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

Main structural component of cell membrane Phospholipids Main structural component of cell membrane

Proteins Proteins 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 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 TRANSPORT MOVEMENT 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

DIFFUSION Movement 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

FACILITATED DIFFUSION Transport 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, so, it is still passive transport. WHAT MOLECULES NEED HELP? Polar molecules and ions are diffused across through channel proteins. They have charges and are repelled by the ends of the phospholipid molecules of the membrane Large molecules like amino acids and glucose are diffused across with the help of both channel and gated-channel proteins. Example: insulin ‘unlocks’ the gate to allow glucose into the cell

OSMOSIS Very similar to diffusion with two exceptions: MOVEMENT OF WATER ACROSS A SEMI-PERMEABLE MEMBRANE From an area of greater concentration Down a concentration gradient Toward equilibrium

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!

HYPERTONIC: HIGH SOLUTE CONCENTRATION outside cell membrane LOW WATER CONCENTRATION WATER MOVES OUT OF THE CELL CAUSING IT TO SHRIVEL UP, THIS IS CALLED PLASMOLYSIS

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.

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

OSMOSIS PRACTICE Environment= 75% water Environment= 30% solute Cell = 25% water Cell = 30% solute Water moves__________ Water moves__________ Environment= 40% solute Environment is 10% water Cell = 60% solute Cell = 90% water

I INITIAL OBSERVATION H PRELAB QUESTIONS What does the dialysis tubing represent? What is an indicator? For what substance is Lugol’s solution used as an indicator? How does Lugol’s indicate its presence? 7. How does the test strip indicate the presence of glucose? 8. Why were you asked to test starch with a test strip? A semi-permeable cell membrane A chemical that tests for the presence of another, usually with a color change Starch Turns dark blue/black Turns from teal to brown As a control. Starch is made of glucose monomers. There can be no ‘free’ glucose in the starch. I INITIAL OBSERVATION H FINAL OBSERVATION BEAKER STARCH GLUCOSE IODINE MEMBRANE

I INITIAL OBSERVATION H Homeostasis in Cells I INITIAL OBSERVATION H FINAL OBSERVATION BEAKER STARCH NO GLUCOSE IODINE YES MEMBRANE NO YES YES YES UNKNOWN YES GLUCOSE STARCH HYPOTONIC HYPERTONIC STARCH GLUCOSE WATER STARCH GLUCOSE IODINE WATER DID NOT MOVE TOO LARGE IODINE WATER OUT OF MEMBRANE DIFFUSION INTO MEMBRANE DIFFUSION SEA SHELLS INTO MEMBRANE OSMOSIS

I INITIAL OBSERVATION H Homeostasis in Cells I INITIAL OBSERVATION H FINAL OBSERVATION BEAKER STARCH GLUCOSE IODINE MEMBRANE

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

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