Citric Acid Cycle Lecture Notes

Flashcards about Citric Acid Cycle

Citric Acid Cycle

A metabolic wheel used by aerobic cells to generate energy by acetyl CoA oxidation.

Citric Acid Cycle

The final common pathway for the oxidation of fuel molecules like amino acids, fatty acids, and carbohydrates.

Acetyl Coenzyme A

The main molecule that enters the citric acid cycle.

Pyruvate

End product of glycolysis.

Acetyl-CoA

End product of β-Oxidation.

Acetyl-CoA

Starting point for TCA cycle.

PDHC - Pyruvate Dehydrogenase Complex

Enzyme complex that converts pyruvate to Acetyl-CoA.

Pyruvate translocase (PT)

Transports pyruvate into the mitochondria in symport with H+.

TPP (thymine pyrophosphate)

Active form of thiamine — Vitamin B1

Beriberi

Vitamin B1 deficiency.

TPP

Used for decarboxylation reactions.

Lipoic Acid

Involved in Acetyl transfer and oxidation reactions.

FAD+ and NAD+

Oxidizing agent/electron acceptors and get reduced

Tricarboxylic Acid Cycle

Another name for the Citric Acid Cycle.

Krebs Cycle

Another name for the Citric Acid Cycle.

Hans Adolf Krebs

He discovered the ‘Krebs cycle’ of chemical reactions

Oxaloacetate

A four-carbon molecule that condenses with a two-carbon acetyl unit to yield a six-carbon citrate.

Citrate Synthase

Enzyme that Forms citrate from acetyl CoA and oxaloacetate.

Citrate Synthase

Only cycle reaction with C-C bond formation

Aconitase

Enzyme that catalyzes Elimination of H2O from citrate to form C=C bond of cis- aconitate

Isocitrate Dehydrogenase

Enzyme that catalyzes Oxidative decarboxylation of isocitrate to α-ketoglutarate

α-Ketoglutarate Dehydrogenase Complex

Enzyme complex Similar to pyruvate dehydrogenase complex

Succinyl-CoA Synthetase

Enzyme that Free energy in thioester bond of succinyl CoA is conserved as GTP or ATP

Succinate Dehydrogenase

Complex of several polypeptides, an FAD+ prosthetic group and iron-sulfur clusters Embedded in the inner mitochondrial membrane

Fumarase

Enzyme that catalyzes the Addition of water to the double bond of fumarate to form L-malate

Malate Dehydrogenase

Enzyme that Malate is oxidized to form oxaloacetate.

Two

The number of carbon atoms that enter the cycle in the form of acetyl CoA.

Two

The number of carbon atoms that leave the cycle in the form of CO2.

10

Number of ATP generated from one acetyl CoA approximately

Functions of the Citric Acid Cycle

The cycle is involved in the aerobic catabolism of carbohydrates, lipids and amino acids.

Three enzymes that have regulatory properties in the citric acid cycle

citrate synthase, isocitrate dehydrogenase a-ketoglutarate dehydrogenase complex

Fluoroacetate

is a suicide inhibitor of TCA cycle by inhibiting Aconitase

Arsenite

inhibits the enzymes PDHC and α- ketoglutarate dehydrogenase

Arsenic poisoning Symptoms

Symptoms may include vomiting, abdominal pain, encephalopathy, and watery diarrhea that contains blood.

Citric Acid Cycle

Krebs Cycle provides intermediates for biosynthesis