Bioenergetics Flashcards

A complete study guide of vocabulary terms and definitions based on lecture notes covering cellular bioenergetics and metabolic pathways.

ATP-PC pathway

The reaction $\text{Phosphocreatine (PC)} + \text{ADP} \rightarrow \text{ATP} + \text{Creatine (Cr)}$, catalyzed by creatine kinase.

Creatine kinase

The enzyme that catalyzes the ATP-PC reaction and acts as the rate-limiting enzyme of the ATP-PC system; activated by rising ADP and inhibited by high ATP.

Phosphocreatine (PC)

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

ATP-PC (phosphagen) system

A simple one-enzyme energy system that provides energy for the first $5\text{--}15\,\text{seconds}$ of high-intensity exercise and is the fastest ATP source available.

Lactic acid

The acid form of lactate that carries an extra $H^+$.

Lactate

The ionized conjugate-base form left once $H^+$ dissociates from lactic acid, which is the primary form present in the body at physiological pH.

Glycolysis

The pathway in the cytosol/sarcoplasm that breaks down glucose or glycogen, yielding a net gain of $2\,\text{ATP}$ starting from glucose or $3\,\text{ATP}$ starting from glycogen.

Glucose

The primary 6-carbon blood sugar that enters glycolysis.

Glycogen

The stored, branched polysaccharide form of glucose kept in muscle and liver cells and broken down via glycogenolysis.

Glucose 6-phosphate (G-6-P)

A charged molecule formed by phosphorylating glucose that traps glucose inside the cell.

Fructose 6-phosphate (F-6-P)

A structural isomer of G-6-P that serves as the substrate immediately before the main rate-limiting step of glycolysis.

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

A 6-carbon molecule formed by PFK during the second ATP-investment step that splits into two 3-carbon molecules.

Phosphofructokinase (PFK)

The rate-limiting enzyme of glycolysis that catalyzes $\text{F-6-P} \rightarrow \text{F-1,6-BP}$; stimulated by ADP and Pi, and inhibited by ATP, $H^+$, and citrate.

Pyruvate

The 3-carbon product of glycolysis formed when NADH does not donate its hydrogen to it, which aerobically goes on to form acetyl-CoA.

Lactate dehydrogenase

The enzyme that catalyzes the reaction $\text{Pyruvate} + \text{NADH} + H^+ \rightarrow \text{Lactate} + \text{NAD}^+$.

NADH

An electron and hydrogen carrier ($2$ produced per glucose or glycogen in glycolysis) that fuels the ETC aerobically or transfers hydrogen to pyruvate to form lactate anaerobically.

FAD / FADH2

An electron/hydrogen carrier derived from riboflavin (vitamin B2) that enters the ETC at Complex II, yielding $1.5\,\text{ATP}$ per molecule compared to $2.5\,\text{ATP}$ for NADH.

Oxidative phosphorylation

The aerobic ATP production process occurring in the mitochondria that combines the citric acid cycle and the electron transport chain.

Beta oxidation

The mitochondrial process that breaks fatty acids down into 2-carbon acetyl-CoA fragments so they can enter the Krebs cycle.

Krebs cycle

A mitochondrial process that completes the oxidation of acetyl-CoA using NAD+ and FAD as carriers, producing $3\,\text{NADH}$, $1\,\text{FADH}_2$, and $1\,\text{GTP}$ per turn.

Isocitrate dehydrogenase

The rate-limiting enzyme of the Krebs cycle; inhibited by ATP and stimulated by ADP and calcium.

GTP

An energy-rich compound formed directly in the Krebs cycle via substrate-level phosphorylation that transfers its terminal phosphate to ADP to form ATP.

Cytochrome c oxidase

The rate-limiting enzyme of the electron transport chain located in Complex IV; inhibited by high ATP and stimulated by rising ADP.

ATP synthase

The enzyme that produces ATP as $H^+$ flows back through it into the mitochondrial matrix down the proton gradient built by the ETC.