Medicinal Chemistry Chapter 06 Key

Type: matching Title: Chapter 06 - Question 01 01) Match the following structures to their names. Feedback: The structures shown are nucleic acid bases. a.# = Adenine b.# = Guanine c.# = Cytosine d.# = Thymine END OF QUESTION Type: matching Title: Chapter 06 - Question 02 02) Name the following structures (i) – (iv) i) ii) NH2 N N HO O HO O H H H H H H OH H H N N HO O NH2 CH3 HN N N iv) O N HN N N iii) O O HO O H H H H OH H N O H H H OH H H H OH H Feedback: The 'deoxy' portion of the name refers to the lack of a hydroxyl group at position 2 of the ribose ring. a.# Deoxyadenosine = (i) b.# Deoxyguanosine = (ii) c.# Deoxythymidine = (iii) d.# Deoxycytidine = (iv) END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 03 03) Consider the following representation of DNA. What is the blue region called? Feedback: The backbone consists of alternating deoxyribose sugars and phosphate groups. Therefore, it is the sugar phosphate backbone. incorrect a.# The carbohydrate backbone. incorrect b.# The phosphate backbone. Correct c.# The sugar-phosphate backbone. incorrect d.# The nucleic acid base backbone. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 04 04) Consider the following representation of DNA. What are the groups shown in black? Feedback: The nucleic acid bases are linked to the sugar-phosphate backbone. Deoxyribose is the sugar in DNA. A nucleoside is a nucleic acid base linked to a sugar moiety. A nucleotide is a nucleoside linked to one or more phosphate groups. Correct a.# Nucleic acid bases. incorrect b.# Deoxyribose. incorrect c.# Nucleosides. incorrect d.# Nucleotides. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 05 05) Consider the following representation of DNA. What is the term used to describe the end of the chain marked J? Feedback: The numbering relates to the numbering of the deoxyribose sugar moiety. The sugar-phosphate chain is extended from the 5’ and 3’ positions of each sugar moiety. The 5’ end of the chain is closest to the 5’ position of the final sugar moiety. The 3’ end is closest to the 3’ end of the final sugar moiety. The sugar phosphate backbone does not have a 2’ end or a 4’ end, since the chain is not extended from those positions of the sugar ring. incorrect a.# The 2’ end. incorrect b.# The 3’ end. incorrect c.# The 4’ end. Correct d.# The 5’ end. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 06 06) Consider the following representation of DNA. What type of DNA structure is shown here? Feedback: The primary structure is the sequence in which the nucleotides are linked together in a DNA strand. The secondary structure refers to the double helix arrangement of two complementary DNA strands. The tertiary structure refers to the supercoiling of the DNA double helix into a more compact shape. There is no quaternary structure for DNA. Correct a.# Primary. incorrect b.# Secondary. incorrect c.# Tertiary. incorrect d.# Quaternary. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 07 07) What type of structure is the double helix of DNA? Feedback: The primary structure is the sequence in which the nucleotides are linked together in a DNA strand. The secondary structure refers to the double helix arrangement of two complementary DNA strands. The tertiary structure refers to the supercoiling of the DNA double helix into a more compact shape. There is no quaternary structure for DNA. incorrect a.# Primary. Correct b.# Secondary. incorrect c.# Tertiary. incorrect d.# Quaternary. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 08 08) What does the following diagram demonstrate? Feedback: The diagram shows base pairing between the nucleic acid bases adenine and thymine as well as between the nucleic acid bases guanine and cytosine. The interaction is through hydrogen bonding. incorrect a.# Dimerisation. incorrect b.# Receptor binding. Correct c.# Base pairing. incorrect d.# Polymerisation. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 09 09) Which of the following statements is not true about DNA secondary structure? Feedback: The phosphate groups are ionised and are positioned to the outside of the structure such that they interact favourably with surrounding water molecules. The base pairs are hydrophobic and are stacked on top of each other in the centre of the structure such that they interact with each other and not with water. incorrect a.# There is a minor groove and a major groove. incorrect b.# A purine base pairs up with a pyrimidine base. Correct c.# incorrect d.# The phosphate groups are positioned to the inside of the structure. The base pairs are stacked. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 10 10) What non-covalent bonding interactions do the nucleic acid bases form in DNA secondary structure? Feedback: Hydrogen bonds are involved in forming the base pairs. The base pairs are stacked and van der Waals interactions take place between the various stacks of base pairs. There are no ionic interactions involving nucleic acid bases. The phosphate groups on the outside of the double helix can form ionic interactions. incorrect a.# Ionic bonds only. incorrect b.# Hydrogen bonds only. incorrect c.# Van der Waals interactions only. Correct d.# Hydrogen bonds and van der Waals interactions. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 11 11) What is the significance of base pairing to the function of DNA? Feedback: Base pairing results in two complementary chains. Each chain can be used as a template for a new chain, allowing genetic information to be passed on from generation to generation. There is an element of truth in the other statements but they serve no purpose in the function of DNA. incorrect a.# It neutralises basic groups and controls the cell pH. Correct b.# incorrect c.# incorrect d.# It means that the chains of DNA are complementary allowing replication. It stabilises the molecule such that its lifetime in the cell is increased. It prevents water interacting with the nucleic acid bases. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 12 12) Which of the following is not true when RNA is compared with DNA? Feedback: RNA contains uracil, but it is in place of thymine and not adenine. Uracil can base pair with adenine in certain regions of RNA secondary structure. incorrect a.# RNA contains ribose and not deoxyribose. Correct b.# RNA contains uracil and not adenine. incorrect c.# RNA does not form a double helix. incorrect d.# RNA is smaller than DNA. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 13 13) Which of the following mutations is most likely to be disruptive to protein synthesis or function? Feedback: UAU to UAC results in tyrosine being coded in each case. There is no disruption to protein synthesis or function. UAU to UUU results in a change from tyrosine to phenylalanine. This is a similar amino acid to tyrosine and so the chances of disruption are slight unless the tyrosine phenolic group is particularly important to function. UAU to UAA results in a stop code which prevents further synthesis of the protein. This will be the most drastic effect and will lead to a non-functioning protein. UAU to CAU results in a change from tyrosine to histidine. Only one amino acid is altered and the protein may still be functional if the tyrosine is not crucial to activity. incorrect a.# UAU to UAC. incorrect b.# UAU to UUU. Correct c.# UAU to UAA. incorrect d.# UAU to CAU. END OF QUESTION Type: matching Title: Chapter 06 - Question 14 14) Match the structure to the process described. Feedback: Different processes take place at different organelles in the body. Gene transcription takes place in the nucleus and the newly transcribed mRNA is modified by the spliceosome. The mRNA then departs the nucleus and moves to the endoplasmic reticulum where protein synthesis will take place. The actual synthetic process requires ribosomes, which are made up of protein and ribosomal RNA. The ribosomes bind the components required for protein synthesis and also catalyse the reaction. a.# The organelle in the cell’s = Endoplasmic reticulum cytoplasm where protein synthesis occurs. b.# The structure where transcription = Nucleus occurs. c.# The structure which catalyses = Ribosome protein synthesis and which is sometimes called the protein factory. d.# The structure which is = Spliceosome responsible for modifying newly transcribed mRNA prior to translation. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 15 15) What is the term for the portion of messenger RNA that is excised when the molecule undergoes a splicing modification? Feedback: The intron is the excised region. The exons are the regions that are spliced together. Exclusion and inclusion are terms that are not used in descriptions of the splicing mechanism. Correct a.# Intron. incorrect b.# Exon. incorrect c.# Exclusion. incorrect d.# Inclusion. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question16 16) Which of the following molecules is not a nucleotide? Feedback: Adenosine is a nucleoside. All the others have phosphate groups linked to the nucleoside and are nucleotides. Correct a.# Adenosine. incorrect b.# Adenosine monophosphate. incorrect c.# Adenosine diphosphate. incorrect d.# Adenosine triphosphate. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 17 17) Which of the following structures is uracil? Feedback: Structure A is uracil. Structure D is thymine, but structures B and C are not present in DNA. Correct a.# Structure A. incorrect b.# Structure B. incorrect c.# Structure C. incorrect d.# Structure D. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 18 18) Which of the following structures is a purine structure? Feedback: Structure B is guanine which is a purine structure. Structure A is a pteridine. Structure C is a pyrrolopyrimidine. Structure D is an imidazopyridine. incorrect a.# Structure A. Correct b.# Structure B. incorrect c.# Structure C. incorrect d.# Structure D. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 19 19) Which of the following structures is a pyrimidine structure? Feedback: Structure D is cytosine which is a pyrimidine structure. Structures A and B are pyridinones. Structure C is a triazinone. incorrect a.# Structure A. incorrect b.# Structure B. incorrect c.# Structure C. Correct d.# Structure D. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 20 20) Which of the following structures is adenosine? Feedback: Structure A is adenosine. Structure B is deoxyadenosine. Structure C is deoxyadenosine monophosphate. Structure D is adenosine monophosphate (AMP). Correct a.# Structure A. incorrect b.# Structure B. incorrect c.# Structure C. incorrect d.# Structure D. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 21 21) Which of the following structures is a nucleotide building block for DNA? Feedback: Structure C is deoxyadenosine monophosphate and is a nucleotide building block for DNA. Structure D (adenosine monophosphate) is also a nucleotide, but it is a building block for RNA. Structures A and B (adenosine and deoxyadenosine respectively) are nucleosides. incorrect a.# Structure A. incorrect b.# Structure B. Correct c.# Structure C. incorrect d.# Structure D. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 22 22) Which of the following structures is guanosine? Feedback: Structure A is guanosine. Structure B is deoxyguanosine. Structure C is deoxyguanosine monophosphate. Structure D is guanosine monophosphate (GMP). Correct a.# Structure A. incorrect b.# Structure B. incorrect c.# Structure C. incorrect d.# Structure D. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 23 23) Which of the following structures is a nucleotide building block for DNA? Feedback: Structure C is deoxyguanosine monophosphate and is a nucleotide building block for DNA. Structure D (guanosine monophosphate) is also a nucleotide but it is a building block for RNA. Structures A and B (guanosine and deoxyguanosine respectively) are nucleosides. incorrect a.# Structure A. incorrect b.# Structure B. Correct c.# Structure C. incorrect d.# Structure D. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 24 24) To which of the following does adenine form hydrogen bonds in DNA? Feedback: Thymine base pairs with adenine. Guanine base pairs with cytosine. incorrect a.# Adenine. Correct b.# Thymine. incorrect c.# Cytosine. incorrect d.# Guanine. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 25 25) To which of the following does cytosine form hydrogen bonds in DNA? Feedback: Thymine base pairs with adenine. Guanine base pairs with cytosine. incorrect a.# Adenine. incorrect b.# Thymine. incorrect c.# Cytosine. Correct d.# Guanine. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 26 26) Which of the following statements is not true about DNA secondary structure? Feedback: A purine base always pairs up with a pyrimidine base. incorrect a.# There is a minor groove and a major groove. Correct b.# Purine bases pair up with each other. incorrect c.# incorrect d.# The phosphate groups are positioned to the outside of the structure. The base pairs are stacked. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 27 27) Which of the following is not true when RNA is compared with DNA? Feedback: RNA molecules are smaller than DNA. incorrect a.# RNA contains ribose and not deoxyribose. incorrect b.# RNA contains uracil and not thymine. incorrect c.# RNA does not form a double helix. Correct d.# RNA is larger than DNA. END OF QUESTION Type: matching Title: Chapter 06 – Question 28 28) Match the processes to their descriptions. Feedback: Transcription is the process by which the genetic code for a single protein is ‘copied’ in the form of messenger RNA. This molecule leaves the nucleus and moves to the endoplasmic reticulum and binds to ribosomes. Translation then occurs where the mRNA codes for the individual amino acids required for the protein. This takes place on ribosomes. Replication is the process by which one DNA molecule is copied to give two identical daughter DNA molecules, each of which contains one strand of the original DNA. Reproduction is the term that describes the overall physiological process by which new progeny are produced. Replication, Transcription and translation describe processes at the molecular level. a.# The process by which DNA is copied to two daughter DNA molecules. b.# The process by which a segment of DNA is copied to produce a molecule of messenger RNA. c.# The process by which proteins are synthesised from a genetic code. d.# The overall physiological process by which new progeny are produced in a particular species. END OF QUESTION = Replication = Transcription = Translation = Reproduction Type: multiple choice Title: Chapter 06 - Question 29 29) Which of the following descriptions applies to the process of translation? Feedback: Replication is the copying of DNA into two daughter DNA molecules. Translation is the process by which the genetic code for a specific protein (carried in messenger RNA) is used for the synthesis of a new protein. Transcription is the term used to describe how the genetic code relevant for the synthesis of one protein (a gene) is copied from DNA to form messenger RNA. Reproduction is the term used for the overall physiological process by which new progeny are produced in a particular species. incorrect a.# The process by which DNA is copied to produce two daughter DNA molecules. incorrect b.# The process by which a segment of DNA is copied to produce a molecule of messenger RNA. Correct c.# The process by which proteins are synthesised from a genetic code. incorrect d.# The overall physiological process by which new progeny are produced in a particular species. END OF QUESTION Type: matching Title: Chapter 06 - Question 30 30) Match the type of RNA to its function. Feedback: The first stage in the generation of a new protein is the copying of the genetic information which codes for that protein. This is a process called transcription and results in a molecule of messenger RNA (mRNA). The mRNA may be modified in the nucleus of eukaryotic cells by structures called spliceosomes which include molecules of snRNA. The modified mRNA departs the nucleus to the endoplasmic reticulum where translation takes place on ribosomes. Ribosomes are made up of proteins and rRNA. The rRNA plays an important catalytic role in the mechanism of translation. mRNA acts as the code for the amino acids making up the protein and transfer RNA (tRNA) translates the code. a.# The RNA which catalyses protein = rRNA synthesis. b.# The RNA which provides the = mRNA genetic blueprint for a protein. c.# The RNA which is responsible = tRNA for translating the triplet code into a specific amino acid. d.# The RNA which participates in = snRNA modifying mRNA prior to protein synthesis. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 31 31) Which of the following types of RNA helps to catalyse the synthesis of proteins? Feedback: The process of protein synthesis is catalysed by ribosomal RNA (rRNA). Messenger RNA (mRNA) provides the genetic blueprint for the protein. Transfer RNA (tRNA) is responsible for translating the triplet code into a specific amino acid. Messenger RNA molecules are modified prior to protein synthesis by small nuclear RNA (snRNA). Correct a.# rRNA. incorrect b.# mRNA. incorrect c.# tRNA. incorrect d.# snRNA. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 32 32) Which of the following types of RNA translates the genetic code for the synthesis of proteins? Feedback: The process of protein synthesis is catalysed by ribosomal RNA (rRNA). Messenger RNA (mRNA) provides the genetic blueprint for the protein. Transfer RNA (tRNA) is responsible for translating the triplet code into a specific amino acid. Messenger RNA molecules are modified prior to protein synthesis by small nuclear RNA (snRNA). incorrect a.# rRNA. incorrect b.# mRNA. Correct c.# tRNA. incorrect d.# snRNA. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 33 33) What expression is given for the three nucleic acid bases present on transfer RNA that base pair with a triplet of bases on messenger RNA? Feedback: The codon is a triplet of nucleic acid bases present on messenger RNA that will code for a specific amino acid. The anticodon is the complementary triplet of nucleic acid bases on transfer RNA that will link a specific transfer RNA to that codon. In doing so, a specific amino acid is carried to the site of protein synthesis by transfer RNA. There is no such thing as a translation factor. Correct a.# Anticodon. incorrect b.# Triplet. incorrect c.# Codon. incorrect d.# Translation factor. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 34 34) How many nucleic acid bases on messenger RNA are responsible for the coding of one amino acid? Feedback: Since three bases code for one amino acid, the genetic code is also called the triplet code. incorrect a.# 1 incorrect b.# 2 Correct c.# 3 incorrect d.# 4 END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 35 35) What amino acid is coded by the triplet of bases UUU? Feedback: The triplet code for phenylalanine can be UUU or UUC. For serine it can be UCU, UCC, AGU, or AGC. For tyrosine, it is UAU or UAC. For cysteine it can be UGU or UGC. Correct a.# Phenylalanine. incorrect b.# Serine. incorrect c.# Tyrosine. incorrect d.# Cysteine. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 36 36) Which of the following mutations is most likely to be disruptive to protein synthesis or function? Feedback: GAG to GAA results in glutamic acid being coded in each case. There is no disruption to protein synthesis or function. GAG to GAC or GAU results in a change from glutamic acid to aspartic acid. This is a similar amino acid to glutamic acid and so the chances of disruption are slight. GAG to UAG results in a stop code which prevents further synthesis of the protein. This will be the most drastic effect and will lead to a non-functioning protein. incorrect a.# GAG to GAA. incorrect b.# GAG to GAC. incorrect c.# GAG to GAU. Correct d.# GAG to UAG. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 37 37) What sort of reaction is catalysed by a restriction enzyme in recombinant DNA technology? Feedback: An esterase enzyme cleaves ester bonds. A restriction enzyme cleaves sugar phosphate bonds in DNA. A reductase enzyme reduces ketones. A ligase enzyme forms sugar phosphate bonds. incorrect a.# The hydrolysis of an ester group. Correct b.# The cleavage of a sugar phosphate bond. incorrect c.# The reduction of a ketone. incorrect d.# The formation of a sugar phosphate bond. END OF QUESTION Type: matching Title: Chapter 06 - Question 38 38) Match the enzyme to the reaction catalysed. Feedback: Enzymes are often named according to the reaction they catalyse. Thus Esterases catalyse the hydrolysis of esters and reductases catalyse reductions. Restriction enzymes and ligases are used in genetic engineering. The former are used to cleave sugar phosphate bonds in a DNA chain, and the latter are used to rejoin them. a.# The hydrolysis of an ester group. = Esterase b.# c.# The cleavage of a sugar phosphate bond. The reduction of a ketone. d.# The formation of a sugar phosphate bond. END OF QUESTION = Restriction enzyme = Reductase = Ligase Type: multiple choice Title: Chapter 06 - Question 39 39) Which amino acid in the enzyme topoisomerase II is responsible for cleaving a phosphate-sugar link in a DNA strand? Feedback: Tyrosine contains a phenolic group which forms a bond to a phosphate group on the DNA backbone, resulting in cleavage of a phosphate-sugar bond in the DNA backbone. Correct a.# Tyrosine. incorrect b.# Threonine. incorrect c.# Serine. incorrect d.# Cysteine. END OF QUESTION Type: multiple choice Title: Chapter 06 - Question 40 40) What role does the enzyme topoisomerase II have? Feedback: The enzymes responsible for the four actions described are telomerase, DNA polymerase, helicase, and topoisomerase II. It catalyses the formation of protective units at the end of incorrect a.# chromosomes. incorrect b.# It catalyses the synthesis of DNA. incorrect c.# It catalyses the unwinding of the DNA double helix. Correct d.# It catalyses crossing over of DNA strands to relieve the tension created in DNA when the DNA double helix is unravelled. END OF QUESTION