Draw the Lewis structure of HS-.
> What is a cloning vector?
> l-Alanine can be converted to pyruvate. Can l-alanine also be converted to glucose? Explain your answer.
> a. What causes the genetic disease xeroderma pigmentosum? b. Why are people who suffer from xeroderma pigmentosum prone to cancer?
> If the sequence of a codon on the mRNA is 59-AUG-39, what will the sequence of the anticodon be? Remember that the hydrogen bonding rules require antiparallel strands. It is easiest to write the anticodon first 3−9 −−−→ 59 and then reverse it to the 5−9−
> What is the role of guanosine triphosphate in gluconeogenesis?
> Use the periodic table and determine the shorthand electron configuration of each of the following atoms. a. I b. Al c. V
> Of what value is the NADPH that is produced in the pentose phosphate pathway?
> A family started a batch of wine by adding yeast to grape juice and placing the mixture in a sealed bottle. Two weeks later, the bottle exploded. What metabolic reactions—and specifically, what product of those reactions—caused the bottle to explode?
> What enzymes catalyze the conversion of pyruvate to ethanol and carbon dioxide?
> Explain the value of alcohol fermentation in bread making.
> Write a balanced chemical equation for the conversion of pyruvate to lactate.
> What molecule serves as an allosteric inhibitor of hexokinase?
> What are the major products of glycolysis?
> What features do the reactions catalyzed by hexokinase and phosphofructokinase share in common?
> Draw the intermediate that would be formed in each of these reactions. (а) (b) CH,OH С-Н Н-С-ОН НО-С—Н НО-С—Н Н-С—ОН H--OH Н-С-ОН Н-С—ОН H-C-H H-Ć-H "0-P-O -O-P-O- (с) CH,OH (d) C=O C-H H-C-H Н-С—ОН H-C-H -0-P-0- -O-P-O-
> Why are red blood cells particularly susceptible to a deficiency of an enzyme in the glycolysis pathway?
> How does the presence of the insulin receptor on the surface of a cell identify that cell as a target cell?
> Match each of the following enzymes with the appropriate class of enzymes that it represents. (Hint: An enzyme classification may be used more than once or not at all.) a. Phosphoglucose isomerase b. Phosphofructokinase c. Triose phosphate isomerase d
> Write a chemical equation for the transfer of a phosphoryl group from ATP to fructose-6-phosphate.
> Where in the muscle cell does glycolysis occur?
> How many molecules of ATP are produced by substrate level phosphorylation during glycolysis?
> What are the end products of glycolysis?
> How are amino acids transported into the cell?
> How are fatty acids taken up into the cell?
> Write an equation showing the hydrolysis of sucrose.
> What is a hydrolysis reaction?
> What is meant by the term high-energy bond?
> All of the following Lewis structures are incorrect. Find the errors and write the correct structures. а. с. H :F: H-C=0=H :F-S - F H. :F: b. :0: Н-с—Н
> Describe the structure of ATP.
> Referring to the structures in Figures 20.1 and 20.3, draw the structures for nucleotides consisting of the following units. Figures 20.1: Figures 20.3: a. 29-Deoxyribose, thymine, one phosphoryl group b. Ribose, cytosine, three phosphoryl groups c.
> How does insulin affect the storage and degradation of glycogen?
> Describe the reaction catalyzed by the branching enzyme.
> What components of nucleic acids are heterocyclic amines?
> What do the three irreversible reactions of glycolysis have in common?
> Write a “word” equation showing the reaction catalyzed by glycogen synthase.
> What is the function of the ribosomal A-site in protein synthesis?
> What structural features of trypsin, chymotrypsin, and elastase account for their different specificities?
> Draw a DNA sequencing gel that would represent the sequence shown below. Be sure to label which lanes of the gel represent each of the four dideoxynucleotides in the chain termination reaction mixture. 59-GACTATCCTAG- 39
> What is meant by the term chromosome walking?
> How does a dideoxynucleotide cause chain termination in DNA replication?
> Where are the proteolytic enzymes pepsin and trypsin formed? Where do they carry out their function?
> What are the potential benefits of the information gained in the Human Genome Project?
> How is the polymerase chain reaction applied in forensic science?
> A wax found in the head of sperm whales is cetyl palmitate. What fatty acid and what alcohol are used to form this compound?
> Explain why UV lights are effective germicides on environmental surfaces.
> What is an allosteric enzyme?
> What are deletion and insertion mutations?
> Draw the structure of an alanine residue bound to the 39 position of adenine at the 39 end of alanyl tRNA. The amino acyl linkage is formed between the 39—OH of the tRNA and the carboxylate group of the amino acid methionine. АТР
> What peptide sequence would be formed from the mRNA. 59-AUGUGUAGUGACCAACCGAUUUCACUGUGA-39?
> Why must pyruvate be used and NADH be reoxidized so that glycolysis can continue?
> Why does an enzyme lose activity when the pH is drastically changed from optimum pH?
> What are the two tRNA binding sites on the ribosome?
> Which amino acids are encoded by six codons?
> Why is the genetic code said to be mutation-resistant?
> What is meant by a triplet code?
> What is the function of the cap structure on eukaryotic mRNA?
> What is the purpose of the poly(A) tail on eukaryotic mRNA?
> What are snRNPs? How do they facilitate RNA splicing?
> What is the function of each of the classes of RNA molecules?
> The following is the unspliced transcript of a eukaryotic gene: What would the structure of the final mature mRNA look like, and which of the above sequences would be found in the mature mRNA? exon 1 intron A exon 2 intron B exon 3 intron C exon 4
> Distinguish among the four plasma lipoproteins in terms of their composition and their function.
> If an RNA strand has the nucleotide sequence 59-AUGCCAUAACGAUACCCAGUC-39 what was the sequence of the DNA strand that was transcribed?
> On what molecule is the codon found?
> What is the binding site of an enzyme active site?
> Define the term active site.
> What does a graph of enzyme activity versus substrate concentration tell us about the nature of enzymecatalyzed reactions?
> What is occurring at the replication fork?
> If the sequence of a double-stranded DNA molecule is what would the sequence of the two daughter DNA molecules be after DNA replication? Indicate which strands are newly synthesized and which are parental. 5'-CATAAGTCGAGACCGTTACTCACTACTGGAC-3' 3'-G
> If an enzyme does not alter the equilibrium constant of a reaction, how does it speed up the reaction?
> Define the term product.
> Write the structure that results when adenosine-59- monophosphate is linked by a −3−−9− → 59 phosphodiester bond to uridine-59-monophosphate.
> Using the periodic table, write the electron configuration and orbital diagram of each of the following atoms: a. V b. Cd c. Te
> Draw the guanine-cytosine base pair and indicate the hydrogen bonds that link them.
> What is the most common characteristic used to classify enzymes?
> List three differences between DNA and RNA.
> One of the energy-harvesting steps of the citric acid cycle results in the production of GTP. What is the structure of the GTP nucleotide?
> a. Draw the ring structure of the pyrimidines. b. In a nucleotide, which nitrogen atom of pyrimidine rings is bonded to the sugar?
> Heating is an effective mechanism for killing bacteria on surgical instruments. How does elevated temperature result in cellular death?
> What is the relationship between pepsin and pepsinogen?
> Repeat Question 19.95 for the peptide trp-pro-gly-tyr. Question 19.95: Draw the complete structural formula for the peptide tyrlys- ala-phe. Show which bond would be broken when this peptide is reacted with chymotrypsin.
> What properties are shared by chymotrypsin, trypsin, and elastase?
> The addition of phenylthiourea to a preparation of the enzyme polyphenoloxidase completely inhibits the activity of the enzyme. a. Knowing that phenylthiourea binds all copper ions, what conclusion can you draw about whether polyphenoloxidase requires a
> As you increase the temperature of an enzyme-catalyzed reaction, the rate of the reaction initially increases. It then reaches a maximum rate and finally dramatically declines. Keeping in mind that enzymes are proteins, how do you explain these changes i
> Why are irreversible enzyme inhibitors often called poisons?
> Fibrinogen and prothrombin are both involved in formation of blood clots when they are converted into proteolytic enzymes. However, they are normally found in the blood in an inactive form. Develop an explanation for this observation.
> Three proenzymes that are involved in digestion of proteins in the stomach and intestines are pepsinogen, chymotrypsinogen, and trypsinogen. What is the advantage of producing these enzymes as inactive peptides?
> What is the transition state in an enzyme-catalyzed reaction?
> How do sickled red blood cells hinder circulation?
> Why do extremes of pH inactivate enzymes?
> Describe the structure of myoglobin.
> An increase in temperature will increase the rate of a reaction if a nonenzymatic catalyst is used; however, an increase in temperature will eventually decrease the rate of a reaction when an enzyme catalyst is used. Explain the apparent contradiction of
> Define the optimum pH for enzyme activity.
> Explain why a-keratins that have many disulfide bonds between adjacent polypeptide chains are much less elastic and much harder than those without disulfide bonds.
> Draw the Lewis structure of NO2-.
> How does a coenzyme function in an enzyme-catalyzed reaction?
> If an enzyme catalyzed a reaction by modifying the local pH, what kind of amino acid R groups would you expect to find in the active site?
> What is the relationship between an enzyme active site and its substrate?
> Describe the transition state.
> Provide an example of an enzyme with stereochemical specificity and explain the advantage of stereochemical specificity for that particular enzyme.
> Provide an example of an enzyme with linkage specificity and explain the advantage of linkage specificity for that particular enzyme.
