TCA cycle

Question 1

How are mitochondria and bacteria similar in relation to size and shape?

Answer 1

bacillus rod shaped, ranging between 1 and 10 microns in length.

Question 2

How are mitochondria and bacteria similar in relation to replication?

Answer 2

Both replicate via binary fission

Question 3

How are mitochondria and bacteria similar in relation to type of DNA?

Answer 3

Both contain circular DNA plasmids

Question 4

How are mitochondria and bacteria similar in relation to ribosome and protein synthesis?

Answer 4

Mitochondria carry their own ribosomes to make proteins which looks more like bacterial ribosomes

Question 5

How are mitochondria and bacteria similar in relation to membranes?

Answer 5

Both inner and outer membrane w/ other membrane with similar proteins like porins

Question 6

Where does the conversion for pyruvate to acetate occur?

Answer 6

Mitochondrial matirx

Question 7

What transports pyruvate across the mitochondrial membrane?

Answer 7

A pyruvate transporter (MPC) transports pyruvate across the impermeable inner mitochondrial membrane.

Question 8

What does the mitochondria contain to increase its surface area?

Answer 8

Cristae

Question 9

Where does the TCA cycle occur?

Answer 9

In the mitochondrial matrix

Question 10

Describe the link reaction between glycolysis and TCA cycle.

Eg reactants products and enzyme

Answer 10

Pyruvate to ACetyl-CoA via pyruvate dehydrogenase

NAD+ turns to NADH and CoA-SH turns to CO2

Question 11

Pyruvate dehydrogenase is a multil-enzyme complex

Explain the steps.

Answer 11

E1: Pyruvate dehydrogenase which uses thiamine pyrophosphate (TPP) as its prosthetic group.
E2: Dihydrolipoyl transacetylase which uses lipoamide and coenzyme A (also known as CoA-SH) as its prosthetic groups.
E3: Dihydrolipoyl dehydrogenase which uses flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NAD+) as its cofactors.

Question 12

Describe the E1 step in pyruvate dehydrogenase

Answer 12

E1: Pyruvate dehydrogenase which uses thiamine pyrophosphate (TPP) as its prosthetic group.

Question 13

Describe the E2 step in pyruvate dehydrogenase

Answer 13

E2: Dihydrolipoyl transacetylase which uses lipoamide and coenzyme A (also known as CoA-SH) as its prosthetic groups.

Question 14

Describe the E3 step in pyruvate dehydrogenase

Answer 14

E3: Dihydrolipoyl dehydrogenase which uses flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NAD+) as its cofactors.

Question 15

Name the 3 prosthetic groups used for pyruvate dehydrogenase

Answer 15

TTP
Lipoate
FAD

Question 16

What is TTP needed for in pyruvate dehydrogenase

Answer 16

Required for pyruvate decarboxylation

Question 17

What is lipoate needed for in pyruvate dehydrogenase

Answer 17

Required for the transfer of the acetyl group to Coenzyme A

Question 18

What is FAD needed for in pyruvate dehydrogenase

Answer 18

Required for the regeneration of the oxidised for of lipoate

Question 19

Why do enzyme complexes exist?

Answer 19

To speed up reactions

Question 20

How many steps are in the TCA cycle?

How many carbons are lost each turn?

Answer 20

8 steps

loses 2 carbons each turn

Question 21

Describe the first step of the TCA cycle

What is the type of the reaction?

What drives the reaction?

Answer 21

Citrate synthase- condensation

Acetyl-CoA + Oxaloacetate -> Citrate
with Citrate synthase and H20 -> CoA-SH

Driven by hydrolysis of the thioester

Question 22

Describe the TCA cycle- Step 2

What is the reaction type
What is the cofactor?
How many steps is this and what is the name of the intermediate?

Answer 22

Aconitase

Isomerisation reaction
FE-S complex= cofactor
2 step reaction/ intermediate= cis-aconitate

Citrate<=>isocitrate

Question 23

Describe the third step of the TCA cycle

What type of reaction?
What is the cofactor?
How many steps and what is the intermediate ?

Answer 23

Isocitrate dehydrogenase
Isocitrate-> Oxalosuccinate ( NAD+ to NADH +H+)
AND oxalosuccinate -> alpha-ketoglutarate (H+-> CO2)

Reaction= oxidative deacarboxylation
Cofactor= NAD+
2 steps intermediate = oxalosuccinate

Question 24

Describe the 4th step in the TCA cycle

What is the reaction type
What is the cofactor

Answer 24

Alpha-ketoglutarate dehydrogenase
Alpha-ketoglutarate -> succinyl-CoA
( CoASH -> CO2 and NAD+ -> NADH+h+)

reaction type= oxidative decarboxylation
Cofactor= NAD+ and CoA-SH

Question 25

Describe the 5th step of the TCA cycle What is the reaction type What is the cofactor

Answer 25

Succinyl CoA synthetase or Succinate thiokinase Succinyl-CoA<=> Succinate ( GDP+Pi-> GTP CoA-SH) Reaction type=substrate level phosphorylation Cofactor= GDP .The GTP can be used to form ATP (nucleoside diphosphate kinase). ATP and GTP are energetically equivalent.

Question 26

Describe the 6th step of the TCA cycle What is the cofactor What is the reaction type? What is significant about the enzyme?

Answer 26

``` Succinate<=> Fumerate Succinate dehydrogenase (FAD->FADH2) ``` Reaction Type=oxidative dehydrogenation Cofactor= FAD reduced to FADH2 Enzyme is the only Krebbs one contained in the inner mitochondrial membrane. Active site faces the mitochondrial matrix

Question 27

Describe Step 7 in the TCA cycle What is the reaction type?

Answer 27

Fumarate<=>L-malate (H20) Fumarase Reaction type: catalyses a stereospecific trans addition of a hydrogen atom and a hydroxyl group

Question 28

Describe step 8 of TCA cycle What is the cofactor? What is the reaction type? What drives the reaction forwards?

Answer 28

L-malate <=> oxaloactate (NAD+-> NADH + H+) malate dehydrogenase Reaction type= oxidative dehydrogenation Cofactor= NAD+ Reaction driven by OAA depletion

Question 29

What is the structure of Acetate?

Answer 29

CH3-Coo^-

Question 30

What is the structure of Acetyl-CoA?

Answer 30

CH3-C=O-S-CoA

Question 31

What is the structure of pyruvate?

Answer 31

O^- -C=O-C=O-CH3

Question 32

Name all 8 enzymes in the Krebs cycle

Answer 32

``` Citrate synthase Aconitase Isocitrate dehydrogenase α-ketoglutarate dehydrogenase Succinyl CoA synthetase Succinate dehydrogenase Fumarase Malate dehydrogenase ```

Question 33

How many NADH needed for production of acetyl Co-A? | How many NADH, FADH2 and GTP/ATP from one turn of the TCA cycle?

Answer 33

1 NADH for the production of acetyl-CoA 3 NADHs from one turn of the TCA cycle 1 FADH2 from TCA 1 GTP (ATP) directly from the TCA cycle

Question 34

What is the net production of ATP from glycolysis and the TCA cycle?

Answer 34

Glycolysis generates 8 ATP TCA cycle generates 30 ATP for 2 pyruvates entering the TCA cycle Total 38 net ATPs