The Cell Membrane and Transport

The membrane is a fluid mosaic with a double layer of

phospholipids and embedded proteins throughout.

Jobs:

Regulates exchange

Creates a barrier

Communication

Identification

Phospholipids have both hydrophilic and hydrophobic regions

The proteins form a mosaic pattern on the membrane.

- Special Membrane Molecules -

Cholesterol - reinforces membrane by connecting phospholipids

Glycolipids and Glycoproteins – used for attachment and cell

communication

Special Membrane Proteins

1. Channel Proteins - form small openings for molecules to diffuse

through

2. Carrier Proteins- binding site on protein surface "grabs" certain

molecules and pulls them into the cell

Gated Channels - carrier proteins that are not always "open"

3. Receptor Proteins – molecule that triggers a cell

responses when the correct molecule attaches

4. Recognition Proteins - ID tags, identify cells to the

immune system

5. Enzymatic Proteins – specific reactions

Transport Across Membrane

*Selectively

permeable – only

some things can

cross

What things can

pass?

What cannot pass?

Passive Transport (no energy)

Simple Diffusion - water, oxygen and other molecules move from

areas of high concentration to areas of low concentration, down a

concentration gradient

Facilitated Diffusion - diffusion assisted by proteins (channel

or carrier proteins)

OSMOSIS

Osmosis - diffusion of water.

Osmosis affects the amount of water inside cells, different

solutions can draw water out or cell or cause cell to absorb

water

Salt Sucks!Simple rule of osmosis

Isotonic – same conc of water and solute, no net movement

Hypotonic – less solute (and therefore more water) outside cell,

water moves into the cell, cell could burst

Hypertonic – more solute (and therefore less water) outside

cell, water moves out of the cell, cell shrinks

Contractile Vacuoles are

found in freshwater

microorganisms to pump out

excess water in hypotonic

environment

Turgor pressure occurs in plants cells as their central

vacuoles fill with water.

Osmosis in U Tubes

Active Transport- involves moving molecules "uphill" against the concentration

gradient, which requires energy

Endocytosis - taking substances into the cell

(pinocytosis for water, phagocytosis for solids)

Exocytosis – reverse

endocytosis to move stuff out of

the cell, such as the removal of

waste

Protein Pump – Any protein that uses ATP to

actively transport a molecule against a

concentration gradient

Sodium-Potassium Pump – protein that pumps

out 3 sodiums for every 2 potassium's taken in

against gradient

A huge amount of energy in our bodies is used

to power this pump and prevent sodium from

building up within our cells.

Drives the signals in our nervous system

SODIUM

POTASSIUM

PUMP