Muscles Flashcards

1
Q

Describe the structure of a myosin protein

A

Bulbous head
Tail
Quaternary structure - two proteins held together

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2
Q

What do the two binding site on the myosin head bind to ?

A

Actin
ATP

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3
Q

Name the ion that binds to troponin

A

Calcium ions

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4
Q

Name the protein that covers the myosin binding sites when the muscle is not contracting

A

Tropomyosin

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5
Q

What is the name of the theory that explain muscle contraction

A

Sliding filament theory

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6
Q

Name the two types of filament involved in the sliding filament theory

A

Myosin and actin

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7
Q

Describe the role of ATP in muscle contraction

A

Attachment of ATP on myosin head causes myosin to detach from actin.
Hydrolysis of ATP (on myosin head) causes myosin to re-cock

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8
Q

Describe the role of calcium ions in muscle contraction

A

Calcium ions diffuse into myofibrils from sacoplasmic reticulum
Bind to troponin
Tropmyosin moves to reveal myosin binding sites
Myosin heads attach to binding sites on actin

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9
Q

Describe the role of glycogen in skeletal muscle

A

Hydrolysed to form glucose
Respired to release ATP

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10
Q

Name the connection that forms when myosin binds to actin

A

Actinomyosin bridge

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11
Q

Name three types of muscle found in the body and state where they are located.

A

Cardiac - exclusively in the heart
Smooth- walls of blood vessels and intestine
Skeletal - attached to bones by tendons

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12
Q

What does the term ‘antagonistic pair’ means in terms of muscles.

A

Muscles act in pairs to pull ketone in opposite directions

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13
Q

Describe the gross structure of the skeletal muscle

A

Muscle cells fused together to form bundles of parallel muscle fibres (myofibrils)

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14
Q

Describe the microscopic structure of skeletal muscle

A

Myofibrils - site of contraction
Sarcoplasm - shared nuclei and cytoplasm with lots of mitochondria and endoplasmic reticulum
Sarcolemma - cell membrane folds inwards to form T tubules

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15
Q

Describe how an action potential is transmitted to the muscle cells at a neuromuscular junction

A

Action potential arrives at junction.
Calcium ion channels open and calcium ions diffuse into the pre-synaptic knob
Vesicles move towards and fuse with pre-synaptic membrane
Acetylcholine released and diffuses across synapse.
Acetylcholine binds to rector site on the muscle cell membrane (sarcolemma).
Sodium ions channels open causing depolarisation.

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16
Q

Outline the sliding filament theory

A

Myosin head with ADP attached forms a cross bridge with actin
Power stroke - myosin head changes shape and loses ADP, pulling actin over myosin
ATP attaches o myosin head, causing it to detach from actin
ATP hydrolase so myosin head can return to original position
Myosin head re-attaches to actin further along the filament

17
Q

How does the sliding filament action cause a myofibril to shorten

A

Myosin heads cause actin filaments to be pulled towards each other.
Distance between adjacent z lines shortens
Repeated up to 100 times per second to shorten the myofibril

18
Q

What happens during muscle relaxation?

A

Calcium ions actively transported back into the endoplasmic reticulum
Troponin changes shape
Causes tropmysoin to move and block actin binding sites.

19
Q

Explain the role of phosphocreatine in muscle contraction

A

Phosphorylates ADP directly to ATP when oxygen is in short supply due to vigorous exercise.

20
Q

Where are slow and fast twitch muscle fibres found in the body?

A

Slow twitch - sites of sustained contraction
Fast twitch - site of short term, rapid, powerful contractions

21
Q

Explain the role of slow and fast twitch muscle fibres

A

Slow twitch - long duration contraction, adapted to aerobic conditions to prevent lactate buildup
Fat twitch - powerful short term contraction, adapted for anaerobic respiration

22
Q

Explain the structure and properties of slow twitch muscles

A

Glycogen store - hydrolysed to release glucose for respiration
Contain myoglobin - higher affinity for oxygen at lower partial pressure
Many mitochondria - aerobic respiration needed to supply ATP
Surrounded by many blood capillaries to supply oxygen and glucose.

23
Q

Explain the structure and properties of fast twitch muscles

A

Large store of phosphocreatine
High concentration of enzymes for anaerobic respiration
Extensive endoplasmic reticulum to allow rapid uptake and release of calcium ions.