Cell Biology – Basic Structures & Functions

Vocabulary flashcards covering the major cell structures, organelles, and concepts discussed in the lecture notes.

Cell Theory

Principle stating that all organisms are made of cells, all cells come from pre-existing cells, and the cell is the most basic unit of life.

Cytoplasm

Jelly-like substance inside cells that contains dissolved building blocks and organelles; site of many chemical reactions.

Ribosome

Tiny organelle made of rRNA and proteins that links amino acids together to build polypeptides; site of protein synthesis.

Organelle

Membrane-bound (or specialized) structure within a cell that performs a distinct process, e.g., nucleus, mitochondrion.

Prokaryotic Cell

Cell lacking a nucleus and membrane-bound organelles; DNA is suspended in cytoplasm; usually single-celled (e.g., bacteria).

Eukaryotic Cell

Cell that contains a nucleus and other membrane-bound organelles; may be single-celled or multicellular.

Cytoskeleton

Flexible network of protein fibers (microtubules, intermediate filaments, microfilaments) that supports cell shape and movement.

Microtubule

Long, hollow cytoskeletal tube that gives a cell shape, serves as a track for organelle movement, and forms spindle fibers.

Intermediate Filament

Cytoskeletal fiber smaller than a microtubule; provides mechanical strength to the cell.

Microfilament

Smallest cytoskeletal fiber (actin filament) that enables cell movement, division, and muscle contraction.

Cytosol

Fluid portion of the cytoplasm (excluding organelles); composed mostly of water.

Protein

Polymer of 20 different amino acids that folds into diverse shapes to perform countless cellular functions.

Nucleus

Large organelle that stores and protects DNA while allowing regulated access for gene expression.

Endoplasmic Reticulum (ER)

Interconnected network of folded membranes where protein (rough ER) and lipid (smooth ER) synthesis occurs.

Lumen (of ER)

Internal space of the ER where newly made proteins and lipids are modified or folded.

Golgi Apparatus

Stack of membrane sacs that processes, sorts, and packages proteins and lipids for delivery.

Vesicle

Small, short-lived membrane sac that separates and transports materials within the cell.

Mitochondrion

Bean-shaped organelle with a double membrane that converts food molecules into usable cellular energy (ATP); has its own DNA and ribosomes.

Vacuole

Fluid-filled sac for storage of water, nutrients, ions, or enzymes; numerous and small in animal cells.

Central Vacuole

Large, water-filled vacuole in plant cells that provides support, stores substances, and may contain pigments or toxins.

Lysosome

Membrane-bound organelle containing activated hydrolytic enzymes that digest waste, damaged parts, or invaders.

Lysosomal Enzymes

Proteins synthesized in the rough ER, activated in the Golgi, and enclosed within lysosomes to break down biomolecules.

Centrosome

Region of cytoplasm that produces microtubules and houses a pair of centrioles; organizes spindle during cell division.

Centriole

Cylinder of short microtubules arranged in a circle; assists in spindle formation, cilia, and flagella development.

Spindle Fibers

Microtubule structures that grow from centrosomes and attach to DNA to separate chromosomes during cell division.

Cilia

Short, hair-like projections formed by microtubules that move fluids past the cell surface or enable locomotion.

Flagellum

Long, whip-like projection powered by microtubules that propels a cell through a fluid environment.

Cell Wall

Rigid layer outside the plasma membrane in plants and some organisms that provides protection, support, and shape.

Chloroplast

Plant organelle with double membrane where photosynthesis occurs; contains chlorophyll, its own DNA, and ribosomes.

Thylakoid

Flattened membrane sac inside chloroplasts that contains chlorophyll and is site of the light-dependent reactions.

Chlorophyll

Light-absorbing green pigment embedded in thylakoid membranes that captures solar energy for photosynthesis.