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Chapter 2.3 Notes
“Materials move across the cell’s membranes”
A. Membranes – “Fluid Mosaic Model”
1- Phospholipids: give the general structure of the membrane
2- Proteins: allow bigger substances to pass through
3- Cholesterol: helps maintain structure
4- Carbohydrates: receptors that send and receive signals
B. Types of Transport in Cells
1. Passive Transport: “go with the flow”, do not require energy
Types of Passive Transport
a. Diffusion
i. Definition- molecules move from a high concentration to a low
concentration to create DYNAMIC EQUILIBRIUM
ii. Effected by:
1. Heat- the hotter, the faster
2. State of Matter
a. solid-slow
b. liquid- faster
c. gas- fastest
3. Size and concentrationBigger= slower
More concentration= faster
Diffusion Experiments- use a colored pencil to show the difference
Perfume- Before I sprayed it
Perfume- After I sprayed it
Food Coloring- When first dropped
Food Coloring- after dropped
b. Facilitated Diffusion: the molecules need a “helper” or “facilitator” to allow
them to cross the membrane when they are too big.
Osmosis: the flow of WATER from a high concentration to a low concentration.
- occurs based on the type of “solution” you have
a. solution: a mixture in which you cannot separate the components.
i. Solute: The substance being dissolved
Ex- Lemonade mix
ii. Solvent: The substance doing the dissolving
Ex- Water
b. solution descriptions:
1. ISOtonic- same amount of solute inside the
membrane as there is outside.
Cell in this solution: nothing happens
2. HYPERtonic- (↓solute ↑solvent)
i. Cell in this solution: shrivels up!
3. HYPOtonic- (↑solute ↓solvent)
ii. Cell in this solution: bursts!
Real life Osmosis Situations…
Situation:
Scenario 1:
A saltwater fish is put into a freshwater lake.
a) What type of solution is the freshwater?
Hypotonic
b) What will happen to the cells of the fish?
The cells will burst
Scenario 2:
A patient at the hospital is given a IV solution that has the PERFECT balance of glucose.
a) What type of solution is in the IV?
Isotonic
b) What will happen to the cells of the patient?
The cells will stay the same.
Scenario 3:
Your garden is infested with slugs. You decide to pour salt
on them to try to get rid of them.
a) What type of solution is the salt?
Hypertonic
b) What will happen to the cells of the slug?
They will shrivel up
2. Active Transport:
a. Definition: when molecules move from a low concentration to a high concentration
and must use ENERGY.
3. Vesicuclar Transport:
a. Endocytosis: When cells absorb molecules by engulfing them. (like pacman)
i. Phagocytosis: When cells engulf solid molecules
ii. Pinocytosis: When cells engulf liquid molecules
b. Exocytosis: When cells expel unwanted materials from vesicles.