SL Paper 2
Consumption of dark chocolate has been shown to have health benefits. A study was undertaken to see the effects of epicatechin (Epi), a substance in dark chocolate, on the aerobic capacity of leg muscles of mice.
A group of adult mice was used to measure the effects of a low dose of Epi given over 15 days. The mice were divided into four groups and given either water or Epi and were either kept idle (no exercise) or made to exercise on a treadmill.
After 15 days, the results were analysed. The blood capillary density in leg muscle was measured under the light microscope.
Leg muscle tension was measured over time during a treadmill exercise in all four groups. The muscle is considered to reach a point of fatigue when there is a decrease in tension to 50 % of the initial tension.
The scientists tested the expression of four different mitochondrial proteins. The protein samples were taken from leg muscles. The technique that was used to quantify the amount of protein expressed was Western blotting. In this procedure the thickness of the band is an indicator of the amount of protein.
State the significance of the statement: p<0.05.
Outline the trends in capillary density in the results of this experiment.
Describe how increased capillary density could affect the aerobic capacity of muscle.
State the time when the point of fatigue occurred in the Epi–exercise group.
Compare and contrast the results for the water–no exercise group and the Epi–no exercise group.
Discuss the effect of exercise on the results of the experiment.
Analyse the effect of exercise on the presence of the mitochondrial proteins in the leg muscle.
Mitochondria are essential for aerobic respiration. Suggest one possible role of the proteins that were studied.
The scientists concluded that Epi significantly increased aerobic capacity in leg muscle.
Evaluate the strength of the evidence provided by all of the data for dark chocolate improving the aerobic capacity of athletes.
Distinguish between the structure of amylose and the structure of amylopectin.
Suggest the reason for cellulose passing undigested through the human gut.
Draw an annotated diagram to show how a peptide bond is formed.
State two structural features that differ between RNA and DNA.
The figure represents a water molecule.
Draw a second water molecule to show how bonds can form between water molecules, including the name of the bond.
Water has important solvent properties. Explain these properties using an example to illustrate your answer.
State one disaccharide and the two monomers from which it can be synthesized.
Disaccharide:
1:
Monomers:
1:
and 2:
Discuss the roles of the enzymes secreted by the pancreas during digestion.
Compare and contrast cis-fatty acids and trans-fatty acids.
Sketch a graph to show the effect of temperature on the activity of enzymes.
Explain enzyme–substrate specificity.
Draw a molecular diagram of an amino acid to show its general structure.
Outline the role of ribosomes in translation.
Some blood proteins are involved in defence against infectious disease. Explain the roles of named types of blood proteins in different defence mechanisms.