FINAL EXAM CHAPTER 12 Membrane Structure and Function

Question 1

What are the structures and properties of membranes?

Answer 1

-Sheetlike structures, two molecule thick, that form closed boundaries

-non-covalent assemblies

-Asymmetric in that the outer surface is always different from the inner surface

-fluid structures

-Electrically polarized such that the inside is negative

Question 2

What are membrane lipids and what do they form?

Answer 2

-They are small amphipathic molecules that form closed bimolecular sheets that prevent the movement of polar or charged molecules

Question 3

Why do we need proteins in membranes?

Answer 3

• because they help polar things across the membrane but non polar are allowed to pass too.

Question 4

What determines the membrane permeability?

Answer 4

• Solubility
• ions
• polar molecules
• Hydrophobicity
• if there are water molecules or not

Question 5

What is the role of Cholesterol in membrane fluidity

Answer 5

• They help maintain proper membrane fluidity in membranes in animals

Question 6

The temperature at which a membrane transitions from being highly ordered to very fluid is called?

Answer 6

Melting Temperature

Question 7

What is the melting temperature dependent on?

Answer 7

-Length of the fatty acids in the membrane lipid
-Degree of cis unsaturation

Question 8

What are the three proteins that associate with the lipid bilayer ?

Answer 8

-Integral Protein
-Peripheral membrane protein
-Anchored membrane protein

Question 9

What are integral proteins?

Answer 9

-Proteins that are embedded in the hydrocarbon core of the membrane

Question 10

What are Peripheral Membrane proteins ?

Answer 10

-Proteins that are bound to the polar head groups of membrane lipids or to the exposed surfaces of integral membrane proteins

Question 11

What are Anchored membrane proteins?

Answer 11

-Proteins that are associated with membranes by attachment to a hydrophobic moiety that is inserted into the membrane

Question 12

What is lateral diffusion ?

Answer 12

This is when a membrane component is attached to a fluorescent molecule and it slowly moves down and the mobility of the it depends on how rapidly the bleached area recovers fluorescence

Question 13

What does lateral diffusion depend on?

Answer 13

-Whether they are attached to other cellular or extracellular components

Question 14

What is transverse diffusion ?

Answer 14

• This is when lipids rapidly diffuse laterally in membranes .

Question 15

What is transverse diffusion dependent on?

Answer 15

-The assistance of enzymes or without it it is very slow

Question 16

What is passive transport?

Answer 16

-It is when a molecule moves down its concentration gradient through a transport protein

Question 17

What is active transport?

Answer 17

Its when protein pumps use energy to move a molecule against its concentration gradient

Question 18

What are symporters?

Answer 18

This powers the transport of a molecule against its concentration gradient by coupling the movement to the movement of another molecule down its concentration gradient, with both molecules moving in the same direction

Question 19

What are Antiporters?

Answer 19

One concentration gradient to power the formation of another, but the molecules move in opposite direction

Question 20

What is the Na/K pump?

Answer 20

This uses the energy of ATP hydrolysis to simultaneously pump three NA+ ions out of the cell and two K+ ions into the cell against their concentration gradients.

Question 21

What are ion channels?

Answer 21

Passive transport systems that allow specific and rapid transport of ions down their concentration gradients.

Question 22

THIS WILL BE ON THE EXAM
How can the K+ channel be selective?

Answer 22

This is because potassium carries water and therefore larger ions are not transported because they are too big to enter the channel. IN order for Potassium to go through the 3 angstrom channel it has to lose the water.