01:447:390 Lecture Notes - Lecture 2: Fluid Mosaic Model, Hopanoids, Permease
3 Oct 2018
School
Department
Course
Professor
I. Cell Membrane
a. Intro
i. Surrounds cell -- separates cytoplasm from external e
ii. Functions
iii. Phospholipid Bilayer
b. The Fluid Mosaic Model
i. Polar head
1. Glycerol - hydrophilic
2. Phosphate group - hydrophilic
3. Organic Group - hydrophilic, varies among species
ii. Tail
1. 2 hydrophobic fatty acid chains
2. Carbon and hydrogen
3. Vary in # of carbons & double bonds
4. Ester linkages which bond the fatty acids to the glycerol
iii. Protein
1. Determine most membrane functions - more than in eukaryotes
a. Ex: Permeases, energy, synthesis, sensory
iv. Hopanoids
1. Found only in Domain Bacteria
2. Pentacyclic, sterol-like molecules
3. Fxn: Stabilize membrane
II. Transport of Substances
a. Passive Transport
i. Simple Diffusion - Fig 4.27
1. Concentration gradient
a. No metabolic energy
2. Few substances that can cross - water, oxygen, carbon dioxide
ii. Facilitated diffusion
1. Membrane protein - Fig 4.28
2. Concentration gradient
3. Rate of diffusion
a. Rate increases with concentration gradient much faster and at a
lower concentration than simple diffusion = Saturation Effect
4. Ex: Aquaporin - increase the rate of H20 transport
b. Active Transport
i. Background
1. Transport substances that cannot move passively
2. Transport protein
a. = permeases
b. = carrier proteins
c. Against concentration gradient
d. Concentrate substances inside cell
ii. Ion-coupled Transport
1. Electrochemical gradient across cell membrane
a. Proton (H+) or Sodium motive force (Na+)
2. Symport
Document Summary
Surrounds cell -- separates cytoplasm from external e. Polar head: glycerol - hydrophilic, phosphate group - hydrophilic, organic group - hydrophilic, varies among species. Tail: 2 hydrophobic fatty acid chains, carbon and hydrogen, vary in # of carbons & double bonds, ester linkages which bond the fatty acids to the glycerol. Protein: determine most membrane functions - more than in eukaryotes, ex: permeases, energy, synthesis, sensory. Hopanoids: found only in domain bacteria, pentacyclic, sterol-like molecules, fxn: stabilize membrane. Simple diffusion - fig 4. 27: concentration gradient, no metabolic energy, few substances that can cross - water, oxygen, carbon dioxide. Background: transport substances that cannot move passively, transport protein, = permeases, = carrier proteins, against concentration gradient, concentrate substances inside cell. Ion-coupled transport: electrochemical gradient across cell membrane, proton (h+) or sodium motive force (na+, symport, simultaneous transport of 2 substances across membrane in the same direction.
