Download Ass3_ans - The University of Sydney

BCHM2072/2972 Semester 2, 2005
Page 1
ANSWERS TO ASSIGNMENT 3, WEEK 7
This assignment is due in the box at the front of the lecture theatre by no later
than 10.10 am on Wednesday 14th September. Late assignments, assignments
not answered on the grid provided, or assignments not covered by a plagiarism
statement (universal or individual) will not be marked. Remember, submission of
assignments is entirely voluntary. Enter your SID and answer all questions by
filling in the relevant circles on the grid provided.
Use the options A-F to answer questions 1-3 (1 mark each).
A.
B.
C.
D.
E.
F.
Every even numbered carbon
Every even numbered carbon except C2
Every even numbered carbon except C16
None of the carbons
Every odd numbered carbon except C3
Every odd numbered carbon except C15
If palmitoyl CoA (pictured below) were made from 14C malonyl CoA,
15
16
13
14
11
12
9
7
10
8
5
6
CO
3
4
SCoA
2
which pattern of labeling would be observed if the malonyl CoA used were
labeled:
1.
at C1 (the terminal carboxylic acid end) D
2.
at C2 (the –CH2- in the middle) C
3.
at C3 (the carbon in a thioester with CoA) F
To help you, here is a picture of malonyl CoA with the carbon atoms numbered
1
HOOC
H2
C
3
2
CO
SCoA
BCHM2072/2972 Semester 2, 2005
4.
Page 2
Which of the following (A-F) is not a fate of cholesterol in mammalian
tissues? (1 mark) E
A. Bile salts
B. Cell membranes
C. Estrogen & Testosterone
D. Incorporation into VLDL
E. CO2
F. Cholesterol esters
5.
Which of the following (A-E) would an inhibitor of lipoprotein lipase directly
prevent? (1 mark) B
A. The uptake of dietary fat in the intestine
B. The conversion from VLDLs to LDLs
C. The release of fatty acids from adipose tissue
D. The uptake of dietary cholesterol by cells from LDLs
E. The formation of lipoproteins
6.
Which of the following changes (A-F) would directly decrease the activity in
vivo of Acetyl CoA Carboxylase? (1 mark) C
A. An increase in insulin
B. An increase in acetyl CoA
C. An increase in palmitoyl CoA
D. An increase in cytoplasmic [citrate]
E. An increase in G6P
F. An increase in HCO3-
BCHM2072/2972 Semester 2, 2005
Page 3
The data in the table below relates to questions 7 – 8 (1 mark each).
Individual
A
B
C
D
E
Endogenous HMG CoA reductase activity
# LDL receptors on cell surface
HDL:LDL
High
High
High
Low
Low
Low
High
Low
Low
Low
High
High
High
Low
High
Based on the data, which of the individuals (A-E) has the:
7.
Highest risk of coronary heart disease C
8.
Lowest risk of coronary heart disease D
The following information relates to questions 9 -18 (1 mark each).
The oxidation of glucose is often summarised as the balanced equation:
C6H12O6 + 6 O2 + 32 ADP + 32 P  6CO2 + 6 H2O + 32 ATP
Of course, this misses out all the juicy steps of glucose transport, glycolysis,
PDH, Krebs cycle, electron transport, F1F0ATPase, etc. However, it does
encapsulate the overall point and function of the pathway. The overall equation is
actually made up of lots of ‘partial’ equations that are added together.
OK, so that was just an example. The overall balanced equation for the synthesis
of fatty acids from glucose (lipogenesis) can be written (for the 16-carbon fatty
acid, palmitate) as:
9 glucose + 8 O2  2 palmitate + 22CO2 + 22 H2O
Hint : At this stage you will find it very useful to draw out the scheme of
lipogenesis from glucose (eg as in the final slide for Lecture 12) to answer these
questions. Do not think that you have to derive the equation. However, you
should reflect on all the juicy steps that actually have to occur to make
lipogenesis happen.
9.
The lipogenesis equation does not mention ATP because: B
A
B
C
D
E
ATP is not produced or consumed in lipogenesis
During lipogenesis as much ATP is produced as is consumed
The equation refers to a section of lipogenesis in which ATP is not
used
The equation shows only the anabolic arm of lipogenesis
The equation shows only the cytosolic part of the pathway
BCHM2072/2972 Semester 2, 2005
10.
In compiling this overall lipogenesis equation, which process would you
NOT take into account? B
A
B
C
D
E
11.
D
E
To provide reducing equivalents
To mop up excess NADPH
Oxygen gas isn't used in the grand scheme, it's just required here
to make a balanced equation
It reflects the consumption of oxygen at the end of the electron
transport chain
To enable carbon dioxide formation
There is carbon dioxide release at several steps during lipogenesis. At
which of the following steps is a carbon dioxide molecule released? A
A
B
C
D
E
13.
The fatty acyl synthase reactions
Esterification of fatty Acyl-CoAs
The fate of 5-carbon sugar phosphates in the pentose phosphate
pathway
The reactions of glycolysis
The trapping of glucose
Why is oxygen required in this lipogenesis equation? D
A
B
C
12.
Page 4
Pyruvate dehydrogenase
Aldolase
Acetyl CoA carboxylase
Glucose 6-phosphate dehydrogenase
ATP-citrate lyase
Which particular segment of the overall lipogenesis pathway does NOT
involve NET release of carbon dioxide? E
A
B
C
D
E
As malonyl CoA is incorporated into the growing fatty acyl chain
As pyruvate molecules are made into acetyl-CoA
As acetyl-CoA molecules are oxidised in the Krebs cycle
As ribulose 5-phosphate is produced in the pentose phosphate
pathway
As acetyl-CoA is made into malonyl-CoA
BCHM2072/2972 Semester 2, 2005
14.
The energetic values for glucose and fatty acids are 16 kJ/g and 37 kJ/g
respectively. The molecular weights of glucose and fatty acids are 180 and
256 respectively. There is 'energy' in the glucose and 'energy' in the fatty
acids. Which statement best describes the 'efficiency' of lipogenesis? B
A
B
C
D
E
15.
2880 kJ of energy in glucose ends up as 9472 kJ fatty acids
27% of the energy in the glucose is lost as it is converted into fatty
acids
The fatty acids products contain about half as much energy as the
glucose substrate
A total energy of 1620 kJ in carbohydrate becomes just 512 kJ in
the final fatty acid products
The total energy of the fatty acid products is about twice that of the
total energy of the glucose substrate
Which description best describes the respiratory quotient of someone
who has consumed a carbohydrate meal and is actively performing
lipogenesis? B
A
B
C
D
E
16.
Page 5
about 0.7
over 1
less than 0.7
exactly 1
exactly 2.75
How would you adapt the lipogenesis equation so that it describes the
conversion of glucose to fat? A
A
B
C
D
E
At least three palmitates would be needed on the right hand side of
the equation, so more glucoses would be needed on the left hand
side
Fewer glucoses would be needed on the left hand side of the
equation because now glycerol would appear on the right hand side
The equation would be exactly the same
Fewer glucoses would be needed on the left hand side of the
equation because glycerol is more reduced than glucose
It would not be possible to produce a balanced equation for fat
synthesis
BCHM2072/2972 Semester 2, 2005
17.
Page 6
You have been asked to write the overall balanced equation for glycogen
synthesis from glucose. It will have a similar form to the lipogenesis
equation above ie:
some amount of glucose (X) + one or more things  some
amount of glucose residues in glycogen + one or more other things
What would best describe the sort of equation you'd come up with: D
A
B
C
D
E
18.
(X) Glucose + some amount of ATP  (X) glucose in glycogen +
some amount of ADP
(X) Glucose + some amount of O2  (X) glucose in glycogen +
some amount of CO2
(X) Glucose + some amount of UTP  (X) glucose in glycogen +
some amount of UDP
(X) Glucose + some amount of O2  less than (X) glucose in
glycogen + some amount of carbon dioxide
(X) Glucose + some amount of UTP  less than (X) glucose in
glycogen + some amount of UDP
Which process would NOT be useful to take into account in making your
balanced glycogenesis equation? D
A
B
C
D
E
UDP-glucose + glycogen  gluocse in glycogen + UDP
UDP + ATP  UTP + ADP
UTP + glucose 1-phosphate  UDP-glucose + 2 phosphate
glucose 6-phosphate + NADP  NADPH + 6-phosphgluconolactone
glucose + 6O2 + 32ADP + 32 phosphate  6CO2 + 6H2O + 32ATP