membranes and microscopy

Question 1

5 membrane functions

Answer 1

1. semi permeable barrier
2. identification - with carbs and proteins
3. signaling
4. compartmentaliztion - organelles
5. energy storage - make a gradient

Question 2

structure of major lipids in cell membrane

Answer 2

• *amphipathic
  1. phospholipids - polar head (PO4 +alc)
  - glycerol or sphingosine backbone
  - hydrocarbon tail: fatty acid or sphingosine w/ hydrocarbons

2. glycolipid - sphingosine backbone + sugar on OH
3. cholesterol - hydrophobic rings with small OH
4. sphingomyelin - sphingosine with fatty acid and hydrocarbon chain, + phosphoryl choline head

Question 3

membrane permeability - who can and cannot cross

Answer 3

small uncharged nonpolar> small uncharged polar (water, CO2) > large polar uncharged > ions

Question 4

properties of peripheral and membrane proteins

Answer 4

• allow for selective permeability
  peripheral - can remove w/o damaging bilayer
  -attached to membrane or integral protein
  integral - amphipathic. alpha helices are hydrophobic and embedded in the middle
  -do not flip flop

Question 5

membrane lipid synthesis

Answer 5

• made on cytosolic side of ER
• glycerophospholipids are made and brought to cystolic half of bilayer
• scramblase - moves random glycerophospholipids to outer half to evenly distribute
• flippase: move specific phospholipids to create asymmetry

Question 6

microscopy techniques

Answer 6

1. conventional light - whole thing, living
2. fluorescence - dyes bind to detect specific macromolecules. different excitation/emission for diff molecules
   (indirect uses a fluorescent 2nd antibody)
3. transmission electron - for subcellular structures. use electrons rather than light.
4. scanning electron - view surfaces in 3D

Question 7

how to tell certain organelles in microscope

Answer 7

peroxisome - gray with dark spot
lysosome - really dark and round
mitochondria - look for cristae
golgi - flattened, tight pancakes, usually surrounds nucleus
ER - rough has ribosomes