4.5- ACTIVE AND PASSIVE TRANSPORT
4.5.1- Tonicity of the solution.
Tonicity describes how an extracellular solution can change the volume of a cell by
affecting osmosis. OR
It describes a solution’s ability to change a cell’s volume by altering its water content
through osmosis.
4.5.2- Different types of solution based on the types of tonicities
HYPERTONIC
Hypertonic solution, the prefix hyper- refers to the extracellular fluid having a higher
concentration than the cell’s cytoplasm; therefore, the fluid contains less water than the
cell does. Because the cell has a relatively higher concentration of water, water will leave
the cell, and the cell will shrink.
HYPOTONIC
In a hypotonic situation, the extracellular fluid has lower concentration than the fluid
inside the cell, and water enters the cell. (In living systems, the point of reference is
always the cytoplasm, so the prefix hypo- means that the extracellular fluid has a lower
concentration of solutes, or a lower concentration, than the cell cytoplasm. )
ISOTONIC
In an isotonic solution, the extracellular fluid has the same concentration as the cell. If
the concentration of the cell matches that of the extracellular fluid, there will be no net
movement of water into or out of the cell, although water will still move in and out.
Changes in Cell Shape Due to
Dissolved Solutes: Osmotic pressure
changes the shape of red blood cells
in hypertonic, isotonic, and hypotonic
solutions.
4.5.3- Effects on plants and animal cells when placed in hypotonic, hypertonic
and isotonic solution.
Effect on ANIMAL CELL:
Hypotonic Solution: Water enters the cell, causing it to swell and potentially burst
(cytolysis) because it lacks a rigid cell wall to counteract the internal pressure.
Hypertonic Solution: Water moves out of the cell, causing it to shrink and shrivel.
Isotonic Solution: There is no net movement of water, so the cell’s size remains stable.
This is the optimal state for animal cells.
Effect on PLANT CELL:
Hypotonic Solution: Water enters the cell, but the rigid cell wall prevents it from
bursting. The cell becomes firm and turgid due to the pressure against the cell wall
(turgor pressure).
, Hypertonic Solution: Water moves out of the cell, causing the plasma membrane to
pull away from the cell wall. This is called plasmolysis, which leads to wilting.
Isotonic Solution: There is no net movement of water, and the cell’s volume remains
constant. It becomes flaccid (limp).
4.5.4- Differentiate between PLASMOLYSIS and DEPLASMOLYSIS:
Plasmolysis DEPLASMOLYSIS
4.5.5- Compare different types of membranes ( permeable, partially permeable
and impermeable)
MEMBRANE TYPE PASSAGE OF CHARACTERISTICS EXAMPLES
SUBSTANCES
PERMEABLE Allows all substances (both Non-selective; acts like an Plant and bacterial
solutes and solvents) to open filter with large pores. cell walls (before
flow freely through it. modification), filter
paper.
SELECTIVELY Allows some solvent Highly selective; "chooses" Cell membrane
PERMEABLE (OR molecules what passes based on size, (plasma
PARTIALLY and specific solute charge, and specific membrane) of
PERMEABLE) molecules to pass, often transporters (channel living organisms,
via transport proteins. proteins). tonoplast.
IMPERMEABLE Does not allow any Acts as a complete barrier, Skin, eggshells,
substances (solutes or often for protection. cutinized cell walls,
solvents) to pass through at polythene,
4.5.1- Tonicity of the solution.
Tonicity describes how an extracellular solution can change the volume of a cell by
affecting osmosis. OR
It describes a solution’s ability to change a cell’s volume by altering its water content
through osmosis.
4.5.2- Different types of solution based on the types of tonicities
HYPERTONIC
Hypertonic solution, the prefix hyper- refers to the extracellular fluid having a higher
concentration than the cell’s cytoplasm; therefore, the fluid contains less water than the
cell does. Because the cell has a relatively higher concentration of water, water will leave
the cell, and the cell will shrink.
HYPOTONIC
In a hypotonic situation, the extracellular fluid has lower concentration than the fluid
inside the cell, and water enters the cell. (In living systems, the point of reference is
always the cytoplasm, so the prefix hypo- means that the extracellular fluid has a lower
concentration of solutes, or a lower concentration, than the cell cytoplasm. )
ISOTONIC
In an isotonic solution, the extracellular fluid has the same concentration as the cell. If
the concentration of the cell matches that of the extracellular fluid, there will be no net
movement of water into or out of the cell, although water will still move in and out.
Changes in Cell Shape Due to
Dissolved Solutes: Osmotic pressure
changes the shape of red blood cells
in hypertonic, isotonic, and hypotonic
solutions.
4.5.3- Effects on plants and animal cells when placed in hypotonic, hypertonic
and isotonic solution.
Effect on ANIMAL CELL:
Hypotonic Solution: Water enters the cell, causing it to swell and potentially burst
(cytolysis) because it lacks a rigid cell wall to counteract the internal pressure.
Hypertonic Solution: Water moves out of the cell, causing it to shrink and shrivel.
Isotonic Solution: There is no net movement of water, so the cell’s size remains stable.
This is the optimal state for animal cells.
Effect on PLANT CELL:
Hypotonic Solution: Water enters the cell, but the rigid cell wall prevents it from
bursting. The cell becomes firm and turgid due to the pressure against the cell wall
(turgor pressure).
, Hypertonic Solution: Water moves out of the cell, causing the plasma membrane to
pull away from the cell wall. This is called plasmolysis, which leads to wilting.
Isotonic Solution: There is no net movement of water, and the cell’s volume remains
constant. It becomes flaccid (limp).
4.5.4- Differentiate between PLASMOLYSIS and DEPLASMOLYSIS:
Plasmolysis DEPLASMOLYSIS
4.5.5- Compare different types of membranes ( permeable, partially permeable
and impermeable)
MEMBRANE TYPE PASSAGE OF CHARACTERISTICS EXAMPLES
SUBSTANCES
PERMEABLE Allows all substances (both Non-selective; acts like an Plant and bacterial
solutes and solvents) to open filter with large pores. cell walls (before
flow freely through it. modification), filter
paper.
SELECTIVELY Allows some solvent Highly selective; "chooses" Cell membrane
PERMEABLE (OR molecules what passes based on size, (plasma
PARTIALLY and specific solute charge, and specific membrane) of
PERMEABLE) molecules to pass, often transporters (channel living organisms,
via transport proteins. proteins). tonoplast.
IMPERMEABLE Does not allow any Acts as a complete barrier, Skin, eggshells,
substances (solutes or often for protection. cutinized cell walls,
solvents) to pass through at polythene,
