| Date | May 2013 | Marks available | 2 | Reference code | 13M.2.HL.TZ2.1 |
| Level | Higher level | Paper | Paper 2 | Time zone | Time zone 2 |
| Command term | Distinguish | Question number | 1 | Adapted from | N/A |
Question
Obesity (excessive weight) is recognized as a global health problem and has been correlated with a large number of health issues, diseases and deaths. The increased consumption of fructose, now widely used as a sweetener, has been associated with the increase in obesity.
In a study, mice were divided into four groups. Each group was given the same amount of food and either a soft drink with a different sweetener or water.
As it has been shown that high triglyceride levels correlate to obesity, another study was undertaken with humans. Over a ten-week period, one group was given glucose-sweetened drinks and the other fructose-sweetened drinks. Triglyceride levels in blood were measured throughout the study.
Studies investigated the role of glucose and fructose in the development of pancreatic cancer cells. Pancreatic cancer cells were grown in equal concentrations of each sugar and the uptake of each into ribose-producing pathways was measured. The graph shows the range of uptake of sugars and the mean value.
Describe the overall trend in body fat accumulation for the four groups of mice.
Compare the body fat accumulation between the four groups.
Distinguish between the results for the two groups.
This study also showed a significant reduction in insulin sensitivity when participants were given fructose-sweetened drinks, but not when they were given glucose-sweetened drinks.
Describe possible effects of the reduction of insulin sensitivity.
Discuss whether the results provide clear evidence of a difference in uptake.
Determine which sugar is primarily used in the production of ribose.
Using all of the data, evaluate the evidence that suggests the consumption of large amounts of fructose poses a risk to human health.
Markscheme
positive/direct relationship / correlation (in all four groups) / (all four groups) accumulated fat over time
a. body fat accumulation increased over time for all four groups;
b. fructose caused the (significantly) greatest accumulation of fat and water the least;
(both needed)
c. sucrose and artificial sweetener/diet soft drink had the same increase;
d. sucrose, artificial sweetener and water did not start accumulating fat until after 20 days while fructose increased from the beginning;
a. glucose-fed group has no/little increase in triglycerides while fructose-fed group has a (large) increase;
b. glucose-fed group has smaller variability than the fructose-fed group;
c. more triglycerides in fructose-fed group than glucose-fed group (from week 2 to week 10);
a. raised blood glucose/sugar levels/higher glucose in the urine;
b. decreased glycogen;
c. excess glucose will be converted to fat/increase obesity;
d. possibility of developing diabetes type II / late/adult onset diabetes; (do not award this mark if answer refers to type 1 diabetes)
a. glucose has a much greater range of uptake / vice versa;
b. but a (much) lower mean/uptake / vice versa;
c. there is no overlap (so there is clear evidence);
fructose
a. evidence that fructose causes (body) fat accumulation/obesity;
b. evidence that fructose is related to increased (blood) triglycerides which are correlated with obesity/coronary heart disease;
c. evidence that fructose is related to reduced insulin sensitivity/diabetes;
d. evidence that fructose is used in ribose synthesis but no clear evidence that fructose causes pancreatic cancer;
Examiners report
Most were able to describe the overall trend.
Most candidates successfully compared the two groups, though weaker candidates gave descriptive answers without using comparative term.
This was another question that was effectively answered though students tended to give descriptive answers.
This question tended to differentiate in terms of preparation as better prepared candidates drew in a discussion of type 2 diabetes, reduced glycogen levels, higher blood sugar and sugar in the urine.
Most believed that the data supported the conclusion that a difference existed. The lower mean and the lack of overlap was noted by most.
Answers were roughly split between both sugars suggesting that students had difficulty making the link that higher rates of uptake suggest higher rates of use.
Prepared candidates were able to draw in the link to fructose and type 2 diabetes. Fewer acknowledged that the link between cancer and fructose was difficult to establish. Most were able to summarize the data but fewer were able to make a link to health effects.
