L37-38 - 1 1 Biochemistry Sixth Edition Chapter 12 Lipids...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 1 Biochemistry Sixth Edition Chapter 12: Lipids and Cell Membranes Berg • Tymoczko • Stryer 2 Four major classes of biomolecules : 1.) Proteins 2.) Nucleic Acids 3.) Carbohydrates 4.) Lipids Chpt 11 Chpt 12 Chpts 4, 5 Chpts 2, 3 3 Bilayer formed by detergent molecules polar heads hydrophobic tails AIR AIR layer 1 layer 2 2 4 •Red-blood-cell plasma membranes Cell Membranes Two general membrane types: •External--aka ‘plasma’ membranes •Internal--those around organelles such as mitochondria, chloroplasts, peroxisomes, lysosomes. General properties of membranes: •DeFne inside and outside of cell. •Prevent molecules generated inside the cell from leaking out, and unwanted molecules from diffusing in. •Contain transport systems that allow the cell to take up or remove certain molecules--’selective permeability’ . 5 Common features underlie the diversity of biological membranes • Membranes are sheet-like structures, only two molecules thick. The thickness of most membranes is 60-100 Å. • Membranes consist mainly of lipids and proteins. (1:4 to 4:1 range, in mass). Can also contain carbohydrates linked to lipid or protein. • Lipids are small molecules with both hydrophilic and hydrophobic moieties. Spontaneously form closed bimolecular sheets in water. ¡orm barriers to ¢ow of polar molecules. • SpeciFc proteins mediate distinctive functions of membranes. Proteins serve as pumps, channels (Chpt 13), receptors, energy transducers, and enzymes. 6 • Membranes are noncovalent assemblies. The protein-lipid interactions are noncovalent and form in a highly cooperative fashion. • Membranes are asymmetric. The two faces of biological membranes always differ from each other. • Membranes are ¢uid structures. Lipid molecules diffuse rapidly in the plane of the membrane, as do proteins (unless anchored). Movement is largely two-dimensional. • Most cell membranes are electrically polarized, such that the inside is negative (typically –60 mV). Membranes are key in transport, energy conversion, and excitability. 3 7 Fatty acids are key constituents of lipds long hydrocarbon carboxylic acid varying degrees of unsaturation ionized at neutrality 8 Some fatty acid nomenclature: •See text for more details on fatty acid nomenclature (pp. 327-328). • ω-3 fatty acids have special health bene¡ts. 1 2 3 9 Fatty acids vary in chain length and degree of unsaturation •Find an even number of carbon atoms, with 16-18 being most common. •The hydrocarbon chain is almost always unbranched. •Can be saturated, or contain one or more double bonds, which are typically cis . •Saturation and longer chain length lead to higher melting points....
View Full Document

This note was uploaded on 07/23/2008 for the course CHEM 476 taught by Professor Bevilacqua,philip during the Fall '07 term at Penn State.

Page1 / 17

L37-38 - 1 1 Biochemistry Sixth Edition Chapter 12 Lipids...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online