Post on 18-May-2018
Chem 452 - Lecture 8Lipids and Cell Membranes
Part 3Question of the Day: What role do proteins play in biological membranes?
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Form vs. Function
• The membrane lipids give form to the cell membranes
• The membrane proteins provide the function
2
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane proteins function as
• Pumps (Chapter 13)
• Channels (Chapter 13)
• Signal transducers (Chapter 14)
• Energy transducers (Chapter 18 & 19)
3
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Different membranes contain different proteins.
• They can visualized using SDS-Polyacrylamide electrophoresis.
4
(Chapter 3, pp.71-75)
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Different membranes contain different proteins
5
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Different membranes contain different proteins
6
RBC plasma membrane muscle cell sarcoplasmic membraneretinal rod cell
photoreceptor membrane
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Proteins can associate with membranes in
different ways.
7
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Proteins can associate with membranes in
different ways.
✦ We will look a three different examples
• Bacteriorhodopsin (pump)
• Porin (channel)
• Prostaglandin H2 synthase-1 (enzyme)
8
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Archaeal Bacteriorhodopsin (Pump)• Uses light energy to transport ions across the
membrane.
9
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Bacteriorhodopsin (7 α-helical bundle)‣ There are 7 non-polar stretches of amino-acids.
10
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Bacteriorhodopsin (7 α-helical bundle)‣ There are 7 non-polar stretches of amino-acids.
10
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Bacteriorhodopsin (7 α-helical bundle)‣ There are 7 non-polar stretches of amino-acids.
10
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Hydropathy plots are used to look for
membrane spanning α-helicies
11
Glycophorin
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Hydropathy plots are used to look for
membrane spanning α-helicies
11
Glycophorin
DeterminingTransfer Energies
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Hydropathy plots are used to look for
membrane spanning α-helicies
11
Glycophorin
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Hydropathy plots are used to look for
membrane spanning α-helicies
12
Glycophorin
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Porin (Channel)
13
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Porin (Channel)
13
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Porin (Channel)
13
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Porin (Channel)
13
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Porin (Channel)
13
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Porin (Channel)‣ Sequence alternates between polar and non-polar
amino acid residues
14
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Porin (Channel)‣ Sequence alternates between polar and non-polar
amino acid residues
15
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Porin (Channel)‣ Sequence alternates between polar and non-polar
amino acid residues
15
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Porin (Channel)‣ Sequence alternates between polar and non-polar
amino acid residues
15
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Prostaglandin H2 synthase-1 catalase (Enzyme)
16
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Prostaglandin H2 synthase-1 catalase (Enzyme)
16
Promotes inflammation and modulates gastric acid secretion
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Prostaglandin H2 synthase-1 (Enzyme)
17
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Prostaglandin H2 synthase-1 catalase (Enzyme)
18
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Three examples of integral membrane proteins
• Prostaglandin H2 synthase-1 (Enzyme)‣ Inhibited by COX inhibitors (NSAID)
19
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Peripheral proteins are often have hydrophobic
lipids attached to them.
20
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Lateral Diffusion in membranes can have a wide
range of values.
21
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Lateral Diffusion in membranes can have a wide
range of values.
21S = (4Dt)1/2
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Lateral Diffusion in membranes can have a wide
range of values.
21
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Transverse diffusion is very slow.
22
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Fluid Mosaic Model of Singer and Nicolson
(1972).
23
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Transverse diffusion is very slow.
24
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Transverse diffusion is very slow.
24
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Transverse diffusion is very slow.
24
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
25
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
26
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
26
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
26
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
26
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
26
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
26
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
26
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
26
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Membrane fluidity is modulated by
• Fatty acid composition• Cholesterol (animals)
26
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins• Membranes are asymmetric
27
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Bacterial cells
28
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Eukaryotic cells
29
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Eukaryotic cells
29
Chem 452, Lecture 8 - Lipids and Cell Membranes
Cell Membrane Proteins✦ Eukaryotic cells
29
Chem 452, Lecture 8 - Lipids and Cell Membranes
Next up✦ Unit V, Lecture 9 - Membrane Channels and
Pumps. (Chapter 13)
30