unit 2 BIOL200

Energy

Capacity to do work, cause change, or supply heat.

Kinetic energy

Energy of motion.

Potential energy

Stored energy due to position or structure.

Chemical energy

Potential energy stored in molecular structure and chemical bonds.

First law of thermodynamics

Energy cannot be created or destroyed; it can only change form.

Second law of thermodynamics

Energy transfers increase the entropy of the universe overall; some usable energy becomes dispersed as heat.

Entropy

Measure of disorder or energy dispersal.

Free energy (G)

Energy available to do work; the course equation is G = H − TS.

Exergonic reaction

Reaction with negative ΔG that releases free energy.

Endergonic reaction

Reaction with positive ΔG that requires an energy input.

Spontaneous reaction

Thermodynamically favorable without continuous external energy input; not necessarily fast.

Activation energy

Energy needed to reach the transition state and initiate a reaction.

Catalyst

Substance that speeds a reaction by lowering activation energy and is not consumed.

Enzyme

Biological catalyst; most are proteins, while some RNA molecules are ribozymes.

Substrate

Reactant that binds to an enzyme.

Active site

Enzyme region where substrate binds and catalysis occurs.

Enzyme-substrate complex

Temporary association of an enzyme and its substrate.

Induced fit

Substrate binding changes or stabilizes enzyme shape to help catalysis.

Cofactor

Non-protein helper, often a metal ion, required by some enzymes.

Coenzyme

Organic cofactor; NAD+ is an important electron-carrying coenzyme.

Competitive inhibition

An inhibitor competes with substrate for the enzyme's active site.

Noncompetitive inhibition

An inhibitor binds away from the active site and changes enzyme activity.

Allosteric site

Regulatory site distinct from an enzyme's active site.

Allosteric inhibitor

Molecule that binds an allosteric site and decreases enzyme activity.

Allosteric activator

Molecule that binds an allosteric site and increases enzyme activity.

Feedback inhibition

A pathway's end product inhibits an early enzyme to prevent overproduction and waste.

Metabolism

The total of all chemical reactions in an organism.

Anabolism

Building larger or more complex molecules; usually requires energy.

Catabolism

Breaking down molecules and harvesting energy.

OIL RIG

Oxidation Is Loss of electrons; Reduction Is Gain of electrons.

Oxidation

Loss of electrons.

Reduction

Gain of electrons.

ATP

Adenosine triphosphate; the cell's short-term energy currency, made of adenine, ribose, and three phosphate groups.

ATP hydrolysis

ATP + H2O → ADP + Pi + released free energy.

Phosphorylation

Addition of a phosphate group to a molecule.

Phospholipid

Amphipathic membrane molecule with a hydrophilic head and hydrophobic fatty-acid tails.

Amphipathic

Having both hydrophilic and hydrophobic regions.

Phospholipid bilayer

Two layers of phospholipids with heads facing watery environments and tails facing inward.

Fluid mosaic model

Model describing a dynamic phospholipid bilayer containing proteins and other components.

Selective permeability

A membrane's ability to allow some substances to cross more readily than others.

Integral membrane protein

Protein embedded in the membrane; some span the entire bilayer.

Peripheral membrane protein

Protein attached to one side of a membrane or to another membrane component.

Glycoprotein

Protein with attached carbohydrate groups; can participate in cell recognition.

Glycolipid

Membrane lipid with attached carbohydrate groups; can participate in cell recognition.

Diffusion

Net movement of particles from higher to lower concentration.

Simple diffusion

Passive movement directly through the lipid bilayer, especially for small nonpolar molecules.

Facilitated diffusion

Passive movement down a concentration/electrochemical gradient through a channel or carrier protein.

Channel protein

Membrane protein that forms a hydrophilic passage for selected substances.

Carrier protein

Protein that binds a specific substance and changes shape to move it across a membrane.

Osmosis

Net diffusion of water across a selectively permeable membrane toward higher solute concentration.

Hypertonic solution

Solution with higher solute concentration than the comparison solution; water tends to move toward it.

Hypotonic solution

Solution with lower solute concentration than the comparison solution.

Isotonic solutions

Solutions with equal effective solute concentrations; no net water movement.

Passive transport

Transport down a concentration/electrochemical gradient without direct energy expenditure.

Active transport

Energy-dependent transport against a concentration gradient.

Uniporter

Transport protein that moves one type of substance at a time.

Symporter

Transport protein that moves two substances in the same direction.

Antiporter

Transport protein that moves two substances in opposite directions.

Sodium-potassium pump

ATP-powered antiporter that moves 3 Na+ out and 2 K+ into the cell per cycle.

Electrochemical gradient

Combined effect of a concentration difference and an electrical charge difference across a membrane.

Cellular respiration

Process that harvests energy from organic molecules and transfers some of it to ATP.

Aerobic respiration equation

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O, with energy captured in ATP and released as heat.

Glycolysis

Cytoplasmic pathway that converts one glucose into two pyruvate, producing net 2 ATP and 2 NADH.

Glycolysis location

Cytoplasm.

Glycolysis net ATP yield

2 ATP per glucose.

Pyruvate

Three-carbon product of glycolysis.

Pyruvate processing

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

Acetyl-CoA

Two-carbon acetyl group attached to coenzyme A; enters the citric acid cycle.

Citric acid cycle location

Mitochondrial matrix in eukaryotic cells.

Citric acid cycle yield per acetyl-CoA

2 CO2, 3 NADH, 1 FADH2, and 1 ATP/GTP.

NAD+

Oxidized electron carrier that can accept electrons and become NADH.

NADH

Reduced electron carrier that carries high-energy electrons to the ETC.

FAD

Oxidized electron carrier that can accept electrons and become FADH2.

FADH2

Reduced electron carrier that donates electrons to the ETC through Complex II.

Electron transport chain (ETC)

Series of membrane-bound electron carriers that pass electrons and use released energy to pump protons.

ETC location in eukaryotes

Inner mitochondrial membrane, including the cristae.

Final electron acceptor in aerobic respiration

Oxygen (O2).

Why oxygen is needed for respiration

Oxygen accepts electrons at the end of the ETC, allowing electron transport to continue and water to form.

Chemiosmosis

Use of energy stored in a proton gradient as protons flow through ATP synthase.

Proton gradient in mitochondria

H+ accumulates in the intermembrane space relative to the matrix.

ATP synthase

Enzyme that uses proton flow down an electrochemical gradient to make ATP from ADP + Pi.

Oxidative phosphorylation

ATP production using the ETC-generated proton gradient and ATP synthase.

Substrate-level phosphorylation

ATP formation by direct transfer of a phosphate group from a substrate to ADP.

Water formation in cellular respiration

Oxygen accepts electrons and combines with H+ to form water at the end of the ETC.

Fermentation

Pathway that regenerates NAD+ by transferring electrons from NADH to an organic molecule when oxygen is unavailable.

Purpose of fermentation

Regenerate NAD+ so glycolysis can continue.

Lactic acid fermentation

Pyruvate accepts electrons from NADH and becomes lactate; NAD+ is regenerated.

Alcoholic fermentation first step

Pyruvate is converted to acetaldehyde and CO2.

Alcoholic fermentation second step

Acetaldehyde accepts electrons from NADH to become ethanol, regenerating NAD+.

ATP yield supported by fermentation

Net 2 ATP per glucose from glycolysis; fermentation itself does not add a separate ATP yield.

Effect of no oxygen on ETC

O2 cannot accept electrons, electron flow backs up, and oxidative ATP production decreases.

Rotenone

Inhibits Complex I of the mitochondrial ETC, reducing electron entry from NADH and tending to reduce proton pumping and oxidative ATP production.

Effect of high ATP on respiration

Signals energy abundance and inhibits key regulatory enzymes, slowing unnecessary ATP production.

Photosynthesis

Process that captures light energy and stores it as chemical energy in carbohydrates.

Photosynthesis equation

Light energy + 6 CO2 + 6 H2O → C6H12O6 + 6 O2.

Chloroplast stroma

Fluid region outside thylakoids; contains enzymes for the Calvin cycle/carbohydrate synthesis.

Thylakoid membrane

Contains chlorophyll, photosystems, electron transport components, and ATP synthase.

Thylakoid lumen

Space inside thylakoids where H+ accumulates during light-dependent reactions.

Granum

Stack of thylakoids.

Light-dependent reactions location

Thylakoid membrane of the chloroplast.