Mod2-Obj1: Structure of plasma membrane&selective permeability

Question 1

The cell membrane

Answer 1

Separates extracellular fluids (ECF) from intracellular fluids (ICF)

• Selective barrier/selectively permeable
• ECF contains interstitial fluid and plasma (blood)

Question 2

Membrane structure

Answer 2

Composed of phospholipids 
-Amphipathic 
Phospholipid bilayer 
-Thin and flexible
contains 
-Phospholipids (75%)
-Glycolipids (5%)
-Cholesterol (20%)

Question 3

Amphipathic

Answer 3

-Polar heads
-Non-polar tails
If comes into contact with water, heads will move, disrupting the bilayer

Question 4

Membrane proteins: Integral proteins

Answer 4

Embedded in the membrane

• Transmembrane
• Carrier and channels

Question 5

Membrane proteins: Peripheral proteins

Answer 5

Attach to integral proteins or float freely

-Plasma membrane, support, enzymes, movement

Question 6

Selective permeability: Lipid-soluble solutes

Answer 6

• Cross the lipid bilayer

i. e.) oxygen, CO2, fate soluble vitamins, fatty acids, steroids, hormones

Question 7

Selective permeability: Integral proteins

Answer 7

Molecules that are too large or lipid insoluble (polar)

• Carrier or protein channels
• Integral proteins are substance specific e.g.) glucose has to use a carrier protein, causing it to change shape and therefore enter the intracellular proteins

Question 8

Transport of water

Answer 8

Crosses the membrane freely, although lipid-insoluble

-Can use aquaporins

Question 9

Functions of the plasma membrane

Answer 9

Selective barrier
-Transport
Communication
-Receptors
Links to adjacent cells
-Skin cells

Question 10

Summary

Answer 10

• The plasma membrane is composed of phospholipids, glycolipids and cholesterol that allows it to continually move (fluid mosaic model)
• The phospholipid bilayer arrangement and membrane proteins permit selective permeability
• Lipid-soluble (non-polar) and small polar molecules can cross the plasma membrane freely
• Lipid-insoluble (polar) molecules use channels and carriers (integral membrane proteins), otherwise they would disrupt the bilayer