Biology - Chapter 2 The Chemistry of Life

Complete Notes Set

Atom

Basic unit of matter; all matter is made of atoms

Democritus

Greek philosopher who proposed matter is made of indivisible particles

Proton

Positively charged subatomic particle found in the nucleus

Neutron

Neutral subatomic particle found in the nucleus

Electron

Negatively charged particle that moves around the nucleus

Atomic number

Number of protons in an atom; determines the element

Element

Pure substance made of only one type of atom

Isotope

Atoms of the same element with different numbers of neutrons

Mass number

Total number of protons and neutrons in an atom

Radioactive isotope

Isotope with an unstable nucleus that breaks down over time

Compound

Substance formed by chemically combining two or more elements in fixed ratios

Chemical formula

Shows the elements and proportions in a compound

Valence electrons

Electrons in the outermost energy level of an atom

Ionic bond

Bond formed by transfer of electrons between atoms

Ion

Charged atom formed by gaining or losing electrons

Cation

Positively charged ion

Anion

Negatively charged ion

Covalent bond

Bond formed when atoms share electrons

Molecule

Smallest unit of a covalent compound

Single covalent bond

Two electrons shared between atoms

Double covalent bond

Four electrons shared between atoms

Van der Waals forces

Weak attractions between nearby molecules due to temporary charges

Polarity

Uneven distribution of charge within a molecule

Water polarity

Oxygen is partially negative; hydrogens are partially positive

Hydrogen bond

Weak attraction between hydrogen and an electronegative atom

Cohesion

Attraction between molecules of the same substance

Adhesion

Attraction between molecules of different substances

Surface tension

Result of cohesive forces at a liquid’s surface

Capillary action

Movement of water upward due to cohesion and adhesion

Heat capacity

Ability to absorb heat without large temperature change

Solution

Mixture with evenly distributed solute particles

Solute

Substance that is dissolved

Solvent

Substance that does the dissolving

Universal solvent

Nickname for water because it dissolves many substances

Suspension

Mixture with undissolved particles that remain dispersed

pH scale

Measures concentration of hydrogen ions (0–14)

Acid

Substance that releases H⁺ ions

Base

Substance that produces OH⁻ ions

Buffer

Weak acid or base that resists changes in pH

Homeostasis

Maintenance of stable internal conditions

Carbon

valence element with four electrons; forms four covalent bonds

Organic compound

Carbon-based compound found in living things

Monomer

Small molecule that can bond to form polymers

Polymer

Large molecule made of repeating monomers

Isomer

Compounds with same formula but different structures

Macromolecule

Large biological molecule built from monomers

Carbohydrates

Macromolecules for quick energy; 1:2:1 C:H:O ratio

Monosaccharide

Simple sugar (e.g., glucose)

Polysaccharide

Complex carbohydrate (starch, glycogen, cellulose)

Lipids

Fats, oils, waxes; long-term energy and membranes

Saturated fat

Lipid with no double bonds; solid at room temperature

Unsaturated fat

Lipid with double bonds; liquid at room temperature

Protein

Macromolecule made of amino acids; structure and function

Amino acid

Building block of proteins

Peptide bond

Bond linking amino acids

Enzyme

Protein that speeds up chemical reactions

Active site

Region of enzyme where substrate binds

Nucleic acid

Macromolecule that stores genetic information

Nucleotide

Subunit of nucleic acids

DNA

Nucleic acid that stores genetic instructions

RNA

Nucleic acid involved in protein synthesis

Chemical reaction

Process that breaks and forms chemical bonds

Reactants

Starting materials of a chemical reaction

Products

Substances formed by a chemical reaction

Activation energy

Energy required to start a chemical reaction

Catalyst

Substance that lowers activation energy

Enzyme specificity

Each enzyme catalyzes only one reaction

Denaturation

Loss of enzyme shape due to temperature or pH changes

Optimal temperature

Temperature at which an enzyme works best

Optimal pH

pH at which an enzyme functions best