LIPIDS AND CELL MEMBRANES

1
LIPIDS AND CELL MEMBRANES

• 1. Functions of membrane
• separating the internal contents or organelles of
  a cell
• from its surroundings
• - plasma membrane
• - mitochondria, chloroplasts. peroxisomes,
  lysosomes
• 2) transport
• - channels
• - pumps
• - carrier proteins
• 3) communications
• - receptors
• - generating signals transduction of information
• 4) energy conversion processes
• - oxidative phosphorylation mitochondria
• - photosynthesis chloroplast
• 5) enzymatic functions

2
(No Transcript)
3
(No Transcript)
4
(No Transcript)
5

• 2. Common features of biological membranes
• 1) sheetlike structure
• - 60 - 100 Å thick
• 2) lipids proteins carbohydrates
• 3) lipid bilayers
• 4) distinct functions of membranes
• - specific proteins
• 4) noncovalent interaction
• 5) asymmetric
• 6) fluid structure
• - 2-dimensional solution
• 7) electrically polarized
• - the inside negative (- 60 mV)

6
(No Transcript)
7

• 3. Nomenclature of fatty acids
• 1) oic acid, enoic acid, dienoic acid, trienoic
  acid
• - octadecanoic aicd ocatadecanoate
• - octadecenoic acid
• - octadecadienoic aicd
• 2) the symbol
• - 180
• - 182
• - a, ß, ? carbon
• 3) the position of a double bond
• - cis-?9
• - trans-?2
• - ?-3 fatty acid

8
(No Transcript)
9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12

• 4. Membrane lipids
• 1) phospholipids
• - phosphoglyceride phosphatidyl serine
  (ethanolamine, choline, inositol)
• - sphingolipid spingosine ? sphingomyelin 
• 2) glycolipids
• - sugar-containing lipids
• - cerebrosides
• - gangliosides
• 3) cholesterol

13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22

• 5. Lipid bilayer
• 1) vs. micelle
• - two bulky fatty acyl chain
• 2) lipid bilayer formation
• - self assembly
• - hydrophobic interactions
• - van der Waals attractions hydrocarbon tails)
• - electrostatic attraction and hydrogen bonding
  polar head groups
• 3) features of lipid bilayers
• - extensive
• - no edges
• - self-sealing
• 4) artificial membranes
• - Liposomes
• - planar bilayer
• 5) permeability of membranes
• - ions
• - polar molecules
• - water

23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33

• 6. Membrane proteins
• 1) identification
• - SDS-polyacrylamide gel electrophoresis
• 2) classification
• - peripheral membrane proteins solubilized by
  relatively mild means
• - integral membrane proteins
• 3) bacteriorhodopsin (Halobacterium halobium)
• - light-activated proton pump
• - electron crystallography
• - 7 transmembrane a-helical segments
• 4) bacterial porin (Rhodobacter capsulatus)
• - ß strands
• - cylinder-like protein
• - the outside surface nonpolar
• - the inside of the channel polar

34
(No Transcript)
35

• 5) prostaglandin H2 synthase-1
• - membrane-bound enzyme
• - arachidonic acid ? prostagladin H2
• - not largely embedded in the memebrane a set of
  a helices with hydrophobic surface
• - integral membrane
• - The substrate, arachidonic acid is the a fatty
  acid generated from membrane lipids
• - aspirin transfer of an acetyl group from the
  aspirin to a serine residue
• 6) two features of membrane protein structure
• - hydrophobic parts
• - hydrogen bonds of all backbone hydrogen-bond
  donors and acceptors
• 7) membrane anchors
• - palmitoylation pamitoyl group (C16) at
  specific cysteine residue
• - farnesylation farnesyl group (C15) at the
  C-terminus
• - glycosyl phosphatidyl inositol units at the
  C-terminus

36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
(No Transcript)
40
(No Transcript)
41
(No Transcript)
42
(No Transcript)
43
(No Transcript)
44

• 8) prediction of transmembrane proteins
• - glycophorin A 131 amino acids
• - membrane-spanning region hydrocarbon core of
  membranes (30 Å),
•   one amino acid (1.5 Å)
• - hydropathy plot
• 9)  diffusion in the plane of the membrane
• - cell fusion mobile
• - some proteins are immobile
• - fluid mosaic model two dimensional solutions
  of oriented lipids and globular proteins
• - lateral diffusion, transverse diffusion
  (flip-flop)
• 10) asymmetry of membrane structure and fucntion
• - different components
• - different activities
• - membrane potential Na-K pump
• - proteins
• - lipids

45
(No Transcript)
46
(No Transcript)
47
(No Transcript)
48
(No Transcript)
49
(No Transcript)
50
(No Transcript)
51
(No Transcript)
52
(No Transcript)
53

• 6. Membrane fluidity
• 1) the number of double bonds
• 2) the length of fatty acyl chains
• 3) cholesterol
• - modulation of membrane fluidity
• - crystallization (more fluid)
• - large motion of fatty acyl chains (less fluid)

54
(No Transcript)
55
(No Transcript)
56
(No Transcript)
57
(No Transcript)
58
(No Transcript)
59

• 7. Compartments of eukaryotic cells
• 1) prokaryotes
• - E. coli two membranes, periplasm
• - gram positive bacteria or archaea a single
  membrane cell wall
• 2) organelles
• - nucleus
• - peroxisome
• - mitochondrion
• - endoplasmic recticulum
• 3) membrane budding
• - endocytosis
• - low-density lipoprotein

60
(No Transcript)
61
(No Transcript)
62
(No Transcript)
63
(No Transcript)
64
(No Transcript)
65
(No Transcript)