Energy  The capacity to do work (put matter into motion)  Types of energy  Kinetic – energy in action  Potential – energy of position; stored (inactive) energy (eg. glycogen)

Forms of Energy  Chemical – stored in the bonds of chemical substances  Electrical – results from the movement of charged particles  Mechanical – directly involved in moving matter  Radiant or electromagnetic – energy traveling in waves (i.e., visible light, ultraviolet light, and X rays)

Major Elements of the Human Body  Oxygen (O)  Carbon (C)  Hydrogen (H)  Nitrogen (N)

Lesser and Trace Elements of the Human Body  Lesser elements make up 3.9% of the body and include:  Calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), magnesium (Mg), iodine (I), and iron (Fe)  Trace elements make up less than 0.01% of the body  They are required in minute amounts, and are found as part of enzymes

Figure 2.8 Comparison of Ionic, Polar Covalent, and Nonpolar Covalent Bonds

Ionic Bonds  Ions are charged atoms resulting from the gain or loss of electrons  Anions have gained one or more electrons  Cations have lost one or more electrons  Ionic bonds form between atoms by the transfer of one or more electrons  Ionic compounds form crystals instead of individual molecules  Example: NaCl (sodium chloride)

Formation of an Ionic Bond Figure 2.5a

Formation of an Ionic Bond Figure 2.5b

Covalent Bonds  Covalent bonds are formed by the sharing of two or more electrons  Electron sharing produces molecules

Single Covalent Bonds Figure 2.6a

Double Covalent Bonds Figure 2.6b

Triple Covalent Bonds Figure 2.6c

Polar and Nonpolar Molecules  Electrons shared equally between atoms produce nonpolar molecules  Unequal sharing of electrons produces polar molecules

Hydrogen Bonds  Too weak to bind atoms together  Common in dipoles such as water  Responsible for surface tension in water  Important as intramolecular bonds, giving the molecule a three-dimensional shape

Hydrogen Bonds Figure 2.9

Biochemistry  Organic compounds  Contain carbon, are covalently bonded, and are often large  Inorganic compounds  Do not contain carbon  Water, salts, and many acids and bases

Salts  Inorganic compounds  Contain cations other than H + and anions other than OH –  Are electrolytes; they conduct electrical currents

Organic Compounds  Molecules unique to living systems contain carbon and hence are organic compounds  They include:  Carbohydrates  Lipids  Proteins  Nucleic Acids

Carbohydrates Figure 2.13a  Contain carbon, hydrogen, and oxygen  Their major function is to supply a source of cellular food  Examples:  Monosaccharides or simple sugars

Carbohydrates Figure 2.13b  Disaccharides or double sugars

Carbohydrates Figure 2.13c  Polysaccharides or polymers of simple sugars

Representative Lipids Found in the Body  Neutral fats (triglycerides)– found in subcutaneous tissue and around organs  Phospholipids – chief component of cell membranes  Steroids – cholesterol, bile salts, vitamin D, sex hormones, and adrenal cortical hormones  Fat-soluble vitamins – vitamins A, E, and K  Eicosanoids – prostaglandins, leukotriens, and thromboxanes  Lipoproteins – transport fatty acids and cholesterol in the bloodstream

Neutral Fats (Triglycerides) Figure 2.14a  Composed of three fatty acids bonded to a glycerol molecule

Other Lipids Figure 2.14b  Phospholipids – modified triglycerides with two fatty acid groups and a phosphorus group

Other Lipids Figure 2.14c  Steroids – flat molecules with four interlocking hydrocarbon rings

Amino Acids  Building blocks of protein, containing an amino group and a carboxyl group  Amino acid structure

Amino Acids Figure 2.15d, e

Protein Figure 2.16  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds

Structural Levels of Proteins  Primary – amino acid sequence  Secondary – alpha helices or beta pleated sheets (H - H bonds)

Structural Levels of Proteins  Tertiary – superimposed folding of secondary structures (S-S bonds)  Quaternary – polypeptide chains linked together in a specific manner (covalent bonds)

Structural Levels of Proteins Figure 2.17d, e S -- S bonds covalent bonds

Fibrous and Globular Proteins  Fibrous proteins  Extended and strandlike proteins  Examples: keratin, elastin, collagen, and certain contractile fibers  Globular proteins  Compact, spherical proteins with tertiary and quaternary structures  Examples: antibodies, some hormones, and enzymes