Chapter 11 notes
Popular in Cell Biology
Popular in Biology
This 2 page Class Notes was uploaded by Brenna Eisenberg on Tuesday October 4, 2016. The Class Notes belongs to 327 at Syracuse University taught by erdman in Fall 2016. Since its upload, it has received 4 views. For similar materials see Cell Biology in Biology at Syracuse University.
Reviews for Chapter 11 notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/04/16
Chapter 11- membrane structure Saturday, October 1, 207:42 PM • Plasma membrane- protein studded, fatty film. Separates cell from external environment ○ Has highly selective channels and transporters • Lipid bilayer- fundamentalstructure of all cell membranes. ○ If there is a tear, the molecules will spontaneouslyrearrange to seal it. ○ Behaves as a 2D fluid ○ Flexible and able to bend • Phospholipids- have a phosphate containing head with a pair of hydrophobic tails. • Hydrocarbon tails determine fluidity ○ The closer and more regular packing of the tails, bilayer is more viscous and less fluid ○ Short chain length reduces the interaction of the tails, increasing fluidity ○ Unsaturated- has a double bond that creates a kink in the tail, making packing together harder. Makes bilayer more fluid ○ Saturated- tail has no double bonds • Cholesterol- short and rigid molecules, stiffens the bilayer and makes it less permeable • New phospholipids are made by enzymes of the ER • Scramblases- enzymes that catalyze the transfer phospholipids from one half of the bilayer to the other half. Redistributes the newly made phospholipidsequally to each monolayer. • Flippases- remove specific phospholipids from the side of the bilayer facing the exterior space and flip them into the inside monolayer. Maintains asymmetric arrangements of animal cells • Glycolipids are located in the monolayer that faces the exterior of the cell • Membrane proteins- carry out the majority of functions of the membrane ○ Each cell has a different set of proteins that reflect the different and specialized functions of the membrane • Membrane proteins can associate with the bilayer in different ways ○ Transmembrane proteins- extend through the bilayer with part of their mass on either side. Amphipathic ○ Some are almost entirely in the cytosolic half of the bilayer. Associated to the bilayer by an alpha helix Some are completely outside the bilayer, attached to the membrane by 1+ covalently attached lipid groups ○ Some are indirectly bound to one of the faces of the membrane. They are held in place by their interactions with other membrane proteins • Proteins that are directly attached to the bilayer can only be removed by disrupting the bilayer with detergents. Known asintegral membrane proteins ○ The remaining membrane proteins are peripheral membrane proteins, they can be released while leaving the bilayer intact • Polypeptide chains usually cross the bilayer as an alpha helix ○ Hydrophobic side chains are exposed on the outside of the helix ○ Atoms in the polypeptide backbone hydrogen bond to each other • Single pass transmembrane proteins- cross the membrane only once. Many are receptors for extracellular signals • Multi-pass transmembrane proteins- consist of a series of alpha helices that cross the bilayer multiple times. Usually channels. • The polypeptidechain of some transmembrane proteins cross the bilayer as a beta sheet that is rolled into a cylinder calleda beta barrel • Detergents- the most widely used disruptive agents. Forms micelles • Bacteriorhodopsin-membrane protein in archaea, acts as a proton pump, gets the energy from sunlight • The underlying cell cortex reinforces the plasma membrane ○ In plants, the cell wall stabilizes ○ In animal cells, there is a meshwork of fibrous proteins • A cell can restrict the movement of its membrane proteins, creating membrane domains, that are functionally specialized regions • The cell surface is coated with carbohydrates ○ Glycoproteins and proteoglycans are proteins with carbohydrates attached to them ○ The carbohydrates form a sugar coating called the glycocalyx. ○ This protects the cell surface from mechanical damage ○ Also lubricates the cell ○ Role in cell-cell recognition and adhesion. ○ Lectins bind to certain oligosaccharide side chains Chapter 11- membrane structure Page 1 Chapter 11- membrane structure Page 2
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'