Use the Nelson text, "Biology 11", pp. 47-49 to complete the blanks. Sentences in bold italics are not in the text and will be discussed in class.

The cell (or plasma) membrane separates a cell's ____________________ from it's _________________ environment. It regulates what _________________ and ______________ the cell. Cell membranes also act like molecular "______________ ___________", uniquely identifying certain kinds of cells and form ___________________ to other cells forming _______________. Cell membranes are found only in _________________ cells. In order to survive, cells must extract ______________________ from the environment. As nutrients are processed, __________________ build up inside the cell. These must be excreted from the cell. So how do cells __________________ which materials to absorb? How does the cell ________________ molecules? Because the cell membrane can determine which materials to pass, it is referred to as _____________________________.

The membrane appears as __________ layers of ____________________ (lipids with _________________ groups). Each ___________________ molecule can be represented by a _____________ with 2 ________________. The tails are actually _________________ acids. The head is _____________________, or water ____________________, and is soluble in ___________________. The tails are ______________________, or water ____________________, and are not soluble in ______________________. The _____________-soluble ends of one layer face the _______________ _________________ environment and the water-soluble ends of the second layer face the ________________ ___________________. The hydrophobic ________________ are forced to face _____________, away from the ___________________ environment and towards each other.

Sketch and label Fig. 1 and Fig. 2

A variety of different ___________________ molecules are embedded with the phospholipid ____________________. Many of these proteins (the building blocks of proteins are ________________ acids) carry special __________________ molecules and are thus referred to as ____________________. The ____________________ provide the cell with a unique ___________________. For example, they help distinguish a ____________ red blood cell from a __________________ red blood cell. Your ________________ system identifies invaders by recognizing the unique ________________ structure on their cell membrane.

The __________________ molecules in the phospholipid bilayer serve different functions. Some act as _____________________, opening and closing _______________ through the cell membrane. Other proteins act as ___________________ sites for ____________________. Hormones are chemical ______________________ that allow cells to __________________ with one another. For example, ________________, secreted by the ____________________, attaches itself to specific _________________ proteins embedded in the membrane, causing it to open a _____________ and allow in _________________ from the blood. Another class of protein is involved in __________________, using cell _________________ to pick up needed materials and move them into or out of the cell.

There are 2 main types of proteins in the cell membranes. Proteins that stud the inner or outer surface of the membrane are called _________________ or __________________ proteins. These are mostly _______________________ or __________________. Proteins that span the membrane, passing from one side to the other, are called ____________________ or ___________________ proteins and they usually function in _________________________ materials.

Sketch and label Fig. 3