Chapter 3 Movement of Substances. 3.1 Diffusion Diffusion is the net movement of particles from a...
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Transcript of Chapter 3 Movement of Substances. 3.1 Diffusion Diffusion is the net movement of particles from a...
Chapter 3 Chapter 3
Movement of SubstancesMovement of Substances
3.1 Diffusion3.1 DiffusionDiffusion is the net movement of
particles from a higher concentration region to a region of lower concentration.
After diffusion, overall concentration remains the same
Only happens in substance in gaseous or liquid state
3.1.1 Concentration Gradient3.1.1 Concentration GradientConcentration Gradient is the
difference in concentration between two regions
The steeper the gradient, the faster rate of diffusion it will occur.
3.1.2 3.1.2 Diffusion across a membraneDiffusion across a membraneCell Surface Membrane
◦Partially permeable surface◦Allow some substances to pass through
but not others◦Only small particles can pass through and
not others.◦Unicellular organism like amoeba get
oxygen and removes carbon dioxide by diffusion through the cell surface membrane.
OsmosisOsmosisOsmosis 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.
Allow some substance to pass through but not other.
Water PotentialWater PotentialHypertonic: Lesser water moleculesHypotonic : More water moleculesIsotonic: Equal water moleculesWater potential is a measure of the
tendancy of water to move from one place to another.
Dilute solution > Concentrated solutionWhen partially permeable membrane
separates 2 solutions of different water potential, a water potential gradient is established.
Hypotonic – High Water Hypotonic – High Water PotentialPotential
Plant Cell Animal Cell-Water enters cell by osmosis.- Plant cell expands and become swollen/turgid causing the cell to be turgor (filled with water)-Pressure exerted by water on cell wall is call turgor pressure
- Cell expands and will eventually burst.
Hypertonic – Low Water PotentialHypertonic – Low Water Potential
Plant Cell Animal Cell-As cell loses water, vacuole decrease in size-Shrinkage of cytoplasm and cell membrane from cell wall is known as plasmolysis-Tissues of plant become flaccid-Plasmolysed cell can be restored to its original state.
-Shrink in size and become spiky Crenation- Cell become dehydrated and eventually die.
Turgor Pressure in PlantsTurgor Pressure in PlantsMaintaining shape of soft tissues in plantsTo keep the plants firm and remains uprightWithout turgor, plants will wiltOpening of flowers, moving of leaves and
opening/closing of guard cells are results of changes in turgor pressure
Plant requires turgor to keep them upright.Cutting stem of plant exposes inner cortex
cells.
Turgor Pressure in PlantsTurgor Pressure in PlantsExertion of cortex cells prevented by
epidermal cells which are prevented by cuticle layer
Cutting releases this restraint exerted by epidermis, thus cortex expands & cause strip to curl outwards.
3.3 Surface Area to Volume 3.3 Surface Area to Volume RatioRatioRate of movement of a substance across
the surface of a cell depends on how big the area of cell membrane is.
The greater the area of cell surface membrane per unit volume, the faster the rate of diffusion of a substance for a given concentration gradient.
Increase rate of diffusion, there must be presence of many small cells instead of one big cell.
3.4 Active Transport3.4 Active TransportMovement of molecule from a region of
low concentration to a region of high concentration against a concentration gradient.
Energy is required.Only occurs in living cells as living cell
respire.For example:
◦ Absorption of dissolved minerals by root hairs◦ Absorption of glucose and amino acids by cells in
small intestine.
Movement of Substances