transport across membranes

Question 1

describe a phospholipid bilayer

Answer 1

hydrophilic head, hydrophobic tail.
hydrophobic tail

Question 2

why are phospholipids described as fluid-mosaic

Answer 2

they are not fixed and can move so are fluid
protein channels embedded in the layer like a mosaic. `

Question 3

function of cell membranes

Answer 3

control entry and exit of materials
separate organelles from cytoplasm

Question 4

does diffusion require energy

Answer 4

diffusion- no
facilitated diffusion- no

Question 5

definition of diffusion

Answer 5

the net movement of molecules or ions from an area of high concentration to an area of low concentration

Question 6

what are protein channels

Answer 6

water filled hydrophobic channels
selective
changes shape

Question 7

definition of osmosis

Answer 7

the passage of water from a region where it has ahgiher water potential to an area where it has a lower water potential through a semi permeable membrane

Question 8

definition of active transport

Answer 8

the movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins