Exam 2 Review – part one

Vocabulary flashcards covering key terms from the Exam 2 review on thermodynamics, metabolism, enzymes, cellular respiration, and membrane structure.

Sodium Gradient at Rest

Higher Na⁺ concentration outside the cell than inside, creating stored (potential) energy.

Potential Energy (in cells)

Energy stored in concentration or electrical gradients, such as the Na⁺ gradient across a membrane.

Triglycerides

Long-term energy-storage lipids composed of glycerol and three fatty acids.

Glucose

Six-carbon monosaccharide that serves as the primary fuel for cellular respiration.

ATP (Adenosine Triphosphate)

Immediate, readily usable energy currency of the cell.

Second Law of Thermodynamics

Energy transformations increase entropy; explains heat production like shivering.

Catabolism

All decomposition (break-down) reactions in the body that release energy (exergonic).

Anabolism

All synthesis (building) reactions in the body that require energy (endergonic).

Exergonic Reaction

Chemical reaction in which reactants have more energy than products, releasing energy.

Endergonic Reaction

Chemical reaction in which products store more energy than reactants, requiring an energy input.

Reduction

Gain of electrons (or H atoms); e.g., NAD⁺ → NADH is a reduction that stores energy.

Oxidation

Loss of electrons (or H atoms); usually releases energy.

NAD⁺

Electron carrier that becomes NADH after accepting two electrons and one proton.

NADH

Reduced form of NAD⁺; carries high-energy electrons to the electron-transport chain.

Enzyme Catalyst

Protein that accelerates a reaction by lowering its activation energy without being consumed.

Activation Energy

Energy barrier that must be overcome for a reaction to proceed; decreased by enzymes.

Beta-Oxidation

Process that converts fatty acids into acetyl-CoA units for entry into the Krebs cycle.

Citric Acid Cycle (Krebs Cycle)

Mitochondrial pathway that oxidizes acetyl-CoA, producing CO₂, NADH, FADH₂, and ATP.

ATP Synthase

Mitochondrial membrane enzyme that uses proton (H⁺) flow to phosphorylate ADP to ATP.

Proton Motive Force

Electrochemical gradient of H⁺ across the inner mitochondrial membrane driving ATP synthesis.

FADH₂

Electron carrier generated in the Krebs cycle; donates electrons to the electron-transport chain.

Pyruvate Dehydrogenase

Enzyme complex that converts pyruvate to acetyl-CoA, producing CO₂ and NADH in the intermediate stage.

Intermediate Stage (Pyruvate Oxidation)

Link between glycolysis and the Krebs cycle that forms acetyl-CoA and CO₂.

Glycolysis

Anaerobic breakdown of glucose to two pyruvate, yielding 2 ATP and 2 NADH; occurs in cytosol.

Stages of Cellular Respiration

1) Glycolysis 2) Pyruvate Oxidation 3) Citric Acid Cycle 4) Oxidative Phosphorylation.

Noncompetitive (Allosteric) Inhibitor

Molecule that binds an enzyme away from the active site, changing its shape and reducing activity; effect is substrate-concentration independent.

Optimal Temperature (Human Enzymes)

Approximately 37–40 °C; temperatures above this increase activity briefly, then denature proteins.

Protein Denaturation

Loss of a protein’s three-dimensional structure (and function) due to extreme heat or other factors.

Oxidoreductase

Enzyme class that catalyzes electron-transfer (redox) reactions.

Scanning Electron Microscope (SEM)

Microscope that images surface topography of specimens with high-resolution electron beams.

Cytosol

Intracellular fluid that surrounds organelles; site of many metabolic reactions.

Plasma Membrane

Phospholipid bilayer that regulates substance movement and separates the cell from its environment.

Cilia

Short, numerous membrane extensions that move fluid or mucus across a cell surface.

Flagellum

Long, singular membrane extension (e.g., sperm tail) that propels the cell.

Microvilli

Microscopic membrane folds that increase a cell’s surface area for absorption.

Phospholipid

Amphipathic molecule with hydrophilic head and hydrophobic tails; main component of membranes.

Integral Protein

Protein embedded within and spanning the phospholipid bilayer; often functions in transport or signaling.

Transport Protein

Membrane protein that aids the movement of ions or molecules across the plasma membrane.