Medical Biochemistry Pathways Exam Questions with
Answers
1. beta-oxidation is trying to make acetyl CoA molecules from activated
fatty acids, which will feed into the TCA cycle or ketone body synthesis (can
also be used in fatty acid synthesis)
essentially, we're oxidizing more reduced molecules, such as the
alkanes (hydrocarbons) of lipids: main purpose of beta-oxidation
2. a free fatty acid is "primed" in an ATP-dependent acylation reaction
the free fatty acid reactant has coenzyme A added to it - along with ATP -
and becomes a fatty acyl CoA product, via the enzyme fatty acyl CoA
synthetase
note: ATP is broken down into AMP + PPi (pyrophosphate), which becomes
2 inorganic phosphate molecules: "1st" step of beta-oxidation:
before fatty acids can be oxidized, they must undergo an initial reaction
to get ready for breakdown
describe this reaction including its reactant, product, and enzyme
3. just read: "1st" step of beta-oxidation
4. true: true or false:
the "1st" step of beta-oxidation is IRREVERSIBLE
5. 1) dehydrogenation (oxidation)
2) hydration
3) dehydrogenation (oxidation)
4) cleavage: the 4 main steps of beta-oxidation
6. acyl-CoA dehydrogenase
FAD is reduced to FADH2: 1st step of beta-oxidation:
a fatty acyl CoA (palmitoyl CoA, a C-16:0 fatty acid) is oxidized to enoyl
CoA via this enzyme
also, via what cofactor?
7. a trans-double bond: the first step of beta-oxidation adds what to the
,structure of the fatty acid?
8. enoyl CoA hydratase: 2nd step of beta-oxidation:
enoyl CoA is hydrated to beta-hydroxyacyl CoA via this enzyme
9. a secondary alcohol: the 2nd step of beta-oxidation adds what to the
beta-car- bon of the fatty acid?
10. beta-hydroxyacyl CoA dehydrogenase
NAD+ is reduced to NADH + H+: 3rd step of beta-oxidation:
beta-hydroxyacyl CoA is oxidized to beta-ketoacyl CoA via
this enyzme also, via what cofactor?
11.a ketone group: the 3rd step of beta-oxidation adds what to the
beta-carbon (carbon 3) of the fatty acid?
12. beta-ketothiolase ("thiolase")
coenzyme A (CoA-SH)
note: after this step is completed, steps 1-4 are repeated until the fatty acid
chain has been completely broken down: 4th step of beta-oxidation:
beta-ketoacyl CoA is cleaved into a C-14:0 fatty acyl CoA and a
molecule of acetyl CoA via this enzyme
also, what is added to break the acetyl CoA off the chain?
13.basically, we added a ketone group to the beta-carbon (carbon 3), and
then clipped off the resulting acetyl CoA molecule, generating a shorter
fatty acid in the process (by 2 carbons): briefly describe the "mechanical"
process of beta-oxidation
14. acetyl CoAs: 8 acetyl CoA molecules
rounds: 7 rounds (since the last round splits a 4C fatty acid into 2 2C
acetyl CoA molecules
reducing power: because 7 rounds have taken place, 7 FADH2 and 7 NADH+
+ H+ molecules were generated: with a C-16:0 palmitoyl CoA molecule:
how many acetyl CoA molecules would be generated by the full process
, of beta-ox- idation?
how many "rounds" would this take?
how much reducing power would this generate in the process?
15. acetyl CoAs: 7 acetyl CoA molecules and 1 proponyl CoA molecule
-because it eventually gets down to a fatty acid molecule C-5:0, it's split into
a C-2:0 (acetyl CoA) and a 3C molecule proponyl, CoA
rounds: 7 rounds (since the last round splits a 4C fatty acid into 2 2C
acetyl CoA molecules
reducing power: because 7 rounds have taken place, 7 FADH2 and 7 NADH+
+ H+ molecules were generated: describe the resulting products of a fatty
acid chain built as C-17:0
include the number of rounds that need to take place, the number of
acetyl CoAs generated, and amount of reducing power generated
16.succinyl CoA: production of propionyl in beta-oxidation is not the
end of the road, however
it must be further broken down to , which is sent to the TCA cycle
17. propionyl CoA (3C) is carboxylated to D-methylmalonyl CoA (4C) via
pro- pionyl CoA carboxylase in an ATP-dependent reaction; this enzymes
requires biotin (which is what transfers CO2 from bicarbonate)
D-methylmalonyl CoA is then isomerized to L-methylmalonyl CoA via
methyl- malonyl CoA isomerase
L-methylmalonyl CoA is then converted to succinyl CoA via
methylmalonyl CoA mutase, which requires vitamin B12
note: this last reaction is unusual in that a hydrogen and a carbonyl CoA
on adjacent carbons switch spots: describe the main reactions
associated with propionyl breakdown, including the important enzymes
and their cofactors
18.a free fatty acid: what kind of molecule is this?
Answers
1. beta-oxidation is trying to make acetyl CoA molecules from activated
fatty acids, which will feed into the TCA cycle or ketone body synthesis (can
also be used in fatty acid synthesis)
essentially, we're oxidizing more reduced molecules, such as the
alkanes (hydrocarbons) of lipids: main purpose of beta-oxidation
2. a free fatty acid is "primed" in an ATP-dependent acylation reaction
the free fatty acid reactant has coenzyme A added to it - along with ATP -
and becomes a fatty acyl CoA product, via the enzyme fatty acyl CoA
synthetase
note: ATP is broken down into AMP + PPi (pyrophosphate), which becomes
2 inorganic phosphate molecules: "1st" step of beta-oxidation:
before fatty acids can be oxidized, they must undergo an initial reaction
to get ready for breakdown
describe this reaction including its reactant, product, and enzyme
3. just read: "1st" step of beta-oxidation
4. true: true or false:
the "1st" step of beta-oxidation is IRREVERSIBLE
5. 1) dehydrogenation (oxidation)
2) hydration
3) dehydrogenation (oxidation)
4) cleavage: the 4 main steps of beta-oxidation
6. acyl-CoA dehydrogenase
FAD is reduced to FADH2: 1st step of beta-oxidation:
a fatty acyl CoA (palmitoyl CoA, a C-16:0 fatty acid) is oxidized to enoyl
CoA via this enzyme
also, via what cofactor?
7. a trans-double bond: the first step of beta-oxidation adds what to the
,structure of the fatty acid?
8. enoyl CoA hydratase: 2nd step of beta-oxidation:
enoyl CoA is hydrated to beta-hydroxyacyl CoA via this enzyme
9. a secondary alcohol: the 2nd step of beta-oxidation adds what to the
beta-car- bon of the fatty acid?
10. beta-hydroxyacyl CoA dehydrogenase
NAD+ is reduced to NADH + H+: 3rd step of beta-oxidation:
beta-hydroxyacyl CoA is oxidized to beta-ketoacyl CoA via
this enyzme also, via what cofactor?
11.a ketone group: the 3rd step of beta-oxidation adds what to the
beta-carbon (carbon 3) of the fatty acid?
12. beta-ketothiolase ("thiolase")
coenzyme A (CoA-SH)
note: after this step is completed, steps 1-4 are repeated until the fatty acid
chain has been completely broken down: 4th step of beta-oxidation:
beta-ketoacyl CoA is cleaved into a C-14:0 fatty acyl CoA and a
molecule of acetyl CoA via this enzyme
also, what is added to break the acetyl CoA off the chain?
13.basically, we added a ketone group to the beta-carbon (carbon 3), and
then clipped off the resulting acetyl CoA molecule, generating a shorter
fatty acid in the process (by 2 carbons): briefly describe the "mechanical"
process of beta-oxidation
14. acetyl CoAs: 8 acetyl CoA molecules
rounds: 7 rounds (since the last round splits a 4C fatty acid into 2 2C
acetyl CoA molecules
reducing power: because 7 rounds have taken place, 7 FADH2 and 7 NADH+
+ H+ molecules were generated: with a C-16:0 palmitoyl CoA molecule:
how many acetyl CoA molecules would be generated by the full process
, of beta-ox- idation?
how many "rounds" would this take?
how much reducing power would this generate in the process?
15. acetyl CoAs: 7 acetyl CoA molecules and 1 proponyl CoA molecule
-because it eventually gets down to a fatty acid molecule C-5:0, it's split into
a C-2:0 (acetyl CoA) and a 3C molecule proponyl, CoA
rounds: 7 rounds (since the last round splits a 4C fatty acid into 2 2C
acetyl CoA molecules
reducing power: because 7 rounds have taken place, 7 FADH2 and 7 NADH+
+ H+ molecules were generated: describe the resulting products of a fatty
acid chain built as C-17:0
include the number of rounds that need to take place, the number of
acetyl CoAs generated, and amount of reducing power generated
16.succinyl CoA: production of propionyl in beta-oxidation is not the
end of the road, however
it must be further broken down to , which is sent to the TCA cycle
17. propionyl CoA (3C) is carboxylated to D-methylmalonyl CoA (4C) via
pro- pionyl CoA carboxylase in an ATP-dependent reaction; this enzymes
requires biotin (which is what transfers CO2 from bicarbonate)
D-methylmalonyl CoA is then isomerized to L-methylmalonyl CoA via
methyl- malonyl CoA isomerase
L-methylmalonyl CoA is then converted to succinyl CoA via
methylmalonyl CoA mutase, which requires vitamin B12
note: this last reaction is unusual in that a hydrogen and a carbonyl CoA
on adjacent carbons switch spots: describe the main reactions
associated with propionyl breakdown, including the important enzymes
and their cofactors
18.a free fatty acid: what kind of molecule is this?
