AP Biology Unit 1: The Molecular Basis of Life

Polarity

A characteristic of water molecules where the oxygen has a partial negative charge and the hydrogens have partial positive charges.

Hydrogen Bonds

Weak intermolecular forces that form between the partially positive hydrogen of one water molecule and the partially negative oxygen of another.

Cohesion

The property of water that allows water molecules to stick to each other, resulting in surface tension.

Adhesion

The property of water that allows it to stick to other polar surfaces, such as cell walls.

High Specific Heat

The property of water that allows it to resist changes in temperature by breaking hydrogen bonds first.

Expansion Upon Freezing

The phenomenon where ice is less dense than liquid water and floats, insulating water below.

Hydrophilic

Substances that are 'water-loving' and dissolve easily in water due to their polarity.

Hydrophobic

Substances that are 'water-fearing' and do not dissolve in water, often non-polar.

CHONPS

A mnemonic for the six major elements: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur, that make up 99% of living matter.

Dehydration Synthesis

A reaction that joins two monomers together by removing a water molecule, forming a covalent bond.

Hydrolysis

A reaction that breaks polymers apart by adding a water molecule, breaking covalent bonds.

Monosaccharides

The simplest form of carbohydrates, examples include glucose, fructose, and galactose.

Disaccharides

Carbohydrates formed by joining two monosaccharides through glycosidic linkages, examples include sucrose, maltose, and lactose.

Polysaccharides

Complex carbohydrates composed of long chains of monosaccharides.

Glycosidic Linkage

The bond formed between two monosaccharides during the formation of disaccharides.

Starch

A storage polysaccharide in plants made of alpha-glucose, used for energy storage.

Glycogen

A highly branched storage polysaccharide in animals, stored in liver and muscle, used for energy.

Cellulose

A structural polysaccharide made of beta-glucose, found in plant cell walls, providing support.

Chitin

A structural polysaccharide found in the exoskeletons of fungi and insects, consisting of glucose and a nitrogen group.

Triglycerides

A type of lipid composed of one glycerol and three fatty acids, used for energy storage.

Saturated Fats

Fats with all single bonds between carbons, solid at room temperature, and 'saturated' with hydrogen.

Unsaturated Fats

Fats that contain at least one double bond between carbons, liquid at room temperature, causing a 'kink' in the chain.

Phospholipids

Molecules that form the bilayer of cell membranes, consisting of one glycerol, two fatty acids, and one phosphate group.

Amphipathic

Molecules that have both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

Steroids

Lipids characterized by a carbon skeleton with four fused rings; examples include cholesterol and hormones.

Amino Acid

The monomer of proteins, consisting of a central carbon, an amino group, a carboxyl group, a hydrogen atom, and an R-group.

Peptide Bonds

Covalent bonds formed between amino acids during protein synthesis through dehydration synthesis.

Primary Structure

The unique linear sequence of amino acids in a protein determined by DNA.

Secondary Structure

Coiling and folding of the polypeptide chain stabilized by hydrogen bonds, forming structures like alpha-helices.

Tertiary Structure

The overall three-dimensional shape of a protein formed by interactions between R-groups.

Quaternary Structure

The arrangement of two or more polypeptide chains into a functional protein.

Denaturation

The process in which a protein loses its shape and function due to environmental changes (like temperature or pH).

Nucleotide

The monomer of nucleic acids, composed of a pentose sugar, phosphate group, and nitrogenous base.

DNA

Deoxyribonucleic Acid; a double-stranded nucleic acid that stores genetic information.

RNA

Ribonucleic Acid; a single-stranded nucleic acid involved in protein synthesis.

Chargaff's Rules

Rules describing the base pairing in DNA, where A pairs with T and G pairs with C.

Trace Elements

Elements required in minute amounts but are essential for biological functions.

Buffers

Substances that minimize changes in pH by accepting or donating hydrogen ions.

pH Scale

A measure of hydrogen ion concentration, indicating how acidic or basic a solution is.

Biological Macromolecules

Large molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids.

Hydrocarbon

An organic molecule consisting only of carbon and hydrogen; typically non-polar and hydrophobic.

Isomer

Compounds with the same molecular formula but different structures and properties.

Hydrogen Ion ($H^+$)

A positively charged ion that influences the acidity of a solution.

Covalent Bond

A type of strong bond formed when two or more atoms share electrons.

Electronegativity

The tendency of an atom to attract electrons towards itself, affecting bond polarity.

Macromolecules

Large and complex molecules, such as proteins, nucleic acids, carbohydrates, and lipids, crucial for biological function.

Homeostasis

The maintenance of stable internal conditions within an organism.