Chapter 2

1. Chapter 2 Chemistry of Life

2. Section 1: Nature of Matter • The atom is the smallest unit of matter that cannot be broken down • Structure is • Positively charged protons and neutrally charged neutrons make up the core, or nucleus, of an atom. What is the charge on the nucleus? • Negatively charged electrons which occupy the area around the nucleus is called the electron cloud. What is the charge of the electron cloud?

3. Section 1: Nature of Matter Q: Why are protons and electrons attracted to each other? A: Because they have opposite charges Atoms typically have one electron for every proton, this equal number of positive and negative charges leave atoms with no electrical charge. An ___element_________ is a pure substance with only one kind of atom. Atoms of an element that contain a different number of neutrons are called _____isotopes_____________.

4. Section 1: Nature of Matter Look at my atomic model!! I said look at it!! The Bohr Model of the Atom

5. Section 1: Nature of Matter • What is a compound? • A compound is a substance made of joined atoms of two or more different elements. • What are the three types of bonds? • Hydrogen bonds • b) Covalent bonds • c) Ionic bonds

6. Section 1: Nature of Matter Hydrogen Bonding Electrons in water are shared between the hydrogen atoms and oxygen atoms. However, the electrons are more strongly attracted to the oxygen. Therefore, water has partially positive and partially negative ends, or poles. Water molecules are said to be polar molecules, molecules with an unequal distribution of charge. The partial positive pole of a hydrogen end of the water is attracted to a partial negative oxygen pole of another water molecule. This is how hydrogen bonding works.

7. Section 1: Nature of Matter Covalent bonding Ionic bonding Ionic bonding is when atoms or molecules lose or gain electrons. Ions are electrically charged because the number of protons and electrons is no longer equal. Here, sodium loses its outer level electron to chlorine. Covalent bonds form when two or more atoms share electrons to form a molecule. Here, electrons of hydrogen and carbon are being shared between atoms in this methane molecule.

8. Section 2: Water and Solutions • Properties of Water: • Makes up 70% of your body • 2/3 of your molecules are H2O molecules • H2O surrounds cells and helps move nutrients and other substances into and out of cells • Water absorbs heat more slowly than many other substances • Water retains heat/energy longer than many other substances • Many organisms release heat through water evaporation • Example: Humans sweat. Water vapor lost through evaporation of sweat carries heat away from the body. This enables cells to maintain a constant internal temperature when the external temperature changes drastically. In this way, water helps cells maintain homeostasis.

9. Section 2: Water and Solutions • Properties of Water (continued): • Hydrogen bonding in water results in cohesion, the attraction between substances of the same kind and adhesion, the attraction between different substances. • Cohesion results in surface tension. Molecules at the surface of water are linked together by hydrogen bonds like a crowd of people linked by holding hands. Surface tension prevents the surface of water from stretching or breaking easily. • Adhesion: Water is attracted to many other similarly polar substances due to its adhesive properties. Adhesion causes capillary action, the ability of water molecules to move through a narrow tube, such as the stem of a plant.

10. Section 2: Water and Solutions • Properties of Water (continued): • Many substances dissolve in water due to its polarity. • Ionic compounds and polar molecules dissolve best in water and form solutions. Solutions are mixtures in which one or more substances are distributed evenly in another substance. Look at how salt dissolves in water. As you can see, the ions are surrounded by water and distribute evenly in the water.

11. Section 2: Water and Solutions Properties of Water (continued): Nonpolar compounds and substances have evenly distributed charges. They do not dissolve well in polar substances such as water. When nonpolar substances such as oil, are placed in water, they do not mix. The water molecules are more attracted to other water molecules than to the oil. This is why oil beads together in water. The inability of nonpolar molecules to dissolve in polar molecules is very important to living organisms. For example, the shape and function of cell membranes depend on the interaction of polar water with nonpolar membrane molecules.

12. Section 2: Water and Solutions Properties of Water (continued): Although water has strong bonds, at any given time, some of the bonds will be broken such that ions will exist in water. This is how chemists show it: H2O H+ + OH- Acids are compounds that form hydrogen ions (H+) when dissolved in water. Bases are compounds that form hydroxide ions(OH-) when dissolved in water. The pH scale is based on the concentration of the hydrogen ions in a solution. All substances have a pH value between 0 and 14.

13. Section 3: Chemistry of Cells Carbon Compounds: There are 4 main classes of carbon compounds… 1) Carbohydrates (“Carbs”) 2) Lipids 3) Proteins 4) Nucleic Acids Your body is mostly composed of water and these four types of organic compounds. Organic compounds contain carbon bound to hydrogen, oxygen, or other carbons.

14. Section 3: Chemistry of Cells I. Carbohydrates: Contain carbon, hydrogen, and oxygen at a 1:2:1 ratio. 1) Key source of energy 2) Found in fruits, veggies, grains, and sweets 3) Monosaccharides are the building blocks of carbs. Examples: Glucose and fructose: C6H12O6 Glucose Fructose

15. Section 3: Chemistry of Cells I. Carbohydrates (continued): 4) Disaccharides form when two monosaccharides are joined together. Examples: Sucrose (table sugar) forms when glucose and fructose are joined together through dehydration.

16. Section 3: Chemistry of Cells I. Carbohydrates (continued): 5) Polysaccharides form when three or more monosaccharides are joined together in a chain. They are examples of macromolecules. Examples: Starch (energy storage for plants), glycogen (energy storage for animals), and cellulose (provides structure for plants) have repeating glucose molecules in their structure.

17. Section 3: Chemistry of Cells II. Lipids: Lipids are nonpolar molecules. This means that they generally do not mix with or dissolve in water. Different types of lipids include: a) fats (lipids that store energy) b) phospholipids (like in your cell membranes) c) steroids (such as cholesterol) d) waxes e) pigments (such as chlorophyll)

18. Section 3: Chemistry of Cells II. Lipids: Fat: A typical fat contains a glycerol molecule backbone with fatty acid tails. Most carbon atoms in a fatty acid are bonded to either one or two hydrogen atoms and one or two carbon atoms. The C-H bonds is where the energy in fats are stored. Fatty acids can be saturated or unsaturated as seen below and in your textbook (fig 9, p. 35) Saturated hydrocarbons are solids at room temperature. Unsaturated hydrocarbons are liquids at room temp.

19. Section 3: Chemistry of Cells III. Proteins: Proteins are usually large molecules composed of linked amino acids. Amino acids are the building blocks of proteins. There are 20 different amino acids, some are polar, some are not. Different amino acids have different charges on them. Proteins fold up into compact shapes partly depending on the amino acids within them. (See p. 36 Fig. 10) Examples of proteins in your body: Collagen Amylase Keratin Pepsin Hemoglobin Antibodies Fibrin Insulin

20. Section 3: Chemistry of Cells IV. Nucleic Acids Long chains of nucleotides can make up either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). An individual nucleotide has three parts: a phosphate group, a sugar (ribose or deoxyribose), and a nitrogen-containing base. nucleotide Nucleotide

21. Section 3: Chemistry of Cells V. ATP: Guess how many phosphate groups (-PO4) Adenosine triphosphate (ATP) has… That’s right…THREE. ATP is a single nucleotide (ribose sugar, adenine base, phosphate group) with two extra energy storing phosphate groups. Remember this when we get to Chapter 5.