2.1 Cell Theory

2.2-2.3 Prokaryotic and Eukaryotic Cells

2.4 Membranes

2.5 Cell Division 

2.4 Membranes

Homework  

Resource:

Click4biology

2.4.1

Draw and label a diagram to show the structure of membranes. 

Cell Membrane or Plasma Membrane

Another model...

John Kyrk Animation

2.4.2

Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes. 

Phospholipid Molecules

• Polar "head" - hydrophilic ("water loving")
•  
  
• Nonpolar "tails" - hydrophobic ("water fearing")

Phopholipid Bilayer Structure

The extracellular fluid and the cytosol are mostly water.

• polar water molecules attract the polar heads.
• polar water molecules repel the nonpolar tails.

The phospholipids arrange themselves in a double layer (bilayer):

• the heads facing the outside of the cell and facing the inside of the cell. 

Cholesterol and Proteins

Cholesterol molecules make the plasma membrane more rigid (less flexible).

Proteins - two groups:

• peripheral proteins - attached to the surface of the membrane.

• integral proteins - extend into or through the phospholipid bilayer.

2.4.3 

List the functions of membrane proteins.

Membrane Proteins

Membrane Protein Functions

• Receptor Protein - has a specific shape to match a specific signal molecule (hormone), responds by signalling inside the cell.
• Enzyme - catalyst for chemical reactions, on the inside or outside (peripheral).
• Channel Protein - passive transport of ions, polar molecules, or large molecules.
• Gated Channel Protein - passive transport, but can open or close.
• Protein Pump - active transport of substances, requires energy.
• Glycoprotein - communication: identifies cell or cell function to other cells.
• Electron Transport Chain - move electrons and pump hydrogen ions across the membrane.

Resource:

Click4Biology 

2.4.4 

Define diffusion and osmosis. 

2.4.5

Explain passive transport across membranes by simple diffusion and facilitated diffusion.  

Passive Transport

• movement of substances without using energy. 

Examples

• diffusion: movement of substances from an area of high concentration to an area of low concentration.
• facilitated diffusion: diffusion though a channel protein.
• osmosis: diffusion of water.

Background Information

• solution: mixture made by dissolving a solute into a solvent.
• dissolve: to break apart one substance into small, separate particles and become thoroughly mixed in another substance.
• solute: the substance with the smaller amount.
• solvent: the substance with the larger amount. 
• concentration: the amount of solute in a solution.

solute + solvent = solution     Example: salt + water = salt water 

Passive transport video

2.4.6 

Explain the role of protein pumps and ATP in active transport across membranes.

Active Transport

• using energy (ATP) to transport substances across a membrane

Using Protein Pumps

• moves substances from low concentration to high concentration.

• requires energy from ATP to function 

Diagram of the sodium-potassium pump.

Note: follow the arrows - the numbers are incorrect. 

Active transport video 

2.4.7 

Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane. 

Vesicle Transport 

2.4.8 

Describe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis.

Active Transport Using Vesicles

Endocytosis and exocytosis video 

Fluid Mosaic Model video