2 Chemical Principles

Important Biological Molecules Organic compounds always contain carbon and hydrogen. Inorganic compounds typically lack carbon.

Inorganic Compounds: Water Polar molecule Figure 2.4a

Inorganic Compounds: Water Solvent Polar substances dissociate, forming solutes. Figure 2.5

Inorganic Compounds: Water H+ and OH participate in chemical reactions

Inorganic Compounds: Water Hydrogen bonding between water molecules makes water a temperature buffer. Figure 2.4b

Acids, Bases, and Salts An acid is a substance that dissociates into one or more H+. HCl  H+ + Cl Figure 2.6a

Acids, Bases, and Salts A base is a substance that dissociates into one or more OH. NaOH  Na+ + OH Figure 2.6b

Acids, Bases, and Salts A salt is a substance that dissociates into cations and anions, neither of which is H+ or OH. NaCl  Na+ + Cl Figure 2.6c

Acid-Base Balance The amount of H+ in a solution is expressed as pH. pH = log[H+] Increasing [H+], increases acidity. Increasing [OH] increases alkalinity. Most organisms grow best between pH 6.5 and 8.5.

Acid-Base Balance Figure 2.7

Organic Compounds The chain of carbon atoms in an organic molecule is the carbon skeleton. Functional groups are responsible for most of the chemical properties of a particular organic compound.

Table 2.3 (1 of 2)

Table 2.3 (2 of 2)

Organic Compounds Small organic molecules can combine into large macromolecules. Macromolecules are polymers consisting of many small repeating molecules. The smaller molecules are called monomers.

Organic Compounds Monomers join by dehydration synthesis or condensation reactions. Figure 2.8

Carbohydrates Are important for structure and as energy sources. Consist of C, H, and O with the formula (CH2O)n. Figure 2.8

Carbohydrates Monosaccharides are simple sugars with three to seven carbon atoms. Figure 2.8

Carbohydrates Disaccharides are formed when two monosaccharides are joined in a dehydration synthesis. Disaccharides can be broken down by hydrolysis. Figure 2.8

Carbohydrates Oligosaccharides consist of 2 to 20 monosaccharides. Polysaccharides consist of tens or hundreds of monosaccharides joined through dehydration synthesis. Starch, glycogen, dextran, and cellulose are polymers of glucose that are covalently bonded differently. Chitin is a polymer of two sugars repeating many times.

Lipids Are the primary components of cell membranes. Consist of C, H, and O. Are nonpolar and insoluble in water.

Simple Lipids Called fats or triglycerides; contain glycerol and fatty acids; formed by dehydration synthesis. Unsaturated fats have one or more double bonds in the fatty acids. Figure 2.9c

Complex Lipids Contain C, H, and O + P, N, or S. Membranes are made of phospholipids. Figure 2.10a

Steroids Consist of four carbon rings with an –OH group attached to one ring. Are part of membranes. Figure 2.11

Proteins Are essential in cell structure and function. Enzymes are proteins that speed chemical reactions. Transporter proteins move chemicals across membranes. Flagella are made of proteins. Some bacterial toxins are proteins.

Proteins Consist of subunits called amino acids. Table 2.4 (1 of 4)

Proteins Table 2.4 (2 of 4)

Proteins Table 2.4 (3 of 4)

Proteins Table 2.4 (4 of 4)

Amino Acids Exist in either of two stereoisomers, D or L. L-forms are most often found in nature. Figure 2.13

Peptide Bonds Peptide bonds between amino acids are formed by dehydration synthesis. Figure 2.14

Levels of Protein Structure The primary structure is a polypeptide chain. Figure 2.15a

Levels of Protein Structure The secondary structure occurs when the amino acid chain folds and coils in a regular helix or pleats. Figure 2.15b

Levels of Protein Structure The tertiary structure occurs when the helix folds irregularly, forming disulfide bonds, hydrogen bonds, and ionic bonds between amino acids in the chain. Figure 2.15c

Levels of Protein Structure The quaternary structure consists of two or more polypeptides. Figure 2.15d

Level of Protein Structure Conjugated proteins consist of amino acids and other organic molecules Glycoproteins Nucleoproteins Lipoproteins

Nucleic Acids Consist of nucleotides. Nucleotides consist of a Pentose Phosphate group Nitrogen-containing (purine or pyrimidine) base Figure 2.16 (1 of 2)

DNA Has deoxyribose Exists as a double helix A hydrogen bonds with T C hydrogen bonds with G Figure 2.16 (2 of 2)

RNA Has ribose Is single-stranded A hydrogen bonds with U C hydrogen bonds with G Figure 2.17

ATP Has ribose, adenine, and three phosphate groups. Figure 2.18

ATP Is made by dehydration synthesis. Is broken by hydrolysis to liberate useful energy for the cell.