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THE CHEMICAL LEVEL OF ORGANIZATION

ATOMS AND MOLECULES

1. Matter is composed of combinations of atoms.

2. Atoms contain three fundamental particles, protons (positive charge), electrons (negative charge), and neutrons (no charge).

3. All of the atoms of a particular element contain the same number of protons. That number represents the atomic number of the element.

4. The number of protons plus the number of neutrons determines the atomic weight of the element.

5. Protons and neutrons form the nucleus of an atom.

6. Electrons occupy electron shells that surround the nucleus. Each electron shell or energy level has a limited capacity to store electrons.

Atomic interactions

The formation of compounds

1. Atoms may combine to form molecules or compounds.

2. Covalent bonds form when atoms are sharing electrons equally.

3. Polar bonds are characterized by unequal sharing of electrons.

4. Ionic bonds result from the attraction between cations and anions.

5. Hydrogen bonds are weak but important in forming crosslinks between molecules, or within a single molecule.

CHEMICAL NOTATION

1. Chemical notation provides a means of describing complex

reactions in a brief and precise manner.

2. Chemical notation should always produce a balanced equation.

CHEMICAL REACTIONS

1. Chemical reactions may be classified as synthesis,

decomposition, or exchange reactions.

2. At equilibrium, two opposing reactions or processes are in balance.

3. Many reversible reactions within the body are regulated by special proteins, called enzymes.

CHEMICAL ORGANIZATION IN THE HUMAN BODY

Inorganic Compounds

1. Chemicals within the body are classified as inorganic or organic. Inorganic compounds usually do not have carbon as the major structural element, and ionic bonds are common.

Water and Minerals

1. Water has unique physical properties, and accounts for most of our body weight.

2. Many compounds will undergo dissociation in water, forming electrolytes with positive or negative charges. Introduce the terms solution, solvent, solute, and ionization.

3. The pH value indicates the concentration of hydrogen ions in a solution. Buffers prevent changes in the pH of a solution.

4. Solutions may be classified as acidic, neutral, or basic (alkaline), on the basis of pH.

Organic Compounds

1. Organic compounds contain carbon, hydrogen, and usually oxygen as well. Covalent bonds are most common.

2. Define essential terms, including catabolism, anabolism, metabolism, nutrients, metabolites, hydrocarbons, hydrophobic, and

hydrophilic.

Carhohydrates

1. Carbohydrates are sugars and starches. They are important energy sources for metabolic operations.

2. A simple sugar, or monosaccharide, has from three to seven carbon atoms. Glucose is the most important monosaccharide.

3. Disaccharides and polysaccharides form by dehydration synthesis. They can be broken apart through hydrolysis.

4. Glycogen is the most important polysaccharide in our bodies; it is a storage form of glucose.

Lipids

1. Lipids are fats, oils, and waxes.

2. Fatty acids are important energy sources.

3. Fatty acids can be linked to a glycerol molecule by dehydration synthesis to form diglycerides and triglycerides. Triglycerides are an important storage form for lipids.

4. Prostaglandins and some steroids function as hormones.

5. Cholesterol is a precursor of steroid hormones, and is an important component of membranes.

6. Cholesterol, phospholipids, and glycolipids are the structural lipids of the body.

Proteins

1. Proteins are composed of amino acids linked by peptide bonds.

2. Structural proteins in the human body contain twenty different amino acids in significant quantities,but there are over 100,000 different proteins.

3. The structure of a protein depends upon the amino acid sequence, and interactions between the amino acids, the surroundingfluid; and other protein molecules.

4. Proteins are important as structural components, hormones, regulators of metabolic activity, and buffers.They also function in movement, transportation of dissolved materials, and defense against disease and physical stresses.

5. Enzymes are proteins that lower the activation energy requirements for chemical reactions.

6. The active site on an enzymes binds to substrates that interact to form products. A cofactor may be required before the reaction can occur.

7. Enzyme names usually end with "-ase." Hydrolases, such as carbohydrases,are important enzymes responsible for breaking down compounds.

8. The sensitivity of a particular enzyme to its environment makes it possible for enzymes to function in the preservation of homeostasis. An example is the regulation of glucose concentrations within a muscle cell.

9. Other special proteins include glycoproteins and proteoglycans.

10. Proteins and large molecules in solution create a colloid.

11. Amino acids and proteins in body fluids normally carry a negative electrical charge.

Nucleic Acids

1. Nucleic acids store and process genetic information concerning the structure of proteins. There are two types of nucleic acids, ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).

2. Nucleic acids are chains of nucleotides. Each nucleotide contains a phosphate group, a sugar, and a nitrogen base.

3. In RNA, the sugar is ribose, and the nitrogen base may be adenine, guanine, cytosine, or uracil.

4. A molecule of RNA is a single strand. The shape depends on the hydrogen bonding along the length of the strand.

5. In DNA, the sugar is deoxyribose, and the nitrogen bases are the same except for the substitution of thymine for uracil.

6. A molecule of DNA consists of a pair of strands, linked by hydrogen bonding between complementary base pairs. Reference:

Other Organic Compounds

1. High-energy compounds store the energy released during the catabolism of other compounds.

2. The energy is stored as a high-energy phosphate bond. Breaking the bond releases the energy.

3. ATP, adenosine triphosphate, is the most important high-energy compound.

4. Vitamins are essential nutrients; many of them act as coenzymes for enzymes.

5. There are fat-soluble and water-soluble vitamins with distinct requirements for absorption and methods of storage and excretion.

6. Porphyrins are important in transporting oxygen and assisting with energy transfer and capture.

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