The Chemistry that Supports Life: Enzymes

These flashcards cover key vocabulary and concepts related to enzymes, energy transformations, and metabolic processes discussed in the lecture.

ATP

Adenosine triphosphate, the molecule that drives most cellular work.

Photosynthesis

The process by which plants convert carbon dioxide and water into organic molecules and oxygen using light energy.

Cellular respiration

The process in mitochondria that breaks down organic molecules to generate ATP.

\Delta G

The change in Gibbs free energy of a reaction, which determines spontaneity.

Endergonic reaction

A reaction that requires an input of energy and is not spontaneous (\Delta G > 0).

Exergonic reaction

A spontaneous reaction that releases energy (\Delta G < 0).

Equilibrium constant (K_{eq})

A value that describes the ratio of concentrations of products to reactants at equilibrium.

Activation energy (E_A)

The energy barrier that must be overcome for a reaction to proceed.

Enzyme

A protein that acts as a catalyst to accelerate a chemical reaction by lowering the activation energy.

Competitive inhibition

A type of enzyme inhibition where structurally similar molecules bind to the active site and block substrate binding.

Non-competitive inhibition

Inhibition where molecules bind to a separate site, blocking enzyme function without blocking substrate binding.

Feedback inhibition

A regulatory mechanism where the product of a pathway inhibits an enzyme involved in its production.

Thermodynamics

The study of energy changes in chemical reactions.

Hydrolysis of ATP

The reaction that releases energy by breaking ATP into ADP and inorganic phosphate (P_i).

Induced fit

The mechanism by which an enzyme changes shape to better fit its substrate.

Transition state

An unstable state during a chemical reaction where the reactants are converted into products.

Covalent bond

A strong bond formed when two atoms share electrons.

First Law of Thermodynamics

The principle stating that energy cannot be created or destroyed, only transformed or transferred.

Second Law of Thermodynamics

The principle stating that every energy transfer or transformation increases the entropy of the universe.

Entropy (S)

A measure of disorder or randomness in a system.

Enthalpy (H)

The total heat content of a chemical system.

Gibbs Free Energy Equation

The mathematical relationship expressed as \Delta G = \Delta H - T\Delta S.

Metabolism

The sum of all chemical reactions that occur within an organism.

Catabolic pathway

A metabolic pathway that releases energy by breaking down complex molecules into simpler compounds.

Anabolic pathway

A metabolic pathway that consumes energy to synthesize complex molecules from simpler ones.

Kinetic energy

The energy related to the relative motion of objects.

Potential energy

The energy that matter possesses because of its location or structure.

Energy coupling

The use of an exergonic process to drive an endergonic one, often mediated by ATP.

Phosphorylation

The chemical addition of a phosphoryl group (PO_3^{2-}) to an organic molecule.

Substrate

The specific reactant molecule upon which an enzyme acts.

Active site

The specific region of an enzyme that binds the substrate and where catalysis occurs.

Enzyme-substrate complex

The temporary complex formed when an enzyme binds to its substrate molecule(s).

Cofactor

Any non-protein molecule or ion that is required for the proper functioning of an enzyme.

Coenzyme

An organic cofactor, such as most vitamins.

Allosteric regulation

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.

Cooperativity

A kind of allosteric regulation whereby a shape change in one subunit of a protein is transmitted to all others.

Denaturation

A process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions.

Autotroph

An organism that obtains organic food molecules without eating other organisms, often using light energy.

Heterotroph

An organism that obtains organic food molecules by eating other organisms or their by-products.

Chlorophyll

A green pigment located within the chloroplasts of plants, algae, and some bacteria.

Thylakoid

A flattened, membranous sac inside a chloroplast where light reactions occur.

Stroma

The dense fluid within the chloroplast involved in the synthesis of organic molecules from carbon dioxide and water.

Light-dependent reactions

The steps in photosynthesis that occur on the thylakoid membranes and convert solar energy to the chemical energy of ATP and NADPH.

Calvin cycle

The second of two major stages in photosynthesis, involving fixation of atmospheric CO_2 and reduction of the fixed carbon into carbohydrate.

NADPH

An electron carrier that provides high-energy electrons for the reduction of carbon dioxide in the Calvin cycle.

Carbon fixation

The initial incorporation of carbon from CO_2 into an organic compound.

Rubisco

The enzyme that catalyzes the first step of the Calvin cycle by adding CO_2 to RuBP.

G3P

Glyceraldehyde 3-phosphate, the three-carbon carbohydrate that is the direct product of the Calvin cycle.

Photorespiration

A metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output.

Redox reaction

A chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another.

Oxidation

The complete or partial loss of electrons from a substance involved in a redox reaction.

Reduction

The complete or partial addition of electrons to a substance involved in a redox reaction.

NAD+ / NADH

A coenzyme that cycles between oxidized (NAD^+) and reduced (NADH) states to carry electrons.

Glycolysis

A series of reactions that ultimately splits glucose into pyruvate, occurring in almost all living cells.

Citric Acid Cycle

A chemical cycle that completes the metabolic breakdown of glucose molecules begun in glycolysis.

Electron Transport Chain

A sequence of electron carrier molecules that shuttle electrons down a series of redox reactions that release energy.

Chemiosmosis

An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient to drive cellular work such as ATP synthesis.

ATP synthase

A complex of several membrane proteins that functions in chemiosmosis to produce ATP.

Oxidative phosphorylation

The production of ATP using energy derived from the redox reactions of an electron transport chain.

Fermentation

A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain.