Atom

A basic unit of matter that cannot be broken down by normal chemical reactions.

Biology

The study of life.

Biosphere

A collection of all ecosystems on Earth.

Cell

The smallest fundamental unit of structure and function in living things.

Community

A set of populations inhabiting a particular area.

Ecosystem

All living things in a particular area together with the abiotic

Eukaryote

An organism with cells that have nuclei and membrane-bound organelles.

Evolution

The process of gradual change in a population that can also lead to new species arising from older species.

Homeostasis

The ability of an organism to maintain constant internal conditions.

Life Science

A field of science

Macromolecule

A large molecule typically formed by the joining of smaller molecules.

Molecule

A chemical structure consisting of at least two atoms held together by a chemical bond.

Natural Science

A field of science that studies the physical world

Organ

A structure formed of tissues operating together to perform a common function.

Organ System

The higher level of organization that consists of functionally related organs.

Organelle

A membrane-bound compartment or sac within a cell.

Organism

An individual living entity.

Phylogenetic Tree

A diagram showing the evolutionary relationships among biological species based on similarities and differences in genetic or physical traits or both.

Physical Science

A field of science

Population

All individuals within a species living within a specific area.

Prokaryote

A unicellular organism that lacks a nucleus or any other membrane-bound organelle.

Science

Knowledge that covers general truths or the operation of general laws

Tissue

A group of similar cells carrying out the same function.

Acid

A substance that donates hydrogen ions and therefore lowers pH.

adhesion

The attraction between water molecules and molecules of a different substance.

amino acid

A monomer of a protein.

anion

A negative ion formed by gaining electrons.

atomic number

The number of protons in an atom.

base

A substance that absorbs hydrogen ions and therefore raises pH.

buffer

A solution that resists changes in pH by absorbing or releasing hydrogen or hydroxide ions.

carbohydrate

A biological macromolecule with a carbon:hydrogen:oxygen ratio of 1:2:1 that provides energy and structural support in cells.

cation

A positive ion formed by losing electrons.

cellulose

A polysaccharide that forms plant cell walls and provides structural support.

chemical bond

An interaction between two or more elements that results in forming molecules.

chitin

A carbohydrate that forms the outer skeleton of arthropods and the cell walls of fungi.

cohesion

Intermolecular forces between water molecules due to water’s polarity; creates surface tension.

covalent bond

A strong bond formed when electrons are shared between atoms.

denaturation

The loss of a protein’s shape due to changes in temperature

deoxyribonucleic acid (DNA)

A double-stranded nucleotide polymer that carries hereditary information.

disaccharide

Two sugar monomers linked together by a glycosidic bond.

electron

A negatively charged particle found outside the atomic nucleus; has a charge of –1.

electron transfer

The movement of electrons from one element to another.

element

One of 118 unique substances that cannot be broken down and retains characteristic properties; defined by its number of protons.

enzyme

A catalyst in biochemical reactions

evaporation

The release of water molecules from liquid water to form vapor.

fat

A lipid composed of three fatty acids and glycerol (a triglyceride); solid at room temperature.

glycogen

A storage carbohydrate found in animals.

hormone

A protein or steroid signaling molecule released by endocrine cells to regulate physiological processes.

hydrogen bond

A weak bond between partially positive hydrogen atoms and partially negative atoms or molecules.

hydrophilic

Describes a substance that dissolves in water (“water-loving”).

hydrophobic

Describes a substance that does not dissolve in water (“water-fearing”).

ion

An atom or compound with an unequal number of protons and electrons

ionic bond

A chemical bond formed between oppositely charged ions.

isotope

Forms of an element with different numbers of neutrons.

lipids

Nonpolar

litmus paper

Paper treated with pH-sensitive dye used to test acidity or basicity.

macromolecule

A large molecule formed by polymerizing smaller monomers.

mass number

the total number of protons plus neutrons in an atom.

matter

Anything that has mass and occupies space.

monosaccharide

A single carbohydrate monomer.

neutron

A particle with no charge found in the atomic nucleus; mass of 1.

nonpolar covalent bond

A covalent bond where electrons are shared equally

nucleic acid

A macromolecule that carries genetic information and instructions for cell function.

nucleotide

A nucleic acid monomer containing a sugar

nucleus (chemistry)

The dense center of an atom containing protons and (except in hydrogen) neutrons.

octet rule

States that atoms with low atomic numbers are most stable with eight electrons in their outer shell.

oil

An unsaturated fat that is liquid at room temperature.

periodic table of elements

A chart organizing elements by atomic number

pH scale

A scale from 0 to 14 measuring hydrogen ion concentration.

phospholipid

A major component of cell membranes composed of two fatty acids and a phosphate group.

polar covalent bond

A covalent bond with unequal electron sharing

polypeptide

A long chain of amino acids linked by peptide bonds.

polysaccharide

A long chain of monosaccharides that may be branched or unbranched.

protein

A macromolecule made of one or more polypeptide chains.

proton

A positively charged particle in the nucleus with mass 1 and charge +1.

radioactive isotope

an isotope that emits particles or energy to become more stable.

ribonucleic acid (RNA)

A single-stranded nucleotide polymer involved in protein synthesis.

saturated fatty acid

A hydrocarbon chain with only single bonds; maximizes hydrogen atoms.

solvent

A substance that dissolves another substance.

starch

A storage carbohydrate in plants.

steroid

A lipid with four fused hydrocarbon rings.

surface tension

The cohesive force at a liquid surface preventing molecules from separating.

temperature

A measure of molecular motion.

trans-fat

An unsaturated fat with hydrogen atoms across from each other at a double bond.

triglyceride

A fat composed of three fatty acids attached to glycerol.

unsaturated fatty acid

A hydrocarbon with one or more double bonds.

van der Waals interaction

A weak interaction caused by slight charges between molecules.

CO₂

Carbon dioxide.

O₂

Molecular oxygen.

CH₄

Methane.