Regulates what enters and leaves the cell, provides protection and support Double layered sheet...

25
Membrane Movement

Transcript of Regulates what enters and leaves the cell, provides protection and support Double layered sheet...

Membrane Movement

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

Dialysis tubing

Diffusion Experiment

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

1) Diffusion – 2) Osmosis

STILL PASSIVE TRANSPORT…..

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

OSMOSIS

lettuce entertain you....

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

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

THINK EGGS!

OSMOSIS

NO ENERGY!!!!

MOVEMENT OF WATER ACROSS A SELETIVELY PERMEABLE MEMBRANE – JUST WATER!!!!!!

ISOTONIC HYPERTONIC HYPOTONIC

Key Facts for Osmosis

1) Diffusion – 2) Osmosis 3) Facilitated Diffusion

STILL PASSIVE TRANSPORT…..

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

NO ENERGY!!!

Need a membrane protein to “help” the molecule across the membrane

Works WITH concentration gradient

Key facts for facilitated diffusion