Cell- Transport across membranes

Question 1

Diffusion

Answer 1

net movement of particles from a an area of high to low concentration

Question 2

Simple diffusion

Answer 2

Simple = molecules move directly through the phospholipid bilayer

Question 3

Facilitated diffusion

Answer 3

molecules pass through transport proteins (large use carrier, charged use
channel)

Question 4

Factors that affect rate of diffusion?

Answer 4

 surface area (increase = increase rate of diffusion)
 concentration gradient (increase = increase rate of diffusion)
 thickness (decrease = decrease diffusion distance = increase rate of diffusion)
 temperature (increase = increase kinetic energy = molecules move faster = increase rate
of diffusion)
 size of molecules (smaller molecules = increase rate of diffusion)

Question 5

What is Ficks Law?

Answer 5

(Surface Area x Concentration Gradient)/Thickness

Question 6

Define Osmosis?

Answer 6

movement of water molecules from an area of high water potential to an area of
low water potential through a partially permeable membrane

Question 7

Which liquid has the highest water potential?

Answer 7

distilled/pure water

 has a value of 0kPa

Question 8

Surround animal cell with pure water?

Answer 8

swells and burst (water enters by osmosis)

Question 9

Surround plant cell with pure water?

Answer 9

 swells but does not burst
 cell wall prevents it from bursting
 made of cellulose – strong material
 the cell is Turgid

Question 10

Surround animal cell with concentrated sugar/salt solution?

Answer 10

shrinks (water leaves by osmosis)

Question 11

Surround plant cell with concentrated sugar/salt solution?

Answer 11

 water leaves by osmosis
 cell wall prevents cell from shrinking, keeps it rigid
 the protoplast (cell membrane plus contents) shrink
 the cell is Plasmolysed

Question 12

Define Active Transport?

Answer 12

movement of molecules against concentration gradient using ATP and carrier proteins (against concentration
gradient)

Question 13

Describe the process of active transport?

Answer 13

 molecules (in area of low concentration) bind to carrier protein
 ATP breaksdown to ADP, Pi and Energy
 the Pi and Energy cause the carrier protein to change shape
 carrier protein releases molecules on opposite side (in area of high concentration)
 the carrier protein releases the attached Pi to return to its original shape

Question 14

Adaptations of Small Intestine?

Answer 14

 folded to form Villus
 cells lining SI have Microvilli (large surface area)
 wall of SI is thin (short diffusion distance)
 rich blood supply (maintains concentration gradient)
 cells lining SI have transport proteins and mitochondria

Question 15

Active Transport of Glucose in SI?

Co-transport

Answer 15

 sodium ions are actively transported from the cells lining the SI into the blood
 lowers the sodium ion concentration in the cell
 therefore sodium ions move from the lumen of the SI into the cell
 this pulls in glucose via a cotransport protein
 therefore glucose builds up in the cell and moves into the blood by diffusion