Cell Transport, Permeability, and Epithelial Tissue: Study Guide for ANP Lab

Cell Transport and Permeability

Overview of Cell Transport Mechanisms

Cells maintain homeostasis by regulating the movement of substances across their membranes. Transport mechanisms are classified as passive or active, depending on whether they require energy input.

• Passive Transport: Movement of substances without energy input, driven by concentration gradients.

• Active Transport: Movement of substances against concentration gradients, requiring cellular energy (ATP).

Key Terms and Definitions

• Simple Diffusion: Movement of molecules from high to low concentration, directly across the membrane.

• Facilitated Diffusion: Passive movement of molecules via membrane proteins.

• Filtration: Movement of water and solutes through a membrane due to hydrostatic pressure.

• Kinetic Energy: Energy of motion driving diffusion.

• Selective Permeability: Property of membranes allowing some substances to pass while restricting others.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Hypertonic Solution: Higher solute concentration outside the cell; water leaves the cell.

• Hypotonic Solution: Lower solute concentration outside the cell; water enters the cell.

• Isotonic Solution: Equal solute concentration inside and outside the cell; no net water movement.

• Crenation: Shrinking of animal cells in a hypertonic solution.

• Plasmolysis: Shrinking of plant cell cytoplasm due to water loss.

• Cytolysis: Bursting of cells in a hypotonic solution.

• Hemolysis: Destruction of red blood cells due to excessive water intake.

• Electrolytes: Substances that dissociate into ions in solution, affecting osmotic balance.

• Endocytosis: Active process of taking substances into the cell via vesicles.

• Exocytosis: Active process of expelling substances from the cell via vesicles.

• Phagocytosis: "Cell eating"; engulfing large particles.

• Pinocytosis: "Cell drinking"; uptake of fluid and dissolved substances.

• Receptor-mediated Endocytosis: Specific uptake of molecules via receptor binding.

• Secretory Vesicles: Membrane-bound sacs for transporting substances out of the cell.

• Concentration Gradient: Difference in concentration across a membrane.

• Dialysis: Separation of small molecules from large ones using a semipermeable membrane.

Examples and Applications

• Osmosis: Red blood cells placed in a hypotonic solution undergo hemolysis.

• Facilitated Diffusion: Glucose transport into cells via carrier proteins.

• Filtration: Occurs in kidney glomeruli, filtering blood plasma.

Relevant Equations

• Fick's Law of Diffusion:

$J = -D \frac{dC}{dx}$

• Osmotic Pressure:

$\Pi = iMRT$

Where: $\Pi$ = osmotic pressure, $i$ = van't Hoff factor, $M$ = molarity, $R$ = gas constant, $T$ = temperature.

Histology: Epithelial Tissues

Classification and Characteristics of Epithelial Tissue

Epithelial tissues cover body surfaces, line cavities, and form glands. They are classified based on cell shape and number of layers.

• Apical Surface: The free surface exposed to the body exterior or cavity.

• Basal Surface: The surface attached to underlying connective tissue.

• Avascular: Lacking blood vessels; nutrients diffuse from underlying tissues.

• Basement Membrane: Thin layer anchoring epithelium to connective tissue.

• Regeneration: High capacity for cell renewal.

• Pseudostratified: Appears layered but all cells touch the basement membrane.

• Simple: Single layer of cells.

• Stratified: Multiple layers of cells.

• Squamous: Flat, scale-like cells.

• Cuboidal: Cube-shaped cells.

• Columnar: Tall, column-shaped cells.

• Non-keratinized: Lacks tough, protective protein keratin.

• Transitional: Specialized for stretching; found in urinary tract.

• Endocrine Gland: Secretes hormones into blood.

• Exocrine Gland: Secretes products into ducts.

• Cilia: Hair-like projections for movement of substances.

• Keratinized: Contains keratin; found in skin.

• Goblet Cell: Unicellular gland producing mucus.

Types of Epithelial Tissue: Location and Function

Type	Location	Function
Simple Squamous Epithelium	Alveoli of lungs, lining of blood vessels	Diffusion, filtration
Simple Cuboidal Epithelium	Kidney tubules, glands	Secretion, absorption
Simple Columnar Epithelium	Digestive tract lining	Absorption, secretion
Pseudostratified Ciliated Columnar Epithelium	Trachea, upper respiratory tract	Secretion, movement of mucus
Transitional Epithelium	Urinary bladder, ureters	Stretching, distension

Examples and Applications

• Simple Squamous: Facilitates gas exchange in alveoli.

• Transitional Epithelium: Allows bladder to expand as it fills.

• Pseudostratified Ciliated Columnar: Moves mucus out of respiratory passages.

Additional info:

• Epithelial tissues are essential for protection, absorption, filtration, and secretion.

• Regeneration is crucial for maintaining tissue integrity after injury.

Lab Assessment and Review

Study Recommendations

• Review all key terms from Exercises 5A and 6A.

• Practice identifying epithelial tissue types, their locations, and functions.

• Complete case studies and Mastering A&P exercises for comprehensive understanding.