Phospholipid & the bilayer structure

Question 1

What is the defining characteristic of Phospholipids?

Answer 1

-They are Amphiphillic= part Polar (Hydrophillic) & Non-polar (Hydrophobic)

Question 2

What is the structure of a Phospholipid?

Answer 2

• Hydrophyllic Head= Phosphate & orients towards water

- Hydrophobic Tail= Fatty Acid chains that interact in the middle of the bilayer

Question 3

What is the purpose of the P.Lipid bilayer?

Answer 3

-The hydrophobic part of the bilayer (middle) forms barrier between inside (cytoplasm) & outside (extracellular fluid)

Question 4

What does it mean when a phospholipid membrane is PURE?

Answer 4

-It has no holes or alterations that are created by other components

Question 5

What would a Pure Phospholipid bilayer be permeable to?

Answer 5

• VERY permeable to Non-polar molecules

- SOME WHAT permeable to small polar molecules

Question 6

What would a Pure Phospholipid bilayer be impermeable to?

Answer 6

• VERY IMPERMEABLE to charges molecules/ ions

- Impermeable to large polar molecules

Question 7

Why can’t ions & large polar molecules pass DIRECTLY through the phospholipid membrane?

Answer 7

-There isn’t a specifc channel or carrier protein to help them cross over

Question 8

What do the proteins do in the pure phospholipid membrane?

Answer 8

-Proteins in the membrane MODIFY its properties greatly to allow important things to enter (glucose) & exit (waste) the cell

Question 9

What are the 2 kinds of membrane proteins?

Answer 9

• Integral membrane proteins

- Peripheral membrane proteins

Question 10

Where are Integral Membrane Proteins located?

Answer 10

• They span COMPLETELY ACROSS the membrane & very tightly bound to it
• Made up of Alpha Helices
• Only serve as 20% of proteins= important group w/ diverse functions

Question 11

Where are Peripheral Membrane proteins located?

Answer 11

-Sit only the surface of the membrane & LOOSELY bound to it

Question 12

What do Intergral Membrane proteins look like?

Answer 12

• They are rods that cut through the membrane

- Some of the rods span the membrane more than 20 times

Question 13

What is the Structure of Integral Membrane Proteins?

Answer 13

-They are divided into 3 domains= Intracellular, Transmembrane, Extracellular

Question 14

What is the Intracellular Domain of Integral Membrane Proteins?

Answer 14

-This domain is nearest cytoplasm= C-terminus

Question 15

What is the Transmembrane Domain of Integral Membrane Proteins?

Answer 15

• This domain cuts across the membrane

- Many have nonpolar amino acids that interact w/ tails

Question 16

What is the Extracellular Domain of Integral Membrane Proteins?

Answer 16

-Located nearest to top of membrane= N-terminus

Question 17

What do Peripheral Membrane Proteins do?

Answer 17

• They ionically & non-covalently bond to either the membrane or intergral membrane proteins
• BUT they don’t make strong interactions w/ membrane unlike the integral membrane proteins do

Question 18

What do Peripheral & Integral membrane proteins have in common?

Answer 18

• They both are critical to membrane function

- They both modify the membrane structure & properties

Question 19

How are membrane proteins chemically modified?

Answer 19

-Via carbohydrates that are glycosylated= forms Glycoproteins

Question 20

What else does the membrane contain?

Answer 20

-Other kinds of lipids= Cholesterol, Sphingolipids, Glycolipids

Question 21

What is Cholesterol, Steroid lipid contain?

Answer 21

-4 Carbon rings

Question 22

What are Sphingolipids?

Answer 22

-Lipids w/ 2 nonpolar tails but connected differently w/ a non-glycerol core

Question 23

What are Glycolipids?

Answer 23

-Lipids w/ carbohydrates attached