Chapter 3 Energy and Cellular Respiration - Vocabulary Flashcards

Vocabulary flashcards covering key terms related to energy, thermodynamics, chemical reactions, enzymes, and cellular respiration.

Energy

The capacity to do work; exists without mass or occupying space and is inferred from its effects on matter.

Kinetic energy

Energy of motion; energy an object has due to its movement.

Potential energy

Stored energy due to position or state; can be converted to kinetic energy.

Concentration gradient

Difference in the amount of a substance across a boundary; a source of potential energy when across membranes.

Chemical energy

Energy stored in chemical bonds; a major form of potential energy in the body.

ATP (adenosine triphosphate)

The cell’s energy currency; produced during cellular respiration and used for energy-requiring processes.

ADP (adenosine diphosphate)

A lower-energy form that can be re-energized to ATP by adding a phosphate.

Pi (inorganic phosphate)

Pi combines with ADP to form ATP during phosphorylation.

Triglycerides

Long-term energy storage molecules in adipose tissue.

Glucose

A primary energy source stored as glycogen in liver/muscle; oxidized to produce ATP.

NAD+/NADH

Nicotinamide adenine dinucleotide; NAD+ accepts electrons to become NADH in redox reactions.

FAD/FADH2

Flavin adenine dinucleotide; FADH2 carries electrons to the electron transport chain.

NADH

Reduced form of NAD+; delivers electrons to the electron transport chain.

FADH2

Reduced form of FAD; donates electrons to the electron transport chain.

Electron transport chain

A series of protein complexes in the inner mitochondrial membrane that transfer electrons and pump protons.

Oxidative phosphorylation

ATP production driven by a proton gradient across the mitochondrial membrane.

Substrate-level phosphorylation

Direct formation of ATP from a substrate during glycolysis or the citric acid cycle.

Glycolysis

Cytosolic pathway that breaks glucose into two pyruvate molecules; yields net 2 ATP and 2 NADH.

Pyruvate

End product of glycolysis; fate depends on oxygen availability (across two pathways).

Lactate

Product of pyruvate reduction when oxygen is limited; regenerates NAD+ to sustain glycolysis.

Intermediate stage

Link between glycolysis and the citric acid cycle; pyruvate converts to acetyl CoA with CO2 release and NADH formation.

Acetyl CoA

Two-carbon molecule that enters the citric acid cycle after the intermediate stage.

Citric acid cycle (Krebs cycle)

Mitochondrial matrix pathway that oxidizes acetyl CoA to CO2; yields 1 ATP, 3 NADH, 1 FADH2 per acetyl CoA.

Oxaloacetate

Four-carbon molecule that combines with acetyl CoA to form citrate and is regenerated at cycle end.

ATP synthase

Enzyme that uses a proton gradient to synthesize ATP from ADP and Pi.

Oxygen as final electron acceptor

O2 accepts electrons at the end of the electron transport chain, forming water.

Carbonic acid reaction (CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3−)

A reversible reaction important in buffering and CO2 transport in blood.

Exergonic reaction

Reaction in which energy is released; reactants have more potential energy than products.

Endergonic reaction

Reaction requiring energy input; products have more chemical energy than reactants.

Catabolism

Metabolic pathways that break down complex molecules to harvest energy.

Anabolism

Metabolic pathways that build complex molecules from simpler ones; energy input required.

Metabolism

All biochemical reactions in the body, including catabolism and anabolism.

Metabolic pathway

A sequence of enzymatic steps where each product becomes the next substrate; often regulated.

Multienzyme complex

Group of enzymes physically linked to catalyze sequential reactions with substrate channeling.

Negative feedback

Product inhibits an enzyme early in a pathway to regulate the overall output.

Phosphorylation

Addition of a phosphate group to a molecule, often modulating enzyme activity.

Dephosphorylation

Removal of a phosphate group from a molecule.

Kinase

Enzyme that adds phosphate groups (phosphorylation) to substrates.

Phosphatase

Enzyme that removes phosphate groups (dephosphorylation) from substrates.

Lactate dehydrogenase

Enzyme that converts pyruvate to lactate, regenerating NAD+ for glycolysis.

Cori cycle

Shuttling of lactate from muscle to liver where it is converted back to glucose.

Beta-oxidation

Breakdown of fatty acids into two-carbon acetyl CoA units in mitochondria.

Deamination

Removal of an amino group from amino acids before entry into metabolism.

Glycolysis location

Occurs in the cytosol; does not require oxygen.

Intermediate stage location

Occurs in the mitochondrial matrix; catalyzed by pyruvate dehydrogenase.

Citric acid cycle location

Occurs in the mitochondrial matrix; requires oxygen.

Direct ATP production (substrate-level)

ATP formed directly in glycolysis and the citric acid cycle without the electron transport chain.

Oxidative phosphorylation location

Takes place across the inner mitochondrial membrane via the electron transport chain.

Beta-oxidation location and oxygen

Occurs in mitochondria and requires oxygen (aerobic).

Cori cycle

Lactate produced in muscle is transported to liver to be converted back to glucose.