BIOSC 0100 Lecture Notes - Lecture 10: Fluid Mosaic Model, Lipid Bilayer, Electrochemical Gradient

14 views2 pages
6 Feb 2017
School
Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Chapter 6 Cont.
Cell membranes:
-Contain almost as much protein as phospholipids
-Early models of the cell membrane suggested that the phospholipid bilayer was sandwiched
between proteins
-Singer and Nicolson challenged the sandwich model and proposed that amphipathic proteins
could span the membrane
-Fluid Mosaic Model (1972) current model of cell membrane structure
Integral Membrane Proteins
-Embedded within the hydrophobic interior of lipid bilayers
-Amphipathic with a hydrophobic region that may cross the entire membrane or extend only
part way into the bilayer
-If the integral proteins span the entire membrane and have hydrophilic inside and outside the
cell is called a transmembrane protein
-Can be isolated from membranes with detergents (amphipathic molecules)
-Detergents break up the membrane
Peripheral Membrane Protein
-Proteins bind to the membrane without passing into the membrane
-Found only on one side of the membrane
-Non-covalent interactions often attached to integral membrane proteins
Transport proteins:
-Transmembrane proteins that transport ions and molecules
-Three classes: channels, carrier proteins/transporters, and pumps
Channel Proteins:
-Act as tunnels for ions or small molecules to cross a membrane
-Highly selective allow only a particular type of ion or molecule to pass through
-Electrochemical gradients occur when ions build up on one side of a plasma membrane
-Ion channels are specialized merae proteis that iruvet the plasa erae’s
impermeability to small, charged compounds
-Diffuse through channels down their electrochemical gradients
CFTR example of an ion channel
-Aquaporins water channels that allow water to cross the cell membrane faster than it would
by simple diffusion (kidneys, eyes = water needs to move faster)
-Flow of ions and small molecules through membrane channels is carefully controlled
-Gated channels: open and close in response to a signal
-Movement of substances through channels does not require an input of energy (high to low
concentration)
-Passive transport: diffusion of a substance across a membrane along an electrochemical
gradient with no energy investment
-Facilitated diffusion: passive transport of substances that would not otherwise cross the
membrane can occur through channels or through carrier proteins
Carrier proteins
-Can change shape during the transport process
-Carrier proteins only move molecules down a concentration gradient
-GLUT-1 is a glucose transporter that increases membrane permeability to glucose
-Carrier/transporter proteins are passive transporters high to low concentration
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows half of the first page of the document.
Unlock all 2 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class