Regulates what enters and leaves the cell, provides protection and support Double layered sheet...
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Transcript of Regulates what enters and leaves the cell, provides protection and support Double layered sheet...
Regulates what enters and leaves the cell, provides protection and support
Double layered sheet called a LIPID BILAYER
Important membrane information
The control of particle movement across the membrane
Some substance pass freely through the membrane : water, glucose, oxygen
Some substance pass with effort or require energy: charged ions like Na
Other substances are not allowed to pass at all: large proteins or starch
SELECTIVE PERMEABILITY
There are so many different kinds of molecules in the membrane that it is called a “mosiac”
Often called a fluid mosiac model.
The Membrane Mosiac Model
Receptor Protein - designed so special molecules can bind to them, and send messages to the cell that trigger some sort of reaction within the cell.
Channel Proteins - proteins (one end polar one end nonpolar) that allow for ions to pass through the membrane down their concentration gradient
Structural Proteins - these proteins anchor to surfaces and help with cell-cell adhesion
Transport Proteins - proteins that change shape when they bind to a substrate and help facilitate diffusion of substances down their concentration gradient
The Membrane Mosiac Model
Proteins on the outer surface act as recognition molecules to help the organism recognize its own cells.
Proteins on the inner surface provide anchorage points for the cytoskeleton
Link to Cell Membrane
Constructing a Cell Membrane
So we built it, now what can it do????????
movement of molecules across the cell membrane and does not require energy
dependent on the permeability of the cell membrane
There are three main kinds of passive transport – ◦Diffusion◦Osmosis ◦Facilitated Diffusion
Passive Transport
CONCENTRATION: Mass of solute/volume of solution
Concentration gradient: the difference in concentration between a region of high concentration and a region of lower concentration◦ (high concentration) – (low concentration)
EQUILIBRIUM: when the concentration of the solute is the same throughout the system
Passive Transport
DEFINITION: the movement of particles from an areas where they are more concentrated to an area where they are less concentrated
diffusion animation
EQUILIBRIUM: when the concentration of the solute is the same throughout the system
Diffusion
NO ENERGY IS USED
◦ Diffusion is based on random movement of molecules to reach equilibrium
EVEN AT EQUILIBRIUM THE MOLECULES ARE STILL MOVING!!
KEY FACTS FOR DIFFUSION
DEFINITION – the diffusion of WATER through a selectively permeable membrane
In order to obtain EQUILIBRIUM, the water will cross from a high WATER concentration to a low water concentration.
Water molecules can cross a membrane that large molecules may not be able to cross.
OSMOSIS
ISOTONIC – both sides of the membrane have equal concentrations, it has reached equilibrium
HYPERTONIC – a higher solute concentration
HYPOTONIC – a lower solute concentration
OSMOSIS
OSMOSIS
osmosis working
What does this mean to the cell???◦ Organisms MUST maintain osmotic pressure to
survive
OSMOSIS
Osmotic pressure – definition – the increase in pressure resulting from the flow of water in osmosis
NO ENERGY!!!!
MOVEMENT OF WATER ACROSS A SELETIVELY PERMEABLE MEMBRANE – JUST WATER!!!!!!
ISOTONIC HYPERTONIC HYPOTONIC
Key Facts for Osmosis
DEFINITION - Movement of specific molecules across cell membranes through protein channels
NO ENERGY IS USED! Works ONLY in the direction of the
concentration gradient (high to low concentration)
Membrane proteins are specific for the molecule
FACILITATED DIFFUSION
Facilitated Diffusion
facilitated diffusion