Term
| How does cytosolic NADH enter the mitochondria? Why is this necessary? |
|
Definition
| NADH doesn't enter the mitochondria. Two different shuttle systems bring the reducing equivalents from NADH across the inner mitochondrial membrane, which is impermeable to NADH. |
|
|
Term
| What are the two shuttle systems for transporting reducing equivalents? |
|
Definition
| Malate-Aspartate Shuttle & Glycerol-3-phosphate Shuttle |
|
|
Term
| How does the Malate-Aspartate shuttle function? |
|
Definition
1. oxaloacetate is converted to malate by cytosolic malate dehydrogenase, NADH is oxidized to NAD+
2. Malate crosses the inner innermitochondrial membrane.
3. Malate is converted back to oxaloacetate by mitochondrial malate dehydrogenase, NAD+ reduced to NADH
4. Oxaloacetate is converted to aspartate which can cross the inner mitochondrial membrane and is converted back to oxaloacetate on the other side. |
|
|
Term
| What are reducing equivalents? |
|
Definition
Electrons. May be accompanied by protons.
Possibilities: electron on its own, H atoms (e + H) or hydride ions (H-) |
|
|
Term
| How does the Glycerol-3-Phosphate Shuttle function? |
|
Definition
1. Dihydroxyacetone is reduced to glycerol-3-phosphate, NADH2 is oxidized to NAD+.
2. Reducing equivalents are passed on to FAD which is reduced to FADH2, when glycerol-3-phosphate is oxidized to dihydroxyacetone phosphate.
3. FADH2 passes reducing equivalents directly to Coenzyme Q (Complex I is bypassed) |
|
|
Term
True or False
Molecules freely cross the inner mitochondrial membrane with the glycerol-3-phosphate shuttle |
|
Definition
False
The mitochondrial glycerol-3-phosphate dehydrogenase enzyme is located on the exterior surface of the inner mitochondrial membrane, so no molecules need cross the membrane. |
|
|
Term
| What is the pyruvate dehydrogenase complex? |
|
Definition
The link between glycolysis and the TCA cycle
Pyruvate is oxidized into Acetyl-CoA |
|
|
Term
| Where is the pyruvate dehydrogenase complex located and what does it do? |
|
Definition
In the mitochondrial matrix.
It catalyzes the irreversible oxidative decarboxylation of pyruvate |
|
|
Term
| What 5 coenzymes are required by the  pyruvate dehydrogenase complex? |
|
Definition
| -NAD+, FAD, CoA, thiamine pyrophosphate and lipate |
|
|
Term
| Describe the substrate-level phosphorylation that occurs in the TCA cycle |
|
Definition
The high energy thioester bond in succinylCoA is hydrolyzed, this reaction is coupled to GTP/ATP synthesis:
-inorganic phosphate binds to succ.CoA & displaces CoA
-a histidine residue accepts the phosphate group, succinate is released
-phosphate group is transferred to a GDP/ADP molecule releasing a free enzyme |
|
|
Term
| What type if intermediate is formed in the hydrolysis of the thioester bond in succinyl CoA? |
|
Definition
| phosphoenzyme intermediate |
|
|
Term
| What is produced by the cataboolism of fatty acids, sugars and some amino acids? |
|
Definition
|
|
Term
| What is the function of the TCA cycle? |
|
Definition
-completely oxidizes acetyl CoA to CO2
-produces a small amount of ATP/GTP (1 per cycle)
-generates FADH2 & 3NADH2 (important for ATP generation in the ETC later!!) |
|
|
Term
True or False
The condensation of acetyl CoA and oxaloacetate to form citrate involves the removal of water |
|
Definition
False
This isn't actually a dehydration synthesis reaction, the molecules are simply joined together |
|
|
Term
| Oxidative decarboxylation of isocitrate converts an ______ to a ________ |
|
Definition
|
|
Term
| What mechanism is identical to the pyruvate dehydrogenase complex? Why is it important? |
|
Definition
alpha-ketoglutarate dehydrogenase
Forms a high-energy thioester bond which will be later involved in substrate level phosphorylation |
|
|
Term
| What are the products of the TCA cycle? |
|
Definition
3 NADH & 3H+
1 FADH2
2 CO2
1 ATP or GTP
1 CoA |
|
|
Term
What enzyme does this?
acetyl-CoA + oxaloacetate form citrate |
|
Definition
|
|
Term
What enzyme does this?
malate is converted to oxaloacete |
|
Definition
|
|
Term
What enzyme does this?
Fumerate is converted to malate |
|
Definition
|
|
Term
What does this enzyme do?
succinyl-CoA synthetase |
|
Definition
| converts succinyl-CoA to succinate |
|
|
Term
What does this enzyme do?
succinate dehydrogenase |
|
Definition
| converts succinate to fumerate |
|
|
Term
| What enzyme converts citrate to aconitate? What is aconitate then converted to? |
|
Definition
enzyme: aconitase
converted to: isocitrate |
|
|
Term
| What enzyme converts alpha-ketoglutarate to succinyl-CoA? |
|
Definition
| alpha-ketogultarate dehydrogenase |
|
|
Term
What does this enzyme do?
isocitrate dehydrogenase |
|
Definition
| Converts isocitrate to alpha-ketoglutarate |
|
|
Term
| What is the most important role of the TCA cycle? |
|
Definition
| To reduce FAD & NAD+ to form FADH2 and 3 NADH, which will later be used to produce lots of ATP in the ETC |
|
|
