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A Level Biology Paper 2 > Muscles > Flashcards

Muscles Flashcards

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
Striated
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
26
What is the result of the sliding filament theory
``` Sarcomere shortens Z lines closer Actin pulled over myosin Increased overlap means appears darker Filaments the same size ```
27
Explain a relaxed myofibril
Tropomyosin covers the binding site on actin filament which myosin attaches to
28
Explain the sliding filament theory
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
Explain Ca²+ in muscles
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
Why can producing less ATP mean people aren't able to maintain strong muscle contractions during exercise
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
Describe the role of tropomyosin and myosin in myofibril contractions
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
Why do mitochondria in muscles contain many cristae
Large face area for the electron transport stem/oxidative phosphorylation Provides ATP needed for muscle contraction
33
Why does increased cardiac output give an advantage in exercise
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
Importance of ATP hydrolase in muscle contraction
Hydrolyses ATP yielding energy | Used to break cross bridges
35
What are the advantages of using aerobic rather than anaerobic respiration to provide ATP for long distance races
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
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
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
Why do cross bridges between actin and myosin remain firmly bound after death and lead to rigor mortis
Respiration stops No more ATP produced ATP needed to break the actin and myosin cross bridges
38
Describe the role of phosphocreatine
Provides a phosphate Phosphorylating ADP To produce ATP
39
Describe fast twitch muscle fibres
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
Describe the role of calcium ions in the contraction of a sarcomere
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
Use of ATP other than in power stroke and recovery stroke
Active transport of calcium ions back into the sarcoplasmic reticulum
42
A muscle fibre can only store enough ATP to sustain muscle contraction for how long
3 to 4 seconds
43
How long does regeneration of ATP by anaerobic respiration take
10 seconds This is too long in fight or flight instances Even longer if aerobic
44
Is phosphocreatine a source of ATP
No Source of Pi Which is used to create ATP from ADP and Pi
45
What is phosphocreatine
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
Slow twitch muscle fibres
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
How are slow twitch muscle fibres adapted/specialised
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
How are fast twitch muscle fibres adapted/specialised
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
Key points to discuss when comparing slow and fast twitch (9)
``` Colour Contraction speed Activity Duration Fatigue Power Storage Mitochondria Sarcoplasmic reticulum ``` SMS CDC PAF
50
Similarities between slow and fast twitch
Both follow sliding filament theory Both use ATP hydrolase Both produce ATP Both allow for shortening of sarcomere
51
Compare colour for slow and fast twitch
Slow; Red due to oxidative phosphorylation and myoglobin as an oxygen store Fast; White due to less oxygen and myoglobin
52
Compare duration for slow and fast twitch
Slow; Longer, more energy provided due to oxidative phosphorylation Fast; Shorter, cannot be sustained for a long time
53
Compare conduction speed for slow and fast twitch
Slow; Slow Fast; Fast
54
Compare storage for slow and fast twitch
Slow; Triglycerides Fast; ATP, phosphocreatine, glycogen
55
Compare Mitochondria for slow and fast twitch fibres
Slow; more, longer Fast; less, shorter
56
Compare sarcoplasmic reticulum for slow and fast twitch fibres
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
Compare power for slow and fast twitch
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
Compare activity for slow and fast fibres
Slow; aerobic respiration Fast; anaerobic respiration
59
Compare fatigue for slow and fast twitch fibres
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
Why do both slow and fast need ATP
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
What is the role of ATP in myofibril contraction
Breaks actin and myosin cross bridge | Provides energy to move the myosin head in the power stroke
62
Role of tropomyosin in muscle contraction
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
Role of myosin in muscle contraction
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
Explain the banding pattern of a single sarcomere
Light band where there is only actin H zone where there is overlap so darkest Dark band where only myosin
65
Describe the advantage of the Bohr effect in intense excercise
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
Why does converting lactate to pyruvate allow the continuous production of ATP by anaerobic respiration
``` Regenerates NAD (Oxidises reduced NADP) So glycolysis can continue and ATP can still be produced ```
67
Slow twitch blood
Rich blood supply Many mitochondria Large store of myoglobin
68
Where is phospbocreatine found
Fast twitch

A Level Biology Paper 2 (16 decks)

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