TCA Cycle and Mitochondria Origins Flashcards

Flashcards to review the TCA cycle, enzyme complexes, and the origins of mitochondria, based on lecture notes.

Why do eukaryotic cells have compartmentalization?

Because they cannot rely on diffusion due to their size and complexity

From what are mitochondria believed to have derived?

Symbiotic bacteria

List similarities between bacteria and mitochondria.

Size and shape, replication by binary fission, circular DNA, similar ribosomes, and inner/outer membranes with porins.

Where does the oxidation of pyruvate occur?

In the mitochondria

What three enzymes comprise the pyruvate dehydrogenase multi-enzyme complex?

Pyruvate dehydrogenase, Dihydrolipoyl transacetylase, Dihydrolipoyl dehydrogenase

What prosthetic group does Pyruvate dehydrogenase use?

Thiamine pyrophosphate (TPP)

What prosthetic groups does Dihydrolipoyl transacetylase use?

Lipoamide and coenzyme A

What prosthetic groups does Dihydrolipoyl dehydrogenase use?

Flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NAD+)

Define a prosthetic group.

A tightly bound, non-polypeptide unit required for enzymatic activity

Why do enzyme complexes exist?

To speed up reactions by passing products directly to the next enzyme and prevent highly reactive products from participating in unfavorable side reactions.

In Step 1 of the TCA cycle, what type of reaction occurs and what enzyme facilitates it?

Condensation reaction facilitated by citrate synthase

What is the reaction type for Step 2 of the TCA cycle?

Isomerization

What is the reaction type for Step 3 of the TCA cycle?

Oxidative decarboxylation

What cofactor is used in Step 3 of the TCA cycle?

NAD+ is reduced to NADH + H+

What is the reaction type for Step 4 of the TCA cycle?

Oxidative decarboxylation

What cofactors are used in Step 4 of the TCA cycle?

NAD+ ,which is reduced to NADH + H+, and COA-SH

What is the reaction type for Step 5 of the TCA cycle?

substrate level phosphorylation where the energy released from the hyrdrolysis of the thioester bond provides energy for the formation of the phosphoanhydride bond of GTP

What happens during substrate level phosphorylation in Step 5?

The enzyme involves an enzyme-succinyl phosphate intermediate. A histidine is phosphorylated during the reaction.

What is the reaction type for Step 6 of the TCA cycle?

Oxidative dehydrogenation of succinate to fumarate

What cofactor is used in Step 6 of the TCA cycle?

FAD is reduced to FADH2

What is unique about Succinate dehydrogenase?

It's the only Krebs enzyme contained within the inner mitochondrial membrane, and its active site faces the mitochondrial matrix.

What happens in the reaction for Step 7 of the TCA cycle?

Catalyses a stereospecific trans addition of a hydrogen atom and a hydroxyl group

What is the reaction for Step 8 of the TCA cycle?

Oxidative dehydrogenation of malate to oxaloacetate (4 of 4 oxid/red reactions).

What cofactor is used in Step 8 of the TCA cycle?

NAD+ is reduced to NADH + H+

What is the net ATP gain from the conversion of glucose to pyruvate, including re-oxidation of NADH?

8 ATPs

What is the enzyme used in step 1 of the TCA cycle

Citrate synthase

What is the enzyme used in step 2 of the TCA cycle

Aconitase

What is the enzyme used in step 3 of the TCA cycle

Isocitrate dehydrogenase

What is the enzyme used in step 4 of the TCA cycle

Alpha-ketoglutarate dehydrogenase

What is the enzyme used in step 5 of the TCA cycle

Succinyl-CoA synthetase

What is the enzyme used in step 6 of the TCA cycle

Succinate dehydrogenase

What is the enzyme used in step 7 of the TCA cycle

Fumarase

What is the enzyme used in step 8 of the TCA cycle

Malate dehydrogenase