BMB 401 Exam 3 – Study Guide, Practice Questions & Revision Notes
Purpose of the TCA cycle - correct answer ✔✔-oxidation of fuel and formation of anabolic
precursors
-produces 1 GTP, 3 NADH, 1 FADH2
What are the three modes of regulation in the TCA cycle? - correct answer ✔✔1. availability of
substrate- increase in substrate will drive reactions forward.
2. enzymes are inhibited by their products
3. competitive feedback by downstream intermediates
Citrate - correct answer ✔✔-6C molecule
-In the mitochondrion, citrate is an intermediate in the TCA cycle
-When these levels build up, citrate leaves the mitochondrion and enters the cytoplasm. This is
a signal that there's a lot of energy around, and a lot of building blocks, indicative of a well-fed
state
-an activator of fatty acid synthesis
-precursor of cytoplasmic acetyl CoA
-potent inhibitor of phosphofructokinase1 that is involved in the breakdown of glucose to make
acetyl CoA
-when citrate levels are high, metabolic processes that are involved in producing storage units
will be activated. These storage units are fats and glycogen.
Citrate synthase - correct answer ✔✔-catalyzes reaction 1
-dimer
-small and large domain
-operates by a sequential ordered reaction
,-Oxaloacetate binds first, and causes the small subunit of citrate synthase to rotate to form the
acetyl CoA binding pocket.
-the enzyme is only active when both substrates are available
-induced fit
Fumarase enzyme - correct answer ✔✔-adds water in trans across the double bond of fumarate
to yield L-malate
-made possible by an iron-sulfur complex within the enzyme
-reaction 7
4 major points of regulation of TCA cycle - correct answer ✔✔1. PDC
+ NAD+ and CoA
- Acetyl CoA, NADH, ATP
2. Citrate synthase
- Succinyl CoA, NADH, ATP
3. Isocitrate dehydrogenase
+ NAD+, ADP
- NADH, ATP
4. Alpha-ketoglutarate dehydrogenase complex
+ AMP
- Succinyl CoA, NADH
Alpha ketoglutarate - correct answer ✔✔can be used to make glutamate, other amino acids,
and purine nucleotides
Succinyl CoA - correct answer ✔✔used to make porphyrins necessary for heme and chlorophyll
, Oxaloacetate - correct answer ✔✔makes amino acid aspartate and used to make other amino
acids and to make purine and pyrimidine nucleotides
What would happen to the TCA cycle if succinylcoA were continually removed to make heme for
hemoglobin and the only input into the cycle was acetyl coA? - correct answer ✔✔-we would
run out of oxaloacetate and since we need that to replenish the cycle, we would eventually slow
the TCA cycle
How do reducing equivalents get from the cytoplasm into the mitochondrial matrix? - correct
answer ✔✔-handing off e- from one carrier to another
-start with an electron carrier that is in the cytoplasm that's reduced, and then we'll pass those
electrons to a mitochondrial electron carrier and reduce that
-glycerol three-phosphate shuttle, and the malate-aspartate shuttle
Chemiosmotic Gradient - correct answer ✔✔-NADH and FADH2 have high e- transfer potential,
so they can be transferred from carriers of high potential to low potential
-energy is released
-this work is going to be pumping of protons from the mitochondrial matrix into the
mitochondrial inter membrane space
-helps power ATP synthesis
Electron Transfer Potential - correct answer ✔✔-the more negative the reduction potential, the
greater the e- potential is for the reductant and the greater the tendency is to donate e-
-the more positive, the greater the tendency to accept electrons
-oxygen has a positive potential so it has a more tendency to be reduced
Q pool - correct answer ✔✔-consists of ubiquinone (oxidized) and ubiguinol (reduced)
-resides in the inner mitochondrial membrane and shuttles back and forth in a lipophilic
environment
Purpose of the TCA cycle - correct answer ✔✔-oxidation of fuel and formation of anabolic
precursors
-produces 1 GTP, 3 NADH, 1 FADH2
What are the three modes of regulation in the TCA cycle? - correct answer ✔✔1. availability of
substrate- increase in substrate will drive reactions forward.
2. enzymes are inhibited by their products
3. competitive feedback by downstream intermediates
Citrate - correct answer ✔✔-6C molecule
-In the mitochondrion, citrate is an intermediate in the TCA cycle
-When these levels build up, citrate leaves the mitochondrion and enters the cytoplasm. This is
a signal that there's a lot of energy around, and a lot of building blocks, indicative of a well-fed
state
-an activator of fatty acid synthesis
-precursor of cytoplasmic acetyl CoA
-potent inhibitor of phosphofructokinase1 that is involved in the breakdown of glucose to make
acetyl CoA
-when citrate levels are high, metabolic processes that are involved in producing storage units
will be activated. These storage units are fats and glycogen.
Citrate synthase - correct answer ✔✔-catalyzes reaction 1
-dimer
-small and large domain
-operates by a sequential ordered reaction
,-Oxaloacetate binds first, and causes the small subunit of citrate synthase to rotate to form the
acetyl CoA binding pocket.
-the enzyme is only active when both substrates are available
-induced fit
Fumarase enzyme - correct answer ✔✔-adds water in trans across the double bond of fumarate
to yield L-malate
-made possible by an iron-sulfur complex within the enzyme
-reaction 7
4 major points of regulation of TCA cycle - correct answer ✔✔1. PDC
+ NAD+ and CoA
- Acetyl CoA, NADH, ATP
2. Citrate synthase
- Succinyl CoA, NADH, ATP
3. Isocitrate dehydrogenase
+ NAD+, ADP
- NADH, ATP
4. Alpha-ketoglutarate dehydrogenase complex
+ AMP
- Succinyl CoA, NADH
Alpha ketoglutarate - correct answer ✔✔can be used to make glutamate, other amino acids,
and purine nucleotides
Succinyl CoA - correct answer ✔✔used to make porphyrins necessary for heme and chlorophyll
, Oxaloacetate - correct answer ✔✔makes amino acid aspartate and used to make other amino
acids and to make purine and pyrimidine nucleotides
What would happen to the TCA cycle if succinylcoA were continually removed to make heme for
hemoglobin and the only input into the cycle was acetyl coA? - correct answer ✔✔-we would
run out of oxaloacetate and since we need that to replenish the cycle, we would eventually slow
the TCA cycle
How do reducing equivalents get from the cytoplasm into the mitochondrial matrix? - correct
answer ✔✔-handing off e- from one carrier to another
-start with an electron carrier that is in the cytoplasm that's reduced, and then we'll pass those
electrons to a mitochondrial electron carrier and reduce that
-glycerol three-phosphate shuttle, and the malate-aspartate shuttle
Chemiosmotic Gradient - correct answer ✔✔-NADH and FADH2 have high e- transfer potential,
so they can be transferred from carriers of high potential to low potential
-energy is released
-this work is going to be pumping of protons from the mitochondrial matrix into the
mitochondrial inter membrane space
-helps power ATP synthesis
Electron Transfer Potential - correct answer ✔✔-the more negative the reduction potential, the
greater the e- potential is for the reductant and the greater the tendency is to donate e-
-the more positive, the greater the tendency to accept electrons
-oxygen has a positive potential so it has a more tendency to be reduced
Q pool - correct answer ✔✔-consists of ubiquinone (oxidized) and ubiguinol (reduced)
-resides in the inner mitochondrial membrane and shuttles back and forth in a lipophilic
environment
