U3 vocab bio

Metabolism

The sum of all chemical reactions in an organism.

Catabolic Pathways

Break down molecules to release energy (e.g., cellular respiration).

Anabolic Pathways

Build complex molecules using energy (e.g., photosynthesis).

Exergonic Reaction

Releases energy; spontaneous (e.g., cellular respiration).

Endergonic Reaction

Requires energy input; non-spontaneous (e.g., photosynthesis).

Enzyme

A protein that acts as a catalyst to speed up reactions.

Activation Energy

The initial energy needed to start a reaction.

Substrate

The reactant that an enzyme acts on.

Active Site

The part of an enzyme where the substrate binds.

Induced Fit

The enzyme changes shape to fit the substrate more tightly.

Cofactor

A non-protein molecule (e.g., metal ions) that assists enzyme function.

Coenzyme

An organic cofactor (e.g., vitamins) that helps enzymes.

Competitive Inhibitor

Blocks the active site, preventing substrate binding.

Non-Competitive Inhibitor

Binds elsewhere, changing the enzyme’s shape.

Allosteric Regulation

A molecule binds to an enzyme at a site other than the active site, regulating activity.

Cellular Respiration

The process of converting glucose into ATP using oxygen.

Aerobic Respiration

Requires oxygen; produces more ATP.

Anaerobic Respiration

Does not require oxygen; produces less ATP.

ATP (Adenosine Triphosphate)

The energy currency of the cell.

ADP (Adenosine Diphosphate)

Formed when ATP loses a phosphate group.

Oxidation

Loss of electrons

Reduction

Gain of electrons

Glycolysis

The first step in cellular respiration; breaks glucose into pyruvate.

Pyruvate

The three-carbon molecule produced from glycolysis.

Pyruvate Oxidation

Pyruvate is converted into Acetyl-CoA before entering the Krebs cycle.

Acetyl-CoA

The molecule that enters the Krebs cycle.

Krebs Cycle (Citric Acid Cycle)

A cycle that generates NADH and FADH₂ by oxidizing Acetyl-CoA.

NADH & FADH₂

Electron carriers that store energy for the electron transport chain.

Electron Transport Chain (ETC)

A series of proteins in the inner mitochondrial membrane that transfer electrons and produce ATP.

Oxidative Phosphorylation

ATP synthesis driven by the movement of electrons through the ETC.

Chemiosmosis

The movement of protons across a membrane to generate ATP.

ATP Synthase

An enzyme that uses the proton gradient to produce ATP.

Final Electron Acceptor

Oxygen (O₂) in aerobic respiration, forming water (H₂O).

Lactic Acid Fermentation

Anaerobic respiration in muscles that produces lactic acid.

Alcoholic Fermentation

Anaerobic process in yeast that produces ethanol and CO₂.

Photosynthesis

The process by which light energy is converted into chemical energy (glucose).

Autotrophs

Organisms that produce their own food (e.g., plants).

Chloroplast

The organelle where photosynthesis occurs.

Thylakoid

The membrane sacs inside chloroplasts where the light-dependent reactions occur.

Grana

Stacks of thylakoids.

Stroma

The fluid-filled space inside chloroplasts where the Calvin cycle occurs.

Light-Dependent Reactions

The first stage of photosynthesis that converts light energy into ATP and NADPH.

Photolysis

The splitting of water to produce oxygen, protons, and electrons.

Photosystem

Protein-pigment complexes in the thylakoid membrane that absorb light energy.

Photosystem II (PSII)

Captures light and starts the electron transport chain; splits water to release O₂.

Photosystem I (PSI)

Captures light and produces NADPH.

Electron Transport Chain (ETC) in Photosynthesis

Transfers electrons to produce ATP and NADPH.

NADPH

An electron carrier used in the Calvin cycle.

ATP Synthase in Photosynthesis

Uses a proton gradient to synthesize ATP.

Calvin Cycle (Light-Independent Reactions)

Uses ATP and NADPH to convert CO₂ into glucose.

Carbon Fixation

The incorporation of CO₂ into organic molecules by Rubisco.

Rubisco

The enzyme that catalyzes carbon fixation in the Calvin cycle.

G3P (Glyceraldehyde-3-Phosphate)

A product of the Calvin cycle that forms glucose.

C3 Plants

Use only the Calvin cycle for carbon fixation (e.g., rice, wheat).

C4 Plants

Have an adaptation that minimizes photorespiration (e.g., corn, sugarcane).

CAM Plants

Store CO₂ at night to prevent water loss (e.g., cacti, succulents).

Photorespiration

A wasteful process where Rubisco binds oxygen instead of CO₂, reducing photosynthesis efficiency.

Energy Coupling

The use of an exergonic process (like ATP hydrolysis) to drive an endergonic process.

Feedback Inhibition

A regulatory mechanism where a product of a pathway inhibits an earlier step.

Proton Gradient

A difference in proton concentration across a membrane that drives ATP production.