Biology 1202B Lecture Notes - Fluid Mosaic Model, Lipid Bilayer, Unsaturated Hydrocarbon

39 views3 pages
Published on 19 Apr 2013
Department
Membranes
Summary
Proteins in the Plasma Membrane
Membrane must have phospholipids that contain proteins to perform a variety of
functions
1. Transport – may or may not involve energy
2. Enzymatic Activity – number of enzymes are actually membrane proteins
3. Signal Transduction – receptors
4. Intercellular Joining – tight junctions, etc.
5. Cell-Cell Recognition – identifying foreigners by orientation/sensing each other for
development
6. Attachment to the cytoskeleton and extracellular matrix
Phospholipids
Made up of phosphate + glycerol (hydrophilic) and 2 fatty acid chains
(hydrophobic)
Types: Micelle (all tails point in), Liposome (inner + outer portions), bilayer (many
phospholipids)
Bilayers are studied by separating the 2 layers (bumps and matching concavities
show proteins)
Fluid Mosaic Model
Hydrophilic regions of proteins/phospholipids are in maximum contact with water,
hydrophobic regions are in a nonaqueous environment
Fluidity of Membranes
Membrane molecules are held in place by relatively weak hydrophobic interactions
oMost lipids and some proteins can drift laterally
Phospholipids are quick/ larger proteins are slow (directed manner may
be due to motor proteins of the cytoskeleton) or don’t move at all
(anchored by cytoskeleton)
Red and green membrane proteins mix freely in experiment
Influenced by temperature (cooling makes the membrane less fluid)
oMembranes rich in unsaturated fatty acids (contain double bonds) are more
fluid
Unsaturated hydrocarbon tails have kinks
Thickness- approx. 1-9 nm
Cholesterol
Amount varies by type of membrane (plasma has 1 per phospholipid
molecule/others have none)
Cells can alter membrane lipid composition to compensate for temperature
changes
oCold-adapted organisms increase percentage of unsaturated phospholipids in
autumn
oAlso can hold phospholipids together when it gets too hot
Membrane Proteins
Determine most of the membrane’s specific functions
oPeripheral Proteins – not embedded in lipid bilayer (loosely bound to the
either surface)
oIntegral Proteins- penetrate hydrophobic core of lipid bilayer, often spanning
membrane
Hydrophobic regions with nonpolar amino acid (alpha-helices) that
Unlock document

This preview shows page 1 of the document.
Unlock all 3 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Phospholipids are quick/ larger proteins are slow (directed manner may be due to motor proteins of the cytoskeleton) or don"t move at all (anchored by cytoskeleton) Red and green membrane proteins mix freely in experiment. Influenced by temperature (cooling makes the membrane less fluid: membranes rich in unsaturated fatty acids (contain double bonds) are more fluid. Unsaturated hydrocarbon tails have kinks: thickness- approx. Membrane proteins: determine most of the membrane"s specific functions, peripheral proteins not embedded in lipid bilayer (loosely bound to the, integral proteins- penetrate hydrophobic core of lipid bilayer, often spanning either surface) membrane. Hydrophobic regions with nonpolar amino acid (alpha-helices) that contact core. Membrane carbohydrates from another: function: organization as tissues/organs, development and rejection of foreign cells by immune system. Chemical specificity each protein is specific to what it will transport. It id digested when the vacuole fuses with a lysosome: pinocytosis (cellular drinking) cell creates a vesicle around a droplet of ecf (nonspecific)

Get OneClass Grade+

Unlimited access to all notes and study guides.

YearlyMost Popular
75% OFF
$9.98/m
Monthly
$39.98/m
Single doc
$39.98

or

You will be charged $119.76 upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.