Transport over membranes

Question 1

describe the naming of the fluid mosaic model of the cell surface membrane

Answer 1

(fluid) as individual phospholipids can move freely past each other- within their particular layer
(mosaic) as proteins are embedded in the membrane of numerous shapes, patterns, and sizes.

Question 2

why is the cell-surface membrane differentially permeable

Answer 2

to separate the internal environment from the external environment

Question 3

what type of molecules can pass through the membrane

Answer 3

non-charged, non-polar, lipid-soluble molecules

Question 4

function of phospholipid in the cell surface membrane

Answer 4

-to form the bilayer
(making the membrane selectively permeable, controlling what molecules can pass through the bilayer)

Question 5

function of cholesterol in the cell surface membrane

Answer 5

to strengthen the membrane and give it the correct tension

Question 6

function of glycolipids in the cell surface membrane

Answer 6

specific shape for cell recognition, stick to each other via hydrogen bonding (increases tension)

Question 7

function of glycoproteins in the cell surface membrane

Answer 7

Acts as receptors
- chemicals from other cells bind to the receptor on the target cells to communicate

Question 8

role of extrinsic proteins in the cell surface membrane

Answer 8

acts as enzymes and catalyses chemical reactions within the cell

Question 9

role of intrinsic channel (hydrophilic pore) in the cell surface membrane

Answer 9

to transport charged, polar, hydrophilic, and non-lipid soluble molecules

Question 10

what are phospholipids made up of

Answer 10

• hydrophobic fatty acid tails
• charged hydrophilic phosphate heads

Question 11

why can’t phospholipids move to the opposite side of the membrane

Answer 11

because the charged phosphate head must move through the hydrophobic fatty acid interior (fatty acid tails) their hydrophobic nature repels anything that is charged or hydrophilic

Question 12

why can’t most molecules freely diffuse across the cell surface membrane

Answer 12

they are:
- not lipid soluble ( cannot pass through the hydrophobic phospholipid bilayer )
- too large
- polar molecules ( require specific transport carriers/channels )

Question 13

what is water potential measured in

Answer 13

KPa

Question 14

water potential of distilled water on an even surface at regular temperature and pressure

Answer 14

0KPa

Question 15

what happens when a solute is added to distilled water at regular temp and pressure

Answer 15

the water potential gets lower (below zero) because the solute renders some of the free to move water particles immobile

Question 16

what is the water potential of a cell made up of

Answer 16

amount of solute + how much pressure the cell is under (solute + turgor)