TCA Cycle Flashcards by Tyler Turner

Does the citric acid cycle generate more ATP from glucose than glycolysis

Yes

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The citric acid cycle requires ______ conditions

Aerobic

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The citric acid cycle takes place in the

Mitochondria

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Glycolysis takes place in the

Cytosol

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The function of the citric acid cycle is

harvesting of high energy electrons from carbon fuels

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what is the carbon source for citric acid cycle

acetyl CoA (via acetyl group)

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Is the outer membrane of the mitochondria fairly smooth

yes

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The inner mitochondrial membrane is highly convoluted, forming folds called

cristae

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What is the function of cristae

it greatly increases the inner membrane’s surface area

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what are the products of the citric acid cycle

2 CO2
1 GTP
3 NADH
1 FADH2

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In the citric acid cycle a four carbon compound ______ condenses with a two-carbon _____ to yield a six-carbon tricarboxylic acid

oxaloacetate

- acetyl unit

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in the citric acid cycle CO2 is released by two successive

oxidative decarboxylations

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how many total electrons does citric acid cycle produce

8 electrons

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Carboydrates—glucose— can be converted to pyruvate in

glycolysis

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Pyruvate from glycolysis can be converted to

acetyle CoA

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under anaerobic conditions pyruvate is converted to

lactate or ethanol

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Aerobic conditions resulte in pyruvate entering the

mitochondria

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Pyruvate dehydrogenase component abbreviation

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Dihydrolipoyl transacetylase abbreviation

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Dihydrolipoyl dehydrogenase abbreviation

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What is the prosthetic group of E1

TPP (Thiamine pyrophosphate)

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What is the prosthetic group of E2

Lipoamide (Lipoic acid)

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What is the prosthetic group of E3

FAD

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E1 catalyzes

oxidative decarboxylation of pyruvate

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E2 catalyzes

transfer of acetyl group to CoA

E3 catalyzes

Regeneration of the oxidized form of lipoamide

The dehydrogenase complex is composed of

E1 (pyruvate dehydrogenase component), E2 (Dihydrolipoyl transacetylase), E3 (Dihydrolipoyl dehydrogenase)

Acetyl CoA formation from pyruvate requires

3 enzymes and 5 coenzymes - Catalytic cofactors (TPP, Lipoic acid, FAD) Stoichiometric cofactors - CoA, NAD+ (cofactors that function as substrates)

What are the 3 steps in the production of Acetyl CoA from pyruvate

- Decarboxylation - Oxidation - Transfer acetyl group to coenzyme A

What is the rate limiting step of Acetyl CoA synthesis

Decarboxylation

decarboxylation and oxidation of pyruvate in the formation of acetyl CoA are catalyzed by

E1 (pyruvate dehydrogenase component)

The transfer of acetyl group to Coenzyme A is catalyzed by

E2 (dihydrolipoyl transcetylase)

Acetyllipoamide has an energy rich

thioester bond

in the oxidation step of acetyl CoA synthesis the hydroxyethyl group attached to TPP is _____ to an acetyl group while being simultaneously transferred to

oxidized, lipoamide (a derivative of lipoic acid that is linked to the side chain of a lysine residue by an amide linkage)

What is preserved as the acetyl group is transferred form acetyllipoamide to CoA to form acetyl CoA

The energy-rich thioester bond

What is the function of E3

``` dihydrolipoyl dehydrogenase (E3) oxidizes dihydrolipoamide to lipoamide (two electrons are transferred to an FAD prothetic group of the enzyme and then to NAD+) ```

Why is the electron transfer potential of FAD in E3 increased

because it is tightly associated with the enzyme

Pyruvate dehydrogenase complex has how many copies of E1

Pyruvate dehydrogenase complex has how many copies of E2

Pyruvate dehydrogenase complex has how many copies of E3

Each E2 subunit is a ____ containing ____ distinct domains

trimer, 3

Flexible arm of ____ containing lipoid allows all domains of the complex to work together

Aconitase catalyzes

Citrate -----> Isocitrate

Isocitrate dehydrogenase catalyzes

isocitrate + (NAD+) ------> Alpha-Ketoglutarate + NADH + (H+) + CO2

Alpha-ketoglutarate dehydrogenase complex catalyzes

alpha-ketoglutarate + (NAD+) + CoA ---------> Succinyl CoA + NADH + (H+) + CO2

Succinyl CoA synthetase catalyzes

Succinyl CoA + GDP + Pi ------> Succinate + GTP + CoA

Succinate dehydrogenase catalyzes

Succinate + FAD -----> Fumarate + FADH2

Fumarase catalyzes

Fumarate + H2O ---> Malate

Malate dehydrogenase catalyzes

Malate + (NAD+) ---> OAA + NADH + H+

Citrate synthase catalyzes

OAA+ H2O + Acetly CoA -----> Citrate + CoA

what is the only step that directly yields a GTP in the TCA cylce

Succinyl CoA ------> Succinate | catalyzed by Succinyl CoA synthetase

inhibitors of PHD E2

NADH ACetyl CoA ATP

Induces PDH E2

Pyruvate, ADP

Succinyl CoA contains a ______ bond

high energy thioester bond (similar to ATP)

Succinate dehydrogenase is located

in the inner mitochondrial membrane and directly associated with ETC and TCA

FADH2 is actually not released form succinate dehydrogenase but electrons are passed directly to ____ in ETC

Coenzyme Q

Malate has a positive fee energy and therfore the reaction malate-----> OAA is driven by the use of the

products: - OAA-citrate synthase - NADH- ETC

Phosphorylated PDH is the ___ form therefore ____ activates it and ____ deactivates it

inactive, kinase deactivates it | phosphatase activates it

Phosphatases (which activate PDH) are stimulated by ___ and ____ and

ADP, Calcium, and insulin

Isocitrate dehydrogenase regulation

- inhibited by: ATP and NADH | - Induced by: ADP

Alpha ketogluturate dehydrogenase regulation

-inhibited by ATP, Succinyl CoA, and NADH

Inhibition of Isocitrate dehydrogenase leads to a build up of _____ which can transport to the cytosol and inhibit

citrate ( easily converted from isocitrate) | can signal phosphofructokinase and inhibit glycolysis

a buildup of alpha-ketoglutarate can be used for

synthesis of amino acids and purine bases , glutamate

Citrate from the TCA can be used for biosynthesis of

Fatty acids, sterols

succinyl CoA from the TCA can be used for biosynthesis of

Porphyrins, heme, chlorophyll

OAA from the TCA can be used for biosynthesis of

Glucose, Aspartate, purines, pyrimidines,

_____ amino acids are a source for TCA intermediates

branched chain amino acids

amino acids converted to pyruvate

- alanine - serine - Glycine - Threonine - Cysteine - Tryptophan

Amino acids converted to OAA

Aspartate | Asparagine

Amino acids converted to alpha-ketoglutarate

``` glutamate glutamine proline histidine arginine ```

Amino acids converted to fumarate

phenylalanine | tyrosine

Amino acids converted to succinyl-CoA

Methionine isoleucine Valine

Amino acids converted to acetyl CoA

``` Leucine Isoleucine lysine phenylalanine tyrosine tryptophan threonine ```