Download questions for lipids

(18 pts.)
1. a. Compare the pathways for fatty acid synthesis and gluconeogenesis using the format shown
below.
Points of comparison
rate-limiting step
(write complete reactions)
gluconeogenesis
fatty acid synthesis
__________________________________________________________________
location in the cell
___________________________________________________________________
endproduct
(show structures)
___________________________________________________________________
substrate
(show structures)
___________________________________________________________________
describe regulation
(give enzymes
and allosteric
effectors, where
known)
___________________________________________________________________
(5)
2. Describe the mechanism of action of steroid hormones such as testosterone or cortisone.
(14)
3. Describe the similarities and differences of triglyceride and glycogen breakdown using the
format below:
glycogen degradation
triglyceride degradation
__________________________________________________________________
hormone action
which triggers
breakdown
___________________________________________________________________
production of
second messenger
__________________________________________________________________
action of
protein kinase
__________________________________________________________________
(13 pts.)
5. Discuss the cholesterol pathway under the following headings:
a. Main function in the cell
b. write the reaction for the rate-limiting step (no structures required)
(3)c. describe the regulation of the rate-limiting step
(1) d. substrate
(2) e. endproduct
(6) f. describe the molecular basis for the genetic defects in hypercholesterolemia and androgen
insensitivity
(10pt)
7. Complete the following statements which describe the regulation of several important
metabolic pathways by writing the correct enzyme or enzymes into each blank.
a. High [ATP] in the mitochondrion inhibits __________________________________
______________________________ activities to slow the degradation of acetyl-CoA.
b. High [citrate] stimulates ______________________ activity to promote synthesis of
palmitic acid.
c. High [NADH] in the mitochondria inhibits _______________________________
activities to decrease citrate formation.
d. High [ATP] inhibits __________________________ activity to increase the
concentration of the substrate for gluconeogenesis in the mitochondrion.
e. High [citrate] in the cytoplasm inhibits ______________________ activity to promote
gluconeogenesis.
(9)
8. Write the letters (corresponding to functions ) in the spaces beside the molecules on the
right.
FUNCTION
cellular molecule
A membrane shuttle
_____ carnitine
B fat-soluble vitamin
_____ glycogen
C hormone receptor
_____ rhodopsin
D ETS component
_____ tripalmitate
E catalyst
_____ ubiquinone
F hormone
_____ chlorophyll
G energy storage
_____ glucagon
H. photoreceptor
_____ citrate lyase
______ cholecalciferol
(3)
b. Write the reaction responsible for generating the reducing power for fatty acid
synthesis.
(6 pts.)
10. a. In the chart below, show the 3 essential links between carbohydrate metabolism and
triglyceride synthesis and briefly describe the function each performs.
molecule in carbohydrate skeleton
molecule's function in lipid synthesis
________________________________________________________________
i.
________________________________________________________________
ii.
_________________________________________________________________
iii.
_________________________________________________________________
p. 5
NAME__________________
(10)
11. On the outline of the carbon skeleton of metabolism below, write the abbreviation for the
missing key intermediate in each box. Add the key intermediates showing where each of the lipid
synthesis pathways originate from the the carbon skeleton.
(12)
6. Complete the following statements by filling in the name of the specific enzyme (from
glycolysis, pyruvate oxidation, TCA cycle, gluconeogenesis, or pentose shunt) in the space
provided.
e.g.high [cholesterol] inhibits HMG-CoA reductaseto slow steroid synthesis
a.high [NADH] inhibits_______________________________to slow acetyl CoA formation.
b.high [acetyl CoA] stimulates______________________to increase rate of gluconeogenesis
c.high [f-1-P] inhibits________________________to prevent glycogen breakdown.
d.high[acetyl CoA] inhibits__________________________________to slow pyruvate
oxidations
e. high [ATP] stimulates _______________________________to promote gluconeogenesis
f. high [cAMP] activates_________________________________ which inactivates glycogen
synthase
(8)
8. Compare the similarities and differences between gluconeogenesis and fatty acid synthesis in
animal tissues .
Gluconeogenesis
fatty acid synthesis
___________________________________________________________________
Substrate(s)
cofactors
origin of reducing
power
immediate product
of CO2 fixation