which is used to create ATP from ADP and Pi

45
Q

What is phosphocreatine

A

A molecule stored in fast twitch muscle fibres
That can donate a Pi to phosphorylate ADP and produce ATP in the short term
Replenished during relaxation

46
Q

Slow twitch muscle fibres

A

Slow sustained contractions over long periods of time with a slower rate of contraction
Lots found in legs and those involved in maintaining posture

47
Q

How are slow twitch muscle fibres adapted/specialised

A

Use aerobic respiration to regenerate ATP so have many large mitochondria and some just under the sarcolemma to provide the ATP needed for active transport of calcium ions, and some deep between the myofibrils

High concentrations of myoglobin act as oxygen stores and give the slow twitch muscle fibres their red colour

Very closely associated with large number of capillaries to provide a good oxygen supply to increase amount of oxygen for oxidative phosphorylation to produce lots of ATP for muscle contraction

Less extensive sarcoplasmic reticulum since less calcium ions required at any one time

Less glycogen as glucose broken down fully by aerobic respiration

48
Q

How are fast twitch muscle fibres adapted/specialised

A

To use PC-ATP anaerobic respiration energy systems to regenerate ATP so have fewer smaller mitochondria

Low myoglobin concentration since primary energy systems are anaerobic

Fewer capillaries associated with fibres

Extensive sarcoplasmic reticulum since more calcium ions required at one time for rapid, intense contraction

More glycogen as more glucose required as anaerobic respiration yields less ATP per glucose

49
Q

Key points to discuss when comparing slow and fast twitch (9)

A 
Colour
Contraction speed
Activity
Duration
Fatigue
Power
Storage
Mitochondria
Sarcoplasmic reticulum

SMS CDC PAF

50
Q

Similarities between slow and fast twitch

A

Both follow sliding filament theory
Both use ATP hydrolase
Both produce ATP
Both allow for shortening of sarcomere

51
Q

Compare colour for slow and fast twitch

A

Slow; Red due to oxidative phosphorylation and myoglobin as an oxygen store

Fast; White due to less oxygen and myoglobin

52
Q

Compare duration for slow and fast twitch

A

Slow; Longer, more energy provided due to oxidative phosphorylation

Fast; Shorter, cannot be sustained for a long time

53
Q

Compare conduction speed for slow and fast twitch

A

Slow; Slow

Fast; Fast

54
Q

Compare storage for slow and fast twitch

A

Slow; Triglycerides

Fast; ATP, phosphocreatine, glycogen

55
Q

Compare Mitochondria for slow and fast twitch fibres

A

Slow; more, longer

Fast; less, shorter

56
Q

Compare sarcoplasmic reticulum for slow and fast twitch fibres

A

Slow; Smaller since less calcium ions needed at any one time

Fast; extensive since more calcium ions required at one time for rapid intense contraction

57
Q

Compare power for slow and fast twitch

A

Slow; stronger, more ATP means more energy to contract all at the same time

Fast; weaker, less ATP means less energy and not enough power to contract all at the same time

58
Q

Compare activity for slow and fast fibres

A

Slow; aerobic respiration

Fast; anaerobic respiration

59
Q

Compare fatigue for slow and fast twitch fibres

A

Slow; resistant due to enough energy to contract for a long time in aerobic respiration without anaerobic to produce lactate

Fast; easily fatigue due to anaerobic respiration producing lots of lactate

60
Q

Why do both slow and fast need ATP

A

To break the cross bridges between actin and myosin
To be hydrolysed to provide the energy needed for the power stroke
To actively transport calcium ions back into the sarcoplasmic reticulum

61
Q

What is the role of ATP in myofibril contraction

A

Breaks actin and myosin cross bridge

Provides energy to move the myosin head in the power stroke

62
Q

Role of tropomyosin in muscle contraction

A

Moves out of the way when calcium ions bind to troponin

Allowing the myosin head to bind to actin and form a cross bridge

63
Q

Role of myosin in muscle contraction

A

Myosin head binds to actin and moves/bends to pull actin past it in power stroke
Myosin detaches from actin and retest/moves further along actin

64
Q

Explain the banding pattern of a single sarcomere

A

Light band where there is only actin
H zone where there is overlap so darkest
Dark band where only myosin

65
Q

Describe the advantage of the Bohr effect in intense excercise

A

Increased dissociation of oxygen
For aerobic respiration at the tissues and muscle cells
So anaerobic respiration is delayed
And less lactate so less muscle fatigue

66
Q

Why does converting lactate to pyruvate allow the continuous production of ATP by anaerobic respiration

A 
Regenerates NAD (Oxidises reduced NADP)
So glycolysis can continue and ATP can still be produced
67
Q

Slow twitch blood

A

Rich blood supply
Many mitochondria
Large store of myoglobin

68
Q

Where is phospbocreatine found

A

Fast twitch

A Level Biology Paper 2 (16 decks)

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