Diffusion and Osmosis

Cell Membrane: A protective layer defining cell borders, controlling environmental interaction, and facilitating communication and identification.
Lipids: Primarily composed of phospholipids ( $2$ fatty acid tails and glycerol) forming a bilayer; polar heads (phosphate and glycerol) face outward, while nonpolar tails face inward.
Proteins: Include integral (within the membrane) and peripheral (on the surface) proteins for transport and communication.
Carbohydrates: Form glycoproteins and glycolipids, which act as identification markers for the immune system.

Permeability Factors: Determined by solute size, charge, polarity, and lipid solubility; small, uncharged, nonpolar molecules pass most easily.
Diffusion: Passive movement of molecules from high to low concentration until equilibrium (net diffusion = $0$ ) is reached.
Predictors: The concentration gradient is the best predictor of movement; temperature and pressure also affect rates.

Osmosis: The diffusion of water across a membrane from a region of low solute concentration to high solute concentration.
Tonicity: The capacity of an extracellular solution to move water into or out of a cell.
Environmental States: Cells are analyzed in hypotonic, hypertonic, and isotonic environments.

Dialysis Bags: Used to mimic membranes; small pores allow water to pass but block larger molecules like glucose.
Beet Cells: Used to study membrane integrity; reddish pigment (betacyanin) is contained within the tonoplast (central vacuole).
Procedure 9.3 Materials: Includes Phenolpthalein (nonpolar), NaCl (polar), Starch (polar), and Iodine (polar).
Procedure 9.4 Parameters: - Bag A: $10\,cm^3$ of $1\%$ sucrose. - Bag B: $10\,cm^3$ of $1\%$ sucrose. - Bag C: $10\,cm^3$ of $10\%$ sucrose. - Bag D: $10\,cm^3$ of $20\%$ sucrose.
Procedure 10.2: Focuses on color intensity and absorbance readings for beet cell integrity analysis.