Unit 3: Cellular Energetics

Vocabulary practice flashcards covering enzymes, cellular energy, photosynthesis, and cellular respiration based on Unit 3 lecture notes.

Enzyme

A protein that speeds up chemical reactions by lowering the activation energy needed for reactions to occur.

Substrate

The specific substance that an enzyme works on.

Enzyme-Substrate Complex

The temporary complex formed when the substrate connects to the enzyme.

Active site

The specific part of the enzyme where the substrate binds.

Catalyst

Something that speeds up a chemical reaction without being consumed or used up.

pH

A scale that measures how acidic or basic something is.

Denature

The process when a protein changes shape and stops working properly, often caused by high temperatures or pH changes.

Competitive inhibitors

Inhibitor molecules that block the active site of an enzyme to prevent substrate binding.

Noncompetitive inhibitors

Inhibitor molecules that bind somewhere other than the active site and change the enzyme's shape or activity.

ATP

The main energy-carrying molecule in a cell that provides energy for cell processes, storing energy in its phosphate bonds and releasing it when the last phosphate is removed.

Kinetic energy

The energy of movement.

Potential energy

Stored energy.

Energy

The ability to do work or cause change.

Exergonic reaction

A chemical reaction that releases energy.

Endergonic reaction

A chemical reaction that requires energy.

Catabolic pathway

A metabolic pathway that breaks down molecules and releases energy.

Anabolic pathway

A metabolic pathway that builds larger molecules and requires energy.

Activation energy

The energy needed to start a chemical reaction.

Laws of Thermodynamics

The rules that explain how energy moves and changes form.

Photosynthesis

The process plants use to convert light energy into chemical energy stored in sugars.

Autotrophs

Organisms that make their own food and serve as primary producers providing energy for other organisms.

Heterotrophs

Organisms that obtain food by consuming other organisms.

Chloroplast

The organelle where photosynthesis occurs, housing the thylakoid membranes and the stroma.

Thylakoid

A flattened membrane sac inside the chloroplast where the light reactions happen.

Grana

Stacks of thylakoids located inside a chloroplast.

Stroma

The fluid inside the chloroplast surrounding the thylakoids where the Calvin cycle takes place.

Mesophyll

The inner leaf tissue cells where most photosynthesis happens.

Chlorophyll

The green pigment in plants that absorbs light for photosynthesis.

Pigments

Molecules that absorb specific colors or wavelengths of light.

Photons

Tiny packets of light energy.

Wavelength

The distance between two matching points on a light wave.

Light-Capturing Complexes

Structures that absorb light and pass energy along to the reaction center.

Reaction Center

The portion of a photosystem where light energy initiates the transfer of electrons.

Photosystems

Groups of pigments and proteins organized within thylakoid membranes to capture light energy.

Photoprotection

Mechanisms that protect the photosynthetic apparatus from excess or damaging light.

NADPH

The primary electron-carrying molecule in photosynthesis that transports high-energy electrons.

Redox Reaction

A chemical reaction in which electrons are transferred between molecules.

Oxidation

The loss of electrons from a molecule, atom, or ion.

Reduction

The gain of electrons by a molecule, atom, or ion.

Calvin Cycle

The series of light-independent reactions occurring in the stroma that fix $CO_2$ to synthesize sugar.

Rubisco

The enzyme that catalyzes carbon fixation in the Calvin cycle by adding $CO_2$ to an organic molecule.

G3P

A three-carbon sugar produced directly during the Calvin cycle, requiring $3\,CO_2$ molecules per net molecule formed.

Photorespiration

A wasteful pathway that occurs when Rubisco binds to oxygen instead of carbon dioxide, reducing sugar production.

Linear electron flow

A photosynthetic pathway utilizing both photosystems that produces ATP, NADPH, and oxygen.

Cyclic electron flow

A photosynthetic pathway utilizing only photosystem I that generates extra ATP without producing NADPH or oxygen.

C4 Plant

A plant adapted to use a specialized pathway to capture carbon dioxide efficiently.

CAM Plant

A plant adapted to arid conditions that opens its stomata at night to take in carbon dioxide and minimize daytime water loss.

Cellular Respiration

The catabolic process cells use to break down food molecules and produce ATP.

$$NAD^+$$

A coenzyme that acts as an electron carrier during cellular respiration.

FADH

A molecule that carries high-energy electrons to the electron transport chain during cellular respiration.

Glycolysis

The metabolic pathway in the cytoplasm that breaks down one molecule of glucose into two pyruvate molecules.

Pyruvate Oxidation

The transition process that converts pyruvate into acetyl-CoA prior to entry into the citric acid cycle.

Citric Acid Cycle

A series of reactions that break down acetyl-CoA to produce electron carriers (NADH, $FADH_2$), ATP, and $CO_2$.

Chemiosmosis

The movement of hydrogen ions across a membrane through ATP synthase to drive the synthesis of ATP.

ATP Synthase

An enzyme that synthesizes ATP from ADP and inorganic phosphate using the electrochemical flow of hydrogen ions.

Anaerobic Respiration

The generation of ATP from fuel molecules without using oxygen as the final electron acceptor.

Fermentation

An anaerobic process that allows glycolysis to continue in the absence of oxygen by regenerating $NAD^+$ from NADH.

Oxidative Phosphorylation

The production of ATP using energy derived from the transfer of electrons down the electron transport chain to generate a proton gradient that powers ATP synthase.

Golgi complex

A cellular organelle analogous to a warehouse or mail facility that modifies, sorts, packages, and ships proteins and other materials.