Unit 3 Cellular Energetics - VOCABULARY Flashcards

Vocabulary-style flashcards covering enzymes, energetics, photosynthesis, and cellular respiration concepts from the notes.

Enzyme

A protein that acts as a biological catalyst to speed up chemical reactions by lowering activation energy.

Activation energy

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

Substrate

The molecule that binds to an enzyme’s active site and undergoes a chemical change.

Active site

The region of the enzyme where the substrate binds.

Enzyme-substrate complex

The temporary bound state formed when an enzyme binds its substrate.

Denaturation

Loss of a protein’s native structure and function due to factors like heat, pH, or chemicals.

Reversible denaturation

Denaturation that can be reversed, allowing the enzyme to regain activity.

Irreversible denaturation

Permanent loss of enzyme function due to irreversible structural changes.

Optimal temperature

The temperature at which an enzyme achieves its maximum activity.

Optimal pH

The pH at which an enzyme achieves its maximum activity.

Thermal denaturation

Change in enzyme structure caused by temperatures outside the optimum range.

pH effect on enzymes

Alterations in hydrogen ion concentration can disrupt bonds and change enzyme shape and function.

Substrate concentration

Amount of substrate available; affects reaction rate until enzymes become saturated.

Product concentration

Build-up of products that can slow down a reaction (product inhibition).

Competitive inhibitor

A molecule that binds reversibly to the enzyme active site, competing with the substrate.

Noncompetitive inhibitor

A molecule that binds to an allosteric site, changing enzyme activity without competing at the active site.

Allosteric site

A regulatory site on an enzyme, separate from the active site, where inhibitors or activators bind.

Gibbs free energy (G)

The portion of a system’s energy available to do work; enzymes do not change G of a reaction.

Activation energy vs Gibbs free energy

Enzymes lower activation energy but do not alter the overall Gibbs free energy change of a reaction.

Exergonic reaction

A reaction that releases free energy.

Endergonic reaction

A reaction that requires input of free energy.

Energy coupling

Using energy from an exergonic reaction to drive an endergonic reaction.

Metabolic pathway

A sequence of chemical reactions where the product of one step becomes the substrate for the next.

Catabolic pathway

Metabolic pathway that breaks down molecules to release energy.

Anabolic pathway

Metabolic pathway that builds complex molecules from simpler ones, requiring energy.

Glycolysis

Glucose breakdown in the cytosol that yields ATP and NADH; does not require oxygen.

Pyruvate oxidation

Conversion of pyruvate to acetyl-CoA in mitochondria, producing NADH and CO2.

Krebs cycle (Citric Acid Cycle)

Mitochondrial matrix process that releases CO2, generates ATP (or GTP), NADH, and FADH2.

Electron Transport Chain (ETC)

A series of proteins in membranes that transfer electrons and create a proton gradient for ATP production.

Oxidative phosphorylation

ATP synthesis driven by the proton gradient across a membrane via the ETC and ATP synthase.

ATP synthase

Enzyme that uses a proton gradient to convert ADP and Pi into ATP.

Chemiosmosis

Movement of ions (protons) down their gradient through ATP synthase to make ATP.

Proton gradient

Difference in H+ concentration across a membrane that powers ATP synthesis.

Mitochondrion

Organelle where aerobic cellular respiration takes place; contains inner membrane folds (cristae) and matrix.

Matrix

Fluid inside the mitochondrion where the Krebs cycle occurs.

Cristae

Folds of the inner mitochondrial membrane that increase surface area for respiration.

Inner mitochondrial membrane

Membrane housing the ETC and creating the proton gradient.

NADH

Electron carrier that donates electrons to the ETC; produced in glycolysis, pyruvate oxidation, and the Krebs cycle.

FADH2

Electron carrier that donates electrons to the ETC; produced in the Krebs cycle.

NADPH

Electron carrier in photosynthesis; provides reducing power for the Calvin cycle.

NADP+

Oxidized form of the NADP/NADPH pair that accepts electrons to form NADPH.

Photosynthesis

Process by which light energy is converted to chemical energy, producing carbohydrates and O2.

Chloroplast

Plant cell organelle where photosynthesis occurs.

Stroma

Fluid inside the chloroplast where the Calvin cycle takes place.

Thylakoid

Membrane-bound sacs where the light reactions occur; contain chlorophyll.

Grana

Stacks of thylakoids within chloroplasts.

Photosystems I and II

Protein complexes in the thylakoid membrane that capture light energy and drive electron transport.

Photolysis

Splitting of water during the light reactions to release electrons, protons, and O2.

Calvin cycle

Light-independent reactions in the stroma that fix CO2 into carbohydrates using ATP and NADPH.

Light reactions

Photosynthetic reactions that convert light energy to ATP and NADPH in the thylakoid membranes.

Photophosphorylation

ATP synthesis driven by light via the proton gradient in photosynthesis.

Chlorophyll

Primary pigment that captures light energy for photosynthesis.

Chlorophyll a

Most abundant photosynthetic pigment that participates directly in light reactions.

Photosystems I and II structure

Two pigment–protein complexes connected by an electron transport chain in the thylakoid membrane.

G3P ( glyceraldehyde-3-phosphate)

Three-carbon sugar produced in the Calvin cycle used to synthesize carbohydrates.

Carbon fixation

Process of incorporating CO2 into organic molecules during the Calvin cycle.

Photophosphorylation product

ATP produced during the light reactions via chemiosmosis.

Oxygen evolution

Release of O2 as a byproduct of the light-driven splitting of water.

Cyanobacteria

Photosynthetic prokaryotes whose activity contributed to the oxygenation of Earth’s atmosphere.

Calvin cycle location

Occurs in the stroma of the chloroplast.

Light reactions location

Occur in the thylakoid membranes of the chloroplast.

Glycolysis location

Takes place in the cytosol of the cell.

Fermentation

Glycolysis continuation in the absence of O2, yielding lactate or alcohol and NAD+.

ATP

Adenosine triphosphate; the cell’s main energy currency.

ADP + Pi

Adenosine diphosphate and inorganic phosphate; substrates to synthesize ATP.

Oxygen as terminal electron acceptor

In aerobic respiration, O2 accepts electrons at the end of the ETC.

Metabolic pathway conservancy

Core pathways like glycolysis and oxidative phosphorylation are conserved across domains.

Entropy

A measure of disorder; governed by the second law of thermodynamics in living systems.