Ch 7.2 Plasma Membrane Yesterday we talked about things all cells have. One of those things was the plasma membrane. Yesterday we talked about things all cells have. One of those things was the plasma membrane. Can you remember the other two? Can you remember the other two?

Plasma Membrane- a boundary that controls what leaves and enters the cell. Plasma Membrane- a boundary that controls what leaves and enters the cell.

Why is it important to control what leaves and enters the cell??? Why is it important to control what leaves and enters the cell???

Properties of the Plasma Membrane helps a cell maintain homeostasis. helps a cell maintain homeostasis. is a thin, flexible boundary that separates a cell from its environment. is a thin, flexible boundary that separates a cell from its environment. allows nutrients to enter and wastes to exit. allows nutrients to enter and wastes to exit. All prokaryotes and eukaryotes have a plasma membrane. All prokaryotes and eukaryotes have a plasma membrane. Selective permeability Selective permeability

Selective permeability- Just a fancy way to say: Allows some things in and keeps others out! Selective permeability- Just a fancy way to say: Allows some things in and keeps others out! Kind of how a fishing net lets water out net lets water out but not the fish!

The plasma membrane has 4 main components. 1. Phospholipid Bilayer 2. Transport proteins 3. Cholesterols 4. Carbohydrates

Structure of the Plasma Membrane The plasma membrane is composed of a phospholipid bilayer – two layers of phospholipids are arranged tail to tail. The plasma membrane is composed of a phospholipid bilayer – two layers of phospholipids are arranged tail to tail.

Other Components of the Plasma Membrane Within the Phospholipids there are 3 other things. Transport proteins -. Transport proteins -. Cholesterols Cholesterols Carbohydrates Carbohydrates

Other Components of the Plasma Membrane Transport proteins - create tunnels through which certain substances enter and leave the cell. Transport proteins - create tunnels through which certain substances enter and leave the cell.

Other Components of the Plasma Membrane Cholesterols contribute to the fluidity of the plasma membrane in that they prevent the fatty- acid tails from sticking together. Cholesterols contribute to the fluidity of the plasma membrane in that they prevent the fatty- acid tails from sticking together.

Other Components of the Plasma Membrane Carbohydrates attached to proteins stick out from the plasma membrane and help identify the cell Carbohydrates attached to proteins stick out from the plasma membrane and help identify the cell

It looks like this

Fluid Mosaic Model mb.htm (YES, check this link out! ) mb.htm (YES, check this link out! ) mb.htm mb.htm The components of the plasma membrane are in constant motion sliding past each other. The components of the plasma membrane are in constant motion sliding past each other. The phospholipids in the bilayer create a “sea” in which other molecules can float, hence “fluid” and “mosaic” because there are many components which appear as a pattern or a mosaic. The phospholipids in the bilayer create a “sea” in which other molecules can float, hence “fluid” and “mosaic” because there are many components which appear as a pattern or a mosaic.

Ok what??? Fluid mosaic model- All the parts of the plasma membrane are moving all the time (hence, why they use the word ‘fluid = free to move around each other’!) Fluid mosaic model- All the parts of the plasma membrane are moving all the time (hence, why they use the word ‘fluid = free to move around each other’!)

7.2 - ACTIVITY (YES! Complete on N.B. Paper & STAPLE to 7.2 Study guide, & then turn in to tray for a grade!) ACTIVITY (YES! Complete on N.B. Paper & STAPLE to 7.2 Study guide, & then turn in to tray for a grade!) 1) DRAW AND LABEL the plasma membrane Use page 188 to help Use page 188 to help Define plasma membrane Define plasma membrane Tell me what the cholesterol does Tell me what the cholesterol does Tell me what the transport protein does Tell me what the transport protein does Tell me what the carbohydrate does Tell me what the carbohydrate does 2) Answer the Review/Study ?’s on next slide; 3) Complete the 7.2 Study Guide; Turn in all 3!

Review/Study Questions How does the plasma membrane help maintain homeostasis? How does the plasma membrane help maintain homeostasis? What does it mean if something is selectively permeable? What does it mean if something is selectively permeable? What makes up the plasma membrane? What makes up the plasma membrane? Why are the phospholipids arranged like they are? Why are the phospholipids arranged like they are?