Chapter 14 Review Quiz

Nitrogen Metabolism I: Synthesis

. In nature, every conceivable source of nourishment is used by some living thing. Vegetarian animals pick foods which contribute a balanced diet of the essential amino acids by selecting appropriate vegetable materials (a combination of grain and legumes, such as corn and beans in Mexico, or rice and lentils in India). Human hair actually contains all the essential amino acids. Assuming that they wanted to, why can't vegans consume their own hair to recycle the essential amino acids?

. Glutamate and α-ketoglutaric acid, as well as oxaloacetic acid and aspartic acid, are especially important in carbohydrate metabolism because:

. Acids taste sour, and bases taste bitter. In nature, we find a number of acidic substances in food which contribute to taste qualities. We also find among our foods and drugs some bitter-tasting natural substances which rarely are consumed. Which of the following fits that category?

. Tyrosine is a non-essential amino acid because we can synthesize it from:

. As recently as 1990, thirty percent of children living in some zip code areas of major cities had blood lead levels in excess of 10 μg/dL. Some neurologists equate one microgram of lead per deciliter with the loss of one IQ point. The major action of lead as an inhibitor of heme synthesis is to:

. Amino acids act both as acids and bases. Each carboxylic acid functional group has a pK below 7, and each amine group has a pK greater than 7. If you treated one mole of glutamic acid with one mole of sodium hydroxide, you would form this substance commonly used as a meat tenderizer:

. S-Adenosylmethionine is used in synthetic reactions to:

. Parkinson's disease appears to result in lower than normal levels of the neurotransmitter dopamine in the substantia nigra portion of the brain. Why couldn't this be treated by intravenous injection of dopamine?

. Hydrolysis of a nucleotide results in release of:

. Serotonin is an important neurotransmitter which fosters sleep, calmness, and non-aggression. Levels of serotonin can be increased slightly by consumption of foods containing:

. Although most plants and some bacteria can synthesize all the amino acids, we need not obtain all our essential amino acids from plants. Another source might be:

. Ten of the amino acids are considered to be essential; the others are not. What makes an amino acid essential?

. Porphyria is a blood disorder usually caused by overproduction of heme. Which amino acid joins with succinyl-CoA to form the starting material for synthesis of heme?

. The brain protects itself against toxic ammonia by converting the ammonia to:

. Nitrogen passes from form to form and from one organism to another, moving from the atmosphere into life forms and eventually passing back into the atmosphere or into minerals as plants and animals die, and then back again into living things. This movement of nitrogen through living and non-living stages is referred to as:

. Transamination of amino acids results in products called:

. A person is in nitrogen balance if the amount of nitrogen consumed in food as proteins or amino acids equals that excreted. We are said to be in positive nitrogen balance if we take in more than is excreted, and in negative balance if we excrete more than we consume. A person who had suffered kidney damage and was found to have high levels of protein in his or her urine would probably be in:

. Fertilizer contains nitrogen, potassium, and phosphorus in proportions necessary to promote plant growth. The phosphorus is usually in the form of phosphates, and the nitrogen is usually either in the form of nitrates or ammonium compounds. Why must nitrogen, phosphorus, and potassium be added yearly to soil?

. Some atmospheric nitrogen may be converted by lightning to soluble compounds usable to plants, but much is fixed by bacteria living in nodules on the roots of typical plants. Which of the following would harbor nitrogen-fixing bacteria?

. We need daily supplies of many vitamins, including folic acid. For what purpose or purposes do we need folic acid?

. One person in eighty carries a recessive gene for phenylketonuria, an inherited error of metabolism resulting from inability to convert phenylalanine to tyrosine. A mating of two carriers for phenylketonuria should result in 25% normal, non-carrier offspring, 50% carriers, and 25% homozygous phenylketonurics. If identified at birth, phenylketonurics can be placed on a special diet which helps prevent neurological damage. Following several years on the diet, the nervous system of the child usually develops well enough to tolerate a normal diet. Which of the following would be most likely components of the special diet?

. ã-Aminobutyric acid (GABA) is an anxiolytic neurotransmitter; if we have sufficient quantities in the brain, we aren't so uptight on the day of organic chemistry exams. The same protein molecule affected by binding GABA is believed to have a receptor site for benzodiazepines and another for ethanol, making a combination of benzodiazepine and alcohol deadly. GABA affects a membrane channel allowing passage of:

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