BMSC 230 Lipids Synthesis Exam With
Complete Solutions
where does FA synthesis occur in the cell - ANSWER cytosol
what enzyme(s) are responsible for FA synthesis - ANSWER a large multi enzyme
complex known as FA synthase
describe the elongation of a FA chain by FA synthase - ANSWER elongated 2 C's at a
time, with the 2 C's coming from AcCoA
When does elongation of a fatty acid chain stop? - ANSWER Once the fatty acid chain
reaches 16 carbons long (Palmitate)
What substrate is used for FA biosynthesis? - ANSWER Acetyl CoA from glucose
breakdown
How does an excess amount of citrate build up when there is excess ATP? - ANSWER
ATP inhibits isocitrate dehydrogenase so isocitrate has to make citrate
What is the citrate shuttle? - ANSWER used to provide acetyl CoA from TAC cycle.
Citrate is pulled out of mitochondria and into the cytosol which is then spit into acetyl
CoA and Oxaloacetate by citrate lyase
What happens to the oxaloacetate in the citrate shuttle? - ANSWER It combines with
NADH to from malate, which then either become pyruvate to enter the matrix or NADPH
to enter the PPP
What is step one in fatty acid biosynthesis? - ANSWER Acetyl CoA is carboxylated to
Malonyl CoA by Acetyl CoA carboxylase in the cytosol
-irreversible, requires ATP and bicarbonate
What is the prosthetic group on Acetyl CoA carboxylase? - ANSWER Biotin
What is the rate limiting step in FA synthesis? - ANSWER Acetyl CoA carboxylase; acetyl
CoA --> malonyl CoA
what states will ACC be active/inactive - ANSWER Active when fed
Inactive when starving
What is the only non enzyme part of the Fatty Acid Synthase? - ANSWER Acyl Carrier
Protein, binds the growing fatty acid to the whole complex
What are the six enzyme components of the FAS? - ANSWER -KS
, -KR
-HD
-ER
-AT
-MT
How many Malonyl CoA and Acetyl CoA are used by FA Synthase? - ANSWER 7 Malonyl
CoA and 1 Acetyl CoA
what are the starting substrates for FA synthase - ANSWER Malonyl CoA + another
AcCoA
list the 7 steps that make up 1 cycle of lipid synthesis - ANSWER 1) Load AcCoA
2) Load Malonyl CoA
3) Condense the 2
4) Reduction
5) Dehydration
6) Another Reduction
7) Translocation
What is the first part of loading the FAS up with substrates? - ANSWER Acetyl CoA is
moved to ketoacyl synthase by acetyl transacylase, attaching an acetyl group to KS
What is the second part of loading the FAS up with substrates? - ANSWER Malonyl CoA
is converted to malonyl ACP by malonyl transacylase, attaching a malonyl group onto
the acetyl group
When is the FAS complex considered charged? - ANSWER When a malonyl and an acetyl
group are both bound
What is the first reaction in the FAS? - ANSWER A CO2 is removed and two carbons from
acetyl CoA are added onto malonyl-ACP, producing beta-ketobutyryl (a four carbon
molecule)
-occurs at KS
Complete Solutions
where does FA synthesis occur in the cell - ANSWER cytosol
what enzyme(s) are responsible for FA synthesis - ANSWER a large multi enzyme
complex known as FA synthase
describe the elongation of a FA chain by FA synthase - ANSWER elongated 2 C's at a
time, with the 2 C's coming from AcCoA
When does elongation of a fatty acid chain stop? - ANSWER Once the fatty acid chain
reaches 16 carbons long (Palmitate)
What substrate is used for FA biosynthesis? - ANSWER Acetyl CoA from glucose
breakdown
How does an excess amount of citrate build up when there is excess ATP? - ANSWER
ATP inhibits isocitrate dehydrogenase so isocitrate has to make citrate
What is the citrate shuttle? - ANSWER used to provide acetyl CoA from TAC cycle.
Citrate is pulled out of mitochondria and into the cytosol which is then spit into acetyl
CoA and Oxaloacetate by citrate lyase
What happens to the oxaloacetate in the citrate shuttle? - ANSWER It combines with
NADH to from malate, which then either become pyruvate to enter the matrix or NADPH
to enter the PPP
What is step one in fatty acid biosynthesis? - ANSWER Acetyl CoA is carboxylated to
Malonyl CoA by Acetyl CoA carboxylase in the cytosol
-irreversible, requires ATP and bicarbonate
What is the prosthetic group on Acetyl CoA carboxylase? - ANSWER Biotin
What is the rate limiting step in FA synthesis? - ANSWER Acetyl CoA carboxylase; acetyl
CoA --> malonyl CoA
what states will ACC be active/inactive - ANSWER Active when fed
Inactive when starving
What is the only non enzyme part of the Fatty Acid Synthase? - ANSWER Acyl Carrier
Protein, binds the growing fatty acid to the whole complex
What are the six enzyme components of the FAS? - ANSWER -KS
, -KR
-HD
-ER
-AT
-MT
How many Malonyl CoA and Acetyl CoA are used by FA Synthase? - ANSWER 7 Malonyl
CoA and 1 Acetyl CoA
what are the starting substrates for FA synthase - ANSWER Malonyl CoA + another
AcCoA
list the 7 steps that make up 1 cycle of lipid synthesis - ANSWER 1) Load AcCoA
2) Load Malonyl CoA
3) Condense the 2
4) Reduction
5) Dehydration
6) Another Reduction
7) Translocation
What is the first part of loading the FAS up with substrates? - ANSWER Acetyl CoA is
moved to ketoacyl synthase by acetyl transacylase, attaching an acetyl group to KS
What is the second part of loading the FAS up with substrates? - ANSWER Malonyl CoA
is converted to malonyl ACP by malonyl transacylase, attaching a malonyl group onto
the acetyl group
When is the FAS complex considered charged? - ANSWER When a malonyl and an acetyl
group are both bound
What is the first reaction in the FAS? - ANSWER A CO2 is removed and two carbons from
acetyl CoA are added onto malonyl-ACP, producing beta-ketobutyryl (a four carbon
molecule)
-occurs at KS
