Key Concepts in Chemistry and Biology

Matter

Anything that occupies space and has mass.

Element

Substance that cannot be chemically broken down.

Compound

Substance of two or more elements in fixed ratio.

Essential elements

20-25% of 92 elements vital for life.

Living matter composition

96% carbon, hydrogen, oxygen, nitrogen.

Trace elements

Required in minute quantities by organisms.

Atom

Smallest unit of matter retaining element properties.

Subatomic particles

Components of atoms: neutrons, protons, electrons.

Atomic number

Number of protons in an element's nucleus.

Mass number

Sum of protons and neutrons in nucleus.

Atomic mass

Approximation based on mass number.

Isotopes

Atoms with same protons, different neutrons.

Radioactive isotopes

Decay spontaneously, emitting particles and energy.

Energy level

Electron's potential energy state in atom.

Valence electrons

Electrons in the outermost electron shell.

Chemical bonds

Attractions holding atoms together in molecules.

Covalent bond

Sharing a pair of valence electrons between atoms.

Molecule

Two or more atoms bonded covalently.

Single covalent bond

Sharing one pair of valence electrons.

Double covalent bond

Sharing two pairs of valence electrons.

Electronegativity

Atom's attraction for electrons in a bond.

Ionic bond

Attraction between an anion and a cation.

Hydrogen bond

Attraction between hydrogen and electronegative atom.

Van der Waals interactions

Attractions due to asymmetrical electron distribution.

Chemical reactions

Making and breaking of chemical bonds.

Reactants

Starting molecules in a chemical reaction.

Products

Final molecules in a chemical reaction.

Polar molecules

Molecules with opposite charges at different ends.

Polar molecules

Molecules with opposite charges at ends.

Hydrogen bonds

Attractions between polar water molecules.

Cohesion

Water molecules sticking together via hydrogen bonds.

Adhesion

Attraction between different substances.

Surface tension

Resistance to breaking a liquid's surface.

Specific heat

Heat needed to change 1g by 1ºC.

High specific heat of water

1 cal/g/°C; stabilizes temperature.

Evaporative cooling

Cooling effect when liquid evaporates.

Density of ice

Ice is less dense due to ordered hydrogen bonds.

Solution

Homogeneous mixture of substances in liquid.

Solvent

Dissolving agent in a solution.

Solute

Substance that is dissolved in a solution.

Aqueous solution

Solution where water is the solvent.

Hydrophilic substance

Substance with affinity for water.

Hydrophobic substance

Substance lacking affinity for water.

Hydronium ion (H3O+)

Formed when a water molecule gains a proton.

Hydroxide ion (OH-)

Formed when a water molecule loses a proton.

Acid

Substance that increases H+ concentration.

Base

Substance that reduces H+ concentration.

pH scale

Measures acidity or basicity of a solution.

Buffers

Minimize changes in H+ and OH- concentrations.

Polymer

Long molecule made of similar building blocks.

Monomer

Small building-block molecule of polymers.

Dehydration reaction

Bonds two monomers by losing a water molecule.

Hydrolysis

Breaks polymers into monomers by adding water.

Carbohydrates

Sugars and polymers of sugars.

Monosaccharides

Simplest carbohydrates, or single sugars.

Polysaccharides

Macromolecules made of many sugar units.

Disaccharide

Two monosaccharides joined by glycosidic linkage.

Starch

Storage polysaccharide in plants, made of glucose.

Glycogen

Storage polysaccharide in animals.

Cellulose

Structural polysaccharide in plant cell walls.

Chitin

Structural polysaccharide in arthropod exoskeletons.

Lipids

Diverse group of hydrophobic molecules.

Lipids

Large biological molecules that do not form polymers.

Hydrophobic

Property of lipids due to nonpolar hydrocarbons.

Fats

Biologically important lipids made from glycerol and fatty acids.

Glycerol

Three-carbon alcohol with hydroxyl groups on each carbon.

Fatty Acid

Molecule with a carboxyl group and long carbon skeleton.

Triacylglycerol

Fat formed by three fatty acids and glycerol.

Saturated Fatty Acids

Fatty acids with maximum hydrogen and no double bonds.

Unsaturated Fatty Acids

Fatty acids with one or more double bonds.

Saturated Fats

Fats that are solid at room temperature.

Unsaturated Fats

Fats that are liquid at room temperature.

Phospholipid

Lipid with two fatty acids and a phosphate group.

Steroids

Lipids with a carbon skeleton of four fused rings.

Proteins

Diverse structures that perform various cellular functions.

Enzymes

Proteins that act as catalysts in chemical reactions.

Polypeptides

Unbranched polymers made from 20 amino acids.

Amino Acids

Organic molecules with carboxyl and amino groups.

R Groups

Side chains that differ among amino acids.

Peptide Bonds

Links that connect amino acids in a polypeptide.

Primary Structure

Unique sequence of amino acids in a protein.

Secondary Structure

Coils and folds in a polypeptide chain.

Tertiary Structure

Protein structure determined by side chain interactions.

Quaternary Structure

Structure formed by multiple polypeptide chains.

Denaturation

Loss of a protein's native structure.

Chaperonins

Proteins that assist in proper protein folding.

Endomembrane System

Regulates protein traffic and metabolic functions.

Endoplasmic Reticulum (ER)

Membrane system accounting for half of eukaryotic cell membranes.

Smooth ER

Lacks ribosomes; synthesizes lipids and detoxifies.

Rough ER

Has ribosomes; secretes glycoproteins and distributes vesicles.

Golgi Apparatus

Modifies, sorts, and packages materials from the ER.

Lysosome

Membranous sac of enzymes for digesting macromolecules.

Vacuoles

Diverse compartments for maintenance in cells.

Mitochondria

Sites of cellular respiration in eukaryotic cells.

Chloroplasts

Sites of photosynthesis in plant cells.

Phospholipids

Most abundant lipids in the plasma membrane.

Phospholipids

Amphipathic molecules with hydrophobic and hydrophilic regions.

Fluid Mosaic Model

Membrane structure with embedded proteins.

Integral Proteins

Proteins that penetrate the membrane's hydrophobic core.

Transmembrane Proteins

Integral proteins spanning the entire membrane.