Transcript CELL MEMBRANES

CELL
MEMBRANE
DEFINITIONS
 Hydrophilic
 Having an affinity for water
 Hydrophobic
 Tending to repel water
 Amphipathic
 Molecules that contain both water soluble
and water insoluble portions
SURFACTANT DEMO
WATER
 Formed by covalent
bonds between 1 oxygen
and 2 hydrogen atoms
 Unequal sharing of
electrons
Hydrogen have partially
positive charge
Oxygen has partially negative
charge
LIPIDS
 A diverse group of
carbon compounds
that are insoluble
in water
 Examples: fat and
oil
PHOSPHOLIPID
 Contain
 hydrophilic
phosphate group
 two hydrophobic
hydrocarbon tails
THOUGHT EXPERIMENT:
PART 1
 draw a beaker, and fill it 2/3 full of water
 imagine and draw how 5-10 phospholipid
molecules would arrange themselves if
they were dropped from above into this
beaker of water
THOUGHT EXPERIMENT:
PART 1
 Lipid Surface Monolayer
THOUGHT EXPERIMENT:
PART 2
 Draw another beaker 2/3 full of water
 Draw more molecules such that they are
submerged and surrounded by water.
THOUGHT EXPERIMENT:
PART 2
 Lipid Micelle
THOUGHT EXPERIMENT:
PART 3
 Draw another beaker 2/3 full of water
 Draw more molecules such that they are
submerged and surrounded by water, but
also able to contain water
THOUGHT EXPERIMENT:
PART 3
 Phospholipid bilayer
Cell Membrane
 In order to survive, cells must take in nutrients
form the non-living environment outside of the
cell and dispose of the wastes that build up
inside the cell.
 These processes occur through the cell
membrane.
 Regulating what enters and exits the cell is the
main function of the cell membrane.
Fluid Mosaic Model
 The current idea about the structure of
the cell membrane is referred to as the
Fluid Mosaic Model. The model was
devised by Singer and Nicolson in 1972.
Fluid Mosaic Model
 The cell membrane consists of two layers
of phospholipids (a bilayer).
Fluid Mosaic Model
Cholesterol
 Component of animal cell
membranes
 Molecule consists of a
hydrophobic hydrocarbon with a
hydrophilic hydroxyl group
 positioned between phospholipids
 Controls the fluidity and
permeability of the membrane
Fluid Mosaic Model
 Additionally, the cell membrane has a
variety of proteins embedded in it.
 The embedded proteins have several
functions.
Types of Proteins
Gatekeeper/ Channel proteins
 Provide paths through the membrane to allow
specific molecules to pass freely.
 molecules move in and out more quickly than
they could through regular diffusion and is known
as facilitated diffusion.
Types of Proteins
Hormone receptors


attach to hormones and pass the chemical
message to the interior of the cell.
Hormones have a special shape that fits into
the protein receptor.
Types of Proteins
Identification proteins
 Display the identity of the cell
 Have a carbohydrate attached. Known as
glycoproteins
 If a cell is not recognized as part of the
organism, it may be attacked by the organism’s
immune system.
Types of Proteins
Transport proteins


Move specific molecules into or out of the cell
against their concentration gradients (from low
concentration to high concentration).
This movement requires the use of energy and
is known as active transport.
Putting it all together
 Draw your version of the Fluid Mosaic
Model
 Include:
 Phospholipids
 A range of proteins
 Cholesterol
 Label all parts