AP Biology Unit 1- The Chemistry of Life

Adhesion

The attractive force between water molecules and other polar substances, allowing water to stick to different surfaces.

Cohesion

The attractive force between water molecules that causes them to stick together, resulting from hydrogen bonding.

Evaporative Cooling

The process by which the evaporation of water removes heat from an organism or environment.

Heat of Vaporization

The energy required to convert a liquid to a gas, enabling water to remove heat from organisms through evaporative cooling.

Homeostasis

The maintenance of stable internal environmental conditions in an organism despite external and internal changes.

Hydrogen Bond

Weak attractive forces between a hydrogen atom bonded to an electronegative atom and another electronegative atom, occurring between or within biological molecules.

Polar Covalent Bonds

Chemical bonds between atoms where electrons are unequally shared, resulting in partial positive and negative charges.

Polarity

The unequal distribution of electrical charge in a molecule, resulting in one end being partially positive and the other partially negative.

Specific Heat Capacity

The amount of energy required to raise the temperature of a substance by one degree, allowing water to resist rapid temperature changes.

Surface Tension

The property of water that allows its surface to resist breaking, resulting from hydrogen bonding between adjacent water molecules.

Carbohydrates

Biological molecules composed of carbon, hydrogen, and oxygen that serve as a primary source of energy and structural support in living organisms.

Carbon

An element that is the most prevalent component of biological molecules and forms the backbone of all organic compounds.

Hydrogen

An element that is a prevalent component of biological molecules and is bonded to carbon, oxygen, and nitrogen in macromolecules.

Lipid

Hydrophobic or amphipathic biological molecules composed primarily of carbon, hydrogen, and oxygen that store energy and form cell membranes.

Macromolecule

Large, complex molecules composed of many atoms that are essential for life processes, including carbohydrates, proteins, lipids, and nucleic acids.

Nitrogen

An element used in the building of nucleic acids and proteins as part of amino groups and nitrogenous bases.

Nucleic Acid

Macromolecules composed of nucleotides containing carbon, hydrogen, oxygen, nitrogen, and phosphorus that store and transmit genetic information.

Oxygen

An element that is a prevalent component of biological molecules and is found in carbohydrates, lipids, proteins, and nucleic acids.

Phospholipid

Amphipathic molecules with hydrophilic phosphate heads and hydrophobic fatty acid tails that form the basic structure of the cell membrane.

Phosphorus

An element used in the building of phospholipids and nucleic acids, particularly in phosphate groups.

Protein

Macromolecules composed of amino acids linked together, containing carbon, hydrogen, oxygen, nitrogen, and often sulfur, that perform diverse functions in cells.

Sulfur

An element used in the building of proteins, often found in disulfide bonds between amino acids.

Covalent Bond

Chemical bonds formed by the sharing of electrons between atoms, which can be broken or formed during macromolecule reactions.

Dehydration Synthesis

A chemical reaction that joins two smaller molecules together through covalent bonding by removing water, resulting in the formation of a larger molecule.

Hydrolysis

A chemical reaction that breaks down molecules by cleaving covalent bonds through the addition of water, splitting polymers into smaller monomers.

Monomer

Small individual molecules that serve as the building blocks for larger polymers.

Polymer

A large molecule composed of many monomers linked together through covalent bonds.

Polymerization

The process by which many monomers are connected together to form a polymer.

Cellulose

A polysaccharide polymer composed of glucose monomers that provides structural support in plant cell walls.

Glycogen

A polysaccharide polymer that serves as an energy storage molecule in animals.

Monosaccharides

Simple sugars that serve as monomers (building blocks) for polysaccharides and carbohydrates.

Polysaccharides

Complex carbohydrates formed by linking many monosaccharide monomers together through covalent bonds.

Starch

A polysaccharide polymer that serves as an energy storage molecule in plants.

Cholesterol

A steroid molecule found in the plasma membranes of vertebrate animals that regulates membrane fluidity and stability.

Fats

Lipids composed of glycerol and fatty acids that provide energy storage, support cell function, and can provide insulation in mammals.

Fatty Acids

Organic compounds consisting of a carboxyl group attached to a long hydrocarbon chain; can be saturated or unsaturated.

Hydrophobic

Water-repelling; referring to nonpolar molecules or regions that do not interact favorably with water.

Lipid Bilayer

A double layer of phospholipids that forms the basic structure of cell membranes and plasma membranes.

Nonpolar

Referring to molecules or groups with even distribution of electrical charge, making them hydrophobic.

Phospholipid

Amphipathic molecules with hydrophilic phosphate heads and hydrophobic fatty acid tails that form the basic structure of the cell membrane.

Plasma Membrane

The selectively permeable membrane that surrounds the cell, composed of phospholipids, proteins, and other molecules that regulate what enters and exits the cell.

Saturated Fatty Acid

Fatty acids that contain only single bonds between carbon atoms.

Steroid

Lipids with a four-ring carbon structure that function as hormones supporting growth, development, energy metabolism, and homeostasis.

Unsaturated Fatty Acid

Fatty acids that contain at least one double bond between carbon atoms, causing the carbon chain to kink.

3’ End

The end of a nucleic acid strand defined by the three prime hydroxyl group of the sugar.

5’ End

The end of a nucleic acid strand defined by the five prime phosphate group of the sugar.

Adenine

A purine nitrogenous base found in both DNA and RNA that pairs with thymine in DNA or uracil in RNA.

Antiparallel

The orientation of the two DNA strands running in opposite directions, with one strand oriented 5' to 3' and the other 3' to 5'.

Base Pairing

The specific pairing of nitrogenous bases between DNA strands (A-T and C-G) or in RNA (A-U).

Cytosine

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

Deoxyribose

A five-carbon sugar found in DNA nucleotides.

DNA

Deoxyribonucleic acid; a double-stranded nucleic acid that stores genetic information using deoxyribose sugar and thymine as a nitrogenous base.

Double Helix

The three-dimensional structure of DNA consisting of two antiparallel strands twisted around each other.

Guanine

A purine nitrogenous base found in both DNA and RNA that pairs with cytosine.

Hydrogen Bond

Weak attractive forces between a hydrogen atom bonded to an electronegative atom and another electronegative atom, occurring between or within biological molecules.

Nitrogenous Base

A nitrogen-containing molecule that is part of a nucleotide; includes adenine, thymine, guanine, cytosine, and uracil.

Nucleotide

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

Phosphate

A chemical group that is part of the nucleotide structure and forms covalent bonds between nucleotides in a nucleic acid strand.

Ribose

A five-carbon sugar found in RNA nucleotides.

RNA

Ribonucleic acid; typically a single-stranded nucleic acid that uses ribose sugar and uracil as a nitrogenous base.

Thymine

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

Uracil

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

Alpha-Helix

A coiled secondary structure of a protein formed by hydrogen bonding between backbone atoms of the polypeptide chain.

Amino Acid

Organic molecules that serve as the building blocks of proteins, each composed of a central carbon atom bonded to a hydrogen atom, a carboxyl group, an amine group, and a variable R group.

Beta-pleated Sheet

An extended secondary structure of a protein formed by hydrogen bonding between backbone atoms of the polypeptide chain, creating a zigzag pattern.

Disulfide Bridge

Covalent bonds formed between sulfur atoms in cysteine R groups that stabilize tertiary protein structure.

Hydrophobic Interaction

Interactions between nonpolar R groups that cluster together in the interior of a protein to avoid contact with water, contributing to tertiary structure.

Ionic Interaction

Electrostatic attractions between oppositely charged R groups that stabilize tertiary protein structure.

Peptide Bond

Covalent bonds formed between the carboxyl group of one amino acid and the amine group of another amino acid, linking amino acids together in a protein chain.

Polypeptide

A chain of amino acids linked together by peptide bonds.

Primary Structure

The linear sequence of amino acids in a polypeptide chain, determined by the specific order of amino acids in the protein.

Quaternary Structure

The arrangement and interactions of multiple polypeptide chains within a protein complex.

R Group

The variable side chain of an amino acid that determines its chemical properties (hydrophobic/nonpolar, hydrophilic/polar, or ionic) and influences protein structure and function.

Secondary Structure

Local folding patterns in a protein formed by hydrogen bonding between atoms of the polypeptide backbone, including alpha-helices and beta-pleated sheets.

Tertiary Structure

The three-dimensional shape of a protein resulting from interactions such as hydrogen bonds, hydrophobic interactions, ionic interactions, and disulfide bridges between R groups.