Human Phys 1.1

Question 1

What is the common structure of all cell membranes?

Answer 1

They are composed as phospholipids

Question 2

What type of structures are cell membranes?

Answer 2

Dynamic and fluid structures

Question 3

What can membrane constituents do?

Answer 3

Move about the plane of the membrane

Question 4

What percentage of proteins encoded in an animal cells genome are membrane proteins?

Answer 4

30%

Question 5

What is the most predominant type of phospholipids?

Answer 5

Phosphoglycerides

Question 6

What do phosphoglycerides contain?

Answer 6

Glycerol backbone

2 hydrocarbon tails

Phosphate group attached to glycerol backbone

Question 7

What is the tail on a phosphoglyceride?

Answer 7

Hydrophobic

Question 8

What is the head on a phosphoglyceride?

Answer 8

Hydrophilic

Question 9

Where does the cis double bond (kink) occur?

Answer 9

In one of the hydrocarbon tails

Question 10

What does the cis double bond (kink) cause?

Answer 10

Width of lipid bilayer to be shorter

More space between lipid bilayer

Question 11

What does the cis double bond (kink) increase?

Answer 11

Increases membrane fluidity (important for proper physiological function)

Question 12

What can phospholipids do?

Answer 12

Spontaneously form bilayers (do it on their own with no help)

Question 13

What do phospholipid bilayers do because of their amphiphilic nature?

Answer 13

Bury their hydrophobic tails in the interior and expose their hydrophilic heads to water

Question 14

What does a cone shaped lipid molecule form?

Answer 14

Micelle

Question 15

What does a cylinder shape lipid molecule form?

Answer 15

Lipid bilayer

Question 16

What is the importance of lipid molecules being able to spontaneously form?

Answer 16

Important for self healing capability

Question 17

How does the spontaneous closure of a phospholipid bilayer work?

Answer 17

Hydrophobic edges are exposed to water (energetically unfavorable)

They fold up into a sphere to prevent water from touching hydrophobic edges (energetically favorable)

Question 18

What can membrane proteins do?

Answer 18

Move freely around the bilayer

Question 19

What are the different mechanisms that cells can tether membrane proteins?

Answer 19

Self assemble

Tethered to macromolecules on the outside

Tethered to macromolecules on the inside

Tethered to macromolecules in the surface of another cell

Question 20

What restricts proteins to specific domains?

Answer 20

Tight junction

Question 21

Why is it important that the tight junction restricts proteins to specific domains?

Answer 21

So functions carry out correctly (everything moves the right direction)