1. CELL BOUNDARIES
Chapter 7, Section 3 Pgs

2. The Cell Membrane
Regulates what goes in an what goes out, like a bouncer at a club
Made up of a lipid bilayer (A fluid, flexible barrier) and proteins
The typical model of a cell membrane is called a Fluid Mosaic Model

3. Quick Stuff Plants have Cell Walls in addition to cell membranes
Walls are made mostly of cellulose
Provide support and protection
Concentration:
Cells contain lots of substances in water
The amount of any given substance (IE: NaCl or KCl) is called the concentration
Diffusion is the process of substance particles moving from areas of high concentration to areas of low concentration

4. Diffusion
Diffusion is the process of substance particles moving from areas of high concentration to low concentration.
When the concentration is equal throughout, equilibrium has been reached
Diffusion across a cell membrane does NOT require energy!

5. Osmosis: The Diffusion of Water
The diffusion of water across a semi-permeable membrane is osmosis
Water moves from areas of high concentration to low concentration just like substances!
Hypotonic  Hypertonic until the solutions are Isotonic
Hypotonic = “under-stuffed”
Hypertonic = “over-stuffed”
Isotonic = Equally stuffed

6. Osmotic Pressure Cells have lots of salts and substances in them
If animal cells come in contact with fresh water, they will expand until they explode, if they come in contact with very salty water, they will shrivel
Animal cells never come in contact with fresh water
Cell walls prevent plant cells from exploding
The pressure water can create in cells is called Osmotic Pressure

7. Passive Transport vs. Active Transport
Facilitated Diffusion occurs when substances cross a cell membrane without using energy.
Often through a tubular membrane protein than never closes
Active Transport uses energy to move membrane proteins so substances can move (usually) from areas of low concentration to high concentration

8. Endocytosis vs. Exocytosis
When cells move very large molecules into the cell body, it’s called Endocytosis
Endo- into, cyto- cell
Cells perform endocytosis in two ways
Phagocytosis
Pinocytosis
Exocytosis occurs when cells release molecules out of their cell body
Exo- out of, cyto- cell
Ex: Contractile vacuoles release water out of a single-cell organism

9. Endocytosis: Both forms in one image

10. Endocytosis: Phagocytosis
Cell membrane expands and surrounds the particle being eaten
Engulfs it creating a food vacuole
Used to eat large particles
Requires energy, therefore active transport

11. Endocytosis: Pinocytosis
Similar to phagocytosis but used to ingest small particles
Small pockets form in the cell membrane, fill with fluid and pinch off into the cytoplasm around the particle

12. Transport Videos Lipid Bilayer 3D view of organelles
3D view of organelles
Active vs. Passive Transport and cell eating
Osmosis
Some cell structures (WAY more info than you need, but cool nonetheless)