Biochemistry Study Notes (Lecture Transcript) 4

Vocabulary flashcards covering key terms from the lecture notes on pH, measurement units, energy, chemical reactions, metabolism, and organic molecules.

pH scale

A 0–14 scale that measures acidity or basicity of a solution; below 7 is acidic, above 7 is basic, 7 is neutral.

Weight per volume

Mass of solute per volume of solution; e.g., 8.5 g NaCl per 1 L of solution.

mg/dL

Milligrams per deciliter; common concentration unit in body fluids (e.g., cholesterol ~200 mg/dL).

Percent solution

Percent by weight/volume; e.g., 5% dextrose means 5 g solute per 100 mL solution.

Molarity

Number of moles of solute per liter of solution; a common concentration unit.

Mole

Amount of substance containing 6.022×10^23 entities; mass in grams equals the substance’s molecular weight.

Millimolar (mM)

Concentration of millimoles per liter; common in biological systems.

Milliequivalents per liter (mEq/L)

Electrolyte concentration that accounts for charge; used in IV fluids and nervous/muscle function.

Kinetic energy

Energy of motion; does work; e.g., muscles moving.

Potential energy

Stored energy that can do work; e.g., water behind a dam or chemical bonds.

Chemical energy

Energy stored in chemical bonds within molecules.

Free energy

Energy available to do work in a system (Gibbs free energy).

ATP

Adenosine triphosphate; cellular energy currency used for muscle contraction and other work.

Endergonic

Reactions that require energy input; energy-consuming.

Exergonic

Reactions that release energy; energy-producing.

Redox reaction

Oxidation–reduction reaction; transfer of electrons between substances.

Oxidation

Loss of electrons by a molecule; oxidized species.

Reduction

Gain of electrons by a molecule; reduced species.

Oxidizing agent

Substance that accepts electrons; becomes reduced.

Reducing agent

Substance that donates electrons; becomes oxidized.

Chemical reaction

Process where bonds are broken and formed; reactants on the left, products on the right.

Decomposition

Large molecule breaks into smaller components.

Synthesis

Two or more small molecules combine to form a larger one.

Exchange

Atoms or groups swap partners between reactants.

Reversible reaction

Reaction that can proceed in either direction; shown with a double-headed arrow; equilibrium may be reached.

Buffer

Substance that resists changes in pH; often part of a system like carbonic acid–bicarbonate in the body.

Carbonic acid–bicarbonate buffer

CO2 + H2O ⇌ H2CO3 ⇌ HCO3− + H+; shifts left/right to maintain pH.

Equilibrium

State where forward and reverse reaction rates are equal; concentrations become stable.

Law of mass action

Reaction rates depend on the concentrations of reactants; higher concentrations drive the reaction.

Catalyst

Substance that speeds up a reaction without being consumed; enzymes are biological catalysts.

Enzyme

Protein that acts as a catalyst; lowers activation energy of a reaction.

Metabolism

All chemical reactions occurring in the body; includes catabolism and anabolism.

Catabolic

Decomposition; large molecules break down, releasing energy.

Anabolic

Builds larger molecules; absorbs energy (endergonic).

Dehydration synthesis

Joining monomers by removing a water molecule to form a polymer.

Monomer

Smallest unit that can join to form a polymer (e.g., glucose, amino acid).

Polymer

Large molecule made of repeating monomer units (e.g., starch, DNA).

Macromolecule

Large organic molecule; usually a polymer with high molecular weight.

Major organic macromolecules

The four main types: carbohydrates, lipids, proteins, and nucleic acids.

Moiety

A component or part of a larger molecule.

Hydroxyl group

OH group; common in sugars and alcohols.

Phosphate group

Group H2PO4; found in nucleic acids and ATP.