|
|
|
AP BIOLOGY: Chapter Three Review Answers 
1. Organic macromolecules are formed through dehydration synthesis. Dehydration synthesis involves the splitting out of water molecules (hydrogen and oxygen), which serves to join individual saccharide, amino acid, fatty acid, or nucleotide units to form carbohydrates, proteins, fats, and nucleic acids, respectively. Hydrolysis is the reverse, inserting water molecules between units of macromolecules and converting them into their component parts. 2. Carbohydrates are composed of carbon, hydrogen, and oxygen in a ratio of 1:2:1. Their many carbon-hydrogen bonds are well suited for storing energy. 3. Glucose, fructose, and galactose are considered isomers because while they have the same empirical formula (C6H12O6), their structures are slightly different. Glucose and fructose are structural isomers, containing a double-bonded oxygen in different places. Glucose and galactose are stereoisomers because their structural formula is the same except for the orientation of a single hydroxyl group. 4. Starch is a polysaccharide composed of a chain of monosaccharide units oriented in the same direction. Cellulose is a polysaccharide chain with every other monosaccharide unit oriented in a facing direction (frontback-front-back). This alternating orientation of monosaccharide units makes cellulose a very difficult carbohydrate to break down. Starch is more readily digested. 5. Fats are composed of long chains of fatty acids (three chains in triglycerides) bound to a molecule of glycerol. 6. Fat molecules that have as much hydrogen as possible bound to their fatty acid chains (by virtue of the fact that they have no double bonds) are said to be saturated (e.g., with hydrogen). Unsaturated fats have one or more double or triple bonds in at least one of their fatty acid chains. Double bonds induce kinks into the fatty acid chain, making the fat more liquid at room temperature. 7. Amino acids are the general subunits that compose proteins. They have a central carbon with attached H, NH2, COOH, and R group. The R group typically determines the subsequent structuring of proteins and, hence, its chemical properties. Amino acids aggregate to form proteins through peptide bonds. 8. The primary structure of a protein is its amino acid sequence. The primary sequence then usually forms sheets or coils, forming the secondary structure. These sheets and coils subsequently fold back on themselves forming the tertiary structure of a protein. Several folded domains of a protein can interact with each other to form a quaternary structure. 9. Nucleotides are composed of a phosphate group, a sugar, and a nitrogenous base. Nitrogenous bases are covalently bound to the sugars, and the sugars and phosphates alternate to form a sugar-phosphate backbone, from which the nitrogenous bases project. The sugars and phosphates are joined by covalent phosphodiester bonds. 10. Purines are double-ring nitrogenous bases including adenine and guanine. Pyrimidines are single-ring nitrogenous bases including thymine and cytosine (and uracil, in RNA). Adenine always pairs with thymine (or uracil, in RNA), and cytosine always pairs with guanine. Base pairs are bound by hydrogen bonds and help maintain the integral structure of the DNA molecule. Being hydrogen bonds, though, they can also break easily when the DNA molecule opens during transcription or replication. 11. DNA is double-stranded, contains deoxyribose as a sugar and thymine as a base, and is located strictly in the nucleus. RNA is single stranded, contains ribose as a sugar and uracil as a base, and may be found in one of three forms inside or outside of the nucleus. DNA contains the genetic information for the cell. RNA functions in copying specific genes and directing protein synthesis. | ||||||||||||
The information contained on the chapter guide pages has been obtained from the publisher's website. They are merely reproduced here for easier access. Please contact Asim Ali if you have any questions or comments.
