Lesson 1, Topic 1
In Progress

04-Organic Chemistry

March 28, 2021

Carbohydrates contain carbon, hydrogen, and oxygen atoms and are best known as sugars. A monosaccharide is a basic unit of carbohydrate molecules. Glucose is a common monosaccharide. A disaccharide is made up of two monosaccharide units. Both sucrose and lactose are well known disaccharides. A polysaccharide is a complex carbohydrate made up of many monosaccharide units. Glycogen is a good example of a polysaccharide and is the storehouse of glucose in the body. In fact, the function of carbohydrates is to store energy for later use.

Lipids are fats and oils, which are needed for several important functions in the body. Triglycerides are formed by a glycerol unit joined to three fatty acids. The primary purpose of triglycerides is to store energy for later use. Phospholipids have a structure that is similar to that of triglycerides, but they also have phosphorus-containing units, each with a head and two tails. The head attracts water and the double tail does not, thus forming stable double layers or bilayers in water. Phospholipids form the membranes of cells. Cholesterol is a steroid lipid, consisting of multiple rings, which stabilizes the phospholipid tails in cellular membranes; cholesterol is also converted into steroid hormones by the body.

Proteins are very large molecules made up of amino acids held together in long, folded chains by peptide bonds. Structural proteins form the essential structures of the body. Examples include collagen, a fibrous protein that holds many tissues together, and keratin, which forms tough, waterproof fibers in the outer layer of the skin. Functional proteins, on the other hand, participate in chemical processes of the body. Examples include hormones, cell membrane channels and receptors, and enzymes. Enzymes are chemical catalysts, which help chemical reactions occur. Enzyme action is sometimes described by a “lock-and-key” model. Proteins can combine with other organic molecules to form “mixed” molecules such as glycoproteins or lipoproteins.

Nucleic acids are made up of nucleotides that include a phosphate unit, a sugar such as ribose or deoxyribose, and a nitrogen base, such as adenine, thymine or uracil, guanine, or cytosine. These base terms are commonly expressed with the abbreviations A, T, U, G, and C, respectively. Deoxyribonucleic acid, or DNA, is the cell’s “master code” for assembling proteins. DNA is a double helix consisting of a deoxyribose sugar backbone with A, T, C, and G as bases. Ribonucleic acid, or RNA, is the temporary “working copy” of a gene, which is a portion of the DNA code. RNA uses ribose as the sugar and A, U (not T), C, and G as bases. By directing the formation of structural and functional proteins, nucleic acids ultimately direct the overall body structure and function.

ATP (adenosine triphosphate) is a modified nucleotide used to transfer energy from nutrients to cellular processes, thus acting as a sort of energy-transfer “battery.“