Biology: Energy, Thermodynamics, and Cellular Respiration Key Concepts

Kinetic energy

Energy of motion.

Potential energy

Stored energy due to position or structure.

First law of thermodynamics

Energy cannot be created or destroyed, only transformed.

Second law of thermodynamics

Energy transfers increase entropy (disorder).

Entropy

Measure of disorder or randomness.

Exergonic

Releases energy (spontaneous).

Endergonic

Requires energy input (non-spontaneous).

Energetic coupling

Using exergonic reactions to drive endergonic ones.

Redox reactions

Transfer of electrons between molecules.

Oxidation

Loss of electrons.

Reduction

Gain of electrons.

Electron donor

Substance that gives electrons (oxidized).

Electron acceptor

Substance that gains electrons (reduced).

FAD

Electron carrier (oxidized form). F

FADH2

Reduced electron carrier. F

NAD+

Electron carrier (oxidized form). N

NADH

Reduced electron carrier. N

ATP

Main energy currency of the cell.

ADP

Lower-energy form of ATP.

GTP

Energy molecule similar to ATP.

GDP

Lower-energy form of GTP.

Phosphorylation

Adding a phosphate group to a molecule.

Enzyme

Protein that speeds up reactions.

Activation energy

Energy needed to start a reaction.

Transition state

High-energy intermediate state.

Catalyst

Substance that speeds up reactions without being consumed.

Catalysis

Process of speeding up a reaction.

Substrate

Reactant an enzyme acts on.

Product

Molecule formed from a reaction.

Active site

Region of enzyme where substrate binds.

Induced fit

Enzyme changes shape to better fit substrate.

Cofactors

Inorganic helpers for enzymes.

Coenzymes

Organic enzyme helpers (often vitamins).

Prosthetic groups

Tightly bound cofactors.

Competitive inhibition

Inhibitor competes with substrate for active site.

Allosteric regulation

Regulation by binding away from active site.

Metabolic pathways

Series of chemical reactions.

Metabolism

All chemical reactions in a cell.

Metabolic intermediates

Molecules formed during pathways.

Catabolism

Breakdown of molecules releasing energy.

Anabolism

Building molecules requiring energy.

Feedback inhibition

End product shuts down pathway.

Cellular respiration

Process of making ATP from glucose using oxygen.

Glucose

Main fuel molecule (C6H12O6).

Glycolysis

Breaks glucose into pyruvate.

Pyruvate oxidation

Process that converts pyruvate to acetyl-CoA.

Citric acid cycle

Produces NADH and FADH2 from acetyl-CoA.

Electron transport chain

Transfers electrons to create H+ gradient.

Oxidative phosphorylation

ATP production using ETC and chemiosmosis.

Substrate-level phosphorylation

Direct ATP formation by enzymes.

Hexokinase

Enzyme that phosphorylates glucose.

Phosphofructokinase

catalyzes phosphoylation of fructose 6 phosphate to fructose 1,6 bisphosphate

Dehydrogenase

oxidizes, and glyceraldahyde-3-phosphate to 1,3-bisphosphoglycerate

Mitochondria

Organelle where respiration occurs.

Mitochondrial matrix

Inner space where Krebs cycle occurs.

Outer mitochondrial membrane

Outer boundary of mitochondria.

Inner mitochondrial membrane

Location of ETC.

Intermembrane space

Space where H+ accumulates.

Pyruvate

Product of glycolysis.

Pyruvate dehydrogenase

Enzyme converting pyruvate to acetyl-CoA.

Acetyl-CoA

Molecule entering Krebs cycle.

Coenzyme Q

Q Electron shuttle in ETC.

Cytochrome c

Electron shuttle in ETC. C

Complex I

1st ETC protein that pumps H+.

Complex II

2nd ETC protein involved in electron transfer.

Complex III

3 ETC protein that pumps H+.

Complex IV

ETC protein that pumps H+ and forms water.

Proton gradient

Stored energy across membrane.

ATP synthase

Enzyme that produces ATP using H+ flow.

Chemiosmosis

Movement of H+ to drive ATP production.

Fermentation

ATP production without oxygen.

Anaerobic

Without oxygen.

Lactic acid fermentation

Produces lactate.

Ethanol fermentation

Produces alcohol and CO2.

Photosynthesis

Process of converting light energy to chemical energy.

Autotrophs

Organisms that make their own food.

Heterotrophs

Organisms that consume others.

Chloroplasts

Organelle where photosynthesis occurs.

Thylakoids

Membrane sacs for light reactions.

Thylakoid membrane

Contains chlorophyll and ETC.

Stroma

Fluid where Calvin cycle occurs.

Light

Electromagnetic radiation from the sun.

Wavelength

Distance between wave peaks.

Electromagnetic spectrum

Full range of light.

Visible light

Light humans can see.

Photon

Particle of light energy.

Chlorophyll

Pigment that absorbs light.

Carotenoids

Accessory pigments.

Absorption spectrum

Light wavelengths absorbed.

Photosystem II

Splits water and releases oxygen.

Photosystem I

Produces NADPH.

Photophosphorylation

ATP production using light energy.

Calvin cycle

Process that makes sugar using ATP and NADPH.

NADP+

Electron carrier in photosynthesis (oxidized).

NADPH

Electron carrier (reduced).

Rubisco

Enzyme that fixes CO2.

RuBP

CO2 acceptor molecule.

Carbon fixation

Incorporating CO2 into organic molecules.

G3P

Sugar produced in Calvin cycle.