BCH 3120 Midterm 2 Exam Study
Set 100% Pass
how are fatty acids abbreviated? - ANSWER number of carbons : number of double
bonds/cis/where double bond is
eg. a saturated fatty acid with 12 carbons would be 12:0
a unsaturated fatty acid with 12 carbons and 1 double bond at C3 would be 12:1cΔ9
*note: C1 is at the carboxyl end
cis vs trans fatty acids - ANSWER cis = hydrogens on the same side of the double bond
trans = hydrogens on opposite sides of the double bond
*note: cis fatty acids are found in nature, while trans are produced industrially
why are some fatty acids liquids while some are solids? - ANSWER based on the
properties of fatty acids:
saturated fatty acids have higher melting points
liquids, such as olive oil, have a higher percentage of unsaturated fatty acids
*note: think how saturated fats can pack tightly to form a solid
what are the primary sources of triacyl glycerides? - ANSWER 1. diet
2. de novo synthesis in the liver
3. storage in adipocytes
(eat, make and store)
how is storage of triacyl glycerides regulated? - ANSWER the release of stored fats is
regulated by hormones
if storage is "unregulated" -> obesity (keep eating)
*note: there is unlimited storage capacity since we never evolved to limit ourselves
what are the 3 enzymes that work to convert triacyl glycerides to free fatty acids +
glycerol? - ANSWER 1. adipose triglyceride lipase (ATGL): cut 1 fatty acid off from 3
2. hormone sensitive lipase (HSL): cuts second fatty acid
,3. monoacylglycerol lipase (MGL): cuts last fatty acid
*note: used for specific fatty acids at specific times (TAGs stored in adipose -> FAs and
glycerol to blood for glycolysis/gluconeogenesis)
3 stages of fatty acid oxidation - ANSWER 1. activation of FA (to make better substrate)
2. transport of FA (to the mitochondria)
3. beta-oxidation (break into acetyl-CoA)
what occurs during FA activation? - ANSWER 1) carboxylate ion (fatty acid) is
adenylated by ATP to form fatty acyl-adenylate and PPi via fatty acyl-CoA synthetase
the PPi is hydrolyzed to 2 Pi molecules via inorganic pyrophosphatase
2) thiol group of coenzyme A attacks acyl-adenylate displacing AMP and forming the
thioester fatty acyl-CoA via fatty acyl-CoA synthetase
*note: invest 2 ATP (use 1 but release AMP) and 1 CoA
what is special about the enzyme involved in FA activation? - ANSWER multiple genes
encode fatty acyl-CoA synthetase -> multiple isoforms dependent on chain length:
short chains are activated in mitochondrial matrix (don't require transport)
long chains are activated by acyl-CoA synthetase bound to mitochondrial outer
membrane
what occurs during FA transport? - ANSWER the carnitine shuttle is used to cross the
outer and inner mitochondrial membrane
1) acylation of carnitine via CPT1 = fatty acyl-carnitine (releasing CoA) -> enter through
porins and translocase
2) deacylation of fatty acyl-carnitine by CPT2 = fatty acyl-CoA (releasing carnitine)
*note: opposite reactions
why is a complex shuttling method used to bring FA into the mitochondria? - ANSWER
allows for regulation:
CPT1 is inhibited by malonyl-CoA (the first committed intermediate of fatty acid
synthesis)
therefore, conditions favouring fatty acid synthesis prevent fatty acids from entering the
mitochondria where beta-oxidation occurs
*note: synthesis costs energy so don't want to immediate breakdown after building
what is beta-oxidation of fatty acids? - ANSWER in the mitochondrial matrix, beta-carbon
, (C3) is modified:
chain shortened by 2 carbons at a time through a cyclic pathway involving 4 reactions
what is the 1st reaction of beta-oxidation? - ANSWER dehydrogenation of acyl-CoA in
trans-Δ-enoyl-CoA
by acyl-CoA dehydrogenase (ACAD) bound to FAD
FADH2 is generated -> electrons to ETF bound to FAD -> CoQ via ETF-Q oxidoreductase
*note: forming a trans double bond between alpha and beta carbons (C2 and C3)
what is the 2nd reaction of beta-oxidation? - ANSWER hydration of trans-Δ2-enoyl-CoA
to form L-3-hydroxyacyl-CoA
catalyzed by enoyl-CoA hydratase
*note: use water to create OH on beta carbon (remove double bond)
what is the 3rd reaction of beta-oxidation? - ANSWER dehydrogenation of
L-3-hydroxyacyl-CoA to form 3-ketoacyl-CoA via 3-L-hydroxyacyl-CoA dehydrogenase
NADH is generated
*note: forms ketone on C3
what is the 4th reaction of beta-oxidation? - ANSWER thiolytic cleavage of
3-ketoacyl-CoA to form a Cn-2 acyl-CoA + acetyl-CoA via thiolase
a new CoA is added to the end of the chain
*note: acetyl-CoA comes in to attack the ketone
how many ATP will be generated by the beta-oxidation of C16:0 fatty acid? - ANSWER
106 ATP
7 cycles of beta-oxidation = 7 FADH2, 7 NADH, 8 acetyl-CoA
8 cycles of TCA = 24 NADH, 8 FADH2, 8 GTP
ETC = (1.5 x 15) + (2.5 x 31) + 8 = 108 - 2 invested during activation
*note: 8 acetyl-CoA generated from 7 cycles because 2 produced at the end
the last oxidation cycle of odd number fatty acids produces a __ carbon molecules
called __
through a different pathway, it will be converted to __
this will generate ________ - ANSWER 3, propionyl-CoA
Set 100% Pass
how are fatty acids abbreviated? - ANSWER number of carbons : number of double
bonds/cis/where double bond is
eg. a saturated fatty acid with 12 carbons would be 12:0
a unsaturated fatty acid with 12 carbons and 1 double bond at C3 would be 12:1cΔ9
*note: C1 is at the carboxyl end
cis vs trans fatty acids - ANSWER cis = hydrogens on the same side of the double bond
trans = hydrogens on opposite sides of the double bond
*note: cis fatty acids are found in nature, while trans are produced industrially
why are some fatty acids liquids while some are solids? - ANSWER based on the
properties of fatty acids:
saturated fatty acids have higher melting points
liquids, such as olive oil, have a higher percentage of unsaturated fatty acids
*note: think how saturated fats can pack tightly to form a solid
what are the primary sources of triacyl glycerides? - ANSWER 1. diet
2. de novo synthesis in the liver
3. storage in adipocytes
(eat, make and store)
how is storage of triacyl glycerides regulated? - ANSWER the release of stored fats is
regulated by hormones
if storage is "unregulated" -> obesity (keep eating)
*note: there is unlimited storage capacity since we never evolved to limit ourselves
what are the 3 enzymes that work to convert triacyl glycerides to free fatty acids +
glycerol? - ANSWER 1. adipose triglyceride lipase (ATGL): cut 1 fatty acid off from 3
2. hormone sensitive lipase (HSL): cuts second fatty acid
,3. monoacylglycerol lipase (MGL): cuts last fatty acid
*note: used for specific fatty acids at specific times (TAGs stored in adipose -> FAs and
glycerol to blood for glycolysis/gluconeogenesis)
3 stages of fatty acid oxidation - ANSWER 1. activation of FA (to make better substrate)
2. transport of FA (to the mitochondria)
3. beta-oxidation (break into acetyl-CoA)
what occurs during FA activation? - ANSWER 1) carboxylate ion (fatty acid) is
adenylated by ATP to form fatty acyl-adenylate and PPi via fatty acyl-CoA synthetase
the PPi is hydrolyzed to 2 Pi molecules via inorganic pyrophosphatase
2) thiol group of coenzyme A attacks acyl-adenylate displacing AMP and forming the
thioester fatty acyl-CoA via fatty acyl-CoA synthetase
*note: invest 2 ATP (use 1 but release AMP) and 1 CoA
what is special about the enzyme involved in FA activation? - ANSWER multiple genes
encode fatty acyl-CoA synthetase -> multiple isoforms dependent on chain length:
short chains are activated in mitochondrial matrix (don't require transport)
long chains are activated by acyl-CoA synthetase bound to mitochondrial outer
membrane
what occurs during FA transport? - ANSWER the carnitine shuttle is used to cross the
outer and inner mitochondrial membrane
1) acylation of carnitine via CPT1 = fatty acyl-carnitine (releasing CoA) -> enter through
porins and translocase
2) deacylation of fatty acyl-carnitine by CPT2 = fatty acyl-CoA (releasing carnitine)
*note: opposite reactions
why is a complex shuttling method used to bring FA into the mitochondria? - ANSWER
allows for regulation:
CPT1 is inhibited by malonyl-CoA (the first committed intermediate of fatty acid
synthesis)
therefore, conditions favouring fatty acid synthesis prevent fatty acids from entering the
mitochondria where beta-oxidation occurs
*note: synthesis costs energy so don't want to immediate breakdown after building
what is beta-oxidation of fatty acids? - ANSWER in the mitochondrial matrix, beta-carbon
, (C3) is modified:
chain shortened by 2 carbons at a time through a cyclic pathway involving 4 reactions
what is the 1st reaction of beta-oxidation? - ANSWER dehydrogenation of acyl-CoA in
trans-Δ-enoyl-CoA
by acyl-CoA dehydrogenase (ACAD) bound to FAD
FADH2 is generated -> electrons to ETF bound to FAD -> CoQ via ETF-Q oxidoreductase
*note: forming a trans double bond between alpha and beta carbons (C2 and C3)
what is the 2nd reaction of beta-oxidation? - ANSWER hydration of trans-Δ2-enoyl-CoA
to form L-3-hydroxyacyl-CoA
catalyzed by enoyl-CoA hydratase
*note: use water to create OH on beta carbon (remove double bond)
what is the 3rd reaction of beta-oxidation? - ANSWER dehydrogenation of
L-3-hydroxyacyl-CoA to form 3-ketoacyl-CoA via 3-L-hydroxyacyl-CoA dehydrogenase
NADH is generated
*note: forms ketone on C3
what is the 4th reaction of beta-oxidation? - ANSWER thiolytic cleavage of
3-ketoacyl-CoA to form a Cn-2 acyl-CoA + acetyl-CoA via thiolase
a new CoA is added to the end of the chain
*note: acetyl-CoA comes in to attack the ketone
how many ATP will be generated by the beta-oxidation of C16:0 fatty acid? - ANSWER
106 ATP
7 cycles of beta-oxidation = 7 FADH2, 7 NADH, 8 acetyl-CoA
8 cycles of TCA = 24 NADH, 8 FADH2, 8 GTP
ETC = (1.5 x 15) + (2.5 x 31) + 8 = 108 - 2 invested during activation
*note: 8 acetyl-CoA generated from 7 cycles because 2 produced at the end
the last oxidation cycle of odd number fatty acids produces a __ carbon molecules
called __
through a different pathway, it will be converted to __
this will generate ________ - ANSWER 3, propionyl-CoA
