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 bondscovalent 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