Citric Acid Cycle Overview

<p>NADH (B), Citrate (D)</p> Signup and view all the answers

<p>1.5 ATP (A)</p> Signup and view all the answers

<p>It converts oxaloacetate and acetyl-CoA into citrate. (D)</p> Signup and view all the answers

<p>It is an example of ordered sequential kinetics. (C)</p> Signup and view all the answers

<p>They act as allosteric inhibitors. (B)</p> Signup and view all the answers

<p>It participates in both catabolism and anabolism. (B)</p> Signup and view all the answers

<p>They are lost as CO2 by the end of the cycle. (B)</p> Signup and view all the answers

<p>Oxaloacetate is converted into citryl-CoA before forming citrate. (D)</p> Signup and view all the answers

<p>Induced fit allows for effective substrate binding and catalysis. (A)</p> Signup and view all the answers

<p>It occurs in the cytoplasm of the cell. (A)</p> Signup and view all the answers

<p>Facilitation of the Warburg effect (B)</p> Signup and view all the answers

<p>Thiamine (C)</p> Signup and view all the answers

<p>It binds to sulfurs and inhibits enzyme activity. (C)</p> Signup and view all the answers

<p>It forms a complex that can be excreted. (A)</p> Signup and view all the answers

<p>Modification of methylation patterns (D)</p> Signup and view all the answers

<p>Diabetic neuropathy (A)</p> Signup and view all the answers

<p>It increases when phosphorylated by cancer-related enzymes. (D)</p> Signup and view all the answers

<p>Aerobic glycolysis (A)</p> Signup and view all the answers

<p>They can facilitate both one-electron and two-electron transfer reactions. (B)</p> Signup and view all the answers

<p>Activating acyl groups for nucleophilic attack and α-hydrogen activation. (B)</p> Signup and view all the answers

<p>It forms thioester linkages with acyl groups necessary for its functions. (A)</p> Signup and view all the answers

<p>It couples acyl-group transfer to electron transfer during specific reactions. (A)</p> Signup and view all the answers

<p>Pyruvate dehydrogenase and α-ketoglutarate dehydrogenase. (C)</p> Signup and view all the answers

<p>Assisting in the decarboxylation of α-keto acids (C)</p> Signup and view all the answers

<p>E1 and E3 enzymes (B)</p> Signup and view all the answers

<p>It inactivates PDH by promoting its phosphorylation (B)</p> Signup and view all the answers

<p>They interact to create a catalytic trimer (D)</p> Signup and view all the answers

<p>Two-electron transfer reactions (D)</p> Signup and view all the answers

<p>Sixty (C)</p> Signup and view all the answers

<p>Small domain (D)</p> Signup and view all the answers

<p>Pyruvate dehydrogenase phosphatase (PDP) (A)</p> Signup and view all the answers

<p>To serve as the main fuel for the cycle (D)</p> Signup and view all the answers

<p>Pyruvate dehydrogenase complex (B)</p> Signup and view all the answers

<p>E4: aspartate aminotransferase (D)</p> Signup and view all the answers

<p>They control the phosphorylation state of E1 (B)</p> Signup and view all the answers

<p>Pyruvate (B)</p> Signup and view all the answers

<p>5 (B)</p> Signup and view all the answers

<p>A carbanion forms from TPP (D)</p> Signup and view all the answers

<p>In the mitochondrial matrix (A)</p> Signup and view all the answers

Coenzymes like FAD/FADH2 and FMN/FMNH2 that can exist in three oxidation states.

They participate in one- and two-electron transfer reactions in biological systems due to their three oxidation states.

A coenzyme that activates acyl groups for transfer and activates α-hydrogen for proton abstraction.

The sulfhydryl group on CoA forms thioester linkages with acyl groups, mediating the activation functions.

Couples acyl-group transfer and electron transfer during oxidation and decarboxylation of α-keto acids.

A multi-enzyme complex responsible for converting pyruvate to acetyl-CoA. It consists of three main enzymes: E1 (pyruvate dehydrogenase), E2 (dihydrolipoyl transacetylase), and E3 (dihydrolipoyl dehydrogenase).

The central component of the PDC, forming the core structure. It contains three domains: a lipoamide-binding domain, a small domain interacting with E3, and a large transacetylase catalytic domain.

The peripheral enzyme in the PDC, responsible for decarboxylating pyruvate and transferring the acetyl group to lipoamide.

Another peripheral enzyme in the PDC, responsible for oxidizing the reduced lipoamide and regenerating NAD+.

A flexible arm attached to E2, carrying the acetyl group from E1 to E2 and then to CoA.

Pyruvate dehydrogenase kinase: an enzyme that inactivates PDH by phosphorylation.

Pyruvate dehydrogenase phosphatase: an enzyme that activates PDH by dephosphorylation.

A coenzyme essential for the decarboxylation of pyruvate in the PDC. It assists in the removal of carbon dioxide from pyruvate.

An enzyme that catalyzes the reversible oxidation of malate to oxaloacetate in the citric acid cycle. This reaction is energetically unfavorable, requiring energy input.

An enzyme that catalyzes the condensation of acetyl-CoA with oxaloacetate to form citrate, the first step in the citric acid cycle.

The citric acid cycle is regulated at specific points to ensure efficient energy production. These control points involve key enzymes that respond to cellular energy needs.

The citric acid cycle is an exergonic process, generating a net free energy change of -40 kJ/mol per cycle. This energy is used to produce ATP.

A series of protein complexes embedded in the mitochondrial membrane that accept electrons from NADH and FADH2 and use them to generate a proton gradient, which drives ATP synthesis.

A series of chemical reactions that occur in the mitochondria of cells. It's a central pathway in cellular respiration, where energy is extracted from glucose and other fuel molecules.

A process that removes a carbon dioxide molecule from a molecule, often involving the use of an oxidizing agent. This process is crucial for the citric acid cycle.

A central molecule in metabolism. It's derived from pyruvate and carries two carbon atoms that enter the citric acid cycle. It's the fuel for the citric acid cycle.

The 'powerhouse' of the cell, where ATP is produced through cellular respiration. The citric acid cycle takes place within the mitochondrial matrix.

The PDH complex catalyzes the oxidative decarboxylation of pyruvate, converting it into acetyl CoA, which is the main fuel for the citric acid cycle. It's a crucial step in cellular respiration, linking glycolysis to the citric acid cycle.

Oxidative decarboxylation is an essential process for cellular respiration. It generates energy in the form of NADH and acetyl CoA, which drives the citric acid cycle and ultimately ATP production.

Coenzymes are non-protein molecules that assist enzymes in their catalytic activity. In PDH, coenzymes like thiamine pyrophosphate (TPP), lipoic acid, NAD+, and FAD are essential for the complex's function. They help in the transfer of electrons and groups during the reactions.

A metabolic pathway that participates in both anabolism and catabolism.

Citrate synthase exhibits induced fit, where oxaloacetate binding induces structural changes, forming the acetyl CoA binding site. This ensures the reaction proceeds efficiently and prevents unwanted side reactions. Citryl CoA formation triggers a structural change, enabling thioester cleavage.

DG°’ refers to the standard free energy change of a reaction, indicating the overall energy change under standard conditions. A negative DG°’ indicates an exergonic reaction, releasing energy and favoring product formation.

These molecules act as allosteric inhibitors of citrate synthase, slowing down the reaction when energy levels are high or there's an abundance of intermediates.

The acetyl group in acetyl-CoA is activated through the formation of a thioester bond with coenzyme A. This bond is high-energy, making the acetyl group more reactive and prone to participate in reactions.

The carbon atoms of acetyl-CoA are ultimately oxidized to CO2, generating energy in the form of ATP and reducing equivalents. However, a portion can also be used for biosynthesis, producing important metabolites like fatty acids and amino acids.

A molecule produced by mutations in isocitrate dehydrogenase. It alters DNA methylation patterns, affecting gene expression and promoting cell growth.

The metabolic switch in cancer cells from oxidative phosphorylation to aerobic glycolysis, favoring rapid glucose consumption and lactate production.

Mitochondrial enzyme that normally produces ketone bodies for fuel, but in some cancers becomes phosphorylated and acts as a protein acetyltransferase.

The inactivation of pyruvate dehydrogenase complex, a key enzyme in carbohydrate metabolism, by factors like thiamine deficiency, mercury or arsenic poisoning.

Lack of thiamine (vitamin B1) that leads to insufficient activity of key enzymes like pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase, resulting in beriberi.

A neurologic and cardiovascular disorder caused by thiamine deficiency, characterized by fatigue, muscle weakness, and neurological impairments.

The toxic effect of mercury on the body, specifically inhibiting pyruvate dehydrogenase complex activity by binding to sulfur atoms in the enzyme.

A complication of diabetes characterized by numbness, tingling, or pain in limbs and digits, possibly caused by inhibition of pyruvate dehydrogenase complex in peripheral nerves.