Cellular Transport

Cell membrane is selectively permeable Factors that affect permeability: –Size –Polarity –Presence or Absence or Protein Channels or Receptors

Diffusion Movement of substances from high concentration to low concentration Movement “down a concentration gradient” Due in part to random, rapid motion of molecules. Net Movement Equilibrium State Simple Diffusion. Roles in the Body Factors that Affect Rate: –permeability of membrane –Size of gradient –temperature

Osmosis Diffusion of water through a selectively permeable membrane. Movement of water –from “less salty” to “more salty” side of membrane –from low solute concentration to high solute concentration. –from high water concentration to low water concentration. Hypertonic Hypotonic Isotonic In everyday life: –Preservation of food –Eating of salty or sugary foods –Salt on a slug –contractile vacuoles –turgur pressure in plants

OSMOSIS DEMONSTRATION (DIALYSIS BAGS)

OSMOSIS EXPERIMENTAL RESULTS

OSMOSIS IN PLANT CELLS HYPERTONIC SOLUTION= PLASMOLYSIS HYPOTONIC SOLUTION= NORMAL TURGOR PRESSURE

OSMOSIS IN PLANT CELLS (Elodea) Plasmolyzed cells

Osmosis and Animal Cells CRENATION WILL LYSE NO CHANGE

OSMOSIS AND ANIMAL CELLS WILL LYSECRENATENO CHANGE

Facilitated Diffusion Movement from high concentration to low concentration through carrier proteins. Used to move ionic or large substances into or out of cells Passive process Carrier proteins are specific (will only move one substance) Important for moving sugars and amino acids into cells

Active Transport Movement of substances against a concentration gradient. –From low concentration to high concentration. requires energy pumping a substance ATP must be hydrolyzed to fuel this process Sodium-Potassium Pump Pumps sodium out of cells and potassium into cells. Important for the functioning of nerves and muscles. Pump is a membrane protein and an enzyme-- ATPase.

Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential

Moving the “Big Stuff” Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. Exocytosis Exocytosis - moving things out. This is how many hormones are secreted and how nerve cells communicate with one another This is how many hormones are secreted and how nerve cells communicate with one another.

Pinocytosis Cell forms an invaginationCell forms an invagination Materials dissolve in water to be brought into cellMaterials dissolve in water to be brought into cell Called “Cell Drinking”Called “Cell Drinking”

Example of Pinocytosis pinocytic vesicles forming mature transport vesicle Transport across a capillary cell (blue).

Receptor-Mediated Endocytosis Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.

Endocytosis – Phagocytosis Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating”

Three Forms of Transport Across the Membrane

Cellular Communication Cells communicate with each other via molecular messengers. Communication between adjacent cells occurs in animals via gap junctions, which are like doorways between cells. In plants, plasmodesmata serve as the doorways.

Cellular Communication Cells communicate with each other via molecular messengers. Communication between adjacent cells occurs in animals via gap junctions, which are like doorways between cells. In plants, plasmodesmata serve as the doorways.