1. Biology Rainier Jr/Sr High School Mr. Taylor

2. An atom is the smallest particle of an element. An element is made of only one kind of atom and cannot be broken down further by ordinary chemical means. Each atom of an element contains the same number of protons in its nucleus. Carbon, Hydrogen, Oxygen, and Nitrogen compose 95% of the mass of humans... and most other organisms are similar.

3. A compound is two or more elements chemically combined. The chemical formula for a compound tells what kind and how many atoms are present in the compound. An atom that has gained or lost electrons is an electrically charged particle called an ion. Compounds that are formed between charged particles are called ionic compounds. Ions are important in the body and are often called electrolytes.

4. Some atoms share electrons to form covalent bonds. Covalent bonds tend to be stable. Most of the compounds in organisms are covalently bonded.

5. All the processes of living organisms take place in water. Because of unequal sharing of electrons between hydrogen and oxygen, water has a very slight electrical charge. This allows water molecules to “stick” to each other and to other charged (polar) substances.

6. Hydrogen bonding creates certain properties of water: High specific heat: it takes a lot of energy to cause the molecules of water to separate. That means it takes a lot of energy to increase the temperature of water. (This stabilizes internal temperatures in cells.) Cohesion: the molecules of water stick to each other. This causes surface tension of water drops. Adhesion: the molecules of water stick to other charged substances. This helps plants transport water from roots to leaves.

7. Water is often called the “universal solvent” because so many things will dissolve in it. Water will dissolve other polar substances like salt and sugar. Water will NOT dissolve non-polar substances like oils and fats. Things that dissolve in water often change the pH (or acid-base balance). pH measures Hydrogen ion concentrations Lots of hydrogen ions results in an acid (pH = 1-7) Few hydrogen ions present results in a base (or alkali) (pH = 7-14)

8. Carbon atoms form the “backbone” of almost all molecules made by organisms. These substances are called organic molecules. Carbon atoms have 4 electrons available for sharing. Carbon atoms often join in long chains that can be straight or branched, or sometimes forms rings. Carbon compounds can also form sub-units that can unite to form other substances The single sub-unit is called a monomer. The multiple-unit molecule is called a polymer.

9. There are 4 main types of polymers in organisms: 1.Carbohydrates Are made of Carbon, Hydrogen, and Oxygen Simple carbohydrates are sugars; sugars are monosaccharides (a monomer) Complex carbohydrates are starches; starches are polysaccharides (a polymer) Carbohydrates are excellent sources of energy. Cellulose (a starch) makes up the cell walls of most plants.

10. T here are 4 main types of polymers in organisms: 2. Lipids: non-polar molecules that make up fats, oils, and cholesterol. T he monomers of lipids are called fatty acids. F ats and oils are usually made of three long chains of fatty acids held together by a molecule called glycerol. C holesterol is needed as part of your cell membranes and forms the basic structure of cortisones, estrogens, and testosterone.

11. There are 4 main types of polymers in organisms: 3. Proteins: these molecules form most of the structures and perform most of the work for organisms. The monomers for proteins are amino acids. Organisms use 20 different amino acids to make all proteins. The amino acids are held together by a covalent bond called a peptide bond. Proteins are sometimes called polypeptides. Because the amino acids that make up proteins have specific shapes, the resulting protein has a specific shape. It is the shapes that allow proteins to do all that they do for organisms.

12. There are 4 main types of polymers in organisms: 4. Nucleic acids: store the information to build proteins The monomers for nucleic acids are called nucleotides. There are two kinds of nucleic acids: DNA and RNA. These will be covered in more detail later this semester.

13. Enzymes are catalysts for reactions inside organisms. A catalyst increases the speed at which a reaction occurs. Enzymes basically work by holding two substances in the correct position so they can be linked together or broken apart. Enzymes are usually proteins; it is their specific shapes that allow them to hold the correct substances in the correct position.

14. We’re finished!!