Chapter 02 – Levels of Organization of the Human Body (Vocabulary)

A comprehensive set of vocabulary flashcards covering the key terms and concepts from Chapter 02: Levels of Organization of the Human Body.

Atom

Smallest unit of an element containing protons, neutrons, and electrons.

Element

A pure substance composed of only one kind of atom.

Isotope

Atom of the same element with a different number of neutrons; may be radioactive.

Radioisotope

An isotope that spontaneously emits particles or energy.

Matter

Anything that has mass and occupies space.

Molecule

Two or more atoms chemically bonded together.

Covalent Bond

Chemical bond formed when atoms share electrons.

Ionic Bond

Chemical bond formed when atoms transfer electrons, creating charged ions.

Ion

An atom or molecule with an electrical charge due to loss or gain of electrons.

Electrolyte

Ion in solution that can conduct an electric current.

Water (H₂O)

Universal solvent that lubricates, transports, participates in reactions, allows ions in solution, and regulates temperature.

Solution

Homogeneous mixture of a solute dissolved in a solvent.

Tonicity

Relative solute concentration of two fluids separated by a membrane.

Hypertonic Solution

More concentrated solution that causes cells to lose water.

Isotonic Solution

Solution with equal solute concentration to another; no net water movement.

Hypotonic Solution

Less concentrated solution that causes cells to gain water.

Acid

Substance that donates hydrogen ions (H⁺); pH < 7.

Base

Substance that accepts hydrogen ions; pH > 7.

pH Scale

Logarithmic scale (0–14) measuring acidity/alkalinity; each unit is ten-fold.

Organic Molecule

Carbon- and hydrogen-containing compound such as carbohydrates, lipids, proteins, or nucleic acids.

Carbohydrate

Organic molecule of C, H, O (2 H per O); primary cellular energy source.

Monosaccharide

Simple sugar; building block of carbohydrates (e.g., glucose).

Disaccharide

Carbohydrate made of two monosaccharides (e.g., sucrose).

Polysaccharide

Large carbohydrate of many monosaccharides (e.g., glycogen).

Glucose

Six-carbon sugar (C₆H₁₂O₆) that is the main cellular fuel.

Glycogen

Animal storage form of glucose.

Lipid

Hydrophobic organic molecule rich in C and H; includes fats, phospholipids, steroids.

Triglyceride (Fat)

Lipid formed from glycerol and three fatty acids; energy storage.

Phospholipid

Lipid with glycerol, two fatty acids, and a phosphate group; forms cell membranes.

Steroid

Lipid characterized by four fused carbon rings (e.g., cholesterol).

Protein

Polymer of amino acids folded into specific shapes for diverse functions.

Amino Acid

Building block of proteins containing amine group, acid group, and variable R group.

Polypeptide

Chain of many amino acids before final folding into a protein.

Nucleic Acid

Polymer of nucleotides; DNA or RNA.

Nucleotide

Monomer of nucleic acids composed of a pentose sugar, phosphate, and nitrogenous base.

DNA (Deoxyribonucleic Acid)

Double-stranded nucleic acid storing genetic information; bases A, T, C, G.

RNA (Ribonucleic Acid)

Single-stranded nucleic acid involved in protein synthesis; bases A, U, C, G.

Triplet

Three-nucleotide sequence in DNA that codes for an amino acid.

Gene

Segment of DNA that contains instructions to synthesize a protein.

Metabolism

Sum of all chemical reactions in the body.

Catalyst

Substance that speeds up a chemical reaction without being consumed.

Enzyme

Protein catalyst in biological systems.

Cellular Respiration

Process that converts glucose and O₂ to CO₂, H₂O, and ATP.

ATP (Adenosine Triphosphate)

Molecule that stores and supplies usable cellular energy.

Organelle

Specialized structure within a cell with a specific function.

Cytoplasm

Intracellular fluid that suspends organelles.

Cell Membrane (Plasma Membrane)

Phospholipid bilayer that encloses the cell and controls transport.

Nucleus

Organelle that houses DNA and controls cellular activities.

Mitochondrion

Organelle where cellular respiration produces ATP.

Ribosome

Organelle that assembles proteins from amino acids.

Rough Endoplasmic Reticulum

ER studded with ribosomes; site of protein synthesis.

Smooth Endoplasmic Reticulum

ER lacking ribosomes; site of lipid synthesis.

Golgi Complex

Organelle that modifies, sorts, and packages proteins and lipids.

Secretory Vesicle

Membranous sac that transports materials to the cell surface for exocytosis.

Lysosome

Organelle containing digestive enzymes for intracellular breakdown.

Passive Transport

Movement of substances across a membrane without energy input.

Filtration

Passive transport that forces fluid through a membrane by hydrostatic pressure.

Simple Diffusion

Net movement of molecules from high to low concentration without assistance.

Facilitated Diffusion

Diffusion of molecules across a membrane via transport proteins.

Osmosis

Diffusion of water through a selectively permeable membrane.

Active Transport

Energy-requiring movement of substances against a concentration gradient.

Sodium-Potassium Pump

Active transport protein that expels Na⁺ and imports K⁺.

Bulk Transport

Movement of large quantities across the membrane via vesicles.

Endocytosis

Bulk transport process bringing material into the cell.

Exocytosis

Bulk transport process expelling material from the cell.

Transcription

Nuclear process where DNA is copied into mRNA.

Translation

Cytoplasmic process where ribosomes build proteins based on mRNA codons.

Codon

Three-nucleotide sequence on mRNA specifying an amino acid.

Anticodon

Three-nucleotide sequence on tRNA complementary to an mRNA codon.

Chromatin

Loose arrangement of DNA and proteins in the nucleus.

Chromosome

Condensed thread of DNA visible during cell division.

Mitosis

Somatic cell division producing two identical daughter cells.

Prophase

First mitotic stage when chromosomes condense and spindle forms.

Metaphase

Mitotic stage where chromosomes align at the cell equator.

Anaphase

Mitotic stage where sister chromatids separate to opposite poles.

Telophase

Final mitotic stage where nuclear membranes re-form around chromosomes.

Mutation

Permanent change in DNA sequence.

Telomere

Protective noncoding DNA at chromosome ends that shortens with division.

Histology

Study of tissues.

Epithelial Tissue

Tissue that covers surfaces and lines cavities.

Connective Tissue

Tissue that supports, binds, and protects other tissues; has matrix.

Muscle Tissue

Tissue specialized for contraction and movement.

Nervous Tissue

Tissue that conducts electrical impulses and supports neurons.

Squamous Cell

Flat, thin epithelial cell type.

Cuboidal Cell

Cube-shaped epithelial cell type.

Columnar Cell

Tall, column-shaped epithelial cell type.

Simple Epithelium

Single layer of epithelial cells.

Stratified Epithelium

Multiple layers of epithelial cells.

Matrix (in Connective Tissue)

Intercellular substance of fibers and ground material surrounding connective cells.

Collagen

Strong, fibrous protein common in connective tissues.

Skeletal Muscle

Voluntary muscle that moves the body.

Smooth Muscle

Involuntary muscle in walls of hollow organs and vessels.

Cardiac Muscle

Involuntary muscle of the heart with intercalated disks.

Neuron

Nervous tissue cell that conducts impulses.

Neuroglia

Supportive cells of nervous tissue.

Hyperplasia

Tissue growth by increasing cell number.

Hypertrophy

Tissue growth by enlarging existing cells.

Neoplasm

Abnormal tissue growth forming a tumor.

Metastasis

Spread of malignant cells to distant sites.

Atrophy

Shrinkage of tissue due to disuse or aging.