Biology CLEP Unit #1

Matter

Anything that occupies space and has mass; all living and non-living things are made of matter.

Element

A pure substance composed of only one type of atom that cannot be broken down by ordinary chemical reactions.

Atom

The smallest unit of an element that retains its properties; it consists of protons, neutrons, and electrons.

Compound

A substance made when two or more different elements bond together in fixed proportions, such as sodium chloride (NaCl).

Molecule

Two or more atoms chemically bonded together. Molecules can contain atoms of the same or different elements.

Valence Electron

An electron in the outermost shell of an atom that determines how that atom bonds or reacts with others.

Electronegativity

A measure of how strongly an atom attracts shared electrons.

Covalent Bond

A strong bond formed when atoms share pairs of electrons. These can be polar (unequal sharing) or nonpolar (equal sharing).

Noncovalent Bond

A weak bond formed when oppositely charged atoms attract each other like tiny magnets. These bonds do not involve sharing electrons.

Ionic Bond

A bond formed when one atom donates an electron to another, creating positively and negatively charged ions that attract each other.

Hydrogen Bond

A weak attraction between the slightly positive hydrogen atom of one molecule and a slightly negative atom (like oxygen or nitrogen) of another. This bond gives water many of its unique properties.

van der Waals interactions

Very weak noncovalent bond between atoms with opposite partial charges due to movements of electrons around atoms.

Reactants and Products

Reactants are the starting materials of a chemical reaction; products are the new substances formed. Both follow the law of conservation of matter—no atoms are lost, only rearranged.

Exothermic and Endothermic Reactions

Exothermic reactions release heat (like combustion), while endothermic reactions absorb heat (like melting ice). Both are vital for biological processes and energy flow.

Exergonic and Endergonic Reactions

Exergonic reactions release energy and are spontaneous, whereas endergonic reactions require an input of energy and are nonspontaneous.

Laws of Thermodynamics

The First Law states that energy cannot be created or destroyed, only transformed. The Second Law states that every energy transfer increases disorder (entropy), reducing usable energy over time.

Polarity and Hydrogen Bonds

Water’s polarity allows it to form hydrogen bonds, which are responsible for its unique physical and chemical properties.

Density of Ice

Ice is less dense than liquid water because its hydrogen bonds hold molecules in a fixed lattice that keeps them farther apart.

Cohesion and Adhesion

Cohesion makes water molecules stick together; adhesion helps them cling to other surfaces, enabling capillary action.

High Specific Heat and Evaporation

Water absorbs heat slowly and releases it gradually, stabilizing temperature. Evaporation carries heat away, cooling organisms and environments.

Acids, Bases, and Buffers

Acids increase hydrogen ions in water, bases reduce them, and buffers keep pH stable to maintain biological homeostasis.

Lipids

fatty compounds that perform a variety of functions in your body. They’re part of your cell membranes and help control what goes in and out of your cells. They help with moving and storing energy, absorbing vitamins, and making hormones.

Carbohydrates

essential food nutrients. Your body turns carbs into glucose (blood sugar) to give you the energy you need to function.

Proteins

molecules that support everything your body does. From helping you flex your muscles to breaking down nutrients in the foods you eat.

Nucleic Acids

, naturally occurring chemical compound that serves as the main information-carrying molecule of the cell and that directs the process of protein synthesis, thereby determining the inherited characteristics of every living thing.

Cell organelles

Mini specialized structures inside a cell that keep a cell alive

Nucleus

houses the cell’s chromosomal DNA, which carries the genetic blueprint for life.

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