AP Biology Unit 1

acid

substance that increases the hydrogen ion concentration of a solution

base

substance that reduces hydrogen ion concentration of a solution

disaccharide

A double sugar, consisting of two monosaccharides joined by a glycosidic linkage formed by a dehydration reaction.

abiotic reservoir

a non-living part of an ecosystem where nutrients and chemical elements (like carbon, nitrogen, or phosphorus) accumulate and are stored

adhesion

The clinging of one substance to another, such as water to plant cell walls, in this case by means of hydrogen bonds

aldehyde

is a type of functional group where a carbon atom shares a double bond with an oxygen atom (a carbonyl group) and a single bond with a hydrogen atom

alpha helix

A coiled region constituting one form of the secondary structure of proteins, arising from a specific pattern of hydrogen bonding between atoms of the polypeptide backbone (not the side chains)

amino acid

An organic molecule possessing both a carboxyl and an amino group; serve as the monomers of polypeptides

amino group

A chemical group consisting of a nitrogen atom bonded to two hydrogen atoms; can act as a base in solution, accepting a hydrogen ion and acquiring a charge of plus one

amphipathic

Having both a hydrophilic region and a hydrophobic region

anion

A negatively charged ion

atomic mass

The total mass of an atom, numerically equivalent to the mass in grams of 1 mole of the atom. (For an element with more than one isotope, it is the average mass of the naturally occurring isotopes, weighted by their abundance.)

beta pleated sheet

One form of the secondary structure of proteins in which the polypeptide chain folds back and forth. Two regions of the chain lie parallel to each other and are held together by hydrogen bonds between atoms of the polypeptide backbone (not the side chains

biotic reservoir

Pertaining to the living factors—the organisms—in an environment

buffer

A solution that contains a weak acid and its corresponding base; minimizes changes in pH when acids or bases are added to the solution

carbohydrate

A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides)

carboxyl group

A chemical group present in organic acids and consisting of a single carbon atom double-bonded to an oxygen atom and also bonded to a hydroxyl group

cation

a positively charged ion

cellulose

A structural polysaccharide of plant cell walls, consisting of glucose monomers joined by beta glycosidic linkages

chaperonin

a giant protein "nanomachine" that helps newly made polypeptide chains fold into their correct, functional three-dimensional shapes

cholesterol

A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as many hormones

cohesion

The linking together of like molecules, often by hydrogen bonds

colloid

a heterogeneous mixture with microscopic particles (1 to 1000 nm) suspended in a continuous medium that do not settle out over time

compound

A substance consisting of two or more different elements combined in a fixed ratio

condensation synthesis

a chemical reaction where two monomers join to form a larger polymer by covalently bonding and releasing a water molecule as a byproduct

covalent bond

A type of strong chemical bond in which two atoms share one or more pairs of valence electrons

dalton

A measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu

dehydration synthesis

a chemical reaction that joins small molecules (monomers) into large chains (polymers) by removing a water molecule and forming a new covalent bond

denature

In proteins, a process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions, thereby becoming biologically inactive

electronegativity

The attraction of a given atom for the electrons of a covalent bond

element

Any substance that cannot be broken down to any other substance by chemical reactions

enantiomers

One of two compounds that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon

enzyme

A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction; most are proteins

equilibrium

a stable state of balance where no net change occurs within a system

evaporative cooling

The process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state.

fatty acid

A carboxylic acid with a long carbon chain; vary in length and in the number and location of double bonds; three of them linked to a glycerol molecule form a fat molecule, also called triacylglycerol or triglyceride

functional groups

A specific configuration of atoms commonly attached to the carbon skeletons of organic molecules and involved in chemical reactions

geometric isomers

One of several compounds that have the same molecular formula and covalent bonds between atoms but differ in the spatial arrangements of their atoms owing to the inflexibility of double bonds; also called cis-trans isomers

glycerol

a small 3-carbon organic molecule with three hydroxyl groups that acts as the backbone for triglycerides and phospholipids

glycogen

An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch

glycosidic linkage

A covalent bond formed between two monosaccharides by a dehydration reaction

hydrocarbon

An organic molecule consisting only of carbon and hydrogen

hydrogen bond

A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule

hydrolysis

A chemical reaction that breaks bonds between two molecules by the addition of water; functions in disassembly of polymers to monomers

hydrophilic

having an affinity for water

hydrophobic

Having no affinity for water; tending to coalesce and form droplets in water

hydroxyl group

A chemical group consisting of an oxygen atom joined to a hydrogen atom. Molecules possessing this group are soluble in water and are called alcohols

inorganic

a compound that generally does not contain a combination of both carbon and hydrogen atoms

ion

an atom or molecule with a net electrical charge caused by an unequal number of protons and electrons

ionic bond

A chemical bond resulting from the attraction between oppositely charged ions

isomers

One of two or more compounds that have the same numbers of atoms of the same elements but different structures and hence different properties

isomorphic

Referring to alternating generations in plants and certain algae in which the sporophytes and gametophytes look alike, although they differ in chromosome number

isotope

One of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass

ketone

a chemical functional group (a carbonyl group bonded to two carbon atoms)

lipids

Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water

macromolecules

A giant molecule formed by the joining of smaller molecules; polysaccharides, proteins, and nucleic acids

mass number

The total number of protons and neutrons in an atom’s nucleus

methyl group

A chemical group consisting of a carbon bonded to three hydrogen atoms; may be attached to a carbon or to a different atom

monomer

The subunit that serves as the building block of a polymer

monosaccharide

The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides. Also called simple sugars, they have molecular formulas that are generally some multiple of C-H-subscript-2-O

nonpolar covalent bond

A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity

nucleic acid

A polymer (polynucleotide) consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA

nucleotide

The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one to three phosphate groups

orbital

The three-dimensional space where an electron is found 90 percent of the time

organic molecules

a carbon-based compound that typically contains hydrogen atoms and is synthesized by or found in living organisms

peptide

a short chain of amino acids (typically 2 to 50) linked together by covalent peptide bonds

peptide bond

The covalent bond between the carboxyl group on one amino acid and the amino group on another, formed by a dehydration reaction

pH

a logarithmic measure of the hydrogen ion concentration in an aqueous solution; 1-6 is acidic, 7 is neutral and 8-14 is basic

phosphate group

A chemical group consisting of a phosphorus atom bonded to four oxygen atoms; important in energy transfer

phospholipid

A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head

polar molecule

A molecule (such as water) with an uneven distribution of charges in different regions of the molecule

polarity

the unequal sharing of electrons across a covalent bond

polymer

A long molecule consisting of many similar or identical monomers linked together by covalent bonds

polynucleotides

A polymer consisting of many nucleotide monomers in a chain. The nucleotides can be those of DNA or RNA

polypeptide

A polymer of many amino acids linked together by peptide bonds

polysaccharide

A polymer of many monosaccharides, formed by dehydration reactions

potential energy

The energy that matter possesses as a result of its location or spatial arrangement (structure)

primary structure

The level of protein structure referring to the specific linear sequence of amino acids

protein

A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure

purine

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring; Adenine (A) and guanine (G)

pyrimidine

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring; cytosine (C), thymine (T), and uracil (U)

quaternary structure

the fourth and highest level of protein structure formed when two or more separate polypeptide chains join together to create a single functional macromolecule

saccharide

a structural unit or monomer of carbohydrates

saturated

where a solvent holds the maximum amount of dissolved solute

secondary structure

Regions of repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bonding between constituents of the backbone (not the side chains)

solute

A substance that is dissolved in a solution

solvent

The dissolving agent of a solution. Water is the most versatile one known

specific heat

The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1 degree C

starch

A storage polysaccharide in plants, consisting entirely of glucose monomers joined by glycosidic linkages

steroid

A type of lipid characterized by a carbon skeleton consisting of four fused rings with various chemical groups attached

structural isomers

One of two or more compounds that have the same molecular formula but differ in the covalent arrangements of their atoms

surface tension

A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high one because of the hydrogen bonding of surface molecules

tertiary structure

The overall shape of a protein molecule due to interactions of amino acid side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges

trace elements

An element indispensable for life but required in extremely minute amounts

transpiration

The evaporative loss of water from a plant

unsaturated

a substance that has fewer hydrogen atoms than the maximum possible amount

valence

The bonding capacity of a given atom; the number of covalent bonds that an atom can form, which usually equals the number of unpaired electrons in its outermost shell.

x-ray crystallography

A technique used to study the three-dimensional structure of molecules. It depends on the diffraction of an X-ray beam by the individual atoms of a crystallized molecule