Anatomy & Physiology

Anatomy & Physiology Study Guide Body fluid pH is vital for homeostasis: • The pH of a solution indicates the concentration of hydrogen ions it contains. Solutions are classified as neutral, acidic, or basic (alkaline) by the pH. Acids, bases, and salts are inorganic compounds with important physiological roles: • An acid releases hydrogen ions; a base removes hydrogen ions from a solution. Strong acids and strong bases ionize completely, whereas weak acids and weak bases do not. • A salt is an electrolyte whose cation is not hydrogen ( H + ) and whose anion is not hydroxide. • Buffers remove or replace hydrogen ions in solution. Buffers and buffer systems in body fluids maintain the pH within normal limits. Carbohydrates contain carbon, hydrogen, and oxygen in a 1:2:1 ratio: • Carbohydrates are most important as an energy source for metabolic processes. The three major types of carbohydrates are monosaccharides (simple sugars), disaccharides, and polysaccharides. Lipids contain a carbon-to-hydrogen ratio of 1:2: • Lipids include fats, oils, and waxes; most are water-insoluble molecules. The five common classes of lipids are fatty acids, eicosanoids, glycerides, steroids, and phospholipids and glycolipids. • Triglycerides (neutral fats) consist of three fatty acid molecules attached by dehydration synthesis to a molecule of glycerol Proteins are formed from amino acids and contain carbon, hydrogen, oxygen, and nitrogen: • Proteins are chains of amino acids. Each amino acid consists of an amino group, a carboxylic acid group, a hydrogen atom, and an R group (side chain) attached to a central carbon atom. A polypeptide is a linear sequence of amino acids held together by peptide bonds; proteins are polypeptides containing over 100 amino acids. • The four levels of protein structure are primary structure (amino acid sequence), secondary structure (amino acid interactions, such as hydrogen bonds), tertiary structure (complex folding, disulfide bonds, and interaction with water molecules), and quaternary structure (formation of protein complexes from individual subunits). • The reactants in an enzymatic reaction, called substrates, interact to yield a product by binding to the enzyme’s active site. Cofactors are ions or molecules that must bind to the enzyme before substrate binding can occur. • The shape of a protein determines its functional characteristics. DNA and RNA are nucleic acids: • Nucleic acids store and process information at the molecular level. The two kinds of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Achieve Page 59 of 368 ©2018