1. Cellular Transport Indicator B-2.5:
Explain how active, passive, and facilitated transports serve to maintain the homeostasis of the cell.

2. Key Concepts
Homeostasis
Passive Transport
Active Transport

3. It is essential for you to know…
Materials needed for cellular processes must pass into cells so they can be utilized.
Waste materials from cellular processes must pass out of cells as they are produced.
The cell membrane regulates the passage of material into and out of the cell.
Each individual cell exists in a fluid environment, and the cytoplasm within the cell also has a fluid environment.
A cell membrane is semipermeable.
Materials can enter or exit through the cell membrane by passive or active transport.

4. OBJECTIVES Identify the main functions of the cell membrane.
Describe what happens during diffusion.
Explain the processes of osmosis, facilitated diffusion, and active transport.

5. Vocabulary Cell membrane Phospholipid Fluid mosaic model
Selective permeability
Passive transport
Diffusion
Concentration gradient
Osmosis
Isotonic
Hypertonic
Hypotonic
Facilitated diffusion
Active transport
Endocytosis
Phagocytosis
Exocytosis

7. TEM picture of a real cell membrane.
Cell Membranes
All cells have a cell membrane
Functions:
Controls (regulates) what enters and exits the cell to maintain an internal balance called homeostasis
Provides protection and support for the cell
TEM picture of a real cell membrane.

8. Lipid Bilayer -2 layers of phospholipids
Cell Membranes
Structure of cell membrane
Lipid Bilayer -2 layers of phospholipids
Phosphate head is polar (water loving)
Fatty acid tails non-polar (water fearing)
Proteins embedded in membrane
Phospholipid
Lipid Bilayer

9. Cell Membranes 4. Cell membranes have pores (holes) in it
Selectively permeable: Allows some molecules in and keeps other molecules out
Sometimes referred to as semi-permeable
The structure helps it be selective!
Pores

10. Fluid Mosaic Model of the cell membrane
Polar heads love water & dissolve.
Each individual cell
exists in a fluid
environment and the
cytoplasm within the
cell also has a fluid
environment. The
presence of a liquid
makes it possible for
substances (oxygen,
nutrients, and waste
products) to move in
and out of the cell.
Non-polar tails hide from water.
Carbohydrate cell markers
Proteins

11. Structure of the Cell Membrane
Outside of cell
Carbohydrate
chains
Proteins
Lipid
Bilayer
Transport
Protein
Phospholipids
Inside of cell
(cytoplasm)
Animations
of membrane structure
Go to Section:

12. Types of Cellular Transport
high
low
Weeee!!!
Passive Transport
cell does not use energy (ATP)
Diffusion
Facilitated Diffusion
Osmosis
Active Transport
cell uses energy (ATP)
Protein Pumps
Endocytosis
Exocytosis
high
low
This is gonna be hard work!!

13. Passive Transport (High  Low) cell uses no energy (ATP)
molecules move randomly
Molecules spread out from an area of high concentration to an area of low concentration.
(NOTE: A concentration gradient is a difference in concentrations across a plasma membrane)
(High  Low)

14. 3 Types of Passive Transport
Diffusion
Facilitated Diffusion – diffusion with the help of transport proteins
Osmosis – diffusion of water

16. Passive Transport: 1. Diffusion
Diffusion: random movement of particles from an area of high concentration to an area of low concentration.
(High to Low)
Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out.

17. Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer)
Passive Transport: 2. Facilitated Diffusion A B
2. Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane
Transport Proteins are specific – they “select” only certain molecules to cross the membrane
Transports larger or charged molecules
Facilitated diffusion (Channel Protein)
Diffusion (Lipid Bilayer)
Carrier Protein

18. Passive Transport: 2. Facilitated Diffusion High Low Transport Protein
Glucose
molecules
Cellular Transport From a-
High
High Concentration
Cell Membrane
Low Concentration
Protein
channel
Low
Transport Protein
Through a 
Go to Section:

20. Passive Transport: 3. Osmosis
3.Osmosis: diffusion of water through a selectively permeable membrane
Water moves from high to low concentrations
Water moves freely through pores.
Solute (green) to large to move across.

22. Active Transport (Low  High) cell uses energy (ATP)
actively moves molecules to where they are needed
Movement from an area of low concentration to an area of high concentration
(Low  High)

23. Types of Active Transport
1. Protein Pumps -transport proteins that require energy to do work
Example: Sodium / Potassium Pumps are important in nerve responses.
Protein changes shape to move molecules: this requires energy!

24. Types of Active Transport
2. Endocytosis: taking bulky material into a cell
Uses energy
Cell membrane in-folds around food particle
“cell eating”
forms food vacuole & digests food
This is how white blood cells eat bacteria!

25. Types of Active Transport
3. Exocytosis: Forces material out of cell in bulk
membrane surrounding the material fuses with cell membrane
Cell changes shape – requires energy
EX: Hormones or wastes released from cell

27. Effects of Osmosis on Life
Osmosis- diffusion of water through a selectively permeable membrane
Water is so small and there is so much of it the cell can’t control its movement through the cell membrane.

28. Osmosis Diffusion of water through a semi-permeable membrane
Semi-permeable: permeable to solvents (WATER), but not to large molecules
High [water] to low [water]
Dissolved molecules (i.e. glucose, starch) are called solutes
REMEMBER:
Water = solvent
Glucose, Starch = solutes

29. Effect of Water on Cells
Hypertonic Environment
High [solute], low [water]
Hypotonic Environment
High [water], low [solute]
Isotonic Environment
[water] = [solute]
Hypertonic
Hypotonic
Isotonic

30. Osmosis in Living Cells
Cellulose in cell wall

31. Osmosis in Living Cells

32. Effect of Water on RBC