the
cell
MEMBRANES & PROCESSES Robert Perry MALIBU HIGH SCHOOL
ALL CELLS HAVE AN EXTERNAL PLASMA MEMBRANE and all EUKARYOTES also have membrane-enclosed organelles
WHAT ARE THE 3 GENERAL FUNCTIONS OF ALL MEMBRANES ? 1- TO ENCLOSE AND PROTECT FROM THE ENVIRONMENT. 2- TO CONTROL THE PASSAGE OF SUBSTANCES IN AND OUT. 3- TO COMMUNICATE WITH THE EXTERNAL ENVIRONMENT.
DIFFUSION is the net movement of molecules from higher a region of______ concentration to a lowerregion of
THE FORCE OF THE MOLECULES “BOUNCING” AGAINST EACH OTHER IN A CONCENTRATED SOLUTION CAUSES THEM TO MOVE APART
SUPPOSE THE LOCKED ROOM WAS PACKED WITH PEOPLE. PEOPLE COULDN’T MOVE AROUND AND BUMPED INTO EACH OTHER AT EVERY TURN.
SUPPOSE WHAT WOULD HAPPEN IF SOMEBODY OPENED UP THE DOORS.
DIFFUSION !
( these people have no confusion about diffusion ! )
DIFFUSION occurs when a system is not at equilibrium.
A concentration gradient exists. Dynamic equilibrium occurs when the movement of molecules is equal in all directions.
HIGH
LOW
Simple, inorganic, lipidsoluble molecules such as O2 , CO2, and H2O
(cytosol)
CONCLUSION: MOLECULES IN A SOLUTION DO NOT STOP MOVING, BUT AT EQUILIBRIUM THEIR MOVEMENT IS EQUAL IN ALL DIRECTIONS.
FACILITATED DIFFUSION
MOVES IONS AND MOLECULES THAT CANNOT DIFFUSE EASILY THROUGH WATER-FILLED TRANSPORT PROTEINS.
OSMOSIS diffusion of water semipermeable
v
through a membrane.
HYPOTONIC SOLUTION
HAS A LOW CONCENTRATION OF DISSOLVED SUBSTANCES COMPARITIVELY
ISOTONIC SOLUTION
HAS A THE SAME CONCENTRATION OF DISSOLVED SUBSTANCES COMPARITIVELY
HYPERTONIC SOLUTION
HAS A HIGH CONCENTRATION OF DISSOLVED SUBSTANCES COMPARITIVELY
OSMOSIS
Weight Change & NaCl Solutions 6
4
Wt. Change (g)
2
0 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
-2
-4
0.25 0.26 0.27 0.28 0.29 New % Salt Solutions for more precise data.
-6 % NaCl
OSMOSIS AND RED BLOOD CELLS:
Osmotic effects: plants vs. animals
Whole cell shrinks
Normal
Explodes
Cell interior shrinks
Flaccid
Turgid (normal)
ACTIVE TRANSPORT MOVEMENT OF MOLECULES AGAINST THE CONCENTRATION GRADIENT…AGAINST DIFFUSION…REQUIRES CELLULAR ENERGY IN THE FORM OF ATP
USES ENERGY
HOW DOES THE CELL TAKE IN & GET RID OF LARGE CHUNKS OF MATERIAL ?
food molecules or water molecules
membrane pinches together vacuole forms
digestion---->
release of secretions or wastes
vacuole reaches membrane
wastes or other molecules
SUMMARY: “FREE”
DIFFUSION
NO ENERGY USED
OSMOSIS SMALL STUFF: ATOMS and MOLECULES !
SUMMARY: “NOT FREE”
ACTIVE TRANSPORT
ENERGY IS USED
ENDOCYTOSIS EXOCYTOSIS
AGAINST CONCENTRATION GRADIENT
BIG STUFF: CHUNKS of FOOD, WATER or WASTES
THE END
The fluid mosaic model of MEMBRANES fluid molecules that easily move and flow. mosaic
made of different molecules put together in a pattern.
model
a scientific description or theory
OUTSIDE
FLUID MOSAIC MODEL
OUTER PROTEIN fat with sugar attached
INNER PROTEIN protein with sugar attached INSIDE
large channel protein
(leave room to add functions to this
THE PHOSPHOLIPID BILAYER THE FOUNDATION OF ALL MEMBRANES.
PHOSPHOLIPID
TRANSPORT PROTEINS (aka Channel Proteins) CARBOHYDRATE CHAINS
ACTIVELY TRANSPORT SUBSTANCES ACROSS MEMBRANE CELL INDENTITY AND RECOGNITION
OUTER PROTEINS
RECEIVE SIGNALS AND SEND TO CELL INTERIOR
INNER PROTEINS
ANCHOR POINTS FOR CYTOSKELETON
CHOLESTEROL
KEEPS PHOSPHOLIPID BILAYER FLUID
(add functions to your membrane diagram)