Exam 4 (Topic 17)

Question 1

The plasma membrane is

Answer 1

A selective barrier

Fluid

Question 2

A selective barrier

Answer 2

Plasma Membrane

Question 3

In eucaryotes, the plasma membrane

Answer 3

Separates the contents of organelles

Question 4

Three important functions of cell membranes

Answer 4

1. Communicate with the outside environment
2. Allow waste material to exit the cell and nutrients to enter the cell
3. Allow expansion and movement of the cell

Question 5

The plasma membrane can be deformed without

Answer 5

Tearing (Usually)

Question 6

If the plasma membrane is pierced

Answer 6

it quickly reseals

Question 7

When an area of the plasm membrane is enlarged, it

Answer 7

adds more membrane

Question 8

The plasma membrane of cells is composed of

Answer 8

Lipids AND Proteins

Question 9

Lipid bilayer

Answer 9

two opposing layers of lipids (proteins associate with

Question 10

Long hydrocarbon chain (hydrophobic) and Carboxyl group (hydrophili)

Answer 10

Fatty Acids

Question 11

Fatty acids are

Answer 11

amphipathic

Question 12

The hydrocarbon tail has no double bonds

Answer 12

Saturated Fatty Acid

Question 13

C=C double bonds create a kink in the fatty acid tail

Answer 13

Unsaturated Fatty Acids

Question 14

Fatty Acid saturation is in the ______ formation

Answer 14

Cis

Question 15

What provides the kink in the FA tail

Answer 15

Cis-double bonds

Question 16

Fatty Acids are linked together by

Answer 16

Ester Linkages

Question 17

FAs linked to glycerol molecule

Answer 17

Triacylglycerols

Question 18

Major component of cell membranes

Answer 18

Phospholipids

Question 19

Triacylglycerol but with a phosphate and hydrophilic group attached to a carbon instead of a fatty acid

Answer 19

Phospholipids

Question 20

Most common phospholipid in cell membranes

Answer 20

Phoshatidylcholine

Small molecule choline (charged molecule) added to the phosphate

Question 21

Small molecule choline (charged molecule) added to the phosphate

Answer 21

Phoshatidylcholine

Question 22

All membrane lipids are

Answer 22

amphipathic

Question 23

Lipids with sugar group instead of phosphate group

Answer 23

Glycolipid

Question 24

Because of the amphipathic nature of phospholipids, the lipid bilayer is the

Answer 24

most stable arrangement of lipids

Question 25

Why does the lipid bilayer sheet fold into a sphere?

Answer 25

Because it can’t have any edges exposed to water

Question 26

Pure phospholipids in water form a spherical bilayer called

Answer 26

A Liposome

Question 27

The water outside and inside the cells prevent the phospholipids from

Answer 27

Coming out of the lipid bilayer

But that doesn’t prevent movements within the lipid bilayer

Question 28

Four possible SPONTANEOUS movements of phospholipids

Answer 28

1. Flexing
2. Lateral Diffusion
3. Rotation
4. Flip-flop (very rare)

Question 29

The fatty acid tails are somewhat bendable

Answer 29

Flexing

Question 30

The phospholipids within one monolayer of the lipid bilayer can move around

Answer 30

Later diffusion

Question 31

The phospholipid itself can spin in a circle

Answer 31

Rotation

Question 32

The phospholipid can move from one monolayer to the other

Answer 32

Flip-flop (RARE- about once a month)

Question 33

How fluid a membrane is depends on

Answer 33

1. Phospholipid Composition
2. Length of hydrocarbon tails
3. Degree of saturation

Question 34

Phospholipid composition

Answer 34

Contain different polar heads and have different properties

Question 35

Most phospholipids have a hydrocarbon tail length of

Answer 35

14-24 carbons (18-20 most common)

Question 36

A shorter hydrocarbon chain reduces

Answer 36

Hydrophobic interactions causing the membrane to be more fluid

Question 37

Unsaturated is

Answer 37

more fluid

Question 38

Hydrogenated oil is a process that

Answer 38

saturates the oil and make it more solid

Question 39

Liquid at room temps

Answer 39

Unsaturated lipids

Question 40

In animal cells membrane fluidity is adjusted by

Answer 40

the addition of cholesterol

Question 41

Polar head group (-OH) and rigid non-polar ring structure

Answer 41

Cholesterol

Question 42

Makes up roughly 20% of the weight of plasma membranes

Answer 42

Cholesterol

Question 43

Fill spaces between phospholipids and stiffens the bilayer

Answer 43

Cholesterol

Question 44

Less Fluid to More Fluid

Answer 44

Saturated, 1/3 Unsat 1/3 sat 1/3 cholesterol, 1/2 sat and 1/2 unsat

Question 45

The lipid bilayer is

Answer 45

asymmetrical

Question 46

The lipid bilayer contains

Answer 46

Cytosolic leaflet and Non-cytosolic leaflet

Question 47

New phospholipids are made and added to the

Answer 47

Cytoplasmic leaflet of the lipid layer on the ER

Question 48

________ selectively transfer specific types of lipids to the non-cytoplasmic leaflet

Answer 48

Flippases

maintains asymmetry and allows membrane to grow evenly

Question 49

ER membrane that contains newly made lipid bilayer pinches off in vesicles and

Answer 49

Fuses with other organelles and the plasma membrane

Question 50

All animal cells are coated with

Answer 50

Sugars (glycolipids and glycoproteins)

Question 51

Glycolipids are only found in

Answer 51

The non-cytoplasmic leaflet of lipid bilayers

Question 52

Some lipids are synthesized in the

Answer 52

Smooth ER lumen and placed in the non-cytoplasmic leaflet

Question 53

Vesicles pinch off from the ER and fuse with the golgi where the lipids acquire

Answer 53

Sugar molecules

Question 54

Vesicles pinch off from the Golgi and

Answer 54

Fuse with the plasma membrane

Question 55

Glycolipids on the non-cytoplasmic leaflet of the organelles and vesicles now face

Answer 55

The extracellular environment

Question 56

Two mechanisms to maintain asymmetry in the lipid bilayer

Answer 56

Flippases

Addition of lipids from the lumen of the organelle