cellular energetics

Metabolism

The sum of all chemical reactions that occur within a living organism to maintain life, including both anabolic and catabolic processes.

Autotroph

An organism that can produce its own food using light, water, carbon dioxide, or other chemicals; also known as a producer.

Heterotroph

An organism that cannot produce its own food and must obtain nutrients by consuming other organisms or organic matter; also known as a consumer.

ATP (Adenosine Triphosphate)

The primary energy currency of the cell, a nucleotide that stores and releases chemical energy.

Enzyme

A biological catalyst, usually a protein, that speeds up chemical reactions by lowering the activation energy.

Activation Energy

The minimum amount of energy required to start a chemical reaction.

Cellular Respiration

A set of metabolic reactions occurring in cells to convert chemical energy from oxygen molecules or nutrients into ATP, and then release waste products.

Glycolysis

The first stage of cellular respiration, occurring in the cytoplasm, where glucose is broken down into pyruvate, producing a small amount of ATP and NADH.

Citric Acid Cycle (Krebs Cycle)

The second stage of cellular respiration, occurring in the mitochondrial matrix, where pyruvate is further oxidized, generating CO2, ATP, NADH, and FADH2.

Electron Transport Chain (ETC)

The final stage of cellular respiration, located in the inner mitochondrial membrane, where electrons are passed through a series of protein complexes, generating a proton gradient used to produce ATP.

Oxidative Phosphorylation

The process in cellular respiration where ATP is synthesized using the energy derived from the electron transport chain and the movement of protons across the mitochondrial membrane.

Fermentation

An anaerobic process that allows glycolysis to continue by regenerating NAD+ in the absence of oxygen; produces less ATP than cellular respiration.

Photosynthesis

The process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose or other organic molecules.

Light-Dependent Reactions

The first stage of photosynthesis, occurring in the thylakoid membranes, where light energy is absorbed and converted into chemical energy in the form of ATP and NADPH.

Calvin Cycle (Light-Independent Reactions)

The second stage of photosynthesis, occurring in the stroma, where ATP and NADPH are used to fix carbon dioxide and synthesize glucose.

Chloroplast

An organelle found in plant and algal cells where photosynthesis takes place.

Mitochondria

An organelle found in eukaryotic cells that is the primary site of cellular respiration.

Anaerobic

Occurring in the absence of oxygen.

Aerobic

Occurring in the presence of oxygen.