BIOL005A Lecture 11: Cellular Respiration I

Vocabulary practice flashcards covering fundamental metabolism, redox reactions, cellular respiration energetics, and the enzymes and steps of glycolysis from BIOL005A Lecture 11.

Metabolism

The sum total of all chemical reactions carried out by living organisms, encompassing energy conversion, the synthesis of biological building blocks, and waste elimination.

Anabolic Pathway

A metabolic pathway that builds complex molecules from simpler ones and consumes energy in the process.

Catabolic Pathway

A metabolic pathway that breaks down complex molecules into simpler ones, releasing energy.

Redox Reaction

A reduction-oxidation reaction involving the chemical transfer of electrons from one reactant to another.

Oxidation

The loss of electrons from a substance during a chemical reaction, causing that substance to become more positively charged.

Reduction

The addition or gain of electrons to a substance during a chemical reaction, which reduces the amount of positive charge on that substance.

Reducing Agent

The electron donor in a redox reaction that loses electrons and reduces the other reactant.

Oxidizing Agent

The electron acceptor in a redox reaction that gains electrons and oxidizes the other reactant.

Standard Free-Energy Change of Glucose Breakdown ($\Delta G$)

The total energy released from the complete cellular breakdown of glucose ($\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}$), which equals $-686\,\text{kcal/mol}$ of glucose.

$\text{NAD}^+$ (Nicotinamide Adenine Dinucleotide)

A coenzyme and dinucleotide electron carrier that accepts two electrons and two protons to form $\text{NADH} + \text{H}^+$, carrying high-energy electrons to the mitochondrion.

$\text{FAD}$ (Flavin Adenine Dinucleotide)

A dinucleotide electron carrier that accepts two electrons and two protons to become reduced to $\text{FADH}_2$.

Reducing Power

The ability of molecules such as $\text{NADH}$ and $\text{FADH}_2$ to donate electrons, allowing downstream metabolic processes to harness their stored potential energy.

Substrate-Level Phosphorylation

The synthesis of $\text{ATP}$ occurring via the direct transfer of a phosphate group from an organic substrate to $\text{ADP}$ by an enzyme.

Glycolysis

A catabolic pathway occurring in the cytosol that splits glucose into two molecules of pyruvate, generating a net of $2\,\text{ATP}$ and $2\,\text{NADH}$ without requiring oxygen.

Hexokinase

The enzyme in step 1 of glycolysis that consumes one $\text{ATP}$ to phosphorylate glucose into glucose-6-phosphate.

Phosphoglucoisomerase

The enzyme in step 2 of glycolysis that catalyzes the conversion of glucose-6-phosphate into its isomer, fructose-6-phosphate.

Phosphofructokinase

The key regulatory enzyme in step 3 of glycolysis that uses $\text{ATP}$ to phosphorylate fructose-6-phosphate into fructose-1,6-bisphosphate; it is subject to feedback inhibition by high levels of $\text{ATP}$.

Aldolase

The enzyme in step 4 of glycolysis that cleaves fructose-1,6-bisphosphate into two distinct three-carbon sugars: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.

Isomerase (Glycolysis)

The enzyme in step 5 of glycolysis that catalyzes the reversible interconversion of dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.

Triose Phosphate Dehydrogenase

The enzyme in step 6 of glycolysis that oxidizes glyceraldehyde-3-phosphate to produce 1,3-bisphosphoglycerate, reducing $\text{NAD}^+$ to $\text{NADH} + \text{H}^+$.

Phosphoglycerokinase

The enzyme in step 7 of glycolysis that produces $\text{ATP}$ via substrate-level phosphorylation by transferring a phosphate group from 1,3-bisphosphoglycerate to $\text{ADP}$, yielding 3-phosphoglycerate.

Phosphoglyceromutase

The enzyme in step 8 of glycolysis that relocates the remaining phosphate group of 3-phosphoglycerate to form 2-phosphoglycerate.

Enolase

The enzyme in step 9 of glycolysis that extracts a molecule of water ($\text{H}_2\text{O}$) from 2-phosphoglycerate to create phosphoenolpyruvate (PEP).

Pyruvate Kinase

The enzyme in step 10 of glycolysis that catalyzes the substrate-level phosphorylation of $\text{ADP}$ to $\text{ATP}$ using a phosphate from phosphoenolpyruvate, yielding pyruvate.