1. Transport Across the Cell Membrane

2. The Particle Model of Matter
In order to survive and function properly cells need to move gases, ions, nutrients, and waste material across their selectively permeable membrane.

3. Understanding how particles move
Particle Model
All matter is made of particles
The particles of matter are constantly moving or vibrating
the particles of matter are attracted to one another
particles have spaces between them
Particle Movement is described by Brownian motion: the random movement of microscopic particles suspended in a fluid. Applet

4. Particle Movement

5. Methods of Transport
Passive Transport: The movement of particles across the membrane without the cell expending energy
Simple Diffusion
Osmosis
Facilitated Transport

6. Diffusion
the movement of particles down their concentration gradient - from an area of high concentration to an area of low concentration. (animation)
Ex. O2, CO2

7. Osmosis
diffusion of water molecules down their concentration gradient across a semi-permeable membrane. (animation)
Ex. H2O Only
Isotonic, Hypotonic & Hypertonic Solutions

8. Isotonic solution
solution outside the cell has the same amount of solute particles as found in the cell
no net movement of water particles

9. Hypertonic solution
solution outside the cell has a higher concentration of solute than found in the cell
lower concentration of water outside
water moves out of cell

10. Hypotonic solution
solution outside the cell has a lower concentration of solute
higher concentration of water ouside
net movement of water into cell

12. Facilitated Diffusion
movement with the concentration gradient, but assisted by carrier proteins in the membrane. (animation)
Ex. Glucose and Ions

13. Active Transport
Moving molecules against their concentration gradient using energy (ATP). (animations 2)
Ex. Na+, K+, & H+ Pumps

14. The Na+ K + Pump

15. Endocytosis and Exocytosis
movement of larger molecules in and out of the cell with transport vesicles. (animation)

16. Endocytosis:
Bringing substances into the cell by wrapping them in part of the cell membrane
Ex. nutrients
Phagocytosis: Bringing in a large particle (animation)
Pinocytosis: Brining in many small particles
Receptor Mediated Endocytosis: process is triggered by a receptor on the surface of the membrane

18. Exocytosis
Removing/secreting large substances or groups of particles from the cell.
Ex. Waste products, enzymes, chemical messengers, hormones