Pathways That Harvest Chemical Energy Flashcards

Flashcards covering the metabolic pathways of glucose oxidation, including glycolysis, the Krebs cycle, oxidative phosphorylation, and fermentation as described in the Chapter 9 lecture notes.

Metabolic Pathways

A series of separate reactions where complex transformations occur, each catalyzed by a specific enzyme, often compartmentalized in specific organelles in eukaryotes.

Glycolysis

An anaerobic catabolic process occurring in the cytoplasm that converts 1 molecule of glucose into 2 molecules of pyruvate, yielding a net of $2\,ATP$ and $2\,NADH$.

Cellular Respiration

An aerobic catabolic process that involves the conversion of glucose to energy, resulting in a net of $36\,ATP$ in organisms like air breathers.

Fermentation

An anaerobic catabolic process that metabolizes pyruvate produced by glycolysis in the absence of oxygen, yielding a net of $2\,ATP$.

Kinase

An enzyme whose general function is the addition of a phosphate group to a molecule.

Isomerase

An enzyme responsible for the rearrangement of bonds within a single molecule.

Dehydrogenase

An enzyme that performs oxidation of a molecule by removing a hydrogen atom plus an electron (REDOX).

Mutase

An enzyme that facilitates the shifting of a chemical group from one position to another within a molecule.

Energy-Investing Reactions

Steps 1–5 of glycolysis which require the input of $ATP$ to break down the glucose molecule.

Energy-Harvesting Reactions

Steps 6–10 of glycolysis (the payoff phase) which yield $NADH$ and $ATP$.

Hexokinase

The enzyme used in Step 1 of glycolysis to convert glucose into glucose-6-phosphate.

Phosphofructokinase (PFK)

The enzyme used in Step 3 of glycolysis to facilitate the preparatory phase of glucose breakdown.

Pyruvate Oxidation

The process in the mitochondrial matrix where pyruvate is oxidized to acetate and $CO_2$, and acetate binds to coenzyme A to form acetyl CoA.

Pyruvate Dehydrogenase Complex

A complex of three enzymes that catalyzes the intermediate steps of pyruvate oxidation.

Acetyl CoA

The end product of pyruvate oxidation that donates its acetyl group to oxaloacetate to initiate the citric acid cycle.

Citric Acid Cycle (Krebs Cycle)

A series of eight reactions in the inner mitochondrial compartment that completely oxidizes the acetyl group to 2 molecules of $CO_2$, capturing energy in $GDP$, $NAD^+$, and $FAD$.

Oxaloacetate

The molecule regenerated in the last step of the citric acid cycle.

Oxidative Phosphorylation

The process by which $ATP$ is synthesized by the reoxidation of electron carriers in the presence of $O_2$, consisting of electron transport and chemiosmosis.

Electron Transport

A component of oxidative phosphorylation where electrons move through a chain in the inner membrane of mitochondria, shuttling $H^+$ from the inner to the outer compartment.

Chemiosmosis

The movement of $H^+$ flow back to the inner mitochondrial compartment through $ATP$ synthase to drive the formation of $ATP$.

ATP Synthase

A transport protein and enzyme complex that joins $ADP + P_i \rightarrow ATP$ as $H^+$ ions flow through it.

Alcoholic Fermentation

An anaerobic process performed by yeast and some bacteria that produces $CO_2$, ethanol, and a net of $2\,ATP$.

Lactate Fermentation

An anaerobic process in some bacteria and human muscle cells that produces lactate and a net of $2\,ATP$ when oxygen is depleted.