Outline the process of glycolysis.

Describe how pancreatic cells directly affect blood glucose levels.

Explain why diabetes could be detected through the analysis of urine.

occurs in cytoplasm;
hexose is phosphorylated using ATP;
hexose phosphate is split into two triose phosphates;
oxidation by removal of hydrogen; (do not accept hydrogen ions/protons)
conversion of NAD to NADH (+H⁺);
net gain of two ATP / two ATP used and four ATP produced;
pyruvate produced at the end of glycolysis;
Accept glucose/fructose/6C sugar instead of hexose.
Accept 3C sugar/glyceraldehyde instead of triose.

α cells (of pancreas) produce glucagon;
glucagon promotes release of glucose/breakdown of glycogen by liver cells;
glucagon secreted when blood glucose levels are low / raises blood glucose levels;
β cells (of pancreas) produce insulin;
insulin promotes glucose uptake/storage of glycogen by liver/body/muscle cells;
insulin secreted when blood glucose levels are high / lowers blood glucose levels;
negative feedback mechanism;
Do not accept answers implying that insulin or glucagon catalyse glucose-glycogen conversions directly.
Award [3 max] if the response suggests that the hypothalamus has a role in regulation of blood glucose.

urine of diabetics contains glucose;
whereas urine of non-diabetics contains no glucose;
glomerular filtrate contains glucose / glucose filtered out;
glucose (normally) reabsorbed from filtrate/into blood;
through wall of / in the proximal convoluted tubules;
blood glucose concentration higher than normal in diabetics;
reabsorption not completed / pumps cannot reabsorb all glucose in diabetics;
glucose in urine can be detected using test strips;
type I diabetes is lack of insulin secretion / lack of β cells;
type II diabetes is body cells not responding to insulin / not absorbing glucose;

This question was answered by large numbers of candidates. The better-prepared ones had little difficulty in scoring highly in both parts (a) and (b). As in part (a) of Question 5, it was possible to score marks in 6(a) with a clearly annotated drawing, in this case a flow diagram of glycolysis. The only caveat is that one of the quality marks for Section B questions depends on at least two of the three parts being written in continuous prose. In weaker answers there was confusion about what was being oxidized and what reduced. Teachers should stress that oxidation in respiration is achieved by removal of hydrogen from respiratory substrates, because each removed hydrogen has an electron. Oxidation is loss of electrons.

In part (b) a familiar problem was in the spelling of glucagon and glycogen. This is one place where terms do need to be spelt correctly to avoid confusion. Two other common errors were the implication that insulin and glucagon catalyze interconversions between glucose and glycogen directly and the suggestion that the hypothalamus controls hormone secretion by the pancreas.

Part (c) was often well answered, with candidates write detailed accounts of cause and effect, linking the high blood glucose levels that characterize diabetes with the presence of glucose in urine.