5.1 Mini Lecture AP Biology

Which model was correct? PDQ 1. Singer and Nicholson

PDQ #2 Polar group – phosphate group  negative charge Net negative charge

Add descriptions/functions PDQ #3 Membrane Parts Add descriptions/functions Integral Proteins transports molecules across membrane B. Peripheral Proteins – transports molecules from protein to protein do NOT penetrate the membrane are hydrogen bonded to membrane

Add descriptions/functions PDQ #3 Membrane Parts Add descriptions/functions C. lipid Bilayer Hydrophilic end of phospholipids Polar head Has a negative charge Hydrophobic end of phospholipids Nonpolar tail Cholesterol Maintain fluidity of membrane See steroid structure?

Add descriptions/functions PDQ #3 Membrane Parts Add descriptions/functions Glycolipid Carbohydrate + lipid Cell recognition Glycoprotein Carbohydrate + protein Assist in binding of hormones Oligosaccharides Small polysaccharides Cytoskeleton Cell shape, movement of organelles

#4. What is meant by the phrase, membranes are asymmetric. Proteins are embedded asymmetrically across the membrane

#5. What components of the cell membrane contribute to the fluid quality of the cell membrane? Cholesterol – maintain the fluidity Fatty acids on hydrophobic portion (nonpolar tails)

Cholesterol Controls the fluidity of the cell membrane

Phospholipids Phospholipids may differ in: Fatty acid chain length Degree of saturation Kinds of polar groups present

PDQ 6 Two important factors in membrane fluidity: Lipid composition—types of fatty acids can increase or decrease fluidity Temperature—membrane fluidity decreases in colder conditions APPLY THE CONCEPT Biological membranes have a common structure and are fluid INTERACTIVE TUTORIAL 5.1 Lipid Bilayer: Temperature Effects on Composition

Proteins Peripheral membrane proteins lack hydrophobic groups and are not embedded in the bilayer. Integral membrane proteins are partly embedded in the phospholipid bilayer. PDQ 7. transmembrane protein extends through the bilayer on both sides

PDQ 8. Amphipathic – has hydrophilic and hydrophobic portions permanent

9. Types of amino acid side chains interface with fatty acid chains Nonpolar Hydrophobic Non-charged

10. Glycoprotein vs. Glycolipid Glycoprotein – carbohydrate attached to a protein Glycolipid – carbohydrate attached to a lipid

11. Roles of carbohydrates on surface of cell membrane Binding sites for molecules Help hold adjacent cells together