Matter, Water, pH, Buffers & Cellular Transport – Week 3 Vocabulary

A comprehensive set of vocabulary flashcards covering matter, water properties, acid–base chemistry, biomolecules, enzymes, and membrane transport mechanisms as presented in the Week 3 Biochemistry lecture.

Matter

Anything that has mass, occupies space, and is composed of atoms.

Atom

Smallest unit of an element that retains the element’s identity.

Element

Pure substance consisting of only one kind of atom.

Compound

Substance made of two or more different atoms in a fixed ratio.

Molecule

Smallest unit of a compound that retains its chemical properties.

Solid

State of matter with fixed shape and volume.

Liquid

State of matter with fixed volume but shape of its container.

Gas

State of matter with neither fixed shape nor fixed volume.

Water (H₂O)

Polar molecule composed of two hydrogens covalently bonded to oxygen.

Polar Molecule

Molecule with uneven distribution of charge, having positive and negative ends.

Hydrogen Bond

Weak attraction between a hydrogen in one polar molecule and an electronegative atom in another.

Cohesion

Attraction between like molecules; causes surface tension in water.

Adhesion

Attraction between unlike substances; enables capillary action.

Surface Tension

Measure of the strength of water’s surface film due to cohesion.

Capillary Action

Movement of water up narrow tubes through cohesion and adhesion.

Specific Heat

Heat needed to raise 1 g of a substance by 1 °C.

Heat of Vaporization

Energy required to convert 1 g of liquid to gas; high for water (≈540 cal).

Density Anomaly of Water

Ice is less dense than liquid water because of hydrogen-bonded lattice.

Solution

Homogeneous mixture in which solute is evenly dispersed in solvent.

Solvent

Substance (often water) that dissolves a solute.

Solute

Substance dissolved in a solvent.

Suspension

Mixture with undissolved particles dispersed but not settled in a fluid.

Acid

Substance that releases H⁺ ions in solution; pH < 7.

Base

Substance that provides OH⁻ ions or accepts H⁺; pH > 7.

pH

Log scale indicating H⁺ concentration; 0 (acidic) to 14 (basic), 7 neutral.

Buffer

Weak acid/base system that resists sudden pH changes by neutralization.

Carbon

Element with four valence electrons that forms diverse organic compounds.

Macromolecule

Very large molecule formed by polymerization of smaller units.

Polymerization

Chemical process that joins monomers to form polymers.

Monomer

Small repeating unit that builds polymers.

Carbohydrate

Organic compound of C, H, O; primary energy source; includes sugars and starches.

Monosaccharide

Single sugar unit such as glucose, fructose, or galactose.

Polysaccharide

Many-sugar macromolecule; e.g., starch, glycogen, cellulose.

Starch

Plant: polysaccharide used for energy storage.

Glycogen

Animal: polysaccharide for glucose storage in liver and muscle.

Lipid

Hydrophobic organic molecule mainly of C and H; includes fats, oils, waxes.

Fatty Acid

Long hydrocarbon chain with carboxyl group; building block of many lipids.

Saturated Fat

Lipid whose fatty acids contain only single C–C bonds.

Unsaturated Fat

Lipid with at least one C=C double bond in fatty acids.

Polyunsaturated Fat

Lipid with multiple C=C double bonds in fatty acids.

Protein

Polymer of amino acids; performs structural, enzymatic, transport roles.

Amino Acid

Monomer containing amino, carboxyl, and variable R-group; builds proteins.

Nucleic Acid

Polymer of nucleotides that stores and transmits genetic information.

Nucleotide

Monomer of nucleic acids: 5-carbon sugar, phosphate, nitrogenous base.

DNA

Deoxyribonucleic acid; double-stranded molecule carrying hereditary code.

RNA

Ribonucleic acid; single-stranded molecule involved in protein synthesis.

Chemical Reaction

Process that changes reactants into products by making/breaking bonds.

Reactant

Substance that enters a chemical reaction.

Product

Substance formed by a chemical reaction.

Activation Energy

Minimum energy required to start a reaction.

Catalyst

Substance that lowers activation energy and speeds a reaction without being consumed.

Enzyme

Protein catalyst that accelerates cellular reactions.

Substrate

Reactant on which an enzyme acts.

Enzyme-Substrate Complex

Temporary association where substrate binds enzyme’s active site.

Homeostasis

Maintenance of stable internal conditions despite external changes.

Cell Membrane

Phospholipid bilayer with selective permeability controlling substance passage.

Selective Permeability

Property allowing some molecules to cross membrane more easily than others.

Passive Transport

Movement of substances across membrane without energy input.

Diffusion

Net movement of particles from high to low concentration down gradient.

Concentration Gradient

Difference in solute concentration between two regions.

Osmosis

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

Isotonic Solution

Solution with solute concentration equal to cell cytoplasm; no net water change.

Hypotonic Solution

Solution with lower solute concentration than cell; water enters, cell may swell or lyse.

Hypertonic Solution

Solution with higher solute concentration than cell; water leaves, cell shrinks (crenates).

Facilitated Diffusion

Passive transport aided by membrane proteins (channels or carriers).

Membrane Channel

Protein tunnel allowing specific ions/molecules to cross membrane.

Carrier Molecule

Membrane protein that binds and transports specific solutes across membrane.

Active Transport

Energy-requiring movement of substances against concentration gradient via carrier proteins.

Sodium-Potassium Pump

ATP-driven pump moving 3 Na⁺ out and 2 K⁺ into cells to maintain gradients.

Secondary Active Transport

Coupled transport using gradient made by primary active transport to move another substance.

Cotransport

Secondary transport where substances move in same direction across membrane.

Countertransport

Secondary transport where substances move in opposite directions.

Endocytosis

Energy-using process that engulfs material into vesicles from the plasma membrane.

Phagocytosis

“Cell eating” form of endocytosis for large particles or organisms.

Pinocytosis

“Cell drinking” endocytosis of extracellular fluid and dissolved solutes.

Receptor-Mediated Endocytosis

Selective uptake triggered by ligand binding to membrane receptors.

Exocytosis

Process where vesicles fuse with membrane to release contents outside the cell.