1. Day 1

2. Homeostasis • All living things respond to their environments. • Remember living things are made of cells that contain carbon. • Homeostasis is the maintenance of stable internal conditions in achanging environment. • One way that a cell maintains homeostasis is by controlling the movement of substances across the cell membrane.

4. Intro to membranes • Every cell is surrounded by a cell membrane. • The cell membrane protects the cell and helps move substances and messages in and out of the cell. • By regulating transport the cell membrane helps the cell maintain homeostasis. • SEMI PERMEABLE – body guard

6. Membranes • Cells are suspended in a fluid environment. • Even cell membranes are fluid. • They are a sea of lipids in which proteins float. • They also provide structural support for the cytoplasm, recognizes foreign material and communicates with other cells.

7. Lipid Bilayer • The cell membrane is made up of a phospholipid bilayer, which consists of a phosphate (hydrophilic/polar) head and a two fatty acid (hydrophobic/nonpolar) tails. • These phospholipids form a double membrane in which both heads are facing out of the cell. • The phospholipids forma barrier through which only small nonpolar substances can pass.

9. Membrane Proteins • Some proteins found within the membrane face out, some face in the membrane, and some stretch across the entire membrane. • Proteins are made of amino acids (some amino acids. are polar and others are nonpolar). • Polar proteins are attracted to the outside water of the membrane while nonpolar proteins are forced inside the membrane.

10. Activity • Use the rest of the Power Point or your book to make a diagram of the phospholipid bilayer. You should also include a legend for each item explaining what it is and it’s function. Parts that should be included are: • Phosphate • Lipid • Layer 1 and 2 • Cytoplasm • Enzymes • Surface marker • Transport proteins (channel and carrier)

11. Listen to these songs while you work • Cell membrane song • Enzyme SONG • Enzyme SONG • Cell song

12. Types of Interior Proteins • Cell surface markers • Receptor proteins • Enzymes • Transport proteins

13. Cell Surface Markers • Similar to a name tag • A chain of sugar identifies each type of cell • These sugars are attached to the cell surface by proteins called glycoproteins. • Glycoproteins (sugar (glyco is short for glucose) marker= nametag) help cells work together.

14. Cell Surface marker – sugar name tag

15. Receptor Proteins • Enable a cell to sense its surroundings • They bind to certain substances outside the cell. • Once they are bound to the substances outside the cell changes within the cell take place.

17. Enzymes • Proteins with in the cell membrane that help with important biochemical reactions inside the cell. • These can be to increase the speed of a reaction or decrease the speed of a reaction.

18. Transport Proteins • Many substances the cell needs cannot pass through the lipid bilayer in between the two phosphate heads. • WHY??? • Transport proteins aid the movement of substances that cannot typically pass into and out of the cell through the cell membrane. • What kind of substance would need help?

19. Channel Proteins • Ions, sugars, and amino acids can diffuse through the cell membrane through channel proteins. • These proteins aka pores serve as tunnels through the lipid bilayer. • Each tunnel allows for a specific substance to diffuse through it. This substance has a specific size and charge.

20. Channel – tunnel

21. Carrier Proteins- hand • Transport substances that fit within their binding site. • A carrier protein binds to a specific substance on a specific side of the cell membrane. • This binding causes the substance to change shape. • As the shape changes the protein is moved across the membrane and release on the other side. • This is enzyme activation across the membrane

22. Carrier – Hand