Lecture 2: Cellular organisation I – structure and membrane transport (EPBIOL259)

Flashcards covering core concepts of cellular structure, organelles, membrane components, and transport mechanisms from Lecture 2.

Cell Theory

Fundamental biology theory stating that all living things are composed of cells; cells are the smallest units of life; all cells arise from pre-existing cells; hereditary information is passed between generations; vital organism functions occur within cells.

Plasma membrane

The cell’s outer boundary; a phospholipid bilayer with embedded proteins and carbohydrates; regulates substance movement and maintains differences between the extracellular and intracellular environments.

Nucleus

Cell’s control center containing DNA/chromatin; enclosed by the nuclear envelope with pores; nucleolus synthesizes ribosomes.

Chromatin

DNA complex with proteins inside the nucleus that condenses into chromosomes during cell division.

Nuclear envelope

Double membrane surrounding the nucleus with nuclear pores for exchange of materials.

Nucleolus

Nuclear region where ribosomal RNA is synthesized and ribosome subunits are assembled.

Cytoplasm

Everything inside the cell membrane except the nucleus; includes cytosol, organelles, cytoskeleton, and inclusions.

Cytosol

Intracellular fluid; a clear, gel-like substance within the cytoplasm.

Organelles

Membrane-bound or cytoplasmic structures inside the cell that perform specific functions (e.g., mitochondria, ER, Golgi).

Inclusions

Aggregates of cell products or foreign material (lipids, glycogen, pigments, microbes) not enclosed by membranes.

Cytoskeleton

Network of protein filaments that provides structure, support, and movement; includes microfilaments, intermediate filaments, and microtubules.

Microfilaments (actin)

Thin protein filaments important for cell movement and shape changes; part of the cytoskeleton.

Intermediate filaments

Medium-thickness filaments providing mechanical support and structural integrity to cells.

Microtubules

Hollow tubules that support cell shape, organize organelles, and form the mitotic spindle during cell division.

Endoplasmic reticulum

Network of folded membranes; site of protein and lipid synthesis; continuous with the nuclear envelope.

Rough endoplasmic reticulum

ER studded with ribosomes; synthesizes secretory proteins and membrane components.

Smooth endoplasmic reticulum

ER without ribosomes; synthesizes lipids, detoxifies, and stores calcium in some cells.

Ribosomes

Ribonucleoprotein particles that synthesize proteins; free ribosomes for internal use; attached ribosomes for secreted or membrane proteins.

Golgi apparatus

Processing, sorting, and shipping center; adds carbohydrates to proteins; produces secretory vesicles and lysosomes.

Vesicles

Membrane-bound sacs that transport materials; include secretory and endocytic vesicles.

Lysosomes

Membrane-bound organelles with digestive enzymes that break down biomolecules and debris.

Peroxisomes

Organelles with enzymes to break down fatty acids and detoxify; produce hydrogen peroxide and neutralize free radicals.

Mitochondria

Cell’s powerhouses; generate ATP via cellular respiration; numerous in energy-demanding cells; have cristae to house enzymes.

Centrosome

Organelle near the nucleus that organizes microtubules and spindle apparatus during cell division.

Centrioles

Cylindrical structures within the centrosome that organize spindle fibers during mitosis.

Microvilli

Small, finger-like extensions that increase surface area for absorption (e.g., intestinal epithelium).

Cilia

Hair-like projections on the cell surface; move mucus and debris along surfaces; built on a microtubule core.

Flagella

Long whip-like tail used for cell movement; in humans, primarily the sperm tail.

Pseudopods

Temporary cytoplasmic extensions used for cell locomotion and phagocytosis.

Tight junctions

Cell junctions that seal adjacent epithelial cells at their apical surfaces to prevent leakage.

Desmosomes

Strong cell–cell junctions that hold cells together in tissues, providing mechanical strength.

Gap junctions

Intercellular channels that allow rapid passage of ions and small molecules between neighboring cells.

Glycocalyx

Carbohydrate-rich coating on the cell surface composed of glycolipids and glycoproteins; involved in adhesion, protection, and self/non-self recognition.

Na+/K+ pump

Sodium–potassium ATPase that maintains resting membrane potential by pumping Na+ out and K+ in; requires ATP.

Endocytosis

Process by which cells engulf external material via vesicle formation to bring substances into the cell.

Exocytosis

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

Phagocytosis

Engulfment and ingestion of large particles or microbes by cells.

Pinocytosis

Cell drinking; uptake of extracellular fluid and solutes via small vesicles.

Receptor-mediated endocytosis

Selective endocytosis triggered when ligands bind to cell-surface receptors, initiating vesicle formation.

Transcytosis

Transport of substances across a cell via endocytosis on one side and exocytosis on the other.

Diffusion

Passive movement of molecules down a concentration gradient; simple diffusion for lipid-soluble substances; facilitated diffusion uses channels or carriers.

Facilitated diffusion

Passive transport that requires a membrane protein (channel or carrier) to help solute movement down its gradient.

Osmosis

Passive diffusion of water across a selectively permeable membrane from higher to lower water concentration.

Filtration

Force-driven movement of water and solutes through a membrane, such as across capillary walls or in kidneys.

Isotonic

Solution with the same osmotic pressure as the cell interior; no net water movement.

Hypotonic

Solution with lower solute concentration than the cell interior; net water movement into the cell.

Hypertonic

Solution with higher solute concentration than the cell interior; net water movement out of the cell.

Passive transport

Transport that does not require ATP; includes diffusion, osmosis, and facilitated diffusion.

Active transport

Energy-requiring transport that moves substances against their concentration gradient (e.g., Na+/K+ pump).