AP Biology Exam Study Guide: Unit 1 Chemistry of Life

A comprehensive vocabulary review of Unit 1: Chemistry of Life for AP Biology, covering properties of water, macromolecule structure and function, and biological reactions.

Atom

The smallest unit of matter that retains the properties of an element.

Element

A substance consisting of only one type of atom.

Molecule

A substance formed by two or more atoms held together by chemical bonds.

Covalent Bond

A chemical bond formed when atoms share electrons.

Polar Covalent Bond

A type of covalent bond in which electrons are shared unequally between atoms.

Polarity

The uneven distribution of electrical charge within a molecule.

Hydrogen Bond

A relatively weak attraction involving a partially positive hydrogen atom and an electronegative atom.

Cohesion

The attraction between water molecules that helps maintain a continuous column of water as it moves through plant tissues.

Adhesion

The attraction between water molecules and other substances, enabling water to cling to the walls of narrow tubes.

Capillary Action

The movement of water through narrow tubes, driven partly by the combined effects of adhesion and cohesion.

Surface Tension

The resistance of water molecules to being separated at the surface.

Heat Capacity

The property of water requiring a relatively large amount of energy to change temperature, allowing organisms to resist rapid temperature changes.

Ice

The solid form of water, which is less dense than liquid water.

Density

The amount of mass contained in a given volume of a substance.

Dissolution

The process in which a substance becomes dispersed throughout a solvent.

Ion

An atom or molecule that has gained or lost electrons and therefore carries an electrical charge.

Ionic Bond

A chemical bond formed through attraction between oppositely charged ions.

NCHOPS

An abbreviation representing the major elements commonly found in biological molecules: nitrogen, carbon, hydrogen, oxygen, phosphorus, and sulfur.

Hydrophilic

Describing a molecule or region that interacts readily with water.

Hydrophobic

Describing a molecule or region that does not interact readily with water and tends to avoid water.

Carbohydrate

An organic molecule composed primarily of carbon, hydrogen, and oxygen that commonly provides energy or structural support.

Monosaccharide

A carbohydrate consisting of a single sugar unit; also termed a simple sugar.

Hexose

A six-carbon sugar, such as glucose.

Disaccharide

A carbohydrate consisting of two monosaccharides joined together.

Polysaccharide

A carbohydrate polymer consisting of many sugar units joined together.

Starch

A storage polysaccharide used by plants to store glucose for energy.

Glycogen

A storage polysaccharide used by animals to store glucose for later use.

Cellulose

A structural carbohydrate found in plant cell walls that provides structural support.

Lipid

A biological macromolecule that generally does not dissolve readily in water.

Triglyceride

A lipid molecule consisting of glycerol bonded to three fatty acids.

Glycerol

A three-carbon molecule that forms the backbone of a triglyceride.

Fatty Acid

A long hydrocarbon chain found in many lipids.

Saturated Fatty Acid

A fatty acid containing only single bonds between carbon atoms.

Unsaturated Fatty Acid

A fatty acid containing one or more carbon-carbon double bonds.

Phospholipid

A lipid consisting of glycerol, fatty acids, and a phosphate-containing region, possessing a hydrophilic head and hydrophobic tails.

Amino Acid

The monomer subunit of proteins, containing an amino group, a carboxyl group, and a variable R-group.

R-group

The variable side chain of an amino acid that gives each amino acid its distinct chemical properties.

Peptide Bond

The covalent bond that links amino acids together during the formation of a polypeptide.

Polypeptide

A chain of amino acids joined together by peptide bonds.

Protein

A functional biological molecule made of one or more folded polypeptide chains.

Primary Structure of a Protein

The specific sequence of amino acids in a polypeptide chain.

Secondary Structure of a Protein

Coils and folded regions formed by interactions along a polypeptide backbone, including $\alpha$ helices and $\beta$ pleated sheets.

$\alpha$ Helix

A spiral-shaped form of protein secondary structure.

$\beta$ Pleated Sheet

A sheet-like form of protein secondary structure.

Tertiary Structure of a Protein

The overall three-dimensional shape of a single polypeptide chain.

Disulfide Bond

A covalent bond formed between certain R-groups that helps stabilize a protein's three-dimensional structure.

Quaternary Structure of a Protein

The structural level produced by the association of multiple polypeptide chains.

Denaturation

The process in which a protein loses its normal three-dimensional shape and function.

Hydrophobic Core

The interior region of a protein formed by nonpolar R-groups clustering away from water.

Nucleic Acid

The macromolecule class comprising DNA and RNA that stores and transmits hereditary information.

Nucleotide

The monomer of a nucleic acid, consisting of a five-carbon pentose sugar, a phosphate group, and a nitrogenous base.

Deoxyribose

The five-carbon pentose sugar found in DNA nucleotides.

Ribose

The five-carbon pentose sugar found in RNA nucleotides.

DNA

The nucleic acid that stores hereditary information in cells.

RNA

The nucleic acid involved in several stages of gene expression and protein synthesis.

Purine

A nitrogenous base containing a two-ring structure, specifically adenine and guanine.

Pyrimidine

A nitrogenous base containing a one-ring structure, specifically cytosine, thymine, and uracil.

Thymine

The pyrimidine nitrogenous base found in DNA that pairs with adenine.

Uracil

The pyrimidine nitrogenous base found in RNA that pairs with adenine.

Cytosine

A pyrimidine nitrogenous base that pairs with guanine in both DNA and RNA.

Dehydration Synthesis

A chemical reaction that joins smaller molecules together to form larger polymers while removing water.

Hydrolysis

A chemical reaction that breaks polymers into monomers by the addition of water.