2.4.4~diffusion

Question 1

where does diffusion occur

Answer 1

across the cell membrane

Question 2

diffusion definition

Answer 2

the net movement, as a result of the random motion of its molecules or ions, of a substance from a region of its higher concentration to a region of lower concentration

Question 3

diffusion concentration gradient

Answer 3

molecules/ions move down a concentration gradient

Question 4

what is the random movement of diffusion caused by

Answer 4

natural kinetic energy of the molecules/ions

Question 5

arrangement after diffusion

Answer 5

molecules/ions tend to reach an equilibrium (given sufficient time), where they are evenly spread within a given volume of space

Question 6

how does steepness of concentration gradient effect rate of diffusion

Answer 6

faster rate of diffusion

Question 7

what is steepness of concentration gradient

Answer 7

difference in the concentration of the substance on the two sides of the surface

Question 8

what causes faster rate of diffusion in steeper concentration gradients

Answer 8

if there are more molecules on one side of the membrane than the other, more molecules will randomly move across the membrane from that side to the other –> greater difference in number of molecules passing in the two directions means faster rate of diffusion

Question 9

how does temperature effect rate of diffusion

Answer 9

higher temperatures means faster rate of diffusion

Question 10

why does higher temperatures increase rate of diffusion

Answer 10

molecules/ions have more kinetic energy at higher temperatures so faster movement results in higher rate of diffusion

Question 11

how does surface area effect rate of diffusion

Answer 11

greater the surface area the greater the rate of diffusion

Question 12

why does grater surface area increase rate if diffusion

Answer 12

the grater the surface area, the greater the number of ions/molecules that can cross it at any moment

Question 13

how can surface area of membrane be increased

Answer 13

folding (such as cristae in mitochondria)

Question 14

how does cell size effect rate of diffusion

Answer 14

as cell size increases, surface area to volume ratio decreases which slows down rate of diffusion as distance required becomes too great

Question 15

molecule size effects diffusion

Answer 15

large molecules diffuse more slowly than smaller ones as they require more energy to move

Question 16

polarity effects diffusion rate

Answer 16

uncharged and non-polar molecules diffuse directly across phospholipid bilayer so diffuse more quickly than polar molecules as they are soluble in phospholipid bilayer

Question 17

what substances can only cross membrane by facilitated diffusion

Answer 17

-large polar molecules such as glucose and amino acids
-ions such as Na+ and Cl-

Question 18

proteins enabling facilitated diffusion

Answer 18

-channel proteins
-carrier proteins

Question 19

channel and carrier proteins specificity

Answer 19

highly specific as only allow one type of molecule or ion to pass through

Question 20

what are channel proteins

Answer 20

water-filled pores

Question 21

what do channel proteins allow

Answer 21

charged substances such as ions to diffuse through cell membrane

Question 22

how do channel proteins work

Answer 22

diffusion of the ions do not occur freely, most channel proteins are gated, meaning that part of the channel protein on the inside surface of the membrane cannot move in order to close or open the pore

Question 23

what do channel proteins control

Answer 23

exchange of ions

Question 24

carrier protein shape

Answer 24

can switch between two shapes

Question 25

how do carrier proteins work

Answer 25

binding site of the carrier protein is open to one side of the membrane first, then open to the other side when carrier protein switches shape

Question 26

direction of diffusion using carrier proteins

Answer 26

depends on relative concentration on each side of the membrane (net diffusion occurs down the concentration gradient)