Describe how a decrease in pH reduces the ability of calcium ions to stimulate muscle contractions. (4)
- low pH changes shape of calcium ion receptors
- fewer calcium ions bind to troponin
- fewer binding sites on actin revealed
- so fewer cross-bridges form
Compare and contrast slow and fast twitch muscle fibres. (5)
Similarities:
- both produce energy and help in movement
- both generate force
-by contraction - both present in equal amounts in human bodies
Differences:
- slow twitch is for endurance, fast is for short bursts of activity
- fast twitch fibres are thicker, slow twitch fibres are thinner
Explain why elite sprinters tend to be bulkier using your knowledge of fast and slow twitch muscle fibres. (2)
- elite sprinters have greater percentage of fast twitch muscle fibres
- fast twitch muscle fibres have a larger diameter
Describe how a pair of antagonistic muscles work together and an example. (3)
- as one muscle contracts, the other muscle relaxes
- extensor muscle straightens a joint during contraction
- example: biceps & triceps
Explain how muscles maintain posture. (3)
- by using antagonistic muscles
- working at joints
- both contract to keep body upright
When myofibril contracts, which bands decrease in length? (1)
- H- & I-bands
When myofibril contracts, which band will remain the same length? (1)
- A-band
Identify and name the light and dark bands. (2)
- light = I-bands
- dark = A-bands
Describe the structure of the light and dark bands of muscle. (2)
- light bands = only thin actin molecules
- dark are thick myosin molecules and thin actin molecules
Explain why I- & H- bands decrease when myosin contracts. (4)
- H-band is myosin only
- I-band is actin only
- they move closer together by sliding over one another
- I- & H-bands get shorter
Explain how ATP hydrolysis being inhibited reduces the contraction of skeletal muscles. (2)
- cross-bridges cannot be broken
- myosin cannot reattach
Explain how the release of calcium ions from the sarcoplasmic reticulum being inhibited reduces the contraction of skeletal muscles. (2)
- calcium cannot bind to troponin
- tropomyosin cannot move to expose myosin binding sites
Whats the function of alkali within the aerobic respiration experiment. (1)
- removes CO2 released by the living organisms
Explain the movement of the water droplet within the aerobic respiration experiment. (2)
- maggots are consuming oxygen
- this decreases pressure in boiling tube, causing movement of water droplets
Deduce the effect of mitochondrial dysfunction on the production of ATP. (3)
- would produce less ATP
- bcs smaller amount of internal mitochondrial membrane
- so fewer electron transport chains
State 2 things that can happen to lactate after its produced. (2)
- oxidised back into pyruvate
- converted into glucose by liver cells
Describe the role of coenzymes in ATP synthesis. (3)
- hydrogen attaches to NAD
- H ions transferred to inner mitochondrial membrane
- which is site of ETC & oxidative phosphorylation
Explain why the link reaction is described as an oxidative decarboxylation reaction. (2)
- pyruvate is decarboxylated
- pyruvate is oxidised by removal of hydrogen
Describe how ATP is formed in mitochondria. (6)
- Krebs cycle produces reduced NAD & FAD
- H atoms donated by red NAD & FAD
- H atoms split into protons & electrons
- high energy e-s release energy as they move through ETC
- which is used to transport protons across inner mitochondrial membrane
- movement of protons down their conc. gradient provides energy for ATP synthesis
Explain importance of certain organisms in maintaining a constant body temp. (4)
- to ensure body temp is optimum for enzyme activity
- extreme heat denatures enzymes
- enz-substr complexes cannot form & enzymes cannot catalyse reactions
- reaction will stop
Define: negative feedback loop (1)
- where a change triggers a response which reverses the effect of a change
Name a part of the brain responsible for thermoregulation. (1)
- hypothalamus
Describe the homeostatic mechanism that will regulate the mountaineer’s body temp near the top of the mountain. (5)
- thermoreceptors in hypothalamus & skin detect decrease in temp
- hypothalamus sends impulses along motor neurones to effectors
- results in vasoconstriction of blood vessels
- erector pili muscles contract, hair strands stand up forming insulating layer
- increases body temp back to normal
Describe the reason why gloves prevent frostbite. (2)
- avoids moisture around fingers that could freeze
- prevents decrease in temp around fingers that could lead to frostbite
