Cellular Transport

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 LYSENO CHANGE

OSMOSIS AND ANIMAL CELLS

WILL LYSE CRENATE NO 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 Sodium-Potassium PumpPump

3 Na+ pumped in for every 2 K+ pumped out; creates a membrane

potential

Moving the “Big Stuff”Moving the “Big Stuff”

Molecules are moved out of the cell by vesicles Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.that fuse with the plasma membrane.

ExocytosExocytosisis-

moving things out.

This is how many hormones are secreted and how This is how many hormones are secreted and how nerve cells communicate with one anothernerve cells communicate with one another.

PinocytosisPinocytosis

• Cell forms an Cell forms an invaginationinvagination

• Materials dissolve Materials dissolve in water to be in water to be brought into cellbrought into cell

• Called “Cell Called “Cell Drinking”Drinking”

Example of Example of PinocytosisPinocytosispinocytic vesicles forming mature transport vesicle

Transport across a capillary cell (blue).

Receptor-Mediated EndocytosisReceptor-Mediated Endocytosis

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

Endocytosis – Phagocytosis Endocytosis – Phagocytosis

Used to engulf large particles such Used to engulf large particles such as food, bacteria, etc. into vesiclesas food, bacteria, etc. into vesicles

Called “Cell Eating”Called “Cell Eating”

Three Forms of Transport Across the MembraneThree 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.