EQ: EXPLAIN HOW ACTIVE AND PASSIVE TRANSPORT HELP

THE CELL MAINTAIN HOMEOSTASIS.

SC B-2.5EXPLAIN HOW ACTIVE,

PASSIVE, AND FACILITATED TRANSPORT SERVE TO

MAINTAIN HOMEOSTASIS OF THE CELL

Cell Transport

CELL TRANSPORTCHAPTER 7 SECTION 3

DEFINITIONS: Equilibrium: state that exists when the

concentration of a substance is the same throughout a space

Concentration Gradient: difference in the concentration of a substance across a distance

Passive Transport

dfn: movement of substances across a cell membrane without requiring energy expenditure by the cell

Types: Diffusion Facilitated Diffusion Osmosis

Passive transport

Particles are said to move “down their concentration gradient”

It is free!

DIFFUSION

The movement of particles from regions of higher density to regions of lower density

Also called simple diffusion

Small, nonpolar molecules pass through the cell membrane by simple diffusion Ex: oxygen, carbon dioxide

SIMPLE DIFFUSION

DIFFUSION RATE

Rate of diffusion affected by: Temperature Surface area Concentration gradient Size of molecule

SIMPLE DIFFUSION ACROSS a MEMBRANE

FACILITATED DIFFUSION

Same as simple diffusion (particles move down their concentration gradient) except particles require the use of a transport protein to cross cell membrane

FACILITATED DIFFUSION

Because it requires a transport protein there is an upper limit to the # of molecules that can enter/exit a cell at any given moment

(called Tmax)

Facilitated Diffusion

Glucose enters cells via facilitated diffusion

OSMOSIS

Osmosis : the diffusion of water from a more dilute solution a more concentrated solution through a membrane that is permeable to water but not to the solute

solute: what is dissolved in solvent solvent: what dissolves the solute

Osmosis

Allows cells to maintain water balance as their environment changes

http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf

Osmosis

Water Channels (called aquapores) in membrane to allow polar water molecules to enter/exit cell In humans used by:

Respiratory system Reproductive system Urinary system (water conservation) Digestive system Homeostasis of body temperature

Osmosis in Red Blood Cells

Hypertonic Solutions Concentration of solutes higher than that

in cytoplasm Water follows its concentration gradient

and moves from ______________ to ___________

Cells will _________________, called crenation

http://www.tvdsb.on.ca/WESTMIN/science/sbi3a1/cells/Osmosis.htm

Osmosis in Red Blood Cells

If the solution is hypotonic, there is a lower solute concentration outside the cell than inside the cell

Water will move _____________The cell will __________, called hemolysis.

Osmosis with Red Blood Cells

If the solution the red blood cell is in has the same concentration of water as the cytoplasm in the cell there will be _________ movement of water.

This is called an isotonic solution.

Osmosis in Plant Cells

PASSIVE TRANSPORT

http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html

ACTIVE TRANSPORT

Dfn: the movement of substances against their concentration gradient (against the flow)

Substances are moving from an area of lower concentration to an area of higher concentration

This requires the cell to use energy (ATP)

ACTIVE TRANSPORT

TWO TYPES:PUMPSVESICLES

ENDOCYTOSIS EXOCYTOSIS

ACTIVE TRANSPORT PUMPS

Use a carrier protein (like facilitated diffusion) but requires expenditure of energy

Most common pump:Na+/K+/ATP pump

Na+/K+/ATP pump

A carrier protein that uses ATP (1) to actively transport sodium ions (3) out of the cell and potassium ions (2) into the cell.

This pump keeps the [Na+] inside the cell lower so that osmosis will not cause the cell to swell with water.

ACTIVE TRANSPORTVESICLES

Used to transport molecules that are too large to fit thru a carrier protein. Endocytosis

Cell “eating” (phagocytosis) or cell “drinking” (pinocytosis)

Cell wraps membrane around material forming vesicle which is taken into cell

Exocytosis For moving material out of cell Vesicle fuses with cell membrane releasing

contents outside of cell

ENDOCYTOSIS EXOCYTOSIS

Endocytosis Exocytosis

Active Transport Animation

http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html

Review Time

http://www.learnerstv.com/animation/animation.php?ani=164&cat=biology