2-2 Properties of Water

Key Concepts: Why are water molecules polar?

What are acidic solutions?

What are basic solutions?

I. The Water Molecule

  1. A water molecule is polar because there is uneven sharing of electrons between the oxygen and hydrogen atoms.
  2. Hydrogen bonds form when water molecules are attracted to one another.
  3. Cohesion – attraction between molecules of the same substance.
  4. Adhesion – attraction between molecules of different substances.

II. Solutions and Suspensions

  1. Mixture – material composed of 2 or more elements or compounds that are physically mixed together but not chemically combined.
  2. Solutions – mixture of 2 or more substances in which the molecules of the substance are evenly distributed.
  3. solute – the substance that is dissolved.
  4. solvent – the substance in which the solute dissolved.
  5. Suspension – mixture of water and nondissolved materials.

III. Acids, Bases, and pH

  1. pH scale – measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0 to 14
  2. Acid – any compound that forms H+ ions in solution
  3. Acid solutions contain higher concentrations of H+ ions than pure water and have pH values below 7.
  4. Base – a compound that produces hydroxide (OH-) ions in solution
  5. Basic, or alkaline, solutions contain lower concentrations of H+ ions that pure water and have pH values above 7.
  6. Buffers – weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH.
  7. Controlling pH is important in maintaining homeostasis in the human body.

2-3Carbon Compounds

Key Concepts: What are the functions of each group of organic compounds?

I. The Chemistry of Carbon

  1. Carbon has 4 valence electrons and can form 4 covalent bonds with other atoms.
  2. Carbon atoms can bond with other carbon atoms, forming chains or rings with single, double, or triple bonds.

II. Macromolecules

  1. Macromolecules are giant molecules formed by joining small molecules together to make large compounds.
  2. Monomers – small units that can join together with other small units to form polymers
  3. Polymers – large compounds formed from combinations of many monomers
  4. Four groups of organic compounds found in living things are carbohydrates, lipids, nucleic acids, and proteins.

III. Carbohydrates

  1. Carbohydrate – compound made up of carbon, hydrogen, and oxygen atoms, usually in a 1:2:1 ratio
  2. Living things use carbohydrates as their main source of energy. Plants and some animals also use carbohydrates for structural purposes.
  3. Sugars and starches are examples of carbohydrates.
  4. Monosaccharide – single sugar molecule
  5. Monosaccharides are the monomers of carbohydrates.
  6. Polysaccharide – large macromolecule formed from monosaccharides
  7. Animals store excess sugar as glycogen.
  8. Plants store excess sugar as plant starch.
  9. Plants also make cellulose, a fiber that gives plants their strength and rigidity. Cellulose is the most abundant organic compound found on the Earth.

IV. Lipids

  1. Lipid – macromolecule made mainly from carbon, hydrogen, and oxygen atoms not in a 1:2:1 ratio
  2. Lipids include fats, oils, waxes, and steroids.
  3. Lipids can be used to store energy. Some lipids are important parts of biological membranes (ex. cholesterol) and waterproof coverings.
  4. Fatty acids are the monomers of all lipids. Many lipids are formed when a glycerol molecule combines with 3 fatty acids.
  5. In saturated fatty acids, the carbon atoms are joined by single bonds giving the compound the highest possible number of hydrogen atoms.
  6. If there is at least one double or triple bond in the lipid, it is unsaturated because it does not contain the most possible hydrogen atoms.
  7. Lipids whose fatty acids contain more than one double or triple bond are said to be polyunsaturated.

V. Nucleic Acids

  1. Nucleic acids – macromolecules containing carbon, hydrogen, oxygen, nitrogen, and phosphorus
  2. Nucleic acids are polymers assembled from individual monomers called nucleotides. An important nucleotide is ATP, the direct source of energy used by cells.
  3. Nucleotides consist of 3 parts:
  4. a 5-carbon sugar
  5. a phosphate group, and
  6. a nitrogenous base
  7. Nucleic acids store (ex. DNA) and transmit (ex. RNA) hereditary, or genetic information.
  1. Two types of nucleic acids:
  2. RNA – ribonucleic acid (contains the sugar ribose) and
  3. DNA – deoxyribonucleic acid (contains the sugar deoxyribose)

VI. Proteins

  1. Proteins – macromolecules that contain carbon, hydrogen, oxygen, and nitrogen
  2. Proteins are polymers of molecules called amino acids.
  3. Amino acids are composed of 3 parts: an amino group (-NH2) on one end, a carboxyl group (-COOH) on the other end, and a side chain called an R-group.
  4. There are over 20 different R-groups so there are over 20 different amino acids.
  5. The order of the amino acids deterimes the basic structure of all proteins, ths proteis are the most diversitifed of all macromolelcules, as well as the most abundant compounds ofund in living things.
  6. Some proteins control the rate of reactions (ex. enzymes) and regulate cell processes (ex. hormones). Some are used to form bones and muscles (ex. actin & myosin.) Others transport substances into or out of cells or throughout the body (ex. hemoglobin), or help to fight disease (ex. antibodies).
  7. Proteins can have up to 4 levels of organization, which determine the shape of the protein, therefore they are quiet large and complex.

2-4Chemical Reactions and Enzymes

Key Concepts: What happens to chemical bonds during chemical reactions?

How do energy changes affect whether a chemical reaction will

occur?

Why are enzymes important to living things?

I. Chemical Reactions

  1. Chemical reaction – process that changes one set of chemicals into another set of chemicals
  2. Reactants – elements or compounds that enter into a chemical reaction
  3. Products – the elements or compounds produced by a chemical reaction
  4. Chemical reactions always involve the breaking of bonds in reactants and the formation of new bonds in products.

II. Energy in Reactions

  1. Energy is released or absorbed when chemical bonds are broken or formed.
  2. Chemical reactions that release energy often occur spontaneously. Chemical reactions that absorb energy will not occur without a source of energy.
  3. Activation energy – energy needed to get a reaction started.

III. Enzymes

  1. Catalyst – a substance that speeds up the rate of a chemical reaction
  2. Enzyme - protein that acts as a biological catalyst
  3. Cells use enzymes to speed up chemical reactions that take place in cells.
  4. Enzymes act by lowering the activation energy.

IV. Enzyme Action

  1. Enzymes provide a site where reactants can be brought together to react.
  2. Substrate – reactant of an enzyme-catalyzed reaction
  3. Substrates bind to a site on an enzyme called the active site, fitting together like a lock and key.
  4. Once the enzyme-substrate complex is formed, the enzyme helps convert substrate into product.
  5. Enzymes in the human body work best at body temperature, 37°C.
  6. Enzymes play essential roles in regulating chemical pathways, making materials that cells need, releasing energy, and transferring information.