Bioenergetics Study Guide Vocabulary

Vocabulary flashcards covering key bioenergetic pathways, substrates, enzymes, and ATP yields from Chapter 3 study guide.

Phosphocreatine (PC)

A high-energy phosphate donor that rapidly replenishes ATP at the very start of exercise by directly transferring its phosphate group to ADP.

Creatine Kinase

The single rate-limiting enzyme of the ATP-PC system that catalyzes the breakdown of phosphocreatine to transfer its high-energy phosphate group to ADP, reforming ATP.

Lactic Acid

The acid form of the molecule that carries an extra hydrogen ion ($H^+$).

Lactate

The ionized, conjugate-base form left behind once a hydrogen ion ($H^+$) dissociates from lactic acid; the actual end-product of glycolysis formed when pyruvate accepts hydrogens from NADH via lactate dehydrogenase.

Energy Investment Phase

The initial phase of glycolysis where $2\,\text{ATP}$ are invested when starting with free glucose, or $1\,\text{ATP}$ when starting with glycogen.

Energy Generation Phase

The second phase of glycolysis where $4\,\text{ATP}$ and $2\,\text{NADH}$ are produced per glucose or glycogen molecule.

NADH

A high-energy electron and hydrogen carrier produced during glycolysis and the Krebs cycle that shuttles hydrogens into the mitochondria or donates them to pyruvate.

Anaerobic metabolism

A metabolic pathway that generates energy without the use of oxygen, primarily through glycolysis, yielding products like lactate.

Aerobic metabolism

A metabolic pathway that requires oxygen to produce energy, primarily through the complete oxidation of glucose and fatty acids, yielding high amounts of ATP.

Glycosis

The metabolic pathway that converts glucose into pyruvate, producing a small amount of ATP and NADH in the process.

Glucose

The primary $6$-carbon blood sugar that enters glycolysis, yielding a net of $2\,\text{ATP}$ during anaerobic glycolysis.

Glycogen

The stored, branched polysaccharide form of glucose kept in muscle and liver that yields a net of $3\,\text{ATP}$ during anaerobic glycolysis because it requires only $1\,\text{ATP}$ to prime.

Fructose 6-phosphate (F-6-P)

A structural isomer of G-6-P that acts as the substrate immediately preceding the primary regulatory step of glycolysis.

Glucose 6-phosphate (G-6-P)

The molecule formed by phosphorylating glucose, which traps glucose inside the cell because a charged molecule cannot cross back out through the membrane.

Fructose 1,6-bisphosphate (F-1,6-BP)

A $6$-carbon molecule formed by the second ATP investment catalyzed by PFK, which then splits into two $3$-carbon molecules to move glycolysis into the generation phase.

Pyruvate

The $3$-carbon end-product of glycolysis under aerobic conditions when hydrogens are not passed to it, which goes on to form acetyl-CoA.

Phosphofructokinase (PFK)

The rate-limiting enzyme of glycolysis that catalyzes the conversion of F-6-P to F-1,6-BP; inhibited by ATP and $H^+$, and stimulated by ADP and AMP.

Lactate Dehydrogenase

The cytosolic enzyme that converts pyruvate, NADH, and $H^+$ into lactate and $NAD^+$ during anaerobic metabolism.

Lipolysis

The breakdown of a triglyceride into $3$ fatty acids and $1$ glycerol molecule catalyzed by lipase enzymes.

Beta Oxidation

The metabolic pathway occurring inside the mitochondria that breaks down fatty acids into acetyl-CoA.

Deamination

The process of removing the nitrogen-containing amine group from an amino acid so its carbon skeleton can enter bioenergetic pathways.

Krebs Cycle

A mitochondrial pathway whose purpose is to complete the oxidation of acetyl-CoA using $NAD^+$ and FAD as carriers, producing $3\,\text{NADH}$, $1\,\text{FADH}_2$, $1\,\text{GTP}$, and $CO_2$ per turn.

Acetyl-CoA

A central bioenergetic molecule formed from pyruvate via the pyruvate dehydrogenase complex, from fatty acids via beta oxidation, or from ketogenic amino acids after deamination.

Electron Transport Chain

A series of mitochondrial protein complexes that use energy from high-energy electrons donated by NADH and $FADH_2$ to pump protons into the intermembrane space.

Chemiosmosis

The process where the flow of protons back into the mitochondrial matrix through ATP synthase drives the synthesis of ATP from ADP and inorganic phosphate ($P_i$).

Oxygen (in bioenergetics)

The final electron acceptor at Complex IV of the electron transport chain, which combines with spent electrons and protons to form water ($H_2O$).

Isocitrate Dehydrogenase

The rate-limiting enzyme of the Krebs cycle, inhibited by high ATP levels and stimulated by rising ADP, inorganic phosphate ($P_i$), and calcium.

Cytochrome c Oxidase

The rate-limiting enzyme of the electron transport chain.

Net Aerobic ATP Yield from Glucose

A total net yield of $32\,\text{ATP}$ produced per free glucose molecule, accounting for transport costs into the mitochondrion.

Net Aerobic ATP Yield from Glycogen

A total net yield of $33\,\text{ATP}$ produced per glycogen molecule due to one less ATP being spent during the investment phase.