Membranes

C483 Spring 2013

Trans fatty acids have physical properties like those ofA) w-3 fatty acids.B) cis-fatty acids.C) unsaturated fatty acids.D) saturated fatty acids.

Triacylglycerols are not found in cell membranes because they are A) amphipathic.B) not amphipathic.C) not abundant in cells.D) charged at biological pH.

Glycerophospholipids have ________ heads and long ________ fatty acid tails.A) polar; polarB) polar; hydrophobicC) hydrophobic; polarD) hydrophobic; hydrophobic

Which type of membrane protein might be dissociated from the membrane by changing the pH or the ionic strength? A) Integral membrane protein.B) Lipid-anchored membrane protein. C) Peripheral membrane protein.D) All of the above.

Which can serve as an energy source for secondary active transport? A) Ion concentration gradient. B) Light. C) Electron transport. D) ATP → ADP

Lipids and Membranes

• There is a lot of important biochemistry of lipids.

• We won’t cover it all!• The key points for this class have to do with

their role in membranes and fat metabolism

Overview

• Read chapter 9, sections 1-4, 6, 8-10– Section 9.11 is important in discussion

• Major topics– Metabolism: fatty acids and triacylglyderieds– Membrane components: phosphoglycerides and

steroids– Membrane structure and dynamics– Membrane function: transport

Diversity

Fatty Acids

• Saturated• Unsaturated• Polyunsaturated• Cis and trans

Triacylglyderides

Phosphoglycerides

• aka glycerophospholipids• Polar head, hydrophobic tail

Diversity

Phospholipases

• Wide variety of phosphoglycerides

• Processed by range of lipases

• Snake venom

Steroids

• Structural similarity, functional diversity

Membranes

• Complex• Fluid• Dynamic• Compartment-

alization• Communication• Gradients

Lipid Bilayer

Dynamic

Fluid Mosaic

• Glycoproteins, proteins• Affect of cholesterol

Integral Membrane Proteins

Lipid anchored membrane proteins

Membrane Transport

• No thermodynamics for now• Pores and channels• Selective permeability• Sets up gradients

Types of Transport

• Passive Transport—with concentration or charge gradient– Diffusion across membrane– Facilitated diffusion

• Active Transport—goes against concentration or charge gradient– Requires energy input– Always facilitated

Facilitated Transport

Types of Transport

• Both passive and active transport can be– Uniport– Symport– Antiport

Primary and Secondary Transport

Answers

1. D2. B3. B4. C5. A