1. D
8. E
2. C
9. B
3. D
10. C
4. C
11. D
5. C
12. A
6. B
13. C
7. E
14. A
(c)
Outline how enzymes catalyse reactions.
1.
2.
3.
4.
5.
6.
Enzymes increase rate of (chemical) reaction;
Enzymes remains unused/unchanged at the end of the reaction;
Enzymelower activation energy of the chemical ;
The activation energy of a chemcial is energy needed to overcome energy barrier that
prevents reaction;
The substrate/ chemical reactant joins with enzyme at active site;
When the substrate bonds with the active site of the enzyme they form enzyme-substrate
complex;
7. The active site/enzyme (usually) specific for a particular substrate/ chemical reactant as described by the
lock and key model;
8. Enzyme binding with substrate brings reactants closer together to
facilitate chemical reactions (such as
electron transfer);
High level
Stuff
9. The induced fit model shows how the substrate initiates a change in enzyme conformation
(when
enzyme-substrate/ES complex forms);
10. This change in enzyme conformation makes the substrate more reactive
11. Students may have an annotated graph showing reaction with and without enzyme;
IB Questionbank Biology
1
(c)
Compare competitive and non-competitive inhibition of enzymes.(5)
Explain how end-product inhibition controls metabolic pathways.
1. End-product inhibition is example of negative feedback
eg ATP inhibition of phosphofructokinase, in glycolysis;
2. End-product inhibition controls rate of product synthesis / amount of product produced
/ inhibits earlier stage / switches off pathway when too much
product made;
3. End-product inhibition is when the final product of a metabolic pathway binds to an enzyme at the
beginning of the metabolic pathway.
4. This final product/ inhibitor is usually a non-competitive inhibitor that is it usually does not bond to
the active site of the enzyme, but it binds to an allosteric site on the enzyme;
5. This binding to the allosteric site causes the enzyme changes shape / substrate cannot bind / enzyme
cannot catalyse the first product of the metabolic pathway;
(a) (i)
15.2 mg 3 hrs–1 (allow answers in the range of 15.0 to 15.4)
(ii)
1.93 NAG units 3 hrs–1 (allow answers in the range of 1.92 to 1.95)
1
1
(b) You are asked to compare the correlation between men and women, and so you should make
comparison about positive, negative or no relationships, and you should also compare strength of
relationship (stronger, weaker), and you should compare steepness of the slope of the best fit line
1. Both men and women have a positive relationship;
2. Bothe men and women’s values are very scattered for both;
3. There is a more positive correlation/steeper gradient for men than for women;
4. The data is more scattered in women/greater range in hepatic activity / more scattered/
greater
IB Questionbank Biology
2
range in men in renal activity;
(c)
2 max
Evaluate a hypotheses base on data = Clearly state if the data support the hypothesis or not? The
explain/ discuss how data supports hypothesis or does not support hypothesis.
1. The hypothesis is supported because there is a positive correlation between both increased
hepatic activity and
renal damage/ people with more renal damage have more cytochrome activity
( hepatic activity is meant to be an indirect measurement of cadmium exposure/ toxicity).
2. The data shows a difference in the effect on both renal damage and hepatic activity
between genders, for example: there is a greater hepatic (liver) effect in women than in men
/ there is a greater renal (kidney) effect in men
than women.
This gender difference means
the hypothesis is not fully supported and that their maybe other factors involved.
3. While there is a positive relationship between renal damage and hepatic activity, this
positive trend does not necessarily prove a direct causal relationship between
hepatic and renal function with cadmium toxicity, and thus the hypothesis is not
supported by this data
4. There are problems with the data, for example, there is a very wide range of data, which
makes it very difficult to evaluate and it is possibly
not statistically significant relationship (i.e. no
R-Value is reported/ correlation coefficient is reported) ;
5. From this data it is impossible to establish a causal relationship because there is no
control group /
other factors may be involved/ hepatic activity might not be a good measurement of cadmium
toxicity;
2 max
2 max
IB Questionbank Biology
3