Carbohydrates Carbohydrates have empirical formula CH2O. Carbohydrate means hydrate of carbon. Most abundant carbohydrate is glucose, C6H12O6. Carbohydrates are polyhydroxy (multiple –OH) aldehydes and ketones (C=O).

Disaccharides Glucose and fructose are monosaccharides. Monosaccharides: simple sugars that cannot be broken down by hydrolysis with aqueous acids. Disaccharides are sugars formed by the condensation of two monosaccharides. Examples: sucrose (table sugar) and lactose (milk sugar). Sucrose is formed by the condensation of -glucose and fructose. Glycoside linkage – “ether” bond formed when monosaccharides combine to form disaccharides or polysaccharides (C-O-C).

Lactose is formed from galactose and -glucose. Disaccharides can be converted into monosaccharides by treatment with acid in aqueous solution.

Polysaccharides Polysaccharides are formed by condensation of several monosaccharide units. There are several different types. Example: starches can be derived from corn, potatoes, wheat or rice.

Starch performs storage of glucose in plants and animals. Enzymes catalyze the conversion of starch to glucose. Starch is poly -glucose whereas cellulose is poly -glucose. Enzymes that hydrolyze starch do not hydrolyze cellulose because of the different shapes of the polymers. Ingested cellulose is recovered unmetabolized. This is referred to as dietary fiber. Metabolism: the term used to refer to all chemical processes that occur in the body.

Polysaccharides Cellulases are enzymes that enable animals to use cellulose for food and break down cellulose by hydrolysis. These enzymes are absent in most animals, including mammals.

Major Functions of Carbohydrates Energy sources Energy reserves (glycogen) Structure (cellulose) Dietary Fiber – mainly plant material that is not digested or hydrolyzed by enzymes in the human digestive tract. Importance – may help prevent diverticulitis, IBS, constipation, obesity, Crohn’s disease, hemorrhoids, and diabetes mellitus.

Respiration The process by which glucose is converted to energy. Aerobic – C6H12O6 + 6 O2  6 CO2 + 6 H2O Anaerobic – C6H12O6  2 CO2 + 2 C2H5OH (fermentation)

Nucleic Acids Nucleic acids carry genetic information. DNA (deoxyribonucleic acids) have molecular weights around 6 - 16  106 amu and are found inside the nucleus of the cell. RNA (ribonucleic acids) have molecular weights around 20,000 to 40,000 amu and are found in the cytoplasm outside the nucleus of the cell. Nucleic acids are made up of nucleotides.

Nucleic Acids There are three important parts to a nucleotide: phosphoric acid unit, five carbon sugar (e.g. deoxyribose), and Nitrogen-containing organic base (e.g. adenine). DNA and RNA have different sugars (deoxyribose vs. ribose). The difference is on carbon 2.

There are only five bases found in DNA and RNA: adenine (A), guanine (G), cytosine (C), thymine (T, found in DNA only), and uracil (U found in RNA only). Nucleic acids are formed by condensing two nucleotides (the phosphoric acid condenses with the O-H group of the sugar).

DNA consists of two deoxyribonucleic acid strands wound together in a double helix. The phosphate chains are wrapped around the outside of the DNA molecule. Complementary base pairs are formed from bases which optimize H-bonding: T and A or C and G. The complementary base pairs are held together by hydrogen bonding. During cell division, the DNA double helix unwinds.

A new strand is formed when bases attach to each strand of the unwinding double helix. Because of the optimized hydrogen bonding, there is only one location for each base. Therefore, the order of bases in the new strand is the same as the order of bases in the original strand. This is how genetic information is preserved during cell division.

Codons (triplets) – sequences of three nucleotides that code for amino acids in protein synthesis (also codons for start/stop) DNA structure provides us with the understanding of how protein synthesis occurs, how viruses infect cells, and how other biological problems occur.

DNA Profiling (Forensic Applications) Restriction Enzymes cut DNA into segments (look for specific sequence of bases common to all people) Produces different length segments for different people Gel electrophoresis – separates DNA fragments based on length. Fluorescent dye is used to show bands. Uses include paternity testing, criminal investigation, identifying dead.