Transcript Diffusion and Osmosis

Transport of Molecules in a Cell
Terms to Know
• SOLUTE: refers to the substance that is to be
dissolved (Salt, Sugar)
• SOLVENT: responsible for dissolving the solute
(Water)
• SOLUTION: Solvent and solute after combining
together
• ECF: Extracellular Fluid. Surrounds all living cells
• CONCENTRATION: mass of solute dissolved in the
solvent
• SEMI-PERMEABLE (SELECTIVELY-PERMEABLE):
a membrane that allows only some substances in or
out
Selectively Permeable Membrane
Transportation of Molecules
Passive Transport
Active Transport
• Movement of
•Movement of molecules
molecules across a
across a semi-permeable
semi-permeable
membrane with the gradient
membrane against a
3 types: Osmosis,Diffusion +
concentration
Facilitated Diffusion
gradient with a protein
•Movement of molecules
across a semi-permeable
membrane with a protein
•NO ENERGY required
• ENERGY required
Diffusion
• Solute molecules moving
from an area of high
concentration to an area
of low concentration
• Random motion drives
diffusion
• Movement is based on
kinetic energy (speed),
charge, and mass of
molecules
• Equilibrium is reached
when there is an even
distribution of solute
molecules
(water)
1
2
3
4
Equilibrium Reached
Low Concentration
High Concentration
Osmosis
• Diffusion of water through a semi-permeable
membrane
– Permeable to solvents (WATER), but not to large
molecules
– High [water] to low [water]
[concentration]
• Dissolved molecules (i.e. glucose, starch) are called
solutes
• REMEMBER:
Water = solvent
Glucose, Starch, Salt = solutes
Effect of Water on Cells
• Hypertonic Environment
– High [solute], low [water]
• Isotonic Environment
– [water] = [solute]
• Hypotonic Environment
– High [water], low [solute]
Osmosis
Sucrose will not move but water will
Dialysis Bag Experiment
• Dialysis Bag
– Semi-permeable membrane
– Water, glucose, & starch
• What passes through the
dialysis bag?
– Glucose (Benedict’s Test)
– Starch (Iodine Solution)
• Time Course Experiment
– Every 10 minutes, measure
the amount of glucose &
starch present in the beaker
Dialysis bag
Glucose
Iodine
Starch
Osmosis in Living Cells
Cellulose in
cell wall
plasmolyzed
flaccid
Normal
turgid
RED BLOOD CELLS
Osmosis in Plant Cells
Plasmolysis
• Observe Elodea leaves via a wet
mount of the sample
10% NaCl
Hypertonic
Distilled water
Hypotonic
Recall the Cell Membrane
Proteins in the Plasma (cell) Membrane
Proteins are Specific to certain Solutes
Active Transport
ENDOCYTOSIS
The general term for bringing bulk chemicals into a cell is endocytosis
(endo = inside); the general term for bringing bulk chemicals out of a
cell is exocytosis (exo=outside).
Moving material into the cell by endocytosis involves the pinching in of a
portion of the cell membrane around the material to be transported into
the cell. The pinched-in portion eventually breaks free from the cell
membrane and forms a vesicle in the cytoplasm.
Homework
• Complete your Cheek Cell & Elodea Cell
mini-lab
• Study for your Microscope quiz
• Answer questions on p.25 Q.1-19
 Next topic: Cell cycle & cell division