4 Metabolism and Energy Free Online FlashCards

How does an enzyme speed a chemical reaction?

An enzyme is a biological catalyst that speeds a reaction by lowering its activation energy. It is not consumed and does not change the reaction’s overall energy balance.

What happens at an enzyme’s active site?

A substrate binds to an enzyme’s active site, where the reaction occurs. The products leave, and the enzyme can be used again.

How do catabolic and anabolic pathways differ?

Catabolic pathways break molecules down and release usable energy; anabolic pathways build molecules and require energy.

How can a pathway’s end product regulate the pathway?

When enough end product accumulates, it may inhibit an earlier enzyme in the pathway, helping regulate the pathway’s activity.

How can ATP hydrolysis power cellular work?

ATP hydrolysis to ADP and inorganic phosphate releases free energy that can be coupled to energy-requiring processes, including phosphorylation of a molecule.

What happens to electrons during oxidation and reduction?

Oxidation is the loss of electrons, while reduction is their gain. Carriers such as NADH and NADPH temporarily hold high-energy electrons and deliver them to other reactions.

What are the location and net products of glycolysis per glucose?

Glycolysis occurs in the cytoplasm. It splits one glucose molecule into two pyruvate molecules and yields a net two ATP and two NADH.

How does the electron transport chain drive ATP production?

The electron transport chain pumps protons across the inner mitochondrial membrane, creating a gradient. As protons flow back through ATP synthase, the enzyme uses that energy to make ATP; oxygen accepts the electrons and helps form water.

Why is respiration not a direct conversion of glucose into ATP?

Respiration releases energy in steps, capturing some in carriers and ATP while dissipating some as heat. Plants also respire to supply ATP for cellular work.

How does fermentation allow glycolysis to continue without oxygen?

Fermentation regenerates NAD⁺ from NADH, allowing glycolysis to continue without oxygen. It makes no additional ATP; the net yield remains two ATP per glucose from glycolysis.

What are the main end products of the two fermentation types?

Lactic acid fermentation converts pyruvate to lactate. Alcoholic fermentation converts pyruvate-derived products to ethanol and carbon dioxide.

What distinguishes fermentation from anaerobic respiration?

Fermentation has no electron transport chain. Anaerobic respiration does use one, with a final electron acceptor other than oxygen.