bio sci 93: lecture 5 - single cell dynamics; membrane structure

understand the major differences between eukaryotes and prokaryotes

illustrate and draw the structure and components in the fluid mosaic membrane model. Recognize the function of each components

describe how the orientation of membrane components arise during biosynthesis

probe the fluid model using experimental manipulations, “lateral drifting”

basic feature of all cells:

plasma membrane

semifluid substance called cytosol

chromosomes (carry genes)

ribosomes (make proteins)

prokaryotes DO NOT have a nucleus

eukaryotic cells

membrane-bound organelles

include fungi & protists

why have a plasma membrane?

provides protection from extracellular movement

allows for establishment of fixed environment in cell

provide a way to control traffic of substance in and out of a cell

lipids form fabric of plasma membrane

lipids: phospholipids (amiphiphile or amphipathic molecule)

phospholipids up close

2 fatty acid chains (one unsaturated and other saturated)

polar, hydrophilic phosphate group

FRAP: fluorescence recovery after photobleaching

temperature, saturated & unsaturated phospholipid tails, cholesterol content can all affect fluidity of the PM

plasma membrane is a mosaic

proteins embedded in bilayer and bound to surface of membrane

carbohydrates on extracellular surface as glycoproteins & glycolipids

how can protein be in the lipid bilayer?

alpha helices in bilayers are amphipathic:

one side of helix hydrophobic residues (nonpolar) are exposed to lipids

other side, hydrophilic (polar or changed) amino acids are concentrated

most phospholipids assembled in…

ER

proteins bound for plasma membrane and secreted proteins begin assembly in…

ER

cargo facing interior of vesicle will become…

extracellular face of plasma membrane

cargo facing exterior of a vesicle will become…

cytoplasmic face of plasma membrane