exam 1 plasma membrane and plant cell wall

Question 1

what is the cell bounded by

Answer 1

plasma membrane

Question 2

what is the plasma membrane composed of

Answer 2

phospholipids and sterols (cholesterols in animal cells)

Question 3

what is the basic structure of cellular membranes

Answer 3

bilayers composed on phospholipids

Question 4

what are lipid bilayers

Answer 4

2D fluids that allow lateral diffusion of constituents

Question 5

what are the microdomains of the plasma membranes called

Answer 5

lipid rafts

Question 6

what are leaflets

Answer 6

layers of the bilayer

Question 7

what do they two leaflets have

Answer 7

an asymmetric distribution of phospholipids

Question 8

what is the plasma membrane

Answer 8

a regulated cell boundary - “wall” with windows and doors that can be opened/closed in regulated fashion

Question 9

what is the main purpose of the plasma membrane

Answer 9

prevent water from getting from one side to another

Question 10

why can steroid hormones diffuse freely through the plasma membrane

Answer 10

highly hydrophobic

Question 11

how can water pass through membrane

Answer 11

channels

Question 12

what are the most abundant lipids in plasma membranes

Answer 12

phospholipids

Question 13

what is the polarity of phospholipids

Answer 13

amphipathic - polar head group and two nonpolar hydrocarbon tails

Question 14

what increases membrane fluidity of phospholipids

Answer 14

one tail is saturated (no double-bonds) and the other is unsaturated (one cis double-bond = bent fatty acid tail)

Question 15

what is the charge of phospholipids

Answer 15

net charges are zero

Question 16

what are sterols

Answer 16

important lipid component of membranes

Question 17

why are sterols important for structural stability of membrane

Answer 17

contain rigid ring structures that stiffen portions of phospholipids

Question 18

what is the major sterol of animal cell membranes

Answer 18

cholesterol

Question 19

what are the major sterols of plant cell membranes

Answer 19

phytosterols

Question 20

what is the major sterol of fungi

Answer 20

ergosterol (useful target for antifungal drugs)

Question 21

why can phospholipids spontaneously self-assemble into lipid bilayer membranes

Answer 21

because they are amphiphilic

Question 22

what do polar head groups of phospholipids associate with

Answer 22

water on the “outsides” of the membrane

Question 23

what do hydrocarbon tails of phospholipids associate with

Answer 23

each other on the “inside” of the membrane

Question 24

what is a lipid micelle

Answer 24

a lipid molecule in a conical shape

Question 25

what is a lipid bilayer

Answer 25

the shape of the lipid is planar/cylindrical

Question 26

what form of phospholipid bilayer is energetically favorable

Answer 26

a sealed (sphere-looking) compartment formed by phospholipid bilayer

Question 27

what does the Fluid Mosaic Model describe

Answer 27

the properties of the plasma membrane

Question 28

what does it mean that the plasma membrane is a fluid

Answer 28

molecules are able to move past each other

Question 29

what does it mean that the plasma membrane is a mosaic

Answer 29

it's made up of lots of little pieces (i.e. not continuous) it has discrete regions (neighborhoods)

Question 30

why is it difficult for molecules to diffuse from one region to another

Answer 30

regions have different lipid and protein compositions

Question 31

what are lipid rafts

Answer 31

a type of microdomain that is a region highly concentrated in cholesterol, which makes them stiffer

Question 32

what is lateral diffusion

Answer 32

molecules can move past each other

Question 33

what is the plasma membrane derived from

Answer 33

the ER membrane

Question 34

what is the symmetry of the plasma membrane

Answer 34

asymmetric, which provides voltage across the membrane

Question 35

what do the proteins in the plasma membrane allow for

Answer 35

molecules to cross the membrane (molecular transport) signal transduction anchorage to cytoskeleton interaction with other cells/extracellular matrix

Question 36

what are peripheral membrane proteins

Answer 36

proteins bound to the membrane surface

Question 37

what are integral membrane proteins

Answer 37

proteins inserted into membrane interior

Question 38

how do integral membrane proteins interact with leaflets

Answer 38

may span both leaflets via a transmembrane region, or may be anchored via attachment of lipid groups that insert into one leaflet

Question 39

what are plant cells surrounded by

Answer 39

the plant cell wall

Question 40

what does the plant cell wall do

Answer 40

separates inside and outside of plasma membrane of plant cell

Question 41

what is the major component of the plant cell wall

Answer 41

cellulose, a polymer of glucose that provides tensile strength comparable to steel

Question 42

what is tensile strength

Answer 42

resistance to stretching

Question 43

what is lignin

Answer 43

waterproofing

Question 44

what is pectin

Answer 44

provides resistance to compression

Question 45

what are components of the plant cell wall

Answer 45

pectin and lignin

Question 46

Animals lack a cell wall. What will happen if animal cells are placed in a highly hypotonic environment?

Answer 46

they will expand until they burst OR nothing - animal cells are capable of regulating water flow in and out

Question 47

what is turgor pressure

Answer 47

the hydrostatic pressure resisted by the cell wall, which builds up when water flows into a cell

Question 48

what is the purpose of turgor pressure

Answer 48

allows plant cells to be rigid

Question 49

how does turgor pressure help with growth

Answer 49

it can force the cell to elongate and grow in specific directions