Biology Test 1 Study Guide (Chapters 1-4)

Vocabulary flashcards covering key terms and definitions from Chapters 1-4 of the biology study guide.

Null Hypothesis (H₀)

The default statement that there is no effect or difference; rejected when experimental data show a statistically significant effect.

Alternative Hypothesis (Hₐ)

The statement that there is an effect or difference; accepted when data allow rejection of H₀.

Dependent Variable

The measured outcome in an experiment; changes in response to the independent variable.

Independent Variable

The factor deliberately manipulated by the experimenter to test its effect on the dependent variable.

Control (Experimental Control)

A standard of comparison; a group or condition where the independent variable is not applied.

Confounding Variable

An external factor that can influence the dependent variable and obscure true experimental results.

Acid

A substance that donates H⁺ ions; pH < 7; [H⁺] > [OH⁻].

Base

A substance that accepts H⁺ ions; pH > 7; [H⁺] < [OH⁻].

Neutral Solution

A solution in which [H⁺] = [OH⁻]; pH = 7 (pure water).

pH Scale

A logarithmic scale (0–14) indicating acidity or basicity based on free H⁺ concentration.

Polar Molecule

A molecule with regions of slight positive and negative charge due to unequal electron sharing.

Hydrophilic

“Water-loving”; describes polar molecules that readily dissolve in water.

Hydrophobic

“Water-fearing”; describes non-polar molecules that do not mix with water.

Hydrogen Bond

A weak attraction between a slightly positive hydrogen atom and a slightly negative atom (e.g., O or N).

Bond Breakage

Process that releases energy stored in chemical bonds.

Bond Formation

Process that consumes energy to create chemical bonds.

Activation Energy

The minimum energy required to initiate a chemical reaction.

Catalyst

A substance that speeds up a reaction by lowering activation energy without being consumed.

Organic Molecule

Compound containing carbon atoms (typically with H, O, N, etc.).

Inorganic Molecule

Compound lacking carbon (or with carbon not bonded to H), e.g., water, salts.

ATP (Adenosine Triphosphate)

The cell’s primary energy carrier; releases energy when its phosphate bonds are broken.

Amino Acid

The monomer of proteins; differs by its R-group (side chain).

Phospholipid

A molecule with a polar phosphate head and two non-polar fatty acid tails; main component of cell membranes.

Protein

A folded chain of amino acids; functional only when in its correct 3-D shape.

Denaturation

Loss of a protein’s structure (and therefore function) due to heat, pH extremes, etc.

Enzyme

A protein catalyst that accelerates biochemical reactions.

Active Site

The region on an enzyme where the substrate binds and reacts.

Complementary Fit

The specificity between an enzyme’s active site and its substrate(s).

Monomer

A single building-block molecule (e.g., glucose, amino acid, nucleotide).

Nucleotide

The monomer of nucleic acids (DNA/RNA); composed of a sugar, phosphate, and base.

Dehydration Reaction

Linking of monomers to form polymers while producing water.

Hydrolysis

Breaking polymers into monomers by adding water.

Phospholipid Bilayer

Double layer of phospholipids forming the basic structure of all biological membranes.

Prokaryotic Cell

Cell lacking a nucleus and membrane-bound organelles; DNA in a nucleoid; usually small and unicellular.

Eukaryotic Cell

Cell with a nucleus and membrane-bound organelles; larger; includes plant, animal, fungal, and protist cells.

Cell Membrane

Semi-permeable phospholipid bilayer that encloses the cell and regulates substance entry/exit.

Fluid Mosaic Model

Describes the cell membrane as a dynamic, fluid layer with diverse proteins embedded like a mosaic.

Semi-Permeable

Property of membranes allowing some molecules to cross while restricting others.

Mitochondrion

Organelle that produces ATP through cellular respiration; the cell’s “powerhouse.”

Ribosome

Structure (free or on rough ER) where proteins are assembled from amino acids.

Rough Endoplasmic Reticulum

Membranous network studded with ribosomes; modifies and transports proteins.

Transport Vesicle

Small membrane sac that moves molecules (e.g., proteins, lipids) within the cell.

Cell Wall

Rigid protective layer outside the plasma membrane of plants; composed mainly of cellulose.

Cellulose

A polysaccharide forming the primary structural component of plant cell walls.