Cellular Respiration and Enzymes

Glycolysis produces a net gain of 2 NADH molecules per glucose. The NADH is formed during the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate, with one NADH produced per each of the two 3-carbon molecules.

Aldolase splits fructose-1,6-bisphosphate into two 3-carbon molecules: glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP). DHAP is then converted to G3P.

Enolase converts 2-phosphoglycerate (2PG) to phosphoenolpyruvate (PEP) by removing a water molecule (dehydration). This is the second-to-last step of glycolysis. PEP then donates its phosphate to ADP via pyruvate kinase.

Glycolysis is also called the EMP pathway after Embden, Meyerhof, and Parnas who elucidated the process. It converts glucose to pyruvate. The Calvin cycle fixes CO2, while TCA cycle (also called citric acid cycle) occurs after glycolysis in cellular respiration.

During glycolysis, one molecule of glucose (6-carbon) is broken down into two molecules of pyruvic acid (each 3-carbon). This is a fundamental fact of cellular respiration - the splitting of glucose into two pyruvate molecules.

Argininosuccinate synthase (ASS) is an enzyme that catalyzes the synthesis of argininosuccinate from citrulline and aspartate. ASS is responsible for the third step of the urea cycle and one of the reactions of the citrulline-NO cycle.

The reduction of 1,3-bisphosphoglycerate to glyceraldehyde-3-phosphate is catalyzed by glyceraldehyde-3-phosphate dehydrogenase (G3PDH), using NADPH as a cofactor. PGA kinase phosphorylates 3-PGA, aldolase combines molecules, and RUBP carboxylase fixes CO2.

PGA kinase phosphorylates 3-PGA to 1,3-bisphosphoglycerate using ATP in Calvin cycle. Option B is the next step (G3P formation), C is Rubisco carboxylation, D is regeneration phase.

ATP (Adenosine Triphosphate) is the primary energy currency of the cell, providing energy for cellular processes through hydrolysis of its high-energy phosphate bonds. DNA stores genetic information, genes code for traits, and ribosomes synthesize proteins but don't directly provide energy.

Statement (c) is incorrect because Succinyl CoA is converted to succinic acid by succinyl CoA synthetase (or succinic thiokinase), not succinic dehydrogenase. Succinic dehydrogenase converts succinic acid to fumarate. Statements (a) and (b) are correct: pyruvate is oxidized to acetyl CoA in aerobic conditions and reduced in anaerobic conditions (fermentation).

During oxidative phosphorylation, NADH generates approximately 3 ATP molecules through the electron transport chain ( complexes I, III, and IV), while FADH2 generates only 2 ATP molecules because it enters the chain at complex II, bypassing complex I and thus contributing less proton motive force. The total yield per glucose is approximately 36-38 ATP.

Aerobic respiration of glucose produces 6 CO2 and 6 H2O molecules, releasing approximately 2900 KJ/mol energy. Option A has the correct stoichiometry and energy value. Options B and D incorrectly produce CO (incomplete oxidation). Option C has correct products but wrong energy value.

This is the correct answer as all statements are correct.

CAZy is a database of Carbohydrate-Active enzymes, which contains classification and associated information about enyzmes involved in the synthesis, metabolism and transport of carbohydrates.