Questions If the cell membrane is like a bouncer to a club, then what is its function??? What word or words describes that the membrane only allows certain materials to pass through it? What are the components of the cell membrane?

Chapter 4 - Cells & Their Environment

Function & Structure of the Cell Membrane Function of Cell Membrane -Controls what goes in and out of cells -Selectively Permeable – Only certain substances can pass through the membrane

B. Structure of Cell Membrane - Contains protein floating in 2 layers of phospholipids.

- How are the phospholipids arranged in the cell membrane? Water on the outside of the cell Water on the inside of the cell

-What does the cell membrane look like? Fluid Mosaic Model -Contains diverse elements Phospholipid Bilayer with proteins -Phospholipids – lipids made of a phosphate head with two fatty acids tails

C. Types of Proteins in Cell Membrane Cell Marker Protein Receptor Protein Transport Protein

Cell Marker Protein - Advertise cell type – such as a liver cell, heart cell, muscle cell. Receptor Protein -Responsible for receiving signals from other cells

- Aid in the movement of substances into and out of cell. -Ex: Transport Protein - Aid in the movement of substances into and out of cell. -Ex: Transport Protein http://www.youtube.com/watch?v=ULR79TiUj80

Review Questions What components make up the cell membrane? How are the phospholipids arranged in the cell membrane? Why? What are the three types of proteins in the cell membrane? What is the function of each of these proteins?

Ways Substances Move Across Cell Membrane - There are two main ways substances are transported through the cell membrane Passive Transport Active Transport

A. Passive Transport Movement of substances across cell membrane that does not require energy (ATP). Types of Passive Transport: Diffusion, Facilitated Diffusion, & Osmosis

1. Diffusion -Movement of materials from an area of _____________ high -Movement of materials from an area of _____________ concentration to an area of __________ concentration. -Moves down (with) the concentration gradient -Concentration Gradient – Difference in the concentration of a substance across a space. low

1 2 3 -Materials will continue to move until a balance is reached = dynamic equilibrium 1 2 3

Draw arrows showing how oxygen will diffuse!!!! Blood Vessel Red Blood Cell O2 cell O2 O2 O2 O2 O2 O2 Cell Membrane O2

2. Facilitated Diffusion -The movement of molecules from an area of high concentration to low concentration with the help of transport (carrier) proteins in the cell membrane. http://www.d.umn.edu/~sdowning/Membranes/facilitateddiffusionhigh.html

Example of Carrier Protein Small Proteins

-Movement of water from high to low concentration -Diffusion of water 3. Osmosis -Movement of water from high to low concentration -Diffusion of water

Image showing what happens when a blood cell is in a hypotonic environment & a hypertonic environment

Image showing what happens when a plant cell is in a hypotonic environment & a hypertonic environment

Which side has more water? = salt A B membrane

Which side is Hypertonic? = salt A B membrane

Which way will the water move? = salt A B membrane

If I put a Red blood cell in a hypotonic solution, what will happen to it? Before After

If I put a liver cell in a hypertonic solution, what will happen to it? Before After

Active Transport Low High -If Active Transport is the opposite of Passive Transport, then what are 3 characteristics of Active Transport? 1. Movement of materials from an area of ________ concentration to an area of ________ concentration 2. Against the Concentration Gradient. 3. Cells must use energy (ATP) to move materials into and out of cell Low High

Active Transport These are 2 examples of active transport 1. Endocytosis (in) 2. Exocytosis (out)

Types of Active Transport Endocytosis Material becomes enclosed within an inpocketing of cell membrane. The membrane closes over material which becomes a vesicle inside the cell.

-Types of Endocytosis Pinocytosis - Vesicle forms to take in small dissolved (liquid)particles (cell is drinking).

- Example: When white blood cells engulf bacteria! b. Phagocytosis - Vesicle forms to take in large undissolved particles (cell is eating). - Example: When white blood cells engulf bacteria!

2. Exocytosis -Vesicle within the cell fuses with the cell membrane and releases its contents to the outside

Endocytosis and Exocytosis Compared http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter6/animations.html#