movement of substances

Question 1

what is diffusion?

Answer 1

diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient

Question 2

is energy required for diffusion to occur?

Answer 2

no. no energy is required

Question 3

is a membrane necessary for diffusion to occur?

Answer 3

no. diffusion occurs with or without a membrane

Question 4

what are the factors that affect the rate of diffusion?

Answer 4

• steeper concentration gradient=increased rate of diffusion
  -larger surface area to volume ratio=increased rate of diffusion
  -higher temperature=increased rate of diffusion
  -larger mass=decreased rate of diffusion
  greater barrier thickness=decreased rate of diffusion

Question 5

can water pass through a partially permeable membrane?

Answer 5

yes

Question 6

can salts(ions) pass through a partially permeable membrane?

Answer 6

yes

Question 7

can iodine pass through a partially permeable membrane?

Answer 7

yes

Question 8

can ink/dye molecules pass through a partially permeable membrane?

Answer 8

yes

Question 9

can gases (eg, co2, o2) pass through a partially permeable membrane?

Answer 9

yes

Question 10

can glucose pass through a partially permeable membrane?

Answer 10

yes

Question 11

can amino acids pass through a partially permeable membrane?

Answer 11

yes

Question 12

can sucrose pass through a partially permeable membrane?

Answer 12

no

Question 13

can starch pass through a partially permeable membrane?

Answer 13

no

Question 14

can proteins pass through a partially permeable membrane?

Answer 14

no

Question 15

how does diffusion occur in the nutrient uptake in plants?

Answer 15

plants mostly absorb mineral salts from the surrounding salt solution through diffusion,

Question 16

how does diffusion occur in the gaseous exchange in plants?

Answer 16

for photosynthesis to occur, plants take in carbon dioxide from the surrounding air and release oxygen as a by-product. the movement of gases between the plant and the surrounding air occurs through diffusion.

Question 17

how does diffusion in the nutrient uptake in humans occur?

Answer 17

in the small intestine, nutrients like glucose and amino acids are absorbed through the intestinal epithelial cells and into the bloodstream through diffusion.

Question 18

how does the diffusion in the gaseous exchange in humans occur?

Answer 18

in the lungs, deoxygenated blood in the alveolar capillaries absorb oxygen and remove carbon dioxide through diffusion.

Question 19

what is osmosis?

Answer 19

osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential, down a water potential gradient.

Question 20

is energy required for osmosis?

Answer 20

similarly to diffusion, no energy is required.

Question 21

where can osmosis occur?

Answer 21

it can only occur through a partially permeable membrane.

Question 22

what are some factors that affect the rate of osmosis?

Answer 22

the stepper the water potential gradient=the higher the rate of osmosis
the larger the surface area=the higher the rate of osmosis
the higher the temperature=the higher the rate of osmosis
the greater the barrier of thickness-the slower the rate of osmosis

Question 23

what are the similarities between diffusion and osmosis?

Answer 23

-both are passive processes (no energy required)
-particles move down a gradient

Question 24

what are the differences between diffusion and osmosis?

Answer 24

diffusion does not require a partially permeable membrane however, osmosis does.
diffusion involves the movement of all particles (molecules, ions, etc.) however osmosis involves the movement of water particles only.

Question 25

what is water potential?

Answer 25

the ratio of water molecules to solute molecules (glucose, salt, etc.)

Question 26

what is concentration?

Answer 26

how much solute is dissolved in a volume of a solvent (usually water)

Question 27

what is the water potential of a concentrated solution?

Answer 27

very low

Question 28

what is the water potential of a dilute solution?

Answer 28

very high

Question 29

what is isotonic?

Answer 29

iso=same, tonic=strength
same concentration of solutes and solvent

Question 30

what is hypertonic?

Answer 30

hyper=more, tonic=strength
more solutes and less solvent

Question 31

what is hypotonic?

Answer 31

hype=less, tonic=strength
fewer solutes, more solvent

Question 32

what happens when a plant cell is placed inside a isotonic solution?

Answer 32

the cell cytoplasm and the surrounding solution have the same water potential, and there will be no net movement of water molecules between the cell and the surrounding solution due to the absence of a water potential gradient. water molecules will randomly enter and exit the cell, but there is no net change in water potential between the two regions. there is no observable change in the shape or size of the cell.

Question 33

what happens when a plant is placed in a hypertonic cell?

Answer 33

when place in a hypertonic solution, the cell cytoplasm has a higher water potential than the surrounding solution, causing water molecules to move down a water potential gradient out of the cell via osmosis. the excess water leaving the cell causes the cell to plasmolyse.
the large central vacuole shrinks in size
cell membrane pull away from the cell wall

Question 34

what happens when a plant is placed in a hypotonic solution?

Answer 34

when placed in a hypotonic solution, the cell cytoplasm has a lower water potential than the surrounding solution, causing water molecules to move down a water potential gradient into the cell via osmosis. the excess water entering the cell causes the cell to become more turgid.
the large central vacuole swells and becomes larger
overall cell increases in volume

Question 35

why do animals cells act differently from plant cell when placed in solutions of differing water potentials?

Answer 35

due to their lack of a cell wall

Question 36

what happens when a rbc is placed in an isotonic solution? (human cell)

Answer 36

when placed in an isotonic solution, the cell cytoplasm and the surrounding solution have the same water potential, and there will be no net movement of water molecules between the cell and the surrounding solution due to the absence of a water potential gradient. water molecules will randomly enter and exit the cell, but there is no net change in water potential between the two regions.
there is no observable change in the shape or size of the cell
rbc remains circular and biconcave

Question 37

what happens when a rbc is placed in a hypertonic solution?

Answer 37

when placed in a hypertonic solution, the cell cytoplasm has a higher water potential than the surrounding solution, causing the water molecules to move down a water potential gradient out of the cell via osmosis. the excess water leaving the cell causes the cell to shrivel and crenate.
no cell wall to maintain its regular shape
rbc lose their circular and biconcave shape
cell membrane adopts a spiky texture

Question 38

what happens when a rbc is placed in a hypotonic solution?

Answer 38

when placed in a hypotonic solution, the cell membrane has a lower water potential than the surrounding solution, hence the water molecules move down a water potential gradient into the cell, via osmosis. the excess water entering the cell causes the cell to swell and eventually burst.
no cell wall to maintain regular shape and prevent bursting.