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….

GlycolipidsWhen 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

PASSIVE TRANSPORT

2. OSMOSIS

• The diffusion of WATER through a selectively permeable membrane.

http://highered.mcgraw-hill.com/sites/0072495855/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

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

ACTIVE TRANSPORT

BULK TRANSPORTENDOCYTOSIS• 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).

http://www.youtube.com/watch?v=6MWl3DCa2uM

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

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