8.1 Fluid Mosaic Model

Question 1

What does plasma membrane do?

Answer 1

Plays roles in signaling, entry of nutrients and expulsion of waste, cell recognition, transport of materials between tissues, and even electronic functions.

Question 2

Stabilizing molecules of cell membranes?

Answer 2

• cholesterol and protein

Question 3

Stretchy, flexible component of cell membrane?

Answer 3

• Phospholipids

Question 4

Cell (plasma) membrane

Answer 4

• a semipermeable phospholipid bilayer
• selectivity is mediated by various channels and carriers that poke holes in the membrane and membrane itself
• Composed primarily of two layers of phospholipids, the cell membrane permits fat-soluble compounds to cross easily, while larger and water-soluble compounds must seek alternative entry
• also contain proteins embedded within the lipid bilayer that act as cellular receptors during signal transduction. These proteins play an important role in regulating and maintaining overall cellular activity.

Question 5

What does phospholipid bilayer include?

Answer 5

• proteins and distinct signaling areas within lipid rafts
• Carbohydrates associated with membrane-bound proteins create a glycoprotein coat.
• Plants, bacteria and fungi walls have more carbs.

Question 6

How do phospholipids move rapidly in the plane of the membrane?

Answer 6

• Simple diffusion

Question 7

Lipid Rafts

Answer 7

• Collections of similar lipids with or without associated proteins that serve as attachment points for other biomolecules; these rafts often serve roles in signaling.

Question 8

Can lipids move between membrane layers?

Answer 8

• Yes, but this is
  energetically unfavorable because the polar head group of the phospholipid must be forced through the nonpolar tail region in the interior of the membrane.
• flippases assist in the transition or “flip” between layers