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A BIOL1024 Part 2 > TCA cycle > Flashcards

TCA cycle Flashcards

1
Q

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

A

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

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2
Q

How are mitochondria and bacteria similar in relation to replication?

A

Both replicate via binary fission

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3
Q

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

A

Both contain circular DNA plasmids

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4
Q

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

A

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

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5
Q

How are mitochondria and bacteria similar in relation to membranes?

A

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

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6
Q

Where does the conversion for pyruvate to acetate occur?

A

Mitochondrial matirx

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7
Q

What transports pyruvate across the mitochondrial membrane?

A

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

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8
Q

What does the mitochondria contain to increase its surface area?

A

Cristae

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9
Q

Where does the TCA cycle occur?

A

In the mitochondrial matrix

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10
Q

Describe the link reaction between glycolysis and TCA cycle.

Eg reactants products and enzyme

A

Pyruvate to ACetyl-CoA via pyruvate dehydrogenase

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

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11
Q

Pyruvate dehydrogenase is a multil-enzyme complex

Explain the steps.

A

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.

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12
Q

Describe the E1 step in pyruvate dehydrogenase

A

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

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13
Q

Describe the E2 step in pyruvate dehydrogenase

A

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

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14
Q

Describe the E3 step in pyruvate dehydrogenase

A

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

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15
Q

Name the 3 prosthetic groups used for pyruvate dehydrogenase

A

TTP
Lipoate
FAD

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16
Q

What is TTP needed for in pyruvate dehydrogenase

A

Required for pyruvate decarboxylation

17
Q

What is lipoate needed for in pyruvate dehydrogenase

A

Required for the transfer of the acetyl group to Coenzyme A

18
Q

What is FAD needed for in pyruvate dehydrogenase

A

Required for the regeneration of the oxidised for of lipoate

19
Q

Why do enzyme complexes exist?

A

To speed up reactions

20
Q

How many steps are in the TCA cycle?

How many carbons are lost each turn?

A

8 steps

loses 2 carbons each turn

21
Q

Describe the first step of the TCA cycle

What is the type of the reaction?

What drives the reaction?

A

Citrate synthase- condensation

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

Driven by hydrolysis of the thioester

22
Q

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?

A

Aconitase

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

Citrate<=>isocitrate

23
Q

Describe the third step of the TCA cycle

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

A

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

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

24
Q

Describe the 4th step in the TCA cycle

What is the reaction type
What is the cofactor

A

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

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

25
Q

Describe the 5th step of the TCA cycle

What is the reaction type
What is the cofactor

A

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.

26
Q

Describe the 6th step of the TCA cycle

What is the cofactor
What is the reaction type?
What is significant about the enzyme?

A 
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

27
Q

Describe Step 7 in the TCA cycle

What is the reaction type?

A

Fumarate<=>L-malate (H20)
Fumarase

Reaction type: catalyses a stereospecific trans addition of a hydrogen atom and a hydroxyl group

28
Q

Describe step 8 of TCA cycle

What is the cofactor?
What is the reaction type?
What drives the reaction forwards?

A

L-malate <=> oxaloactate (NAD+-> NADH + H+)
malate dehydrogenase

Reaction type= oxidative dehydrogenation
Cofactor= NAD+
Reaction driven by OAA depletion

29
Q

What is the structure of Acetate?

A

CH3-Coo^-

30
Q

What is the structure of Acetyl-CoA?

A

CH3-C=O-S-CoA

31
Q

What is the structure of pyruvate?

A

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

32
Q

Name all 8 enzymes in the Krebs cycle

A 
Citrate synthase
Aconitase
Isocitrate dehydrogenase
α-ketoglutarate dehydrogenase
Succinyl CoA synthetase
Succinate dehydrogenase
Fumarase
Malate dehydrogenase
33
Q

How many NADH needed for production of acetyl Co-A?

How many NADH, FADH2 and GTP/ATP from one turn of the TCA cycle?

A

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

34
Q

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

A

Glycolysis generates 8 ATP

TCA cycle generates 30 ATP for 2 pyruvates entering the TCA cycle

Total 38 net ATPs

A BIOL1024 Part 2 (18 decks)

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