Chapter 12 Membrane Structure and Function

Question 1

What is the membrane structure like and what does it form?`

Answer 1

It has sheetlike structures, two molecules thick and those form closed boundaries

Question 2

What are membranes composed of?

Answer 2

Lipids and Proteins and either of them can be decorated with carbs

Question 3

What are membrane lipids and what do they form and what is the purpose of them?

Answer 3

They are small Amphiathic molecules that form closed molecular sheets and helps prevent the movement of polar or charged membrane

Question 4

Membranes are _________________ assembiles

Answer 4

Noncovalent

Question 5

Membranes are ____________ in that the outer surface is always different from the inner surface

Answer 5

Asymmetric

Question 6

Membranes are ___________ structures

Answer 6

Fluid

Question 7

Most cell membranes are ____________________ such that the ____________ is negative

Answer 7

Electrically polarized , Inside

Question 8

What is the formation of membranes powered by?

Answer 8

Hydrophobic effect

Question 9

If two non polar molecules are next to each other in water, what will happen if you combined both of them

Answer 9

The entropy would increase

Question 10

What type of lipids form the lipid bilayer in aqueous solution?

Answer 10

Phospholipids and Glycolipids

Question 11

What is a liposome and what do we use them for?

Answer 11

They are aqueous compartments enclosed by a lipid membrane. Liposome is a used as a drug delivery system, so its more targeted and it means less of the body is exposed to potentially toxic drugs.

Question 12

Why are lipid bilayers highly impermeable to ions and most polar molecules?

Answer 12

Its because there is an energy cost for ions and polar molecules as they have to shed water so they can cross the lipid bilayers.

Question 13

What happens to the membrane transition at the melting temperature?

Answer 13

It goes from being highly ordered to very fluid

Question 14

What is melting temperature dependent on ?

Answer 14

It is dependent on the length of the fatty acids in the membrane and the degree of cis unsaturation.

Question 15

In animals, what helps maintain proper membrane fluidity in membranes?

Answer 15

Cholesterol

Question 16

What happens to the fatty acid chains if there is an unsaturated fatty acid in there?

Answer 16

A kink or a bump forms in the structure to show the unsaturated fatty acid

Question 17

What is the role of a membrane protein ?

Answer 17

It helps with transport of molecules and information across the membrane

Question 18

Where are the integral membrane proteins embedded ?

Answer 18

In the Hydrocarbon core of the membrane

Question 19

Where are the Peripheral membrane proteins bound to ?

Answer 19

They are bound to the polar head groups of membrane lipids or to the exposed surfaces of integral membrane proteins

Question 20

What are Hydrophobic moeitys function?

Answer 20

It is another way some proteins associate with membranes, this is an attachment that is inserted into the membrane

Question 21

What is a common structural feature of integral membrane proteins?

Answer 21

The membrane spanning alpha helices

Question 22

What other ways can you embed an integral membrane protein?

Answer 22

By using Beta strand to form a pore in the membrane or by embedding part of the protein into the membrane

Question 23

What is the COX activity of prostaglandin H2 synthase-1 dependent on?

Answer 23

A channel connecting there active site to the membrane interior

Question 24

How does the Aspirin inhibit COX activity?

Answer 24

By obstructing the channel

Question 25

What does the FRAP technique used for?

Answer 25

It allows the measurement of lateral mobility of membrane components

Question 26

What is the lateral diffusion of proteins dependent on?

Answer 26

Whether they are attached to other cellular or extracellular components

Question 27

Transverse diffusion is very rare without the assistance of _____________

Answer 27

Enzymes

Question 28

A small molecule will spontaneously cross a membrane if what two conditions are met?

Answer 28

1.The concentration of the molecule is higher on one side of the membrane than the other
2.The molecule is lipophilic or soluble in non polar solutions

Question 29

Polar molecules can diffuse with the assistance of a particular channel and such movement is called____________

Answer 29

Facilitated diffusion or Passive transport

Question 30

What is active transport?

Answer 30

It is a movement of molecules against a concentration gradient requires a source of energy

Question 31

What is a transport protein?

Answer 31

It is a pump or channel that facilitate the flow of small molecules across the cell membrane

Question 32

The Na and K ATPase uses the energy of ____________________ to simultaneously pump _________ Na ions out of the cell and _________ K ions into the cell against their concentration gradients

Answer 32

ATP hydrolysis, Three, Two

Question 33

What is a Symporter

Answer 33

It is a transport of molecule against its concentration gradient by coupling the movement to the movement another molecule down its concentration gradient with both molecules moving in the same direction.

Question 34

What is an antiporter?

Answer 34

It uses one concentration gradient to power the formation of another but the molecules move in opposite directions.

Question 35

What is a tetrodotoxin?

Answer 35

It is a lethal inhibitor of the Na channel produced by the pufferfish

Question 36

Why are larger ions not transported through the channel

Answer 36

because they are too big to enter