plasma membrane

Question 1

what is water potential

Answer 1

a measure of the tendency of water molecules to move from one area to another

Question 2

what two structures does facilitated diffusion consist of

Answer 2

carrier proteins and channel proteins

Question 3

whats a hypotonic solution

Answer 3

when the water solution outside the cell is higher than the water potential inside the cell thus water moves in

Question 4

what molecules can easily diffuse across the phospholipid bilayer

Answer 4

small and non polar molecules

Question 5

what molecules can pass slowly through the phospholipid bilayer

Answer 5

small polar molecules with a small difference in charge

Question 6

why is the cell membrane described as partially permeable

Answer 6

charged particles (ions) and larger molecules are not able to pas through the phospholipid bilayer however, small and non-polar molecules can pass easily

Question 7

what is the definition of facilitated diffusion

Answer 7

the net movement of particles from an area of high concentration to an area of low concentration across a partially permeable cell membrane via a carrier or channel protein (passive so doesn’t require ATP)

Question 8

give an example of a molecule that can easily pass through the plasma membrane

Answer 8

O2 (small and nonpolar)

Question 9

describe channel proteins?

Answer 9

form aq channels across the cell membrane which specific small, polar molecules(charged) can diffuse through

Question 10

describe carrier proteins

Answer 10

the channel proteins can be open or closed depending on whether a specific ion is present - channel proteins are selective.

Question 11

what do cells that require a lot of water have

Answer 11

special channel proteins called aquaporins

Question 12

describe carrier proteins

Answer 12

some larger charged molecules require carrier proteins, this is where a specific molecule binds to the carrier protein, causing a change in shape known as a conformational change- catalyses molecules to be released

Question 13

6 factors affecting rate of diffusion…

Answer 13

• temp
• conc grad
• sa
• diffusion distance
• size of molecule
• number of channel of carrier proteins

Question 14

whats osmosis

Answer 14

the net movement of water molecules…

Question 15

what does pure water have a water potential of

Answer 15

0

Question 16

does a conc solution have a lower or higher water potential

Answer 16

lower

Question 17

whats an isotonic solution

Answer 17

when the water potential of a solution outside a cell is the same as the water potential inside the cell

Question 18

whats a hypertonic solution

Answer 18

when the water potential outside a cell is lower than inside a cell so water moves out

Question 19

whats the fluid mosaic model

Answer 19

the different components present in the phospholipid bilayer.

• individual phospholipids can move= flexible
• mosaic=proteins (extrinsic and intrinsic) of different shapes and sizes are embedded.

Question 20

what does cholesterol do

Answer 20

steroid molecule- regulates fluidity of the membrane

Question 21

3 factors affecting membrane permeability

Answer 21

TEMPERATURE- high temp denatures membrane proteins- phospholipid molecules have more kinetic e and move further apart
PH- changes in tertiary structure of membrane proteins
use of a SOLVENT- may dissolve membrane

Question 22

how do carrier proteins transport specific molecules?

Answer 22

by changing shape when the molecules bind to the protein

Question 23

what are peripheral proteins held by

Answer 23

held by electrostatic forces

Question 24

what are other important functions of peripheral proteins and integral proteins

Answer 24

• acting as receptors for drugs and hormones to bind
• acting as recognition sites for the immune system
• helping cells adhere together to form tissues

Question 25

what’s a glycoprotein

Answer 25

proteins with a chain of carbohydrate molecules attached

Question 26

what’s a glycolipid

Answer 26

lipids or phospholipids with a chain of carbohydrate molecules attached

Question 27

what are the 4 main roles of glycolipids and glycoproteins

Answer 27

• acting as recognition sites for the immune system
• helping cells adhere to form tissues
• provide stability to the cell membrane
• glycoproteins act as cell receptors thus play a role in cell communication

Question 28

describe the neds of cholesterol and what it does

Answer 28

hydrophilic and and hydrophobic end- regulates membrane fluidity

Question 29

how does cholesterol prevent the membrane from becoming too stiff

Answer 29

prevents phospholipids from grouping together

Question 30

how does cholesterol prevent the membrane from becoming too fluid

Answer 30

by interacting with the fatty acid tails of the phospholipids

Question 31

why are membranes important (5)

Answer 31

• compartmentalisation provides protection
• contains different reactions for different metabolic reactions
• membranes involve proteins that are involved in chemical reactions.
• cell membranes are involved in the secretion of hormones and other chemicals that signal other cells.
• cell membranes also contain cell receptors that hormones and other chemicals can bind to

Question 32

what happens to the phospholipids at a low temp

Answer 32

phospholipids= compressed= stiffened membrane

Question 33

how can the compression of phospholipids be prevented apart from cholesterol

Answer 33

can be reduced by changing the amount of unsaturated and saturated phospholipid tails (kinks push phospholipids apart)

Question 34

what type of phospholipids do animals living in cold environments have?

Answer 34

more unsaturated (maintains fluidity of plasma membrane- kinks push phospholipid molecules further away)

Question 35

what happens to phospholipids at high temps

Answer 35

phospholipids gain kinetic energy and move further apart= increased fluidity and permeability= proteins drift sideways reducing their function ( at really high temp, protein= denatured)

Question 36

what do organic solvents do to the phospholipid bilayer

Answer 36

disrupt the phospholipid bilayer and dissolves the cell membrane
at low conc= cell membrane more permeable to larger charged molecules
at high conc= destroys cells