Bioenergetics and Cellular Metabolism

A set of key vocabulary terms and definitions with grounded diagrams covering bioenergetics, ATP, metabolism, photosynthesis, and cellular respiration.

Bioenergetics

The transformation and management of energy in living organisms that makes life possible.

Oxidation

The chemical process involving the removal or loss of an electron from a compound.

Reduction

The chemical process involving the addition or gain of an electron by a compound.

Oxidation-Reduction Reaction (Redox)

A coupled chemical process where oxidation is the loss of electrons by a compound (reducing agent) and reduction is the gain of electrons by another compound (oxidizing agent).

Adenosine Triphosphate (ATP)

The main energy currency of the cell, composed of an adenine nitrogenous base, a ribose sugar, and three phosphate groups.

Phosphoanhydride Bonds

High-energy chemical bonds connecting the phosphate groups in an ATP molecule.

Sodium-Potassium Pump Mechanism

An active transport process where ATP phosphorylation alters protein conformation to transport intracellular sodium ($\text{Na}^+$) outward, and subsequent dephosphorylation transports extracellular potassium ($\text{K}^+$) inward.

ATP Hydrolysis

A reversible reaction where water splits ATP into ADP and an inorganic phosphate ion ($\text{P}_{i}$), breaking a high-energy phosphate bond to release free energy.

Metabolism

The sum of all chemical activities taking place in an organism.

Catabolism

Metabolic processes that break down larger molecules into smaller ones, releasing energy that can be temporarily stored as ATP.

Anabolism

Metabolic processes that synthesize complex molecules from simpler substances, requiring and storing energy within chemical bonds.

Acetyl-CoA

A metabolic intermediate that participates in carbohydrate and lipid metabolism, delivering an acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production.

Photosynthesis

An anabolic pathway by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose ($\text{C}_{6}\text{H}_{12}\text{O}_{6}$) and oxygen ($\text{O}_{2}$) using carbon dioxide ($\text{CO}_{2}$) and water ($\text{H}_{2}\text{O}$).

Chloroplast Structure

A double-membrane organelle containing disc-shaped thylakoids stacked into grana, stroma lamellae, and fluid stroma where photosynthetic reactions occur.

Light-dependent Reactions

Photosynthetic reactions in the thylakoid membrane where absorbed light energy splits water ($\text{H}_{2}\text{O}$), generating oxygen ($\text{O}_{2}$), ATP, and NADPH via an electron transport chain.

Light-independent Reactions (Calvin Cycle)

Enzymatic processes in the chloroplast stroma that use ATP, NADPH, and carbon dioxide ($\text{CO}_{2}$) across carbon fixation, reduction, and regeneration stages to synthesize glucose ($\text{C}_{6}\text{H}_{12}\text{O}_{6}$).

Cellular Respiration

A catabolic pathway where organisms extract energy from glucose ($\text{C}_{6}\text{H}_{12}\text{O}_{6}$) and oxygen ($\text{O}_{2}$) to produce carbon dioxide ($\text{CO}_{2}$), water ($\text{H}_{2}\text{O}$), and ATP according to the equation $\text{C}_{6}\text{H}_{12}\text{O}_{6} + 6\text{O}_{2} \rightarrow 6\text{CO}_{2} + 6\text{H}_{2}\text{O} + \text{ATP}$.

Stages of Cellular Respiration

The primary stages of cellular respiration—Glycolysis (in cytosol), Krebs Cycle, and Electron Transport Chain & Oxidative Phosphorylation (in mitochondrion)—which together produce up to $\sim 38\,\text{ATP}$.

Bioenergetics Transformation Pathway

The sequential transformation of energy through light capture, photosynthesis, organic molecules, cellular respiration, electron transfer, proton gradient formation, ATP synthesis, cellular work, and life.