chapter 2 pt 1

Question 1

all living cells exist in an

Answer 1

aqueous medium

Question 2

the cell membrane separates

Answer 2

contents of cell from extracellular fluid surrounding cell

Question 3

the cell membrane is selectrively

Answer 3

permeable and controls traffic in and out of cell

Question 4

the cell membrane is made of

Answer 4

phospholipids, proteins, and other macromolecules

Question 5

cells will die if

Answer 5

the membrane does not function properly

Question 6

phospholipids have

Answer 6

fatty acid tails and a phosphate group head

Question 7

phospholipids: fatty acid tails are

Answer 7

hydrophobic: non polar, dont dissolve

Question 8

phospholipids: phosphate group head is

Answer 8

hydrophilic: polar, dissolves

Question 9

phospholipid bilayer: phospholipids align according to

Answer 9

water solubility

Question 10

fluid mosaic model:

Answer 10

phospholipids = scaffold
proteins (+ other macromolec.s) embedded = mosaic

Question 11

in a fluid mosaic model, the molecules in membrane can

Answer 11

move about freely - fluid

Question 12

cell membrane + phos. bilayer must be

Answer 12

fluid + flexible (viscosity like veg. oil)

Question 13

if the phosph. bilayer is too fluid, it

Answer 13

permits too much substance entry

Question 14

if the phosph. bilayer isnt fluid enough, it

Answer 14

prevents too much substance entry

Question 15

factors affecting phosph. bilayer fluidity

Answer 15

temperature
percentage of double bonds in fatty acids
length of fatty acids
cholesterol

Question 16

fluidity of phosph. bilayer: temperature

Answer 16

increase temp, increase fluidity

decrease temp, decrease fluidity (gel state)

Question 17

fluidity of phosph. bilayer: % unsaturated fatty acids in phospholipids

Answer 17

double bonds form kinks in tails => less tightly packed => membrane LESS viscous

Question 18

fluidity of phosph. bilayer: fatty acid tail length

Answer 18

longer = more intermolecular attractions
held together more tightly, REDUCES fluidity
most common length of fatty acid = 16-18 carbons

Question 19

fluidity of phosph. bilayer: cholesterol in membrane

Answer 19

cholesterol = mortar, fills in small gaps in phosp. structure, IMPROVES IMPERMEABILITY to small, water-soluble molecules like glucose

acts as membrane ANTIFREEZE AGENT: decreases fluidity at high temp + vice versa

Question 20

proteins determine membrane’s

Answer 20

specific functions

Question 21

two types of membrane proteins:

Answer 21

peripheral + integral

Question 22

membrane proteins: PERIPHERAL

Answer 22

loosely/temporarily bound to surface of membrane/integral proteins

Question 23

membrane proteins: INTEGRAL

Answer 23

• penetrate lipid bilayer, usually across whole membrane
• stabilize membrane, link with cell cytoskeleton
• transport proteins

Question 24

membrane proteins determine membrane function by performing:

Answer 24

• transport
• reaction catalysis
• cell recognition
• signal reception + transduction

Question 25

membrane protein functions: transport

Answer 25

substances across cell membrane

Question 26

membrane protein functions: reaction catalysis

Answer 26

carry out chem reactions

Question 27

membrane protein functions: cell recognition

Answer 27

carb. chains protruding from glycoproteins enable cells to recognize each other + identify harmful intruders (disease bacteria)

Question 28

membrane protein functions: signal reception and transduction

Answer 28

receptor proteins bind to signal molec.s (e.g. hormones) and change shape + initiates cellular response to signal

Question 29

the proteins' domains

Answer 29

anchor molecules

Question 30

proteins anchoring molecule: within membrane

Answer 30

nonpolar amino acids: hydrophobic, anchor protein into membrane

Question 31

proteins anchoring molecule: outer surfaces of membrane

Answer 31

polar amino acids: hydrophilic, extend into extracellular fluid and into cytosol

Question 32

membrane carbohydrates: play a key role in

Answer 32

cell-cell recognition

Question 33

membrane carb.s: ability of a cell to distinguish

Answer 33

one cell from another (antigens: toxins, bacteria, foreign material that initiates immune response => antibodies production)

Question 34

membrane carb.s: important in organ and

Answer 34

tissue development

Question 35

membrane carb.s: basis for rejection of

Answer 35

foreign cells by immune system