Ch 11

Question 1

what do phospholipids make up?

Answer 1

the cell membrane

Question 2

What are fatty acids

Answer 2

hydrocarbon chains with a -COOH group (carboxylic acid) at the end

Question 3

How is a triacylglycerol constructed?

Answer 3

A glycerol head and 3 fatty acid tails attached by ester linkages via the carboxylic acid group

Question 4

What properties do molecules need to have to get across membranes

Answer 4

small, non polar

Question 5

Do carbon dioxide diffuse across the plasma membrane

Answer 5

Yes, it’s a small nonpolar molecule

Question 6

Do potassium ions diffuse across the plasma membrane

Answer 6

No ions do not: small but charged

Question 7

Why do eucaryotic cells have extensive internal membranes?

Answer 7

To separate reactions and increase the concentration of reactants

Question 8

How many fatty acid tails does a phosopholipid have?

Answer 8

2

Question 9

What are the fatty acid tails attached to?

Answer 9

Polar head group (choline/ethanolamine/serine)-phosphate-glycerol-fatty acid tails

Question 10

Is protein found in the cell membrane?

Answer 10

Yes, hella. peripheral membrane proteins; integral membrane proteins, transmembrane proteins, many ways that proteins are associated with cell membranes (transporters, ion channels, anchoring proteins, receptors, enzymes, kinases etc.)

Question 11

What kind of structures do water molecules form when exposed to fatty acid tails?

Answer 11

Cage-;ike structures to minimize interaction with polar water molecules

Question 12

What happens to water molecules when they are exposed to the fatty acid tails of phospholipids?

Answer 12

water molecules will form a cage around non polar molecules; water has to become more ordered (so decreases entropy) in order to minimize interaction with hydrophobic fatty acid tails

Question 13

Why do phospholipids spontaneously form lipid vesicles or enclosed spheres?

Answer 13

To keep hydrophilic heads towards aqueous environment and hydrophobic tails away from aqueous environment (minimize interaction with water)

Question 14

amphipathic

Answer 14

describing a molecule which has both hydrophobic and hydrophilic groups.

Question 15

What are detergents?

Answer 15

Molecules with amphipathic characteristics, usually a polar head group and a fatty acid tail. They disrupt the lipid bilayer (can interact with both hydrophobic and hydrophilic parts) and pull phospholipids into solution

Question 16

osmosis versus diffusion?

Answer 16

Osmosis: the movement of water from an area of low solute concentration to high solute concentration or the movement of water molecules from a region of high water concentration to lower water concentration

Question 17

What is the action of cholesterol in lipid bilayers?

Answer 17

Stiffens the membrane, decreases disorder, less permeable, keeps the integrity of the cell membrane (lipids shift around too much when it gets warm)

decreases the permeability

Question 18

What has high permeability?

Answer 18

O2, CO2, N2 small, nonpolar molecules.

H2O will go across the membrane rather readily, but not quite as fast. (CO2 = 10^0) (H2O = 10^-2)

Question 19

does glucose have high permeability?

Answer 19

mid ranged. it can go across the membrane but much slower then O2 or H2O
(Large, uncharged and polar)

Question 20

what has low permeability?

Answer 20

Ions

Question 21

what kind of reaction to adds fatty acid tails to glycerol

Answer 21

condensation reactions

Question 22

Are new lipids added to the cytosolic half of the lipid bilayer?

Answer 22

New lipids are added to the cytosolic face

Question 23

Where are the R groups in a membrane spanning segment that’s an alpha helix? are they hydrophobic or hydrophyllic?

Answer 23

Hydrophobic.

hydrophobic R groups face the outside of the barrel towards the hydrophobic tails of the lipids

Question 24

Where are the R groups in a membrane spanning segment that’s an beta sheet? are they hydrophobic or hydrophilic?

Answer 24

Hydrophilic R groups face the inside of the barrel so ions and other small molecules can pass through, and hydrophobic R groups face the outside of the barrel towards the hydrophobic tails of the lipids