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SBS017 Basic Biochemistry
May examination 2012
SECTION C
Answer question 4 OR question 5 in this booklet. Do not use
additional paper or booklets. Do not take the booklet from the
examination room.
Student number:
………………………………………………………………….
Desk number:
………………………………………………………………….
Please fill in BOTH these boxes with the numbers of
the questions you answered:
SECTION B QUESTION ANSWERED
SECTION C QUESTION ANSWERED
Page 2
Section C –Short Answer questions - 33%
Answer question 4 OR question 5 in this booklet.
Each question is worth 33 marks.
Question 4
A
SBS017 – Section C Example
Answer all parts
Fill in the following blanks in these sentences with the candidate terms in
boldface listed below. Note that not all the words are used.
[1 mark each.]
A ____________________________ reaction has a G (the change in freeenergy) that is negative in sign. A reaction of this kind can be used to drive one
that is ____________________________ that is coupled to it in a series of
reactions. The key molecule most used as the energy currency of biological
systems is ________________. This energy carrier molecule contains two
_____________________ bonds, and is an example of an activated carrier. The
group this molecule carries is the ________________ group. Other activated
carriers include ________________ which carries carbon dioxide, and
________________ which is a carrier of electrons in membrane proteins.
Humans obtain their energy via the oxidation of foodstuffs and as such we are
________________. There are three stages in this overall oxidation process. The
first takes Fats, Sugars and Proteins and breaks these large molecules into smaller
ones. These are further processed to generate a common small molecule which is
________________. It is this molecule that links into the final stage, that of
____________________ and oxidative phosphorylation.
Candidate terms:
phototrophs;
cysteine;
phosphoryl;
sulphur;
disulphide;
FADH2;
the Calvin Cycle;
methionine;
biotin;
thermodynamically favourable;
phosphoanhydride;
acetyl-CoA; chemotrophs;
base pairs;
guanine;
tetrahydrofolate;
thermodynamically unfavourable; the Citric
Acid Cycle; ATP
Continued on next page
SBS017 – Section C Example
B
Page 3
Indicate TRUE or FALSE to each of these statements (2 mark each)
i) Glucose is a five carbon containing sugar
_______________________________
ii) Glucose-4-phosphate is a molecule used in glycolysis
_______________________________
iii) 1,3-Bisphosphoglycerate is converted to 3-phosphoglycerate by the enzyme
Phosphoglycerate kinase
_______________________________
iv) Aldolase and Triosphosphate isomerase share a common TIM barrel threedimensional structure
_______________________________
v) Pyruvate is the last molecule produced in the glycolysis pathway
_______________________________
C)
Draw the structures of the molecules indicated below
i) Glucose as a ring structure (5 marks)
Continued on next page
SBS017 – Section C Example
Page 4
ii) Glyceraldehyde 3-phosphate (4 marks)
iii) Pyruvate (4 marks)
SBS017 – Section C Example
Question 5
A
Page 5
Answer all parts
The citric acid cycle is also known as: (1 mark)
The Krebs cycle or __________________________________________
B
Fill in the blanks. (8 marks)
Prior to the citric acid cycle the enzyme complex Pyruvate dehydrogenase
performs the reaction:
Pyruvate + __________________ + _______________________
 __________________ + CO2 + _______________________
C
Fill in the blanks. (4 marks)
The enzyme Citrate synthase performs a condensation reaction:
____________________ + oxaloacetate + H2O
 _____________________
D
+ Citrate
Draw the following molecules.
i) Citrate (5 marks)
Continued on next page
SBS017 – Section C Example
Page 6
ii) Oxaloacetate (5 marks)
E
Fill in the blanks from the list of choices given below. (10 marks).
In the citric acid cycle the enzyme _______________________converts
_______________________to succinyl-CoA. This enzyme process is one of two
_______________________________ steps in the cycle the other being the
previous step in the cycle carried out by the enzyme
___________________________. In each of these processes the coenzyme
________________________ is converted to ______________________. The
enzyme ____________________________ converts succinate to the molecule
_______________________. This molecule is then hydrated by the addition of
water to form malate by the enzyme _________________. From this product by
an ____________________ process we then arrive back at oxaloacetate. It is this
molecule that is involved in the initial processes of the citric acid cycle and proves
that the process is indeed cyclic.
Candidate terms:
NADH; alpha-ketoglutarate dehydrogenase;
transcarbamoylase;
citrate synthase; oxidation;
dehydrogenase; oxidative decarboxylation;
dehydrogenase; fumarate;
citrate;
End of section C
FADH2;
FAD;
CO2;
NAD+;
succinate
chymotrypsin;
dehydration;
ornithine
isocitrate
alpha-ketoglutarate;
argininosuccinate synthetase; fumarase; isocitrate