Anatomical Terms Chapter 2

Matter

Anything that has mass and takes up space.

Mass

The amount of matter in an object.

Chemical Element

A pure substance made of only one type of atom.

Atom

The smallest unit of an element that keeps its chemical properties.

Nucleus

The dense center of an atom that contains protons and neutrons.

Proton

A positively charged particle found in the nucleus of an atom.

Neutron

A particle in the nucleus of an atom that has no electric charge.

Electron

A negatively charged particle that orbits the nucleus.

Electron Shell

Energy levels around the nucleus where electrons move.

Atomic Number

The number of protons in an atom and defines the element.

Mass Number

The number of total protons and neutrons in the nucleus of an atom.

Isotope

A variant form of a chemical element that has the same number of protons but a different number of neutrons in its nucleus.

Ion

An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

Cation

A positively charged ion

Anion

A negatively charged ion

Molecule

The smallest unit of a pure chemical substance composed of two or more atoms held together by chemical bonds

Compound

A substance formed when two or more different elements are chemically joined in a fixed proportion

Free Radical

An atom, molecule, or ion with at least one unpaired valence electron, making it highly reactive.

Antioxidant

A substance that inhibits oxidation, especially one used to counteract the deterioration of stored food products.

Chemical Bond

The force of attraction that holds atoms together to form molecules or compounds, driven by the interactions between their electrons and nuclei.

Ionic Bond

A chemical bond formed when one atom transfers electrons to another, creating oppositely charged ions that attract each other.

Covalent Bond

A chemical bond formed when two atoms share one or more pairs of electrons.

Non-polar Covalent Bond

A type of covalent bond where electrons are shared equally between atoms, resulting in no significant charge separation.

Polar Covalent Bond

A type of covalent bond where electrons are shared unequally, causing partial positive and negative charges on different parts of the molecule.

Hydrogen Bond

A weak attraction between a hydrogen atom covalently bonded to an electronegative atom (like oxygen or nitrogen) and another electronegative atom.

Chemical Reaction

A process in which substances (reactants) are transformed into new substances (products) by breaking and forming chemical bonds.

Reactants

The starting substances that undergo change during a chemical reaction.

Products

The substances formed as a result of a chemical reaction.

Metabolism

The sum of all chemical reactions in a living organism, including those that build up (anabolism) and break down (catabolism) molecules.

Energy

The capacity to do work or cause change; in biology, often refers to chemical energy stored in bonds that organisms use for life processes.

Potential Energy

Stored energy, such as energy held in chemical bonds.

Kinetic Energy

The energy of motion, like a muscle contracting or blood flowing.

Law of Conservation of Energy

Energy cannot be created or destroyed, only transformed from one form to another.

Exergonic Reaction

Releases more energy than it consumes, making it spontaneous.

Endergonic Reaction

Requires an input of energy to proceed.

Activation Energy

The minimum energy needed to start a chemical reaction.

Catalyst

A substance that speeds up a chemical reaction without being consumed in the process.

Enzyme

A biological catalyst, usually a protein, that lowers activation energy and accelerates cellular reactions.

Synthesis Reaction (Anabolism)

Builds larger molecules from smaller ones, requiring energy input.

Decomposition Reaction (Catabolism)

Breaks down larger molecules into smaller ones, often releasing energy.

Exchange Reaction

A chemical reaction where parts of two compounds switch places to form two new compounds

Reversible Reaction

A reaction that can go forward and backward, meaning products can turn back into reactants until a balance (equilibrium) is reached.

Oxidation

The loss of electrons by an atom, molecule, or ion. Often involves adding oxygen or removing hydrogen.

Reduction

The gain of electrons by an atom, molecule, or ion. Often involves removing oxygen or adding hydrogen.

Oxidation - Reduction Reaction

A chemical reaction where one substance is oxidized (loses electrons) and another is reduced (gains electrons) at the same time.

Inorganic Compound

A compound that usually does not contain carbon-hydrogen (C-H) bonds. Examples include water, salts, and minerals.

Organic Compound

A compound that contains carbon and hydrogen, and often other elements like oxygen or nitrogen. Examples include carbohydrates, proteins, fats, and nucleic acids.

Water

A molecule made of two hydrogen atoms and one oxygen atom (H₂O). It is essential for life, a universal solvent, and has unique properties like cohesion, adhesion, and a high heat capacity.

Hydrophilic

Describes a substance that easily mixes with or dissolves in water (water-loving)

Hydrophobic

Describes a substance that does not mix well with water (water-fearing), like oils and fats.

Hydrolysis

A chemical reaction where a molecule is broken down into two or more fragments by the addition of a water molecule.

Dehydration Synthesis

A chemical reaction where two molecules are covalently bonded together, with the removal of a water molecule.

Solution

A homogeneous mixture where one substance (the solute) is evenly dissolved in another (the solvent).

Solvent

The substance that dissolves the solute

Solute

The substance that gets dissolved with the solvent

Concentration

The amount of a specific substance (solute) present within a given volume of a fluid or tissue.

Molarity

The number of moles of solute per liter of solution.

Acid

A chemical substance with a pH lower than 7, produces more H+ ions

Base

A chemical substance with a pH greater than 7, produces more OH- ions

Salt

An ionic compound formed when the hydrogen atoms of an acid are replaced by metal atoms or groups that act like metals, resulting in a neutral compound composed of cations and anions.

Electrolyte

A substance that produces charged particles called ions when dissolved in a solvent, allowing the solution to conduct electricity.

pH Scale

The scale that expresses a solution’s acidity or alkalinity, which extends from 0 to 14. A basic solution has a pH above 7 while an acidic solution has a pH below 7. This scale is based on the concentration of Hᐩ in moles per liter.

Buffer Systems

Systems which function to convert strong acids or bases into weak acids or bases.

Carbon and Organic Molecules

An element that forms the backbone of all organic molecules due to its ability to form four stable bonds with other atoms. Organic molecules are compounds primarily made of carbon atoms bonded with hydrogen, oxygen, nitrogen, and other elements, and are essential to life.

Monomer

Identical or similar small building-block molecules

Polymer

A large molecule formed by the covalent bonding of monomers

Carbohydrate

An organic molecule composed of carbon, hydrogen, and oxygen that serves as a major source of energy for the body

Monosaccharide

Simple sugars that contain from 3 to 7 carbon atoms

Disaccharide

Simple sugars formed from the combination of two monosaccharides by dehydration synthesis

Polysaccharide

The third major group of carbohydrates. Contains tens or hundreds of monosaccharides joined through dehydration synthesis.

Lipid

A group of biological molecules that are mostly nonpolar and hydrophobic (don’t mix with water); includes fats, oils, and some hormones.

Triglyceride

A type of lipid made of one glycerol + three fatty acids; main form of stored fat in the body

Phospholipid

A lipid with a phosphate “head” (hydrophilic) and two fatty acid “tails” (hydrophobic); forms cell membranes.

Steroid

A type of lipid with a four-ring structure; examples include cholesterol, testosterone, and estrogen.

Eicosanoid

Lipid molecules made from fatty acids (like arachidonic acid) that act as signaling molecules, helping control inflammation, immunity, and other body functions.

Protein

A large molecule made of one or more chains of amino acids; responsible for structure, transport, movement, and many functions in the body.

Amino Acid

The building block of proteins; contains a central carbon, an amino group, a carboxyl group, a hydrogen, and an R-group (side chain).

Peptide Bond

The chemical bond that links amino acids together to form proteins.

Denaturation

Loss of enzyme shape (from heat, pH, or chemicals), making it unable to function.

Nucleic Acid

Large molecules (DNA and RNA) that store and transmit genetic information.

DNA (Deoxyribonucleic Acid)

Stores genetic instructions; double-stranded helix with bases A, T, C, G.

RNA (Ribonucleic Acid)

Single-stranded; helps make proteins by carrying and translating DNA’s instructions.

Nucleotide

Building block of nucleic acids; made of a sugar, a phosphate group, and a nitrogen base.

ATP (Adenosine Triphosphate)

The main energy currency of the cell; stores energy in its three phosphate bonds.

ADP (Adenosine Diphosphate)

A lower-energy molecule formed when ATP loses one phosphate group; can be recharged back into ATP.

Water (root word)

hydro-

Break Apart (root word)

lysis

Put Together (root word)

synthesis

Remove (root word)

de-

Oxygen (root word)

oxy-

Carbon (root word)

carb-

Sugar (root word)

sacchar-

Fat (root word)

lip-

Small Protein (root word)

peptide

Nucleus/Nucleic Acid (root word)

nucle-

One (root word)

mono-

Two (root word)

di-

Many (root word)

poly-

Enzyme (root word)

-ase

Sugar (root word)

-ose