Unit 3: Chapter 12

Question 1

Characteristics of Membrane

Answer 1

1. sheetlike structures
2. composed of lipids and proteins which can be decorated with carbohydrates
3. membrane lipids are small amiphipathic molecules which prevent movement of polar or charged molecules
4. proteins serve to mitigate impermeability of membranes
5. noncovalent assemblies
6. asymetric
7. fluid structures
8. electrically polarized

Question 2

What form lipid bilayers in aqueous solutions?

Answer 2

phospholipids and glycolipids

Question 3

Formation of membranes is powered by

Answer 3

Hydrophobic effect

Question 3

Liposome/ Lipid Vesicles

Answer 3

Double layered formed by phospholipids
Amphipathic
Very small aqueous compartment enclosed by a lipid membrnae
Used as drug delivery systems

Question 4

The phospholipid bilyaer membrane is stabilized by

Answer 4

energy gained from hydrophobic groups burying hydrophobic groups out of contact with water
1. hydrophobic chain in water forces the formation of a cage of water around it
2. several hydrophobic regions cluster in bilayer, surface area exposed to water decreases and water molecules in cage are released (increase in entropy to drive formation of water)

Question 5

Micell

Answer 5

Single hydrophobic tail instead of double
Inside is more hydrophobic

Question 6

Lipid bilayerd are highly imermeable to ions and most polar molecules due to

Answer 6

Hydrophobic tail is picky

Question 7

Larger permeability coefficient represents

Answer 7

increasing permeability
(easy to cross membrane)

Question 8

What are the best molecules to cross membrane?

Answer 8

Small, uncharged, nonpolar
Ex. H20, indole, uren, glycerol

Question 9

What is membrane fluidity controled by?

Answer 9

Fatty acid composiiton and cholsterol content

Question 10

Membrane temperature is dependent on

Answer 10

Length of fatty acids and degree of cis saturation

Question 11

Increasing temperature causes what to membrane

Answer 11

Increases fluidity of membrane to make more fluid like

Question 12

Decreasing temperature causes what to membrane

Answer 12

Decreases fluidity of membrane to make more solid like

Question 13

Abrupt transition between fluid like and solid like of membrane depends on

Answer 13

length of fatty acid chains and degree of unsaturation

Question 14

How does cholesterol determine membrane fludiity in animals?

Answer 14

Makes membrane from becoming too rigid and too fluid
helps resist change and acts like buffer
1. prevent solidying at temp below Tm (too rigid)
2. sterically blocks large amount of fatty acids at temperature above Tm (too fluid)

Question 15

What decreases fluidity of membrane?

Answer 15

Increase fatty acid tail
More closely packed
Less double bonds (saturated)

Question 16

Why are proteins second most common componet of membrane?

Answer 16

Proteins allow transport proteins of molecules and information across the membrane

Question 17

Integral membrane proteins

Answer 17

Embedded across entire membrane

Question 18

Peripheral membrane proteins

Answer 18

Bound to polar head groups of membrane lipids or exposed surfaces of integral membrane proteins

Question 19

Common structure of integral proteins

Answer 19

membrnae spanning alpha helices and beta strands

Question 20

Bacteriorhodopism

Answer 20

Integral protein
Made of 7 alpha helices

Question 21

Bacterical porin

Answer 21

Found in mitochondria, chloroplast, and bacteria
Forms pore or channel to help ions pass

Question 22

How do lipids and membrane proteins diffuse

Answer 22

Laterally (side to side) in same layer
Rapid
- But can also use transverse diffusion

Question 23

Fluorescence recovery after photobleaching (FRAP)

Answer 23

Technique that allows measurement of lateral mobility of membrane componets

Question 24

Transverse diffusion

Answer 24

AKA flip flop Very slow Lipids and membrane proteins move to one layer to the other Requires protein and enzyme for help Reason why membrnae composiiton is asymmetric

Question 25

Flippase

Answer 25

Moves membrane lipids from outer leaflet to the inner leaflet during transverse diffusion

Question 26

Major function of membrane proteins is to function as

Answer 26

Transporters (Simple transport and active transport)

Question 27

Small molecules will spontaneously occur if: (simple diffusion)

Answer 27

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

Question 28

Simple diffusion

Answer 28

Passive transport No proteins used to assist

Question 29

Facilitated diffusion

Answer 29

Passive transport Polar molecules diffuse across membrane down their concentration with assistance of channel proteins

Question 30

Active transport

Answer 30

Movements of molecules against concentration from low to high that requires source of energy and proteins

Question 31

2 classes of membrane transport:

Answer 31

Channels and Transporters

Question 32

Channels

Answer 32

Used in passive transport Selective No conformation change

Question 33

Transporters

Answer 33

Used in passive and active transport Specifity Conformational change with gates Function as pumps and channels

Question 34

Passive transport

Answer 34

Molecules move with concentration gradient from high to low concentration No energy required

Question 35

Na+ - K+ pump

Answer 35

Active transport using ATP hydrolysis Simutaneously pump 3 Na+ ions out and 2 K+ ions in against concentration gradient Both against electrochemical agents Keep concentration gradient of Na+ outside Na+ concentration gradient is energy source

Question 36

Most animal cells contain concentrations of

Answer 36

High concentration of K+ and low concentration of Na+

Question 37

What concentration is more outside cell?

Answer 37

Na+ concentration

Question 38

What concentration is more inside cell?

Answer 38

K+ concentration

Question 39

Secondary Transporters

Answer 39

( 2 things moving) Use one concentration gradient to power formation of another

Question 40

Symporters

Answer 40

Secondary transporters Molecules move in same direction

Question 41

Antiporters

Answer 41

Secondary transporters Molecules move in opposite directions

Question 42

How is gluocse moved into animal cells

Answer 42

Active transport against concentration gradient Symporter powered by Na+ concentration as energy source and moves down concentration gradient

Question 43

Ion channels

Answer 43

Passive transport systems Activated by changes in voltage or by binding of specific molecules to the channels

Question 44

Electrochemical gradient forces

Answer 44

1. chemical gradient: concentration gradient 2. electrical gradient: membrnae potential (voltage gradient)