1. Cell Membrane & Transport
Unit 2: Chapter 7
Textbook pages

2. Types of Outer Boundaries:
CELL WALL
found only in plant cells, bacteria and fungi
Thick and inflexible
Function: support and protection
made of carbohydrates (cellulose in plants)

3. Cell (Plasma) membrane
Thin, flexible
Selectively permeable
Functions:
Controls movement in and out of cell
Maintains homeostasis

4. Fluid Mosaic Model
states that: the cell membrane is a lipid bilayer made up of different molecules (mosaic) which are free to move across it(fluid).
Animation: Fluid Mosaic Model

5. Membrane composition:
1. phospholipids:
Hydrophilic heads (Polar): love water
Hydrophobic tails (Non-polar): afraid of water

6. 2. Proteins/glycoproteins:
are embedded
can form channels;
work in transport and recognition.

7. Movement Across the Membrane
PASSIVE Transport: requires no energy, movement from HIGH to LOW concentration
* Examples: diffusion, osmosis, facilitated diffusion
ACTIVE Transport: requires energy, movement from LOW to HIGH concentration
* Examples: endocytosis, exocytosis

8. Types of ACTIVE Transport
Movement AGAINST the “concentration gradient”
ENDOCYTOSIS: cells ingest large particles
Phagocytosis: cell takes in food
Pinocytosis: cell takes in water
EXOCYTOSIS: cells remove large particles exocytosis

9. Types of PASSIVE Transport
Movement WITH the concentration gradient (HIGH TO LOW CONCENTRATIONS)
DIFFUSION: movement of particles from high concentration to low concentration
Does NOT require energy
Substances move across membrane until both sides are equal (DYNAMIC EQUILIBRIUM)

10. FACILITATED DIFFUSION
proteins in the membrane help substances enter the cell
Protein channels are SPECIFIC only allowing some things in/out
Movement from HIGH to LOW

11. OSMOSIS: diffusion of water through a semipermeable membrane
water moves from HIGH TO LOW concentrations
exerts pressure (OSMOTIC PRESSURE) which can cause cell swelling
Higher Concentration
of Water
Water molecules
Lower Concentration
of Water
Sugar molecules

12. Comparison of the ways molecules move into and out of cells.
Name
Type of Transport
Direction of Movement
Conditions
Examples
Diffusion
passive
towards lower concentration
Concentration gradient
Water, gases (02and CO2), and steroid hormones.
Facilitated Diffusion
Concentration gradient, plus channel or carrier proteins
Water, glucose, and amino acids.
Osmosis
Concentration gradient, channel proteins optional
Water 0nly.
Active Transport
active
towards higher concentration
Carrier protein and ATP energy
Ions, sugars, and amino acids.

13. TYPES OF SOLUTIONS
HYPERTONIC:
concentration of water is higher inside the cell than outside
Water rushes OUT of cell causing it to shrivel
Can result in PLASMOLYSIS in plants which causes wilting

14. ISOTONIC:
Water movement into cell equals water movement out of cell
DYNAMIC EQUILIBRIUM

15. concentration of water is lower inside the cell than outside
HYPOTONIC:
concentration of water is lower inside the cell than outside
Water will move INTO cell causing it to SWELL and break (cytolysis)
This increases pressure inside of cell (TURGOR PRESSURE)
TONICITY QUIZ VIDEO