Chap 2) Movement Of Substances

Question 1

Define 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.

Example sentence: Oxygen molecules move from the alveoli of the lungs into the bloodstream through diffusion.

Question 2

Describe the role of diffusion in nutrient uptake & gaseous exchange in animals and plants

Answer 2

Diffusion is an important way for oxygen, carbon dioxide, nutrients & waste materials to move into & out of cells via cell surface membrane.
Diffusion distance & surface area to volume ratio effects nutrient uptake & gaseous exchange.

Question 3

Define osmosis

Answer 3

Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

Question 4

What happens when plant cell is placed in a solution of higher water potential?

Answer 4

-cell sap has a lower water potential than the solution outside the cell.
-by osmosis, water molecules enter cell through ppm
-as water molecules enter cell, vacuole increases in size & pushes the cytoplasm against the cell wall. Cell does not burst as it is protected by inelastic cell wall.
- cell expands/swells, it becomes turgid

Question 5

What happens when plant cell is placed in a solution of lower water potential?

Answer 5

• the cell sap has a lower water potential than the solution outside the cell
  -by osmosis, water molecules from the vacuole & cytoplasm leaves the cell through ppm
  -as cell loses water, vacuole decreases in size. Cytoplasm shrinks away from the cell wall.
  -cell decreases in size, cell becomes flaccid/limp

Question 6

What happens when animal cell is placed in a solution of higher water potential?

Answer 6

-cytoplasm has a lower water potential than the surrounding solution
-water molecules enter by osmosis
-cell expands & bursts

Question 7

What happens when an animal cell is placed in a solution of lower water potential?

Answer 7

-Cytoplasm has a higher water potential than the surrounding solution
-water molecules leave the cell by osmosis
-cell becomes crenated. (Has spikes and shrunk)