Movement of Materials
in the Cell
Diffusion
Osmosis
• Each individual cell exists in a liquid
•
environment. The presence of the liquid
environment makes it easier for materials such
as food, oxygen, and water to move into and
out of the cell.
The exchange of materials between a cell and
its liquid environment takes place at the cell’s
membrane.
Diffusion:
Passive transport
• The process by which molecules of a substance
•
move from areas of higher concentration of that
substance to areas of lower concentration.
Since molecules are in constant motion, the cell
does not have to use any energy during
diffusion (passive transport).
What factors determine whether diffusion
occurs across a membrane?
• First Factor: If two substances are
present in unequal amounts on either side
of a membrane, the substance will tend to
move toward the area of lower
concentration until equilibrium is reached.
- concentration for both are the same.
• Factor 2: Permeability. If a particular substance is able to
diffuse across a membrane, then that membrane is
permeable to that substance.
• Permeable: substance can pass through
• Impermeable: substance cannot pass through.
• Semi-permeable membrane - a physical barrier which only
allows certain particles to pass through it; membranes of
organelles and cells are semi-permeable.
Osmosis
• Osmosis is defined as the diffusion of water through a
•
selectively permeable membrane which separates two
solutions of different solute concentrations.
Water always flows from a higher water
concentration to a lower water concentration.
• Water molecules pass through most cell
membranes very rapidly.
Solution: two parts
• Solvent: Universal solvent is water. It is
what the substance is dissolved into. The
lab: solvent = water
• Solute: The substance that is being
dissolved. The lab: salt = solute
Three types of solutions:
• Always compare two solutions against
each other.
– Isotonic: both solutions are equal. Same
concentration of both substances
– Hypotonic: lower concentration of the
dissolved substance
– Hypertonic: higher concentration of dissolved
substance
The Lab:
• Diffusion, Osmosis or both?
• Questions:
• What do you see happening in the water
when you first place the pig intestine into
the beaker?
• You should have observed the sugar moving from the
inside of the intestine into the beaker.
• Did you observe any change in the color of the water?
If yes, what does that prove?
• Water may have gotten cloudy, however based on 10
minutes may not have observed. It proves that sugar
diffused through membrane.
After heating the test tube and adding Benedict’s solution,
did you observe any change? If yes, what was the change
and why did this change occur?
• The solution turned orange. Proved the
presence of sugar. Darker the orange = more
sugar.
After placing iodine into the beaker, was there any change
in either the pouch of the beaker solution? If yes, what
was the change and why did it occur?
• Iodine diffused into the membrane and turned
the starch purple/black. If the solution in the
beaker changed from a cloudy precipitate into a
dark purple/black then starch was in the beaker.
• Pouch not tied tightly or not rinsed off well
enough.
Conclusion:
• The sugar diffused out and the iodine diffused
in. The starch molecules were to large to pass
through. The water molecules are classified as
a polar covalent bond that has a certain
electronegativity that did not allow the water
molecule to pass.
• Selective permeability.
Quiz Tomorrow:
• Know the 3 types of solutions.
• Know the 3 types of permeability.
• Osmosis/Diffusion
• Carrot/egg lab
• Pig intestine lab
Energy in the Cell
Photosynthesis
Cellular respiration
Producers: green plants
• Change light energy into chemical energy
that the plant could use.
• To carry out photosynthesis , plants take
in water and carbon dioxide. Light
energy is captured by chlorophyll
(contained in the chloroplast) to aid in the
chemical change.
Light
Water + Carbon dioxide --------------Sugar + Oxygen
Chlorophyll
• Oxygen is a waste product for the plant.
• Some sugar used rest is stored.
Cellular respiration
• Once the food is made it must be broken
down. Respiration is that process.
• The breakdown of food occurs in the
mitochondria. During respiration, oxygen
combines with glucose to release stored
energy.