Ap Bio Unit 3 - Cellular Energetics

Metabolism

The sum of all chemical reactions in a cell or organism.

Anabolism

Building complex molecules from smaller molecules; requires energy.

Catabolism

Breaking down complex molecules into smaller molecules; often releases energy.

Kinetic energy

Energy associated with motion.

Potential energy

Stored energy due to position, structure, or arrangement.

Thermodynamics

The study of energy transformations and transfers.

First law of thermodynamics

Energy cannot be created or destroyed, only transferred or transformed.

Second law of thermodynamics

Every energy transfer increases total entropy of the universe.

Entropy

A measure of energy dispersal and possible microscopic arrangements.

Free energy (G)

Energy available to do work under specified conditions.

Exergonic reaction

A reaction with negative ΔG that releases free energy.

Endergonic reaction

A reaction with positive ΔG that requires an energy input.

Spontaneous reaction

A thermodynamically favorable reaction under given conditions; not necessarily fast.

Activation energy

Energy needed to reach a reaction's transition state.

ATP

Adenosine triphosphate; transfers usable energy for cellular work.

ATP hydrolysis

ATP reacts with water to form ADP and phosphate, releasing free energy.

ADP

Adenosine diphosphate; can be converted back into ATP.

Inorganic phosphate (Pi)

Free phosphate used in ATP synthesis and phosphorylation.

Energy coupling

Using an energy

Phosphorylation

Addition of a phosphate group to a molecule.

Chemical work

Using energy to build molecules.

Transport work

Using energy to move substances across membranes.

Mechanical work

Using energy to produce movement.

Catalyst

A substance that speeds a reaction without being consumed overall.

Enzyme

A biological catalyst that lowers activation energy.

Substrate

The reactant upon which an enzyme acts.

Active site

The enzyme region where substrate binding and catalysis occur.

Enzyme

substrate complex

Induced

fit model

Specificity

An enzyme's preference for particular substrates and reactions.

Transition state

High

Denaturation

Disruption of a protein's structure that can impair its function.

Optimal temperature

Temperature at which an enzyme works fastest under tested conditions.

Optimal pH

pH at which an enzyme works fastest under tested conditions.

Competitive inhibition

An inhibitor competes with the substrate for the active site.

Noncompetitive inhibition

An inhibitor binds elsewhere and reduces enzyme activity.

Allosteric regulation

Binding away from the active site changes enzyme activity.

Allosteric activator

A molecule that binds an allosteric site and increases enzyme activity.

Allosteric inhibitor

A molecule that binds an allosteric site and decreases enzyme activity.

Feedback inhibition

A pathway's final product inhibits an earlier enzyme.

Photosynthesis

Process converting light energy into chemical energy in organic molecules.

Chloroplast

Organelle where photosynthesis occurs in plants and algae.

Chlorophyll

Pigment that absorbs light energy for photosynthesis.

Pigment

Molecule that absorbs particular wavelengths of light.

Photon

A discrete packet of light energy.

Wavelength

Distance between successive wave peaks.

Electromagnetic spectrum

The full range of electromagnetic radiation.

Photosystem

Pigment

Reaction

center chlorophyll

Primary electron acceptor

Molecule that captures an excited electron from a reaction center.

Photosystem II

Photosystem that replaces lost electrons by splitting water.

Photosystem I

Photosystem that re

Photolysis

Light

Electron transport chain

Series of carriers transferring electrons and helping establish a proton gradient.

Redox reaction

Chemical reaction involving electron transfer.

Oxidation

Loss of electrons.

Reduction

Gain of electrons.

Reducing agent

Substance that donates electrons and is itself oxidized.

Oxidizing agent

Substance that accepts electrons and is itself reduced.

NADP+

Oxidized electron carrier that accepts electrons to form NADPH.

NADPH

Reduced electron carrier that provides reducing power for carbon fixation.

Proton gradient

Difference in proton electrochemical potential across a membrane.

Chemiosmosis

Proton flow down an electrochemical gradient through ATP synthase to drive ATP production.

ATP synthase

Enzyme complex that makes ATP using energy from a proton gradient.

Photophosphorylation

ATP production powered by light

Noncyclic electron flow

Electrons travel from water through photosystems II and I to NADP+.

Cyclic electron flow

Electrons from photosystem I cycle back through carriers, increasing ATP production.

Thylakoid

Membrane

Thylakoid membrane

Membrane containing photosystems, electron carriers, and ATP synthase.

Thylakoid lumen

Interior of a thylakoid where protons accumulate.

Granum

A stack of thylakoids.

Grana

Multiple stacks of thylakoids.

Stroma

Chloroplast fluid where the Calvin cycle occurs.

Calvin cycle

Reactions that fix CO2 using ATP and NADPH to produce carbohydrate intermediates.

Carbon fixation

Incorporation of inorganic CO2 into an organic molecule.

RuBisCO

Enzyme that catalyzes CO2 fixation by attaching CO2 to RuBP.

RuBP

Five

G3P

Three

Reduction phase of Calvin cycle

ATP and NADPH help convert fixed carbon into G3P.

Regeneration phase of Calvin cycle

ATP is used to regenerate RuBP.

Limiting factor

Factor that restricts the rate of a process.

Stomata

Plant pores that regulate gas exchange and water loss.

Guard cells

Cells that control the opening and closing of stomata.

Cellular respiration

Process that transfers energy from organic molecules to ATP.

Aerobic respiration

Respiration using oxygen as the final electron acceptor.

Glycolysis

Pathway that splits glucose into two pyruvate molecules, producing net ATP and NADH.

Glucose

Six

Pyruvate

Three

Pyruvate oxidation

Conversion of pyruvate into acetyl

Acetyl

CoA

Krebs cycle

Cycle that oxidizes acetyl groups, producing CO2, NADH, FADH2, and ATP equivalents.

Citric acid cycle

Another name for the Krebs cycle.

Oxidative phosphorylation

ATP production driven by electron transport and chemiosmosis.

Mitochondrion

Organelle where most aerobic respiration occurs in eukaryotes.

Mitochondrial matrix

Compartment where pyruvate oxidation and the Krebs cycle occur.

Inner mitochondrial membrane

Membrane containing the respiratory electron transport chain and ATP synthase.

Cristae

Folds of the inner mitochondrial membrane that increase surface area.

Intermembrane space

Space where protons accumulate during mitochondrial electron transport.

NAD+

Oxidized electron carrier that accepts electrons to become NADH.

NADH

Reduced electron carrier that supplies electrons to the respiratory electron transport chain.