cell membrane and tonicity

Question 1

the cell membrane is arranged as a

Answer 1

phospholipid bilayer

Question 2

cell membrane serves as a

Answer 2

cellular barrier/border

Question 3

how permeable is the cell membrane?

Answer 3

selectively permeable

Question 4

the heads of the phospholipids are

Answer 4

polar
hydrophilic

Question 5

the tails of the phospholipid bilayer are

Answer 5

nonpolar
hydrophobic

Question 6

the middle of the phospholipid bilayer is impermeable to

Answer 6

polar molecules

Question 7

when the membrane is fluid, the bilayer is

Answer 7

unsaturated with hydrocarbon kinks

Question 8

when the membrane is viscous, the bilayer is

Answer 8

saturated hydrocarbon tails

Question 9

cholesterol acts as a

Answer 9

fluidity buffer

Question 10

what is the purpose of cholesterol in the cell membrane

Answer 10

resists changes in fluidity as temp changes

Question 11

how often do phospholipids move laterally in the cell membrane?

Answer 11

10^7 times per second

Question 12

how often do phospholipids flip flop in the cell membrane?

Answer 12

once per month

Question 13

where are the hydrophobic regions of a protein in the phospholipid bilayer?

Answer 13

by the tails of the phospholipids

Question 14

where are the hydrophilic regions of a protein in the phospholipid bilayer?

Answer 14

by the heads of the phospholipids

Question 15

membrane proteins determine

Answer 15

membrane’s specific functions

Question 16

6 major functions of membrane proteins

Answer 16

Transport
Enzymatic activity
Signal transduction
Cell-cell recognition
Intercellular joining
Attachment to the cytoskeleton and extracellular matrix (ECM)

Question 17

peripheral proteins

Answer 17

loosely bound to surface of membrane

Question 18

integral proteins

Answer 18

penetrate lipid bilayer, usually across whole membrane
(transmembrane protein)

Question 19

2 types of transport

Answer 19

passive
active

Question 20

3 types of passive transport

Answer 20

diffusion
facilitated diffusion
osmosis

Question 21

does passive diffusion require energy

Answer 21

no

Question 22

does active diffusion require energy

Answer 22

yes

Question 23

simple diffusion

Answer 23

Move from HIGH to LOW concentration
“passive transport”
no energy needed
Solute moves DOWN concentration gradient until reaches equilibrium

Question 24

What molecules CAN get through the phospholipid bilayer directly?

Answer 24

fats & other lipids, hydrocarbons, CO2, Oxygen, hydrophobic molecules

Question 25

What molecules CANNOT get through the phospholipid bilayer directly?

Answer 25

polar molecules (H2O)
ions (charged) (salts, ammonia)
large molecules
(starches, proteins)

Question 26

transport proteins

Answer 26

facilitates = to help
uses proteins to help
no energy needed

Question 27

channel proteins

Answer 27

embedded in the cell membrane & have a pore for materials to cross

Question 28

carrier proteins

Answer 28

can change shape to move material from one side of the membrane to the other

Question 29

osmosis

Answer 29

Diffusion of water from
HIGH concentration of water to
LOW concentration of water
across a
semi-permeable
membrane

Question 30

3 types of solutions

Answer 30

hypertonic
isotonic
hypotonic

Question 31

how is direction of osmosis determined

Answer 31

by comparing total solute concentrations

Question 32

hypertonic

Answer 32

more solute
less water
water moves out

Question 33

hypotonic

Answer 33

less solute
more water
water moves inside cell

Question 34

isotonic

Answer 34

equal solute and water
equillibrium

Question 35

cell survival depends on balancing

Answer 35

water uptake and loss

Question 36

animal cells in freshwater in hypotonic solution - problem and solution

Answer 36

cell gains water, swells & can burst (cytolysis)

contractile vacuole
pumps water out of cell
ATP

Question 37

plant cells in freshwater in hypotonic solution - problem and solution

Answer 37

no problem
normal
cell wall prevents from bursting
becomes turgid (full) with water

Question 38

turgor pressure

Answer 38

pressure that builds up, gives plant shape

Question 39

purpose of a contractile vacuole

Answer 39

forces out excess water

Question 40

animal cells in salt water in hypertonic solution - problem and solution

Answer 40

cell loses water and can die

take up water or pump out salt

Question 41

plant cells in salt water in hypertonic solution - problem and solution

Answer 41

no problem
plasmolysis, wilts
can recover

Question 42

plasmolysis

Answer 42

loss of water, decreasing turgor pressure causing wilting
only in plant cells

Question 43

crenation

Answer 43

animal cells shrivel up

Question 44

animal cells in mild salt solution in isotonic solution - problem and solution

Answer 44

no problem
no net movement of water
flows across membrane equally, in both directions
cell in equilibrium
volume of cell is stable

Question 45

plant cells in isotonic solution

Answer 45

flaccid, wilts

Question 46

Hypertonic or hypotonic environments create

Answer 46

osmotic problems for organisms

Question 47

Osmoregulation

Answer 47

the control of water balance
a necessary adaptation for life in such environments

Question 48

aquaporins

Answer 48

small transmembrane proteins that facilitate the rapid transport of water across cell membranes through a pore, in and out of cells