BIOD 101 Key Terms (Module 1-2 Overview)

Vocabulary-style flashcards covering key terms and concepts from BIOD 101 Module 1–2 notes, including cell structure, biomolecules, membrane biology, and basic genetics.

Passive transport

Movement of substances across the cell membrane without expending cellular energy; includes simple diffusion, osmosis, filtration, and facilitated diffusion.

Active transport

Movement of substances across the cell membrane that requires energy (usually ATP) and often moves substances against their concentration gradient (e.g., sodium–potassium pump).

Biomacromolecules

The four major organic macromolecule groups: carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

Biomolecules made of carbon, hydrogen, and oxygen; primary energy source; monomers are monosaccharides and can form polysaccharides like starch and glycogen.

Monosaccharide

Simple sugar; the basic building block of carbohydrates.

Polysaccharide

Large carbohydrate formed by many monosaccharide units; examples include starch, glycogen, and cellulose.

Starch

Plant storage form of glucose.

Glycogen

Animal storage form of glucose, primarily in liver and muscle.

Lipids

Nonpolar, hydrophobic biomolecules important for energy storage, membranes, and signaling; built from glycerol and fatty acids; includes triglycerides and phospholipids.

Phospholipid

Amphipathic lipid with a polar head group and nonpolar tail; forms the phospholipid bilayer of cell membranes.

Phospholipid head group

Polar, hydrophilic region (usually a phosphate group with an attached group) that faces aqueous environments.

Phospholipid tail group

Nonpolar, hydrophobic hydrocarbon chains that face inward away from water.

Nucleic acids

Biomolecules (DNA and RNA) that store, transmit, and express genetic information.

DNA (deoxyribonucleic acid

Double-stranded nucleic acid that stores hereditary information; base pairings include A–T and C–G.

RNA (ribonucleic acid)

Single-stranded nucleic acid that deciphers genetic information from DNA and guides protein synthesis.

Nucleotide

Monomer of nucleic acids; consists of a phosphate group, a five‑carbon sugar, and a nitrogenous base.

Nucleus

Organelle that houses the cell’s genomic material and acts as the control center of the cell.

Ribosome

Molecular machines that synthesize proteins; can be free-floating or attached to the endoplasmic reticulum.

Endoplasmic reticulum (ER)

Membrane network involved in protein and lipid synthesis; rough ER has ribosomes, smooth ER does not.

Rough endoplasmic reticulum (RER)

ER region studded with ribosomes; synthesizes and begins processing proteins.

Smooth endoplasmic reticulum (SER)

ER region lacking ribosomes; involved in lipid synthesis and detoxification processes.

Golgi apparatus

Organelle that modifies, sorts, and ships proteins and lipids to their destinations.

Lysosome

Membrane-enclosed organelle containing enzymes that recycle or dispose of cellular debris.

Mitochondrion

Powerhouse of the cell; site of cellular respiration; produces ATP; contains inner membrane folds called cristae.

Cristae

Folds of the inner mitochondrial membrane that increase surface area for energy production.

Peroxisome

Small organelle containing enzymes that break down fats and detoxify hydrogen peroxide.

Cytoskeleton

Network of protein filaments that supports cell shape, anchors organelles, and enables movement; composed of microfilaments, intermediate filaments, and microtubules.

Microtubules

Thick cytoskeletal filaments that shape the cell, separate chromosomes during mitosis, and serve as tracks for organelle movement.

Microfilaments

Thin actin filaments that support cell shape and enable movement, including muscle contraction when interacting with myosin.

Intermediate filaments

Cytoskeletal filaments providing tensile strength and structural support; part of the nuclear lamina.

Extracellular matrix (ECM)

The network of proteins and polysaccharides outside cells that provides structural and biochemical support to surrounding cells.

Fibronectin

Glycoprotein in the ECM that helps anchor cells to the ECM.

Integrins

Cell surface receptors that connect the ECM to the cell’s cytoskeleton and mediate signaling.

Cell junctions

Structures that connect adjacent cells; include tight junctions, desmosomes, and gap junctions.

Tight junctions

Cell junctions that wrap around cells to seal spaces and prevent leakage of extracellular fluid.

Desmosomes

Strong, snapping cell junctions that join adjacent cells into sheets, providing mechanical stability.

Gap junctions

Small channels that allow direct passage of ions and small molecules between neighboring cells.

Fluid mosaic model

Model describing the plasma membrane as a phospholipid bilayer with embedded proteins that move laterally within the layer.

Selective permeability

Property of the cell membrane that allows some substances to pass while restricting others.

Solute

Substance dissolved in a solvent.

Solvent

Substance in which solutes are dissolved.

Osmosis

Passive diffusion of water across a selectively permeable membrane.

Isotonic solution

Solution with equal solute concentration on both sides of a membrane.

Hypertonic solution

Solution with higher solute concentration; can cause cells to shrink as water leaves.

Hypotonic solution

Solution with lower solute concentration; can cause cells to swell as water enters.

Simple diffusion

Passive movement of molecules from high to low concentration without energy.

Facilitated diffusion

Passive transport that uses membrane channels or carriers to move substances down their concentration gradient.

Filtration

Movement of fluid through a membrane or small spaces due to pressure.

Endocytosis

Process by which cells engulf external materials into vesicles; includes phagocytosis and pinocytosis.

Exocytosis

Process by which vesicles fuse with the plasma membrane to release contents outside the cell.

Vesicle

Membrane-bound sac used for transport within, into, or out of the cell.

Ligand

Molecule that binds to a specific receptor to trigger a response.

Receptor-mediated endocytosis

Endocytosis initiated when a ligand binds to a receptor, triggering vesicle formation.

Phagocytosis

Endocytosis of large particles by engulfment.

Pinocytosis

Endocytosis of small droplets of fluid.

Electrochemical gradient

Combination of electrical and chemical gradients that drives ion movement across membranes.

Resting membrane potential

Electrical potential difference across the cell membrane when the cell is at rest.

Depolarization

Reduction in the difference in charge across the cell membrane, making the inside less negative.

Prokaryotic cell

Simple cell type lacking a true nucleus and membrane-bound organelles; usually smaller.

Eukaryotic cell

Cell type with a true nucleus and membrane-bound organelles; generally larger and more complex.

Adaptation (evolutionary adaptation)

Generational genetic changes that improve an organism’s ability to survive and reproduce in a given environment.

Population

A group of individuals of the same species living in a defined geographic area.