Key Reactions and Intermediates in Cellular Metabolism

Components of the Alpha-Ketoglutarate Dehydrogenase Reaction

1. CoA (Coenzyme A)
2. NAD⁺
3. α-Ketoglutarate Dehydrogenase Complex
4. NADH + H⁺
5. CO₂
6. α-Ketoglutarate
7. Succinyl CoA

Identifying the Reaction

The following components are involved in the reaction catalyzed by Citrate Synthase:

1. Oxaloacetate
2. Citrate
3. Acetyl CoA
4. Citrate Synthase (Enzyme)

The Acetyl Radical of Acetyl-CoA

What is the role of the acetyl radical of Acetyl-CoA?

The Role of Acetyl CoA in the Krebs Cycle

Acetyl CoA is essential for the Krebs cycle (Tricarboxylic Acid Cycle) to occur. It reacts with Oxaloacetate to start the cycle.

During the cycle, 2 CO₂ and 3 NADH + H⁺ are produced (per Acetyl CoA molecule entering the cycle). Specifically, the production of NADH and CO₂ occurs:

• 1 CO₂ and 1 NADH + H⁺ are generated during the formation of α-Ketoglutarate from Isocitrate (catalyzed by Isocitrate Dehydrogenase).
• 1 CO₂ and 1 NADH + H⁺ are generated during the formation of Succinyl CoA from α-Ketoglutarate (catalyzed by the α-Ketoglutarate Dehydrogenase Complex).
• The third NADH + H⁺ comes from the oxidation of Malate to Oxaloacetate (catalyzed by Malate Dehydrogenase).

Krebs Cycle Intermediates (TCA Cycle)

The following compounds participate in the cycle:

Krebs Cycle Steps: Detailed Sentences (p. 112)

1. Citrate Synthesis: Citrate is synthesized from Oxaloacetate and Acetyl CoA by Citrate Synthase.
2. Isomerization: Citrate is isomerized to Isocitrate by Aconitase.
3. Oxidative Decarboxylation 1: Isocitrate is oxidized and decarboxylated by Isocitrate Dehydrogenase to α-Ketoglutarate, producing CO₂ and NADH.
4. Oxidative Decarboxylation 2: α-Ketoglutarate is oxidatively decarboxylated to Succinyl CoA by the α-Ketoglutarate Dehydrogenase Complex, producing CO₂ and NADH.

Carbohydrate Classification

1. Fill the gaps:

   Monosaccharides

   Ribose, __________________, __________________

   Disaccharides

   Trehalose, __________________, __________________

   Polysaccharides

   __________________

Key Glycolysis Intermediates

• Fructose 1,6-bisphosphate
• Glyceraldehyde 3-phosphate
• Dihydroxyacetone phosphate

20. Net Reaction of Aerobic Glycolysis

Fill the gaps:

22. Pattern of Gluconeogenesis

Fill the gap in the pattern:

1. Carboxylation of Pyruvate
2. Transport of Oxaloacetate to the Cytosol
3. ________________________________________________________________
4. Dephosphorylation of Fructose 1,6-bisphosphate
5. Dephosphorylation of Glucose 6-phosphate

Pentose Phosphate Pathway (Oxidative Phase)

The following sequence illustrates the initial steps: