contraction of skeletal muscles

Question 1

the diagram below shows the banding pattern of a single sarcomere
explain the banding pattern shown in the diagram above (4)

Answer 1

I band- actin- thinner and darker regions
A band- myosin- thicker and lighter regions.

Question 2

Another group of scientists suggested that a decrease in the force of
muscle contraction is caused by an increase in the concentration of
inorganic phosphate, Pi, in muscle tissues.
Their hypothesis is that an increase in the concentration of Pi prevents the
release of calcium ions within muscle tissues.
Explain how a decrease in the concentration of calcium ions within muscle
tissues could cause a decrease in the force of muscle contraction. (3)

Answer 2

tropomyosin protein does not move
actinmyosin bridge does not form
ATPase not activated by calcium ions

Question 3

Another group of scientists suggested that a decrease in the force of
muscle contraction is caused by an increase in the concentration of
inorganic phosphate, Pi, in muscle tissues.
Their hypothesis is that an increase in the concentration of Pi prevents the
release of calcium ions within muscle tissues.
Explain how a decrease in the concentration of calcium ions within muscle
tissues could cause a decrease in the force of muscle contraction.

Question 4

In muscles, pyruvate is converted to lactate during prolonged exercise.
Explain why converting pyruvate to lactate allows the continued production
of ATP by anaerobic respiration (2)

Answer 4

regenerates NAD
glycolysis can continue

Question 5

The scientists then compared the length of time that the control mice and
the trained mice could carry out prolonged exercise. The trained mice were
able to exercise for a longer time period than control mice.
Explain why. (3)

Answer 5

more aerobic respiration- more ATP produced
anaerobic respiration delayed
less lactic acid produced.

Question 6

During vigorous exercise, the pH o f skeletal muscle tissue falls. This fall in
pH leads to a reduction in the ability of calcium ions to stimulate muscle
contraction.
Suggest how. (3)

Answer 6

-low pH causes shape of calcium ions to change
-fewer tropomyosin molecules move otu of the way
-fewer actinmyosin cross bridges formed

Question 7

What is the role of ATP in myofibril contraction? (2)

Answer 7

allows cross bridge to form
provides energy to move myosin head

Question 8

The mice that were not able to produce creatine were homozygous for a
recessive allele of a gene. Mice that are heterozygous for this allele are
able to produce forces similar to those of normal mice that are
homozygous for the dominant allele of the same gene.
Explain why the heterozygous mice can produce forces similar to those of
normal mice (2)

Answer 8

have one normal allele
which leads to the production of enough creatine