CELL TRANSPORT

WHAT IS THE FUNCTION OF THE CELL MEMBRANE? Regulates what enters and leaves the cell Provides protection Provides support

WHAT IS THE FUNCTION OF THE CELL MEMBRANE? Semipermeable barrier that allows for passage of materials in and out of the cell

WHAT IS THE FUNCTION OF THE CELL MEMBRANE? “selects” materials for passage based on: 1.Size of molecule 2.Concentration differences 3.Polarity of molecules

STRUCTURE FLUID MOSAIC Membrane is constantly changing and molecules are able to move FOUR MAIN COMPONENTS

STRUCTURE 1.PHOSPHOLIPID BILAYER *a double layer of lipids HYDROPHOBIC TAIL Afraid/dislikes of water HYDROPHILIC HEAD Loves water

STRUCTURE The interior and exterior have polar (hydrophilic) regions which come in contact with water.

STRUCTURE The “middle” has a nonpolar (hydrophobic) zone which makes it difficult for materials to pass through.

STRUCTURE 2. PROTEINS *act as tunnels (or channels) for materials to pass through the hydrophobic middle of the membrane *two types

STRUCTURE INTEGRAL PROTEINS Found embedded within the lipid bilayer PERIPHERAL PROTEINS Found on the interior or exterior of the lipid bilayer

STRUCTURE 3. CHOLESTEROL *embedded within the “tails” of the bilayer to help maintain fluidity (flexibility) of the cell membrane

STRUCTURE 4. CARBOHYDRATE CHAINS *long chains of sugars that are connected to the exterior surface *main function: cell identification or recognition

STRUCTURE When attached to lipids they are called…. Glycolipids When attached to proteins they are called… Glycoproteins

Passive Transport Active Transport

TRANSPORT PASSIVE No energy is being used. Moves WITH the concentration gradient. (High to Low)

TRANSPORT ACTIVE Energy MUST be used. Moves AGAINST the concentration gradient (Low to High)

PASSIVE TRANSPORT 1. DIFFUSION The movement of particles from an area of higher concentration to an area of lower concentration to reach an EQUILIBRIUM.

PASSIVE TRANSPORT

2. OSMOSIS The diffusion of WATER through a selectively permeable membrane.

hill.com/sites/ /student_view0/chapter2/animation__how_osmosis_works.html

PASSIVE TRANSPORT OSMOSIS—3 Effects Isotonic Hypertonic Hypotonic *Will discuss later

PASSIVE TRANSPORT 3. FACILITATED DIFFUSION Molecules still move from higher to lower concentration. Diffusion… using carrier proteins.

ACTIVE TRANSPORT The movement of materials AGAINST a concentration gradient… Moving from lower concentration to higher concentration. Requires ENERGY!!!

ACTIVE TRANSPORT Solute Pumping Sodium-Potassium Pump “pumps” Sodium (Na) out and Potassium (K) in

ACTIVE TRANSPORT hill.com/sites/ /student_view0/chapter2/animation__how_the_sodium_potassium_pu mp_works.html

ACTIVE TRANSPORT BULK TRANSPORT ENDOCYTOSIS Taking material INTO the cell EXOCYTOSIS Taking material OUT of the cell

ACTIVE TRANSPORT ENDOCYTOSIS—2 TYPES PHAGOCYTOSIS “Cell eating” PINOCYTOSIS “Cell drinking”

THE EFFECTS OF OSMOSIS ON CELLS

ISOTONIC ISO = same The water and solute concentrations inside and outside of the cell are the same.

ISOTONIC RESULT: Equal movement of water into and out of the cell…normal cells-- EQUILIBRIUM

HYPERTONIC HYPER = over, above The solution outside the cell contains more solutes (which means less water).

HYPERTONIC RESULT: Water moves from a greater concentration (inside cell) to lesser concentration (outside cell)…cells CRENATE (they shrink).

HYPOTONIC HYPO = under, below The solution outside the cell contains less solutes (which means more water).

HYPOTONIC RESULT: Water moves from a greater concentration (outside cell) to lesser concentration (inside cell)…cells LYSE (they swell, and possibly burst).

CELL COMMUNICATION

WHY CELLS COMMUNICATE To share information To coordinate activities To find mates

METHODS OF COMMUNICATION DEPEND ON: Whether target is specific or general Whether target is close or far away

HOW CELLS COMMUNICATE 1. Sending signals Direct contact between membranes Hormones (chemical) Nerves (electrical) Environmental (light)

HOW CELLS COMMUNICATE

2. Receiving Signals Receptor proteins (bind to signal molecules) Responds only to signals important for its function Relays info to cell

HOW CELLS COMMUNICATE 3. Responding to Signals Change membrane permeability (open/close protein channels) Activate enzymes (cause chemical reactions) Forms a secondary messenger (acts to signal responses inside cytoplasm)

HOW CELLS COMMUNICATE