Answer Key.docx

1. CHEMICAL COMPONENTS Carbohydrates In living organisms, carbohydrates are almost universally used as an immediate energy source. However, for many organisms, such as plants and fungi, they also have structural functions. Carbohydrates may exist either as saccharide (sugar) monomers or as polymers of saccharides. Typically, the sugar glucose is a common monomer of carbohydrate polymers. The term carbohydrate may refer to a single sugar molecule (monosaccharide), two bonded sugar molecules (disaccharide), or many sugar molecules bonded together (polysaccharide). Lipids Although molecules classified as lipids are quite varied, they have one characteristic in common: They are all hydrophobic and insoluble in water. You may have noticed that oil and water do not mix. For example, salad dressings are rich in vegetable oils. Even after shaking, the vegetable oil will separate out from the water. This is due to the fact that lipids possess long, nonpolar hydrocarbon chains and a relative lack of hydrophilic functional groups. Lipids are very diverse, and they have varied structures and functions. Fats (such as bacon fat, lard, and butter) and oils (such as corn oil, olive oil, and coconut oil) are some well-known lipids. You may wonder about the differences between these terms. In general, fats are solid at room temperature, while oils are liquid at room temperature. In animals, fats are used for both insulation and long-term energy storage. They are used to insulate marine mammals from cold arctic waters and to protect our internal organs from damage. Instead of fats, plants use oils for long-term energy storage. In animals, the secretions of oil glands help waterproof skin, hair, and feathers. Proteins Proteins are of primary importance in the structure and function of cells. Here are some of their many functions: Support Some proteins are structural proteins. Examples include the protein in spiderwebs; keratin, the protein that contributes to hair and fingernails; and collagen, the protein that lends support to skin, ligaments, and tendons (Fig. 3.16a). Metabolism Many proteins are enzymes. They bring reactants together and thereby act as catalysts, speeding up chemical reactions in cells. Enzymes are specific for particular types of reactions and can function at body temperature. Transport Channel and carrier proteins in the plasma membrane allow substances to enter and exit cells. Other proteins transport molecules in the blood of animals—for example, hemoglobin, found in red blood cells, is a complex protein that transports oxygen (Fig. 3.16b). Defense Some proteins, called antibodies, combine with disease-causing agents to prevent those agents from destroying cells and causing diseases and disorders. Regulation Hormones are regulatory proteins. They serve as intercellular messengers that influence the metabolism of cells. For example, the hormone insulin regulates the concentration of glucose in the blood, while human growth hormone (hGH) contributes to determining the height of an individual.

Motion The contractile proteins actin and myosin allow parts of cells to move and cause muscles to contract (Fig. 3.16c). Muscle contraction enables animals to move from place to place and substances to move through the body. It also regulates body temperature. Nucleic Acids DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the nucleic acids found in cells. Early investigators called them nucleic acids because they were first detected in the nucleus. DNA acts as the location within the cell where the genetic information is stored. Each DNA molecule contains many genes, which specify the sequence of the amino acids in proteins. RNA is the molecule that aids in transcribing and translating DNA into proteins. 2. DIFFERENCES BETWEEN PRO AND EU

3. DIFFERENCES BETWEEN ANIMAL AND PLANT CELLS

4. FUNCTION

5. MECHANISM ON CELL