Honors Bio Unit 2 (AP Unit1)

covalent bond

A chemical bond formed when two atoms share electrons.

electron

A subatomic particle with a negative charge, located outside the nucleus.

electronegativity

A measure of an atom's ability to attract shared electrons in a covalent bond.

element

A substance that cannot be broken down into simpler substances by chemical means; defined by its atomic number.

ion

An atom or molecule that has acquired a net electric charge by gaining or losing one or more electrons.

ionic bond

A chemical bond formed through the electrostatic attraction between oppositely charged ions.

molecule

Two or more atoms held together by covalent bonds.

neutron

A subatomic particle with no electrical charge, located in the atomic nucleus.

proton

A subatomic particle with a positive electrical charge, located in the atomic nucleus.

adhesion

The clinging of one substance to a different substance, such as water to plant cell walls.

cohesion

The binding together of like molecules, often by hydrogen bonds.

hydrogen bond

A weak chemical bond formed when a slightly positive hydrogen atom is attracted to a slightly negative atom in another molecule.

polar

Describes a molecule with regions of partial positive and partial negative charge due to uneven electron sharing.

hydrophilic

Having an affinity for water; polar or charged substances that dissolve easily.

hydrophobic

Having an aversion to water; nonpolar, uncharged substances that exclude water.

surface tension

A measure of how difficult it is to stretch or break the surface of a liquid, caused by cohesion.

monomer

The subunit that serves as the building block of a polymer.

polymer

A long molecule consisting of many similar or identical building blocks linked by covalent bonds.

polymerization

The chemical process of combining monomers to form a polymer chain.

dehydration synthesis

A chemical reaction in which two molecules covalently bond with the removal of a water molecule.

hydrolysis

A chemical process that splits molecules by adding water, breaking covalent bonds.

monosaccharide

The simplest carbohydrate, acting as a monomer for disaccharides and polysaccharides (e.g., glucose).

polysaccharide

A polymer of many monosaccharides joined by dehydration reactions (e.g., starch, cellulose).

glycogen

An extensively branched glucose storage polysaccharide found in animals.

starch

A storage polysaccharide in plants consisting entirely of glucose monomers.

cellulose

A structural polysaccharide of plant cell walls consisting of glucose monomers with beta linkages.

glycerol

A three-carbon alcohol with hydroxyl groups, serving as the backbone of fats and phospholipids.

fatty acid

A carboxylic acid with a long carbon chain, found in lipids like fats and phospholipids.

saturated fatty acid

A fatty acid with only single bonds between carbons, maximizing hydrogen atoms.

unsaturated fatty acid

A fatty acid with one or more double bonds between carbons in the hydrocarbon tail.

phospholipid

A lipid made of glycerol, two fatty acids, and a phosphate group; forms cell membranes.

fat

A lipid consisting of three fatty acids linked to one glycerol molecule (triglyceride).

steroid

A lipid characterized by a carbon skeleton consisting of four fused rings (e.g., cholesterol).

cholesterol

A steroid that is a key component of animal cell membranes and a precursor for other steroids.

DNA

A double-stranded helical nucleic acid molecule that stores genetic information.

RNA

A single-stranded nucleic acid containing ribose and uracil, involved in protein synthesis.

nucleotide

The building block of a nucleic acid, consisting of a 5-carbon sugar, a nitrogenous base, and a phosphate group.

nitrogenous base

A nitrogen-containing organic base that is a subunit of nucleotides (A, T, C, G, U).

adenine

A purine nitrogenous base found in DNA and RNA, pairing with thymine or uracil.

guanine

A purine nitrogenous base found in DNA and RNA, pairing with cytosine.

cytosine

A pyrimidine nitrogenous base found in DNA and RNA, pairing with guanine.

thymine

A pyrimidine nitrogenous base found in DNA, pairing with adenine.

uracil

A pyrimidine nitrogenous base found in RNA (replaces thymine), pairing with adenine.

peptide bond

The covalent bond between the carboxyl group of one amino acid and the amine group of another.

carboxyl group

A chemical group (-COOH) present in organic acids and amino acids, acting as an acid.

amine group

A chemical group (-NH2) consisting of a nitrogen atom bonded to two hydrogen atoms, acting as a base.

R group

The variable side chain specific to each amino acid that determines its chemical properties.

primary structure

The specific linear sequence of amino acids in a polypeptide chain.

secondary structure

Local coils (alpha helices) and folds (beta sheets) formed by hydrogen bonding along the polypeptide backbone.

tertiary structure

The overall three-dimensional shape of a polypeptide due to R-group interactions.

quaternary structure

The overall protein structure resulting from the aggregation of two or more polypeptide subunits.