AP BIO UNIT 1

Elements

Substances that cannot be broken down into simpler substances by chemical means.

Oxygen (O)

An essential element for life, used to build biological molecules.

Carbon (C)

A versatile element that forms the backbone of organic compounds.

Hydrogen (H)

A common element in biological molecules, including water.

Nitrogen (N)

An element essential for proteins and nucleic acids.

Trace elements

Elements required in very small amounts, like iron (Fe) or iodine (I).

Atom

The smallest unit of an element that retains its characteristic properties.

Protons

Positively charged subatomic particles in the nucleus of an atom.

Neutrons

Uncharged subatomic particles in the nucleus of an atom.

Electrons

Negatively charged subatomic particles that orbit the nucleus.

Nucleus

The central core of an atom containing protons and neutrons.

Isotopes

Atoms of the same element with different numbers of neutrons.

Radiometric dating

A method to determine the age of an object using isotopes (simplified definition).

Compound

A substance made of two or more elements combined in a fixed ratio.

Chemical reaction

A process in which atoms are rearranged to form new substances.

Chemical bond

A force that holds atoms together in a compound.

Ionic bond

A bond formed when electrons are transferred between atoms, creating charged ions.

Covalent bond

A bond formed when electrons are shared between atoms.

Hydrogen bond

A weak bond between a hydrogen atom and an electronegative atom of another molecule.

Ions

Charged atoms formed by the loss or gain of electrons.

Nonpolar covalent

A covalent bond in which electrons are shared equally.

Polar covalent

A covalent bond in which electrons are shared unequally.

Polar

A molecule with partially positive and partially negative charges.

Cohesion

The attraction between molecules of the same substance (e.g., water sticking to water).

Adhesion

The attraction between molecules of different substances (e.g., water sticking to glass).

Surface tension

The tight “skin” on the surface of water caused by cohesion.

High heat capacity

Water’s ability to absorb and retain heat without a large temperature change.

Expansion on freezing

Water expands as it freezes, unlike most substances.

Adhesive

A substance or force that makes molecules stick to other surfaces.

Capillary action

The movement of water up narrow tubes due to cohesion and adhesion.

Glycerol

A three-carbon molecule that forms the backbone of triglycerides.

Acidic

A solution that has a high concentration of H+ ions.

Basic

A solution that has a high concentration of OH- ions.

Neutral

A solution with equal concentrations of H+ and OH- ions (pH = 7).

Alkaline

Another term for a basic solution.

pH scale

A scale from 0

Organic compounds

Compounds containing carbon and hydrogen, usually associated with life.

Inorganic compounds

Compounds that do not contain both carbon and hydrogen.

Polymer

A large molecule made of repeated smaller units (monomers).

Monomer

The building block of a polymer.

Dehydration synthesis

A reaction that joins monomers together by removing water.

Condensation

Another term for dehydration synthesis.

Hydrolysis

A reaction that breaks down polymers into monomers using water.

Carbohydrates

Organic molecules made of C, H, and O, usually in a 1:2:1 ratio.

Monosaccharides

Simple sugars, such as glucose and fructose.

Disaccharides

Sugars formed from two monosaccharides, e.g., sucrose.

Polysaccharides

Large carbohydrates made of many monosaccharides, e.g., starch, glycogen, cellulose.

Glucose

A monosaccharide that serves as the main energy source for cells.

Fructose

A monosaccharide commonly found in fruits.

Glycosidic linkage

The bond formed between monosaccharides in a disaccharide or polysaccharide.

Starch

A polysaccharide used by plants to store energy.

Cellulose

A polysaccharide that provides structural support in plant cell walls.

Glycogen

A polysaccharide used by animals to store energy.

Amino acids

Organic molecules that are the building blocks of proteins.

Amino group

The -NH2 group in an amino acid.

Carboxyl group

The -COOH group in an amino acid.

R-group / Side chain

The variable part of an amino acid that determines its properties.

Hydrophobic

Nonpolar molecules that repel water.

Hydrophilic

Polar molecules that attract water.

Ionic (amino acids)

Amino acids with a charged side chain.

Dipeptide

A molecule formed by two amino acids joined by a peptide bond.

Peptide bond

The bond connecting amino acids in a protein.

Polypeptide

A chain of many amino acids linked by peptide bonds.

Protein

A folded polypeptide that performs biological functions.

Primary structure

The linear sequence of amino acids in a protein.

Secondary structure

The coiled or folded structure of a polypeptide (alpha helix or beta sheet).

Tertiary structure

The 3D shape of a polypeptide due to interactions among R-groups.

Quaternary structure

The structure formed when multiple polypeptides join together.

Chaperone proteins (chaperonins)

Proteins that help other proteins fold correctly.

Lipids

Nonpolar organic molecules used for energy storage, membranes, and signaling.

Triglycerides

Lipids made of glycerol and three fatty acids.

Phospholipids

Lipids with two fatty acid tails and a phosphate head; form cell membranes.

Steroids

Lipids with four fused carbon rings, including cholesterol and hormones.

Ester linkage

The bond connecting glycerol and fatty acids in lipids.

Saturated

Fatty acids with no double bonds; solid at room temperature.

Unsaturated

Fatty acids with one or more double bonds; liquid at room temperature.

Polyunsaturated

Fatty acids with many double bonds.

Amphipathic molecule

A molecule with both hydrophobic and hydrophilic regions.

Cholesterol

A steroid that affects membrane fluidity and is used in hormone production.

Nucleic acids

Organic molecules made of nucleotides, including DNA and RNA.

Nucleotides

Monomers of nucleic acids, composed of a sugar, phosphate, and nitrogenous base.

Deoxyribonucleic acid (DNA)

Nucleic acid that stores hereditary information.

Ribonucleic acid (RNA)

Nucleic acid essential for protein synthesis.