Day 1

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 a changing environment. One way that a cell maintains homeostasis is by controlling the movement of substances across the cell membrane.

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

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.

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.

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.

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)

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

Types of Interior Proteins Cell surface markers Receptor proteins Enzymes Transport proteins

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.

Cell Surface marker – sugar name tag

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.

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.

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?

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.

Channel – tunnel

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

Carrier – Hand