TRANSPORT IN CELLS

TRANSPORT IN CELLS

Cell Membrane

• Once believed to be a covering like a balloon.• “Gate keeper” allows materials in and out

while maintaining the integrity of the cell.• Actually composed of many different

molecules

Phospholipids

Main structural component of cell membrane

ProteinsProteins embedded in membrane aid in the

transport of large molecules and energy.

Carbohydrates

Function to help cells recognize other cells, hold proteins in place and provide energy for repair

Fluid Mosaic Model

All the molecules of the cell membrane are in constant motion.

What benefit does the motion serve?

http://www.dnatube.com/video/360/Fluid-Mosaic-Model

Cell Size is related to transport. If the surface area to volume increases to much then materials will not be

able to move in or out fast enough. A small cell is a more efficient cell.

PASSIVE TRANSPORTMOVEMENT OF MOLECULES INTO OR OUT OF A

CELL WITHOUT THE CELL USING ANY ENERGY

MOLECULES MOVE DUE TO THEIR OWN KINETIC ENERGY AS LONG AS THERE IS A CONCENTRATION

GRADIENT PRESENT

DIFFUSIONMovement of any molecule

from an area of greater concentration to an area of lesser concentration

down a concentration gradient toward equilibrium.

Important Points…• All states of matter can diffuse.– solids, liquids, gases

• Diffusion can take place across a membrane– O2 and CO2 diffuse across cell membrane

• Factors that affect rate of diffusion– Heat: warm materials diffuse faster– Motion: stirring or shaking increases diffusion– Surface area: greater surface area faster diffusion– Volume: smaller space faster diffusion

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

FACILITATED DIFFUSIONTransport of molecules across a membrane with the

help of cell membrane proteins.Since the molecules are still moving down a concentration gradient, no energy is required.

WHAT MOLECULES NEED HELP? Polar molecules and ions are diffused across by

channel proteins. WHY?Because they are polar and dissolve in water and can’t get

past the hydrophobic ends of the membrane.Large molecules like amino acids and glucose are

diffused across with the help of carrier proteins.

OSMOSIS Very similar to diffusion with two exceptions:

MOVEMENT OF WATER ACROSS A SEMI-PERMEABLE MEMBRANE

From an area of greater concentrationDown a concentration gradient

Toward equilibrium

MERMAID

The direction the water moves,into or out of the cell…

depends upon how much material, or,solute is dissolved in the water!

OK, here’s where it can get confusing!Solutions are named based upon the amount of

dissolved solute not the amount of water…even though it’s the water that’s moving!

HYPOTONIC: LOW SOLUTE CONCENTRATION outside cell membrane

HIGH WATER CONCENTRATION outside cell membrane WATER MOVES INTO THE CELL

CAUSING IT TO SWELL, THIS IS CALLED CYTOLYSIS, IF THE

WATER CANNOT BE CONTROLLED THE CELL WILL RUPTURE. FLOWER

ISOTONIC: SOLUTE CONCENTRATION IS EQUAL

TO WATER CONCENTRATION INSIDE AND OUTSIDE OF CELL

WATER MOVES INTO AND OUT OF CELL

EQUALLY, NET VOLUME IS MAINTAINED= HOMEOSTASIS

HYPERTONIC: HIGH SOLUTE CONCENTRATIONoutside cell membrane

LOW WATER CONCENTRATION outside cell membraneWATER MOVES OUT OF THE CELL CAUSING IT TO SHRIVEL UP, THIS IS CALLED PLASMOLYSIS

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

OSMOSIS PRACTICE

Environment= 75% waterEnvironment= 30% solute Cell = 25% water Cell = 30% soluteWater moves__________ Water moves__________Environment= 40% solute Environment is 10% waterCell = 60% solute Cell = 90% waterWater moves__________ Water moves__________