Muscles and movement

Question 1

How the release of Ca2+ ions in muscle fibre is stimulate

Answer 1

• action potential arrives at the neuromuscular junction
• neurotransmitter is released when membrane is depolarised
• Ca2+ stored in the sarcoplasmic reticulum is released into the sarcoplasm

Question 2

Role of Ca2+ in muscle contraction

Answer 2

• binds to troponin
• moves tropomyosin
• exposing actin-myosin biding site

Question 3

Role of ATP in muscle contraction

Answer 3

• ATP provides energy to break/form the actin-myosin bridge

- ATP used to move Ca2+ ions back into the sarcoplasmic reticulum

Question 4

Which muscle fibre would enable a long distance runner to perform well

Answer 4

• slow twitch muscle fibre
• greater mitochondria density, more aerobic respiration can occur, krebs cycle/ETC can take place
• there are lots of capillaries to provided oxygenated blood to the muscle fibres
• myoglobin concentration is high (myoglobin stores O2 required for aerobic respiration)

Question 5

Summarise the importance of glycolysis in muscle contraction

Answer 5

• in glycolysis two ATP is made
• NAD is reduced
• rNAD used is oxidative phosphorylation/ETC
• pyruvate is formed which is required in the link reaction/krebs cycle

Question 6

Sequence of events that occurs within a muscle fibre after stimulation of neuromuscular junction

Answer 6

• action potential arrives at neurotransmitter arrives at neuromuscular junction
• neurotransmitter releases when membrane is depolarised
• Ca2+ stored in sarcoplasmic reticulum is released into sarcoplasm
• Ca2+ binds to troponin
• troponin causes tropomyosin to move, exposing myosin binding sites on actin
• myosin head binds to binding site on actin, forming actin myosin bridge
• myosin head moves forward (filaments slide)
• ADP + Pi released from myosin head
• actin slides over myosin
• ATP provides energy for myosin-actin bridge to break and myosin head to detach, catalysed by ATPase

Question 7

Outline the differences between fast and slow twitch muscle fibres

Answer 7

slow twitch muscle fibres have

• more mitochondria
• more myoglobin
• less sarcoplasmic reticulum
• more capillaries
• less stored glycogen
• less creatine phosphate
• more resistant to fatigue
• respire aerobically

Question 8

Would predator or prey show a higher proportion of slow twitch fibres

Answer 8

• prey

Question 9

Discuss why predators show different proportions of fast and slow twitch muscle fibres from their prey

Answer 9

• predators have more fast twitch fibres than slow twitch fibres
• anaerobic respiration, glycolysis used

Question 10

During fast movement, lactate builds up in muscles of quick bursts of activity, explain what happens to this lactate

Answer 10

• lactate removed from muscle and diffuses into blood
• the lactate formed (by pyruvate is reduced and rNAD is oxidised) is converted back into pyruvate
• lactate (pyruvate?) is oxidised to form CO2 and H2O
• energy produced to synthesise ATP
• some lactate converted to glycogen to be stored in the liver or muscle cells

Question 11

Name the structures that connect muscles to bones

Answer 11

• tendons

Question 12

Explain why muscles occur in antagonistic pairs

Answer 12

• muscles cannot extend themselves
• need opposing muscle to extend
• antagonistic muscle allows control of movement

Question 13

Describe and explain the role of Ca2+ ions and ATP in muscle contraction

Answer 13

• sarcoplasmic reticulum releases Ca2+
• Ca2+ binds to troponin
• troponin moves tropomyosin exposing binding sites
• allowing myosin to bind to actin
• ATP provides energy for changing shape of myosin
• ATP required to break actin-myosin cross bridges
• ATP required to move Ca2+ ions back into sarcoplasmic reticulum
• ATP for synthesis of neurotransmitter

Question 14

Name the structure that connect bones to bones

Answer 14

• ligaments

Question 15

Describe a ligament

Answer 15

• holds bones together

- stills allows movement at the joint

Question 16

What muscle fibre has only few mitochondria

Answer 16

• fast twitch (suited for intense bursts of activity)

Question 17

Describe how ATP is made available for contraction of fast twitch muscle fibre, despite there being few mitochondria

Answer 17

• ATP from phosphorylation of ADP
• energy required for phosphorylation
• ATP produced from anaerobic respiration in cell cytoplasm (net 2ATP)
• in glycolysis, glucose is converted to pyruvate
• pyruvate is converted to lactate (pyruvate reduced)
• rNAD is oxidised, regenerating NAD for further glycolysis
• ATP from oxidative phosphorylation in mitochondria
• phosphocreatine stored in muscles can be hydrolysed to release energy

Question 18

What is creatine phosphate

Answer 18

• immediate regeneration of ATP is achieved using creatine phosphate stored in muscles
• creatine phosphate can be hydrolysed to release energy
• this energy can be used to regenerate ATP from ADP and phosphate (phosphate from phosphate creatine)
• creatine phosphate breaks down as soon as exercise starts
• creatine phosphate + ADP –> creatine + ATP

Question 19

Explain why fast twitch muscle fibre fatigue quickly

Answer 19

• ATP supply limited
• anaerobic respiration, lots of lactate
• pH is lower
• affects enzymes
• prevents muscle contraction

Question 20

Suggest why different responses of fast and slow twitch fibres to pH may be related to their different functions in muscle

Answer 20

• fast twitch is anaerobic, slow twitch aerobic
• fast twitch more likely to experience low pH
• low pH due to lactate
• fast twitch is less affects by change in pH
• can respond to stimuli at a lower pH

Question 21

How might pH affect muscle contraction of troponin from slow or fast twitch muscle fibres

Answer 21

• calcium binding site on troponin sensitive to pH

- troponin is different in each fibre

Question 22

Suggest why large numbers of mitochondria are found in muscle cells

Answer 22

• provide ATP
• aerobic respiration
• for contraction
• for pumping Ca2+ back into sarcoplasmic reticulum