AP Biology Unit 3 Terms

Enzyme

proteins that catalyze reactions by lowering the activation energy

Substrate

reactants that enzymes act on

Enzyme-substrate complex

the temporary, physical binding of an enzyme to its substrate at the enzyme’s active site during a biochemical reaction

Active site

area for substrate to bind

Catalyst

a substance that increases the rate of a chemical reaction without being permanently altered or consumed in the process

pH: measure of the concentration of H+ in a solution

Denature: the process where an enzyme loses its 3D shape and stops working because of the broken bonds

ATP - the main energy currency of the cell that powers daily tasks

Kinetic energy - the energy of motion

Potential energy - stored energy based on the structure, arrangement, or position of matter

Energy - the capacity to do work or cause change

Exergonic reaction - a chemical reaction that releases free energy

Endergonic reaction - a chemical reaction that absorbs free energy from its surroundings

Catabolic pathway - a series of metabolic reactions that breaks down complex molecules into simpler ones, releasing energy in the process

Anabolic pathway - a series of chemical reactions that builds complex molecules from smaller, simpler pieces

Activation energy - the minimum amount of energy required to start a chemical reaction by pushing reactants over their high-energy transition state

Laws of thermodynamics - describes how energy moves and changes in living systems

C4 Plant - plant that uses a special method of photosynthesis to prevent a wasteful process called photorespiration in hot, sunny weather

Light capturing complexes - a group of proteins and pigments embedded in the thylakoid membrane that absorbs sunlight and funnels the energy toward a reaction center

NADPH - an electron carrier, a reducing agent, that stores and delivers high-energy electrons and hydrogen ions to power reactions in the cell

Light - the first stage of photosynthesis that uses sunlight and water to make chemical energy (ATP and NADPH) and releases oxygen

Stomata - microscopic pores that controls gas exchange and water loss

Stroma - the dense, fluid-filled space surrounding the thylakoid membranes inside a chloroplast

Thylakoid - a flattened, membrane-bound sac inside a plant or algae chloroplast where the light-dependent reactions of photosynthesis take place

Reaction center - the pigment-protein core inside a photosystem where light energy excites an electron and starts the light-dependent reactions of photosynthesis

Chlorophyll - a green pigment found in plants, algae, and cyanobacteria that absorbs light energy to power photosynthesis

Redox reaction - a paired chemical reaction where one molecule loses electrons and another molecule gains electrons

Oxidation - the loss of electrons by a molecule, atom, or ion

Pigments - light-absorbing molecules located in the thylakoid membranes of chloroplasts that capture solar energy to power photosynthesis

Photosynthesis - a metabolic process that converts light energy, CO2, and water into chemical energy stored in glucose, releasing oxygen as a byproduct

Photons - a discrete packet of light that carries a specific amount of energy

Wavelength - the physical distance between two consecutive peaks or valleys of a light wave

Reduction - the process of a molecule gaining electrons

Photoprotection - the process by which plants absorb and safely dissipate excess light energy to prevent damage to their photosynthetic machinery

Heterotrophs - an organism that cannot make its own food and must consume other living or dead organic matter for energy and carbon

Calvin cycle - a series of light-independent reactions in photosynthesis that takes carbon dioxide from the air and turns it into sugar from ATP and NADPH

Chloroplast - a double-membrane organelle found in plant cells and algae that conducts photosynthesis

Grana - stacks of coin-shaped membrane discs called thylakoids

Photosystems - a protein and pigment complex embedded in the thylakoid membrane of chloroplasts that captures light energy and uses it to energize electrons

Mesophyll - the middle layer of tissue in a plant leaf, located between the upper and lower epidermis

Photorespiration - a wasteful metabolic pathway where the enzyme, RuBisCO, binds to oxygen instead of carbon dioxide

G3P - a simple 3-carbon sugar molecule that acts as a key building block and energy-transfer intermediate in both photosynthesis and cellular respiration

CAM plant - a plant adapted to hot, dry environments that separates carbon fixation and the Calvin cycle in time rather than in space

Cellular respiration - the metabolic process by which cells break down glucose and other organic molecules to release energy in the form of ATP

Oxidation - the loss of electrons by a molecule, atom, or ion

Reduction - the gain of electrons by a molecule

NAD+ - a vital coenzyme and electron carrier in cellular respiration

FADH - a high-energy electron carrier using during cellular respiration to make ATP

Glycolysis - the first step of cellular respiration that breaks down a six-carbon glucose molecule into two three-carbon pyruvate molecules inside the cell’s cytoplasm

Pyruvate oxidation - the second step in cellular respiration that converts the pyruvate from glycolysis into acetyl-CoA so it can enter the Krebs cycle

Citric acid cycle - a series of enzyme-driven chemical reactions that breaks down food molecules to harvest high-energy electrons

Chemiosmosis - the movement of hydrogen ions down the electrochemical gradient to power ATP synthase to make ATP from ADP and inorganic phosphate

ATP synthase - a combined protein channel and enzyme that acts like a tiny molecular turbine to make ATP from ADP and inorganic phosphate

Anaerobic respiration - a cellular process that makes ATP without oxygen

Fermentation - an anaerobic cellular process that allows cells to produce a small amount of ATP through glycolysis and regenerate NAD+