2. Elements All matter in the universe- living and nonliving- can be broken down into substances called elements (made of atoms). About 25 are essential for life.

3. Within Cells Most activities that take place within cells involves atoms and molecules interacting. In this process, called a chemical reaction, bonds between atoms are broken and new bonds to make different molecules.

4. Carbohydrates Carbohydrates provide the cell with energy. Inside cells, sugar molecules are broken down. This process provides usable energy for the cell. In plants, when they make more sugar than they can use they are stored in long chains called starch.

5. Lipids Lipids are the fats, oils and waxes found in living things.

6. Proteins Proteins are made of smaller molecules called amino acids. Which contain the elements, carbon, oxygen, hydrogen, nitrogen and sometimes sulfur. Your body gets amino acids from protein in food, such as meat. Your cells then use them to build proteins needed for proper cell functioning.

7. Nucleic Acid Nucleic acids are molecules that hold the instructions for the maintenance, growth, and reproduction of cells. There are two types: DNA: Provides the information use by the cell to produce proteins RNA Produce proteins.

8. Water All of the chemical reactions inside the cell take place in water. About two thirds of every cell is water. Due to its structure a water molecule has a slight positive charge near the hydrogen atoms and a slight negative charge near the oxygen atom.

9. Research Section 16.1 1) What percent of the body is made of Oxygen, Carbon, Hydrogen? 2) What are the four main types of large molecules and what characteristic do they share? 3) What is an important property of lipids? 4) What are some things that proteins do? 5) What are the subunits of nucleic acids called? 6) Use pg 537 to describe how a cell membrane is designed.

10. Answers 1) 93% of the human body is made up of Oxygen, Carbon, and Hydrogen. 2) The four main types of large molecules are Carbohydrates, Lipids, Proteins, and Nucleic Acids. All of theses large molecules contain Carbon atoms and are made up of smaller parts called subunits. 3) An important property of Lipids is that they cannot mix with water. 4) Proteins are needed in the cell for proper cell function. These proteins control chemical reactions, support grown and repair, allow muscles to move, fight infections, delivers oxygen to cells, part of cell membranes, and transport materials into and out of the cell. (must have 3) 5) The subunits are known as nucleotides. 6) Cell membranes function as boundaries, and are made up of a double layer of lipids that have water-loving heads and water-hating tails. The water-hating tails repel the water while the head clings to water.