AP Bio Unit 1: Molecular Structure

Element

A substance consisting of one type of atom, e.g., Carbon.

Compound

A substance made of two or more different atoms, e.g., CO2.

Proton

A positively charged subatomic particle found in the nucleus, contributing to atomic number.

Neutron

A neutral subatomic particle in the nucleus that stabilizes the atom.

Electron

A negatively charged subatomic particle that forms bonds.

Nonpolar bond

A bond where electrons are evenly shared, typically between the same element.

Polar bond

A bond where electrons are unevenly shared, often between elements far apart on the periodic table.

Covalent bond

A bond formed by the sharing of electrons, can be single or double.

Ionic bond

A bond formed by the transfer of electrons, resulting in partially positive and negative charges.

Hydrogen bond

A weak bond involving hydrogen and electronegative atoms (N, O, F), typically between water molecules.

Cohesion

The attraction between water molecules.

Adhesion

The attraction between water and polar surfaces.

High heat of vaporization

Water's high boiling point due to strong hydrogen bonds.

High specific heat

Water's resistance to temperature change.

Densest at 4 degrees Celsius

Water is most dense at this temperature, unlike most substances.

Hydrophilic

Molecules that are water-loving, polar, and asymmetrical.

Hydrophobic

Molecules that are water-fearing, nonpolar, and symmetrical.

Acid

A substance with a pH under 7 that donates H+ ions.

Base

A substance with a pH over 7 that accepts H+ ions.

pH calculation

pH = -log [H+], with [OH-][H+] = 10^-14M.

Carbohydrates

Polymers made of simple sugars, composed of CHO.

Proteins

Polymers made of amino acids, composed of CHON.

Nucleic acids

Polymers made of nucleotides, composed of CHONP.

Lipids

Polymers made of fatty acids, composed of CHO.

Saturated fatty acids

Fatty acids with hydrocarbon chains connected by single bonds.

Unsaturated fatty acids

Fatty acids with one or more double bonds in their chains.

Amine group

A functional group containing nitrogen (NH2, NH3).

Carboxyl group

A functional group containing COOH, associated with acids.

Dehydration reaction

A process that removes water to form polymers from monomers.

Hydrolysis

A process that adds water to break polymers into monomers.

Primary protein structure

A linear sequence of amino acids linked by peptide bonds.

Secondary protein structure

The folding of a polypeptide chain into alpha helices or beta sheets due to hydrogen bonds.

Tertiary protein structure

The overall 3D shape of a single polypeptide chain, stabilized by various interactions among R groups.

Quaternary protein structure

The arrangement of multiple polypeptide chains into a functional protein.

Cohesion-tension hypothesis

Explains how water moves upward in plants due to cohesion between water molecules.

Stomata

Pores on leaves that regulate gas exchange and transpiration.

Guard cells

Cells that control the opening and closing of stomata based on water availability.

Error bars

Graphical representation of variability in data; non-overlapping error bars indicate significant differences.

Standard error of the mean (SEM)

A measure of how much the sample mean is expected to vary, calculated as SEM = s/√n.

Percent change in mass

A formula to calculate the change in mass as a percentage:(Final Mass - Initial Mass) / Initial Mass × 100.