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I. Movement of Materials Through the Cell Membrane
A. Concentration gradient
1. Molecular movement: molecules are constantly colliding, moving down a concentration
gradient from HIGH to LOW,(trying to get to area of lower concentration so they can move
and not collide, pioneers moved from E to W)
2. Concentration gradient: difference btwn the number of molecules inside vs. outside the cell
3. Dynamic equilibrium: NO difference in the # of molecules on either side of the membrane
4. *Hypertonic solution* has a higher concentration of dissolved particles than inside the cell,
water mostly OUT (ocean water to human cells or fresh water fish in salt water, salt on slugs)
5. *Hypotonic solution* has a lower concentration of dissolved particles than inside the cell,
water mostly IN (distilled water to human cells or salt water fish in fresh water)
6. *Isotonic solution* has an equal concentration of dissolved particles as the inside of a cell,
water flows in and out at the same rate. (paramecium in fresh water, has contractile vacuole to
expel excess water)
8. cytolysis- turgor increases, cell gets larger as it takes in water
9. plasmolysis- turgor decreases, cell gets smaller as it loses water
Hypertonic Solution
Isotonic Solution
more water out
water in & out at same rate
Hypotonic Solution
more water in
B. Diffusion or Passive Transport NO ENERGY REQUIRED
1. net movement of the same molecules down a concentration gradient
from *HIGH to LOW*
a. *Osmosis*: diffusion of water across a semi-permeable
membrane from HIGH to LOW
b. *Facilitated diffusion*: molecules allowed or helped across the
membrane by channel proteins
2. Rate is affected by *temperature, pressure, concentration of solution, size of molecules*
C. Active transport ENERGY REQUIRED because a part of the cell is moving
1. movement of molecules against the concentration gradient using energy, *LOW to HIGH*
2. protein pumps in the membrane transport certain ions and large molecules across membranes
3. membrane folding or bulk tansport
a. *Endocytosis* items into a cell; white blood cells engulf invaders
i. *phagocytosis*: taking in food or solid particles
ii. *pinocytosis*: taking in small amounts of liquid (paramecium/contractile vacuole)
b. *Exocytosis* removal of particles from a cell
REMEMBER:
Water, oxygen, carbon dioxide, and amino acids move freely across the membrane b/c they’re small molecules.
Proteins, carbohydrates, & ions need help from protein pumps b/c they’re bigger (ions because they’re charged)!
II. Movement of Materials using the 2 types of Carrier Proteins
**Transport Proteins = Carrier Proteins!!
III. Flow Chart: Overview of Movement of Materials
Transport Overview and Practice:
Identify the processes described below by giving the specific type of movement involved.
Look at the concentration gradient {concentration inside and outside of the cell} to help you decide!!!!!
1. Carrier proteins transport glucose
2. Sodium ions (Na+) are pumped out of
into a muscle cell. *facilitated diffusion*
a red blood cell. *active transport*
3. Fresh water moves into a unicellular
organism (paramecium). *osmosis*
4. An amoeba engulfs a food particle.
*phagocytosis*
5. Pockets of cell membrane fill with water and pinch off to become vacuoles in the cell.
*pinocytosis*
Name the following types of transport in the diagram:
6. *facilitated diffusion*
7. *diffusion*
8. *diffusion*
9. *phagocytosis/endocytosis*
10. *pinocytosis/endocytosis*
11. *osmosis*
12. *exocytosis*
13. *active transport*