DOC-20240912-WA0011..pdf

Medicinal Chemistry Full-Test Bank Prepared by: Amr Al-najjar Type: multiple choice Title: Chapter 01 - Question 01 01) Which of the following molecules is a phospholipid? Feedback: The 'phospho' of phospholipid indicates the presence of a phosphate group. The lipid part of the name refers to the two long hydrocarbon chains. The structure is also known as a phosphoglyceride. Structure ii) is an amino acid, structure iii) is an oligonucleotide, and structure iv is a carbohydrate. Correct a.# i incorrect b.# ii incorrect c.# iii incorrect d.# iv END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 02 02) Which of the following statements is false regarding the phospholipid bilayer in cell membranes? Feedback: The cell membrane is made up of a bilayer of phospholipid molecules where the hydrophobic tails interact with each other in the centre of the membrane by van der Waals interactions. The polar head groups interact with water at the outer and inner surfaces of the membrane. The tails of the phospholipid molecules are hydrophobic (water hating) and repel water and ions. The phospholipid molecules are certainly fluid, but no pores are formed as a result of that. incorrect a.# It is made up of two layers of phospholipid molecules with the tails interacting with each other. incorrect b.# Water and ions are unable to cross the bilayer due to the hydrophobic tails of the phospholipid molecules. incorrect c.# There are charged groups at the inner and outer surfaces of the cell membrane. Correct d.# The molecules in the bilayer are fluid and so the cell membrane is porous allowing the passage of ions and water across the cell membrane. END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 03 03) Which of the following statements is false? Feedback: Some drugs do form covalent bonds to their targets, but most drugs interact by intermolecular binding interactions. The other statements are true. Most drug targets are large molecules (macromolecules) that are far bigger than the drugs that interact with them. There are some inorganic compounds used in medicine, but the vast majority of drugs are organic molecules. incorrect a.# Drug targets are normally macromolecules. incorrect b.# Drugs are generally smaller than drug targets. incorrect c.# Drugs are generally organic molecules. Correct d.# Drugs usually act by forming covalent bonds with drug targets. END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 04 04) Which of the following statements is false with respect to a binding site? Feedback: The binding site is normally a hydrophobic hollow or cleft on the surface of a macromolecular target. In the binding site, there are functional groups and regions that form binding interactions with complementary groups on a drug. incorrect a.# It is part of a macromolecule that acts as a drug target. incorrect b.# It contains binding regions. incorrect c.# It is normally a hollow or cleft on the surface of the drug target. Correct d.# It is usually hydrophilic in nature. END OF QUESTION Type: matching Title: Chapter 01 - Question 05 05) Consider the molecule in blue bound to a binding site and identify the binding interactions (i-iv) that are formed by the various parts of the molecule to the binding site. Feedback: Van der Waals interactions take place between regions of molecules consisting solely of carbon and hydrogen atoms. Ionic bonds occur between charges of opposite sign. Hydrogen bonds occur between a molecule acting as a hydrogen bond donor (RXH; where X is normally oxygen or nitrogen), and a molecule acting as hydrogen bond acceptor where a heteroatom is present (normally oxygen or nitrogen). a.# i = Van der Waals interactions b.# ii = Ionic bond c.# iii = Hydrogen bond acceptor d.# iv = Hydrogen bond donor END OF QUESTION Type: matching Title: Chapter 01 - Question 06 06) Identify the binding interactions that might be possible at the specified positions of the following drug: Feedback: Van der Waals interactions take place between molecular regions consisting solely of carbon and hydrogen atoms; for example alkyl groups or aromatic rings. Ionic bonds occur between charges of opposite sign. Hydrogen bonds occur between a molecule acting as hydrogen bond donor (RXH; where X is normally oxygen or nitrogen), and a molecule acting as hydrogen bond acceptor where a heteroatom is present (normally oxygen or nitrogen). a.# i = Hydrogen bond donor b.# ii = Van der Waals interactions c.# iii = Hydrogen bond acceptor d.# iv = Ionic interactions END OF QUESTION Type: matching Title: Chapter 01 - Question 07 07) Identify the binding interactions that might be possible at the specified positions of the following drug. Feedback: Van der Waals interactions take place between molecular regions consisting solely of carbon and hydrogen atoms; for example alkyl groups or aromatic rings. Ionic bonds occur between charges of opposite sign. Hydrogen bonds occur between a molecule acting as hydrogen bond donor (RXH; where X is normally oxygen or nitrogen), and a molecule acting as hydrogen bond acceptor where a heteroatom is present (normally oxygen or nitrogen). a.# i = Hydrogen bond acceptor b.# ii = Van der Waals interactions c.# iii = Ionic interactions d.# iv = Hydrogen bond donor END OF QUESTION Type: matching Title: Chapter 01 - Question 08 08) Identify the binding interactions that might be possible at the specified positions of the following drug. Feedback: Van der Waals interactions take place between molecular regions consisting solely of carbon and hydrogen atoms; for example alkyl groups or aromatic rings. Ionic bonds occur between charges of opposite sign. Hydrogen bonds occur between a molecule acting as hydrogen bond donor (RXH; where X is normally oxygen or nitrogen), and a molecule acting as hydrogen bond acceptor where a heteroatom is present (normally oxygen or nitrogen). a.# i = Ionic interactions b.# ii = Hydrogen bond donor c.# iii = Van der Waals interactions d.# iv = Hydrogen bond acceptor END OF QUESTION Type: matching Title: Chapter 01 - Question 09 09) Identify the binding interactions that might be possible at the specified positions of the following drug. Feedback: Van der Waals interactions take place between molecular regions consisting solely of carbon and hydrogen atoms; for example alkyl groups or aromatic rings. Ionic bonds occur between charges of opposite sign. Hydrogen bonds occur between a molecule acting as hydrogen bond donor (RXH; where X is normally oxygen or nitrogen), and a molecule acting as hydrogen bond acceptor where a heteroatom is present (normally oxygen or nitrogen). a.# i = Hydrogen bond acceptor b.# ii = Ionic interactions c.# iii = Van der Waals interactions (1) d.# iv = Van der Waals interactions (2) END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 10 10) Which of the following atoms in the structure below is likely to be the strongest hydrogen bond acceptor? Feedback: Generally, the more electron rich the heteroatom, the better it will be as a hydrogen bond acceptor. Thus, a negatively charged oxygen will be the best hydrogen bond acceptor. The negative charge in the carboxylate ion is shared between the two oxygens by resonance, and so each of the carboxylate oxygens will be a better hydrogen bond acceptor than the amide oxygen. This in turn will be a better hydrogen bond acceptor than either of the nitrogens in the structure. The amide and aniline nitrogens will be poor hydrogen bond acceptors since the lone pair of electrons in each case interacts with a neighbouring group (carbonyl group and aromatic ring respectively). Therefore, it is not available to form hydrogen bonds. incorrect a.# The anilino nitrogen. incorrect b.# The carbonyl oxygen. incorrect c.# The amide nitrogen. Correct d.# The carboxylate oxygen. END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 11 11) Which of the following atoms is likely to be the strongest hydrogen bond donor? c OH H d a H HO N H b HO Feedback: The best hydrogen bond donor will be the one where the hydrogen is the most electron deficient. In the alkylammonium ion, the nitrogen has a positive charge and this in turn will make the attached hydrogens electron deficient. The phenol groups are likely to be the next best hydrogen bond donors since the oxygen's lone pair of electrons will interact with the aromatic ring giving it a slightly positive charge. incorrect a.# The phenol group meta to the side chain. incorrect b.# The phenol group para to the side chain. incorrect c.# The alcohol group. Correct d.# The alkylammonium ion. END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 12 12) Which of the following functional groups is most likely to participate in a dipole-dipole interaction? Feedback: The ketone will have the strongest dipole moment due to the electronegative oxygen polarising the carbonyl bond. The alcohol will also have a significant dipole moment, but less than that of the ketone. The alkene and aromatic rings may have small or negligible dipole moments depending on their substituents. Correct a.# Ketone. incorrect b.# Alkene. incorrect c.# Aromatic ring. incorrect d.# Alcohol. END OF QUESTION Type: multiple choice Title: Chapter 01 – Question 13 13) Which of the following statements is false? Feedback: Water molecules surrounding a hydrophobic region of a drug form an ordered layer of molecules with low entropy. incorrect a.# Desolvation is an energy expensive process which involves the removal of water from polar functional groups prior to a drug binding to its binding site. Correct b.# Water molecules surrounding a hydrophobic region of a drug form an ordered layer of molecules with high entropy. incorrect c.# Interaction between the non polar regions of a drug and the non polar regions of a target require the removal of an ordered water coat and represents a gain in binding energy due to increased entropy. incorrect d.# An increase in entropy results in a greater negative value of G and a greater chance of binding. END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 14 14) Which of the following statements is true about the following structure? Feedback: The head group includes a positively charged nitrogen and a negatively charged phosphate group. As a result, it is hydrophilic and polar. The hydrocarbon tails are ‘water hating' i.e. hydrophobic. incorrect a.# It has a polar head group and hydrophilic 'tails'. Correct b.# It has a polar head group and hydrophobic 'tails'. incorrect c.# It has a non polar head group and hydrophilic 'tails' incorrect d.# It has a non polar head group and hydrophobic 'tails' END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 15 15) What is the role of the following structure in cell membranes? Feedback: The cell membrane is made up of a bilayer of phospholipid molecules where the hydrophobic tails interact with each other in the centre of the membrane and the polar head groups interact with water at the outer and inner surfaces of the membrane. Protein receptors in the cell membrane are involved in communication. Carbohydrates can act as antigens. Adenosine triphosphate is an example of a molecule that acts as an energy source. incorrect a.# The structure plays an important role in communication between cells. incorrect b.# The structure acts as an antigen or chemical 'fingerprint' for cells. Correct c.# The structure is present as a structural component of cell membranes. incorrect d.# The structure is an energy source. END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 16 16) What general term is used to describe large biologically important molecules? Feedback: Macro- means large and so the term macromolecule is used. Macromolecules can be considered to be polymeric in the sense that there may be repeating segments (e.g. repeating peptide bonds in proteins) but polymers are generally regarded as having repeating units (e.g. A-B-A-B-A-B etc). This is not true of many non- structural macromolecules. Proteins are examples of macromolecules, but not all macromolecules are proteins. Oligomers is a term used to describe a smaller version of a larger molecule (e.g. an oligonucleotide is a small portion of a larger nucleic acid.) incorrect a.# Polymers. Correct b.# Macromolecules. incorrect c.# Proteins. incorrect d.# Oligomers. END OF QUESTION Type: matching Title: Chapter 01 - Question 17 17) Match the following terms to the descriptions. Feedback: The binding site is normally a hollow or cleft on the macromolecular target into which a drug can bind. Specific binding regions within that site 'recognise' specific binding groups on drugs (or ligands) to allow binding interactions to take place. a.# A hollow or cleft present on = Binding site the surface of a macromolecule to which a drug can bind b.# Functional groups on a drug = Binding groups which are used to bind it to the drug target c.# A region of the drug target = Binding region which can bind to a specific functional group present on a drug END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 18 18) What are the relative strengths of different types of bonds? Feedback: Covalent bonds are strongest since they involve the sharing of electrons between two atoms. Ionic interactions are electrostatic in nature and involve interactions between opposite charges. Hydrogen bonding can be seen as a weak form of ionic interaction. Van der Waals interactions are weakest since they involve attractions between transient regions of charge. incorrect a.# Covalent > H-bond > Ionic > Van der Waals. incorrect b.# Van der Waals > Ionic > H-bond > Covalent. Correct c.# Covalent > Ionic > H-bond > Van der Waals. incorrect d.# Ionic > Covalent > Van der Waals > H-bond. END OF QUESTION Type: multiple choice Title: Chapter 01 - Question 19 19) Which of the following interactions has a directional property? Feedback: The hydrogen bond involves an interaction between the hydrogen of a hydrogen bond donor, and a lone pair of electrons on the heteroatom of a hydrogen bond acceptor. The orbital containing the lone pair of electrons will have a directional property as will the X-H bond of the hydrogen bond donor. This is not the case with the other interactions. incorrect a.# Van der Waals interactions. incorrect b.# Hydrophobic interactions. Correct c.# Hydrogen bond. incorrect d.# Ionic bond. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 01 01) Identify the correct name for the following peptide. Feedback: Peptides are named, starting from the amino end. L-tyrosyl-L-valyl-L-serine is wrong since it is named from the carboxyl end. L-seryl-L-valyl-L-phenylalanine is wrong since tyrosine has been wrongly identified as phenylalanine. L-phenylalanyl-L-valyl-L- serine is wrong since the labelling is from the wrong end of the molecule and tyrosine has been wrongly identified as phenylalanine. Correct a.# L-seryl-L-valyl-L-tyrosine. incorrect b.# L-seryl-L-valyl-L-phenylalanine. incorrect c.# L-phenylalanyl-L-valyl-L-serine. incorrect d.# L-tyrosyl-L-valyl-L-serine. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 02 02) Which of the following single letter codes represents the structure below? Feedback: The order of the amino acids from the N-terminal end of the peptide is serine (S), valine (V) and tyrosine (Y). YVS is wrong since the amino acids are labelled from the C-terminal end. SVF is wrong since it mislabels tyrosine as phenylalanine. FVS has the same mistakes as SVF and is also labelled from the wrong end. incorrect a.# YVS. Correct b.# SVY. incorrect c.# FVS. incorrect d.# SVF. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 03 03) What is unique about glycine with respect to other natural amino acids? Feedback: Glycine is the only amino acid not to have a residue attached to the alpha carbon. The other three characteristics are shared with the rest of the natural amino acids. incorrect a.# It can form peptide bonds with other amino acids. Correct b.# It has no side chain. incorrect c.# It contains an amine functional group and a carboxylic acid functional group attached to the same carbon. incorrect d.# It exists as a zwitterion. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 04 04) Which of the following statements is true about a peptide bond (RCONHR')? Feedback: ‘It is planar’ is correct. The peptide bond has double bond character due to the interaction of the nitrogen lone pair with the carbonyl group. This prevents bond rotation and makes the bond planar. The other options are false. The NH of the amide can act as a hydrogen bond donor and the carbonyl group can act as a hydrogen bond acceptor. The trans isomer is favoured over the cis isomer. Single bond rotation is not allowed due to the double bond character of the group. Correct a.# It is planar. incorrect b.# It is not capable of forming a hydrogen bond. incorrect c.# The cis configuration is favoured over the trans configuration. incorrect d.# Single bond rotation is permitted between nitrogen and the carbonyl group. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 05 05) Which of the following statements is untrue about protein secondary structure? Feedback: The steric influence of amino acid residues is important to secondary structure. In secondary structure, the residues are positioned to minimise interactions between each other and the peptide chain. incorrect a.# The alpha-helix, beta-pleated sheet, and beta-turns are examples of protein secondary structure. incorrect b.# The ability of peptide bonds to form intramolecular hydrogen bonds is important to secondary structure. Correct c.# The steric influence of amino acid residues is not important to secondary structure. incorrect d.# The hydrophilic/hydrophobic character of amino acid residues is not important to secondary structure. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 06 06) Which of the following statements is untrue about protein tertiary structure? Feedback: In general, proteins fold up such that as many hydrophobic residues as possible are positioned in the centre of the protein such that they interact with each other rather than with water. Hydrophilic amino acids can interact favourably with water and are more likely to be on the outside. Several amino acid side chains interact with each other by means of ionic and hydrogen bonding. Correct a.# Proteins fold up into a tertiary structure such that most amino acids with hydrophobic residues are exposed to the aqueous surroundings. incorrect b.# Proteins fold up into a tertiary structure such that most amino acids with hydrophilic residues are exposed to the aqueous surroundings. incorrect c.# Proteins fold up into a tertiary structure such that most amino acids with hydrophobic residues are in the centre and hidden from the aqueous surroundings. incorrect d.# Interactions between amino acid residues are important in protein tertiary structure. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 07 07) Which of the following descriptions best describes the primary structure of proteins? Feedback: Primary structure refers to the order of the amino acids in a protein. Secondary structure indicates regions of ordered structure, and tertiary structure is the overall structure of the protein. Quaternary structure refers to the structure of a multi- protein complex. incorrect a.# The arrangement of different protein subunits in a multiprotein complex. Correct b.# The order in which amino acids are linked together in a protein. incorrect c.# The overall three dimensional shape of a protein. incorrect d.# Regions of ordered structure within a protein. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 08 08) Which of the following descriptions best describes the secondary structure of proteins? Feedback: Primary structure refers to the order of the amino acids in a protein. Secondary structure indicates regions of ordered structure, and tertiary structure is the overall structure of the protein. Quaternary structure refers to the structure of a multi- protein complex. incorrect a.# The arrangement of different protein subunits in a multiprotein complex. incorrect b.# The order in which amino acids are linked together in a protein. incorrect c.# The overall three dimensional shape of a protein. Correct d.# Regions of ordered structure within a protein. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 09 09) Which of the following descriptions best describes the tertiary structure of proteins? Feedback: Primary structure refers to the order of the amino acids in a protein. Secondary structure indicates regions of ordered structure, and tertiary structure is the overall structure of the protein. Quaternary structure refers to the structure of a multi- protein complex. incorrect a.# The arrangement of different protein subunits in a multiprotein complex. incorrect b.# The order in which amino acids are linked together in a protein. Correct c.# The overall three dimensional shape of a protein. incorrect d.# Regions of ordered structure within a protein. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 10 10) Which of the following descriptions best describes the quaternary structure of proteins? Feedback: Primary structure refers to the order of the amino acids in a protein. Secondary structure indicates regions of ordered structure, and tertiary structure is the overall structure of the protein. Quaternary structure refers to the structure of a multi- protein complex. Correct a.# The arrangement of different protein subunits in a multiprotein complex. incorrect b.# The order in which amino acids are linked together in a protein. incorrect c.# The overall three dimensional shape of a protein. incorrect d.# Regions of ordered structure within a protein. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 11 11) Which of the following statements is not true regarding protein tertiary structure? Feedback: Van der Waals interactions may be weak but they have an important role in protein tertiary structure since there are so many of them. Correct a.# Van der Waals interactions between hydrophobic residues are the least important factors in tertiary structure. incorrect b.# Covalent bonds can have an influence on tertiary structure. incorrect c.# Hydrogen bonds, ionic bonds and van der Waals interactions all have a role to play in tertiary structure. incorrect d.# Planar peptide bonds have an indirect influence on protein tertiary structure. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 12 12) Identify the strongest form of intermolecular bonding that could be formed involving the residue of the amino acid threonine. Feedback: Threonine contains a hydroxyl functional group on its side chain and so the strongest possible interaction will be hydrogen bonding where the hydroxyl group could act as a hydrogen bond donor or hydrogen bond acceptor. incorrect a.# Ionic bond. Correct b.# Hydrogen bond. incorrect c.# Van der Waals interactions. incorrect d.# None of the options are correct. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 13 13) Identify the strongest form of intermolecular bonding that could be formed involving the residue of the amino acid histidine Feedback: Histidine contains a heterocyclic ring with two nitrogen atoms. In the neutral form, there is an NH group where the proton can act as a hydrogen bond donor. However, the ring can be protonated resulting in a positively charged nitrogen which could form a stronger ionic interaction. Correct a.# Ionic bond. incorrect b.# Hydrogen bond. incorrect c.# Van der Waals interactions. incorrect d.# Dipole-dipole interactions. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 14 14) Identify the strongest form of intermolecular bonding that could be formed involving the residue of the amino acid alanine Feedback: Alanine has no functional groups on its side chain. There is only a methyl group and so only van der Waals interactions are possible. incorrect a.# Ionic bond. incorrect b.# Hydrogen bond. Correct c.# Van der Waals interactions. incorrect d.# Dipole-dipole interactions. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 15 15) Identify the strongest form of intermolecular bonding that could be formed involving the residue of the amino acid arginine Feedback: Arginine contains a basic functional group on its side chain which could take part in hydrogen bonding. However, it can also ionise allowing a stronger ionic interaction. Correct a.# Ionic bond. incorrect b.# Hydrogen bond. incorrect c.# Van der Waals interactions. incorrect d.# Dipole-dipole interactions. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 16 16) Identify the strongest form of intermolecular bonding that could be formed involving the residue of the amino acid aspartic acid. Feedback: Aspartic acid contains a carboxylic acid functional group which could act as a hydrogen bond donor or hydrogen bond acceptor. However, the group could lose its acidic proton to gain a negative charge allowing a stronger ionic interaction to take place. Correct a.# Ionic bond. incorrect b.# Hydrogen bond. incorrect c.# Van der Waals interactions. incorrect d.# Dipole-dipole interactions. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 17 17) Identify the strongest form of intermolecular bonding that could be formed involving the residue of the amino acid asparagine. Feedback: Asparagine contains a primary amide functional group on its side chain and so the strongest possible interaction will be hydrogen bonding where the carbonyl group can act as a hydrogen bond donor and the NH2 protons can act as hydrogen bond donors. The nitrogen cannot act as a hydrogen bond acceptor since the lone pair is interacting with the carbonyl group of the amide group to produce partial double bond character. incorrect a.# Ionic bond. Correct b.# Hydrogen bond. incorrect c.# Van der Waals interactions. incorrect d.# Dipole-dipole interactions. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 18 18) Identify the strongest form of intermolecular bonding that could be formed involving the residue of the amino acid serine. Feedback: Serine contains a hydroxyl functional group on its side chain and so the strongest possible interaction will be hydrogen bonding where the hydroxyl group could act as a hydrogen bond donor or hydrogen bond acceptor. incorrect a.# Ionic bond. Correct b.# Hydrogen bond. incorrect c.# Van der Waals interactions. incorrect d.# Dipole-dipole interactions. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 19 19) Which of the following statements is incorrect regarding transport proteins? Feedback: Transport proteins carry polar molecules across the cell membrane. Non- polar molecules can dissolve through the hydrophobic cell membrane. incorrect a.# They are present in cell membranes. Correct b.# They serve to carry non polar molecules across the cell membrane. incorrect c.# They are required to transport amino acids across cell membranes. incorrect d.# They are not required to transport steroids across cell membranes. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 20 20) Which of the following statements best describes an amino acid residue? Feedback: The residue is the side chain that is attached to the alpha-carbon of the head group. The head group consists of the amino group, the carboxyl group, and the alpha- carbon atom. The portion of the amino acid remaining when a peptide bond is formed includes both the head group and the residue, since only water is lost from the condensation reaction. The structure formed by hydrolysis of a peptide or protein is the amino acid itself. incorrect a.# The portion of an amino acid that remains once a peptide bond has been formed. incorrect b.# The structure that is formed following the hydrolysis of a peptide or protein. Correct c.# The side chain of an amino acid. incorrect d.# The head group of an amino acid. END OF QUESTION Type: multiple choice Title: Chapter 02 - Question 21 21) Which of the following statements is incorrect regarding transport proteins? Feedback: Steroids are hydrophobic molecules which can pass through the cell membrane without the need for a transport protein. incorrect a.# They are present in cell membranes. incorrect b.# They serve to carry polar molecules across the hydrophobic cell membrane. incorrect c.# They are required to transport amino acids across cell membranes. Correct d.# They are required to transport steroids across cell membranes. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 01 01) Which of the following statements is not true regarding the active site of an enzyme? Feedback: An active site is normally a hollow or cleft on the surface of an enzyme, rather than the surface itself. Correct a.# An active site is normally on the surface of an enzyme. incorrect b.# An active site is normally hydrophobic in nature. incorrect c.# Substrates fit into active sites and bind to functional groups within the active site. incorrect d.# An active site contains amino acids which are important to the binding process and the catalytic mechanism. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 02 02) Some enzymes have a binding site which is not recognised by the normal substrate, and affects the activity of the enzyme if it is occupied by a ligand. What term is used for such a binding site? Feedback: The allosteric binding site affects the activity of an enzyme, depending on whether it is occupied by a ligand or not. It is distinct from the active site where the enzyme catalysed reaction takes place. The terms secondary binding site and inhibitory binding site do not exist. incorrect a.# Active site. Correct b.# Allosteric binding site. incorrect c.# Secondary binding site. incorrect d.# Inhibitory binding site. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 03 03) What term is used to describe the binding site of an enzyme where a reaction is catalysed? Feedback: The active site is where the reaction catalysed by the enzyme takes place. The allosteric binding site affects the activity of an enzyme, depending on whether it is occupied by a ligand or not. It is distinct from the active site. The terms secondary binding site and inhibitory binding site do not exist. Correct a.# Active site. incorrect b.# Allosteric binding site. incorrect c.# Secondary binding site. incorrect d.# Inhibitory binding site. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 04 04) Which of the following terms refers to the process by which a substrate binds to an active site and alters the shape of that active site? Feedback: An induced fit is a consequence of the binding interactions taking place between a substrate and the active site. The term moulded fit does not exist. The lock and key theory is an older theory where it was proposed that the active site was already the correct shape for its substrate. incorrect a.# Moulded fit. incorrect b.# Intermolecular bonding. Correct c.# Induced fit. incorrect d.# Lock and key theory. END OF QUESTION Type: matching Title: Chapter 03 - Question 05 05) Identify which of the amino acids; glutamate, phenylalanine, threonine, and serine, would use the following interactions in an active site; hydrogen bonding, ionic bonding, van der Waals interactions, H-bonding, and van der Waals interactions. Feedback: Serine has a hydroxyl group which can take part in hydrogen bonding. Glutamate is the ionised form of glutamic acid and can take part in ionic interactions. Phenylalanine has an aromatic ring in its side chain that can interact by van der Waals interactions. Tyrosine has an aromatic ring that can interact by van der Waals interactions, and a phenol that can interact by hydrogen bonding. a.# Hydrogen bonding = Serine b.# Ionic bonding = Glutamate c.# Van der Waals interactions = Phenylalanine d.# Hydrogen bonding and van = Tyrosine der Waals bonding END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 06 06) Which of the following descriptions best describes a cofactor? Feedback: A cofactor is a non-protein substance required by an enzyme to function properly. This term covers both organic molecules and metal ions. A co-enzyme is a non-protein organic molecule that is required by some enzymes in order to catalyse a reaction on a substrate. A prosthetic group is a non-protein organic molecule that is bound covalently to the active site of an enzyme, and which is required if the enzyme is to catalyse a reaction on a substrate. A substrate is a compound which is bound to the active site and undergoes a reaction. Correct a.# A non-protein substance that is required by an enzyme if it is to catalyse a reaction. incorrect b.# A non-protein organic molecule that is required by some enzymes in order to catalyse a reaction on a substrate. incorrect c.# A non-protein organic molecule that is bound covalently to the active site of an enzyme, and which is required if the enzyme is to catalyse a reaction on a substrate. incorrect d.# A compound which is bound to the active site and undergoes a reaction. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 07 07) Which of the following descriptions best describes a coenzyme? Feedback: A cofactor is a non-protein substance required by an enzyme to function properly. This term covers both organic molecules and metal ions. A co-enzyme is a non-protein organic molecule that is required by some enzymes in order to catalyse a reaction on a substrate. A prosthetic group is a non-protein organic molecule that is bound covalently to the active site of an enzyme, and which is required if the enzyme is to catalyse a reaction on a substrate. A substrate is a compound which is bound to the active site and undergoes a reaction. incorrect a.# A non-protein substance that is required by an enzyme if it is to catalyse a reaction. Correct b.# A non-protein organic molecule that is required by some enzymes in order to catalyse a reaction on a substrate. incorrect c.# A non-protein organic molecule that is bound covalently to the active site of an enzyme, and which is required if the enzyme is to catalyse a reaction on a substrate. incorrect d.# A compound which is bound to the active site and undergoes a reaction. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 08 08) Which of the following descriptions best describes a prosthetic group? Feedback: A cofactor is a non-protein substance required by an enzyme to function properly. This term covers both organic molecules and metal ions. A co-enzyme is a non-protein organic molecule that is required by some enzymes in order to catalyse a reaction on a substrate. A prosthetic group is a non-protein organic molecule that is bound covalently to the active site of an enzyme, and which is required if the enzyme is to catalyse a reaction on a substrate. A substrate is a compound which is bound to the active site and undergoes a reaction. incorrect a.# A non-protein substance that is required by an enzyme if it is to catalyse a reaction. incorrect b.# A non-protein organic molecule that is required by some enzymes in order to catalyse a reaction on a substrate. Correct c.# A non-protein organic molecule that is bound covalently to the active site of an enzyme, and which is required if the enzyme is to catalyse a reaction on a substrate. incorrect d.# A compound which is bound to the active site and undergoes a reaction. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 09 09) Which of the following descriptions best describes a substrate? Feedback: A cofactor is a non-protein substance required by an enzyme to function properly. This term covers both organic molecules and metal ions. A co-enzyme is a non-protein organic molecule that is required by some enzymes in order to catalyse a reaction on a substrate. A prosthetic group is a non-protein organic molecule that is bound covalently to the active site of an enzyme, and which is required if the enzyme is to catalyse a reaction on a substrate. A substrate is a compound which is bound to the active site and undergoes a reaction. incorrect a.# A non-protein substance that is required by an enzyme if it is to catalyse a reaction. incorrect b.# A non-protein organic molecule that is required by some enzymes in order to catalyse a reaction on a substrate. incorrect c.# A non-protein organic molecule that is bound covalently to the active site of an enzyme, and which is required if the enzyme is to catalyse a reaction on a substrate. Correct d.# A compound which is bound to the active site and undergoes a reaction. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 10 10) Consider the following enzyme-catalysed reaction carried out on glycogen. What is the product? Feedback: Glycogen is the substrate for this reaction. Adrenaline is a hormone that can trigger a cascade of cellular events that will eventually activate phosphorylase a. AMP acts as an enzyme modulator to directly activate the enzyme. Glucose is the structure formed if the phosphate group is hydrolysed from glucose-1-phosphate. Correct a.# Glucose-1-phosphate. incorrect b.# Adrenaline. incorrect c.# Glucose. incorrect d.# AMP. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 11 11) Consider the following enzyme catalysed reaction. What is the substrate? Feedback: Glycogen is the substrate for this reaction. Phosphorylase a is the enzyme. AMP acts as an enzyme modulator to directly activate the enzyme. Glucose-1-phosphate is the product. incorrect a.# Glucose-1-phosphate. incorrect b.# Phosphorylase a. Correct c.# Glycogen. incorrect d.# AMP. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 12 12) Consider the following enzyme-catalysed reaction. What is the enzyme? Feedback: Glycogen is the substrate for this reaction. Phosphorylase a is the enzyme. AMP acts as an enzyme modulator to directly activate the enzyme. Glucose-1-phosphate is the product. incorrect a.# Glucose-1-phosphate. Correct b.# Phosphorylase a. incorrect c.# Glycogen. incorrect d.# AMP. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 13 13) Consider the following enzyme-catalysed reaction. What is the enzyme modulator that activates the enzyme? Feedback: Glycogen is the substrate for this reaction. Phosphorylase a is the enzyme. AMP acts as an enzyme modulator to directly activate the enzyme. Glucose-1-phosphate is the product. incorrect a.# Glucose-1-phosphate. incorrect b.# Phosphorylase a. incorrect c.# Glycogen. Correct d.# AMP. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 14 14) Consider the following enzyme-catalysed reaction. What sort of enzyme is involved? Feedback: The reaction shown is a phosphorylation and so the enzyme involved is a phosphorylase. Esterases catalyse the hydrolysis of esters. Ligases catalyse the joining of two substrates. Transferases catalyse group transfer reactions. incorrect a.# Esterase. Correct b.# Phosphorylase. incorrect c.# Ligase. incorrect d.# Transferas. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 15 15) Consider the following enzyme-catalysed reaction. What chemical messenger triggers a cascade of cellular event that eventually activates the enzyme involved in this reaction? Feedback: Adrenaline is a hormone that can trigger the signalling cascade. The other agents mentioned are neurotransmitters which do not have an affect on this reaction. incorrect a.# Acetylcholine. incorrect b.# Noradrenaline. incorrect c.# Serotonin. Correct d.# Adrenaline. END OF QUESTION Type: matching Title: Chapter 03 - Question 16 16) Identify A-D in the following reaction. Feedback: Nitrous oxide activates cyclase enzymes to generate the secondary messenger cyclic GMP from GTP. a.# A = Guanosine triphosphate b.# B = Nitric oxide c.# C = Cyclase d.# D = Cyclic GMP END OF QUESTION Type: matching Title: Chapter 03 - Question 17 17) Identify A-D in the following diagram. Feedback: Arginine contains a guanidine functional group that provides the nitrous oxide that is eventually formed in this reaction. The enzyme NO synthase converts arginine to citrulline in two steps with release of nitrous oxide. a.# A = Arginine b.# B = NO synthase c.# C = Citrulline d.# D = Nitric oxide END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 18 18) Which of the following statements is not true regarding the active site of an enzyme? Feedback: An active site is normally hydrophobic in nature, not hydrophilic. Nevertheless, there are usually hydrophilic amino acids present which are important in binding the substrate in the active site. incorrect a.# An active site is normally a hollow or cleft on the surface of an enzyme. Correct b.# An active site is normally hydrophilic in nature. incorrect c.# Substrates fit into active sites and bind to functional groups within the active site. incorrect d.# An active site contains amino acids which are important to the binding process and the catalytic mechanism. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 19 19) Which of the following amino acids commonly acts as a nucleophilic group in enzyme-catalysed reaction mechanisms? Feedback: Serine has a hydroxyl functional group that is frequently involved as a nucleophile in enzyme catalysed reactions. Cysteine is another amino acid that is commonly present as a nucleophile in enzyme active sites. Phenylalanine and valine are more likely to be involved in binding interactions. Histidine is commonly present as an acid-base catalyst. Correct a.# Serine. incorrect b.# Phenylalanine. incorrect c.# Histidine. incorrect d.# Valine. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 20 20) Which of the following amino acids acts as a nucleophilic group in enzyme-catalysed reaction mechanisms? Feedback: Cysteine has a thiol functional group that is frequently involved as a nucleophile in enzyme catalysed reactions. Serine is another amino acid that is commonly present as a nucleophile in enzyme active sites. Threonine, tyrosine and glutamine are more likely to be involved in binding interactions. incorrect a.# Threonine. incorrect b.# Tyrosine. Correct c.# Cysteine. incorrect d.# Glutamine. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 21 21) Which of the following amino acids acts as an acid-base catalyst in enzyme-catalysed reaction mechanisms? Feedback: Histidine is a weak base that can equilibrate between a protonated, ionised form and a non-protonated free base. It is, therefore, well placed to act as an acid-base catalyst. Phenylalanine, serine, and tryptophan can all be involved in substrate binding, while serine may act as a nucleophile. incorrect a.# Serine. incorrect b.# Phenylalanine. Correct c.# Histidine. incorrect d.# Tryptophan. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 22 22) From which amino acid is nitrous oxide generated? Feedback: Arginine contains a guanidine functional group that provides the nitrous oxide. The enzyme NO synthase converts arginine to citrulline with release of nitrous oxide. Correct a.# Arginine. incorrect b.# Aspartic acid. incorrect c.# Asparagine. incorrect d.# Lysine. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 23 23) What term is used for enzymes such as COX-1 and COX-2 which vary in structure and location but which catalyse the same reaction? Feedback: Isozymes is the correct term. Isosteres are chemical moieties that have similar size, shape, and valency. Isotopes are elements having the same number of protons, but a different number of neutrons. Isomers are molecules with the same molecular formula but differ in the way the atoms and bonds are linked together or are orientated with respect to each other. incorrect a.# Isosteres. Correct b.# Isozymes. incorrect c.# Isotopes. incorrect d.# Isomers. END OF QUESTION Type: multiple choice Title: Chapter 03 - Question 24 24) Which of the following statements is true with respect to the Michaelis constant? Feedback: The Michaelis constant is determined by measuring how the enzyme- catalysed rate of reaction is affected by substrate concentration. Inhibitors are not involved and so options b) and c) are wrong. The Michaelis constant is the concentration of substrate at which the rate of reaction is half of its maximum value. Correct a.# It is equal to the concentration of substrate at which the reaction rate is half of its maximum value. incorrect b.# It is equal to the concentration of inhibitor at which the reaction rate is half of its maximum value. incorrect c.# It is equal to the concentration of substrate at which the reaction rate is at its maximum value. incorrect d.# It is equal to the concentration of inhibitor at which the reaction rate is zero. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 01 01) Which of the following statements is not true about receptors? Feedback: Some protein receptors are certainly present inside cells, but the majority are present in the cell membrane. The binding site of receptors is analogous to the active site of enzymes. However, no reaction is catalysed. The ligand for the binding site acts as a chemical messenger. It binds and causes an induced fit that result in 'knock on effects' which lead to a message being received in the cell. Receptors do not catalyse reactions and so a messenger departs unchanged. Correct a.# Most receptors are proteins situated inside the cell. incorrect b.# Receptors contain a hollow or cleft on their surface which is known as a binding site. incorrect c.# Receptors bind chemical messengers such as neurotransmitters or hormones. incorrect d.# Receptors do not catalyse reactions on chemical messengers. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 02 02) Which of the following statements is not true? Feedback: The receptors for neurotransmitters are located in the cell membranes of target cells and not within the cell itself. incorrect a.# Neurotransmitters are released by nerves. incorrect b.# Neurotransmitters are required to carry a 'message' from a nerve to a target cell. incorrect c.# Neurotransmitters only have small distances to cover to reach their target cells. Correct d.# Neurotransmitters bind to receptors within target cells. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 03 03) Which of the following is not a neurotransmitter? Feedback: Cyclic GMP is a secondary messenger that is formed 'downstream' of a receptor-activated process. incorrect a.# Glycine. Correct b.# Cyclic GMP. incorrect c.# -Aminobutyric acid. incorrect d.# Serotonin. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 04 04) Which of the following statements is not true regarding the binding site of a receptor? Feedback: The binding site is a hollow or cleft in the surface of the protein and is usually hydrophobic in character. incorrect a.# The binding site is normally a hollow or cleft in the surface of an receptor. Correct b.# The binding site is normally hydrophilic in nature. incorrect c.# Chemical messengers fit into binding sites and bind to functional groups within the binding site. incorrect d.# The binding site contains amino acids which are important to the binding process. END OF QUESTION Type: matching Title: Chapter 04 - Question 05 05) Which of the following amino acid residues is likely to form its strongest binding interaction by means of: Feedback: Valine has an alkyl side chain capable of forming van der Waals interactions. Glycine has no side chain or residue and so cannot form any interactions. Serine has an alcohol functional group capable of hydrogen bonding. Aspartate has an ionised carboxylate group which is capable of ionic bonding. It is also possible for this group to interact by hydrogen bonding as a hydrogen bond acceptor, but this will be weaker than an ionic bond. a.# Hydrogen bonding = Serine b.# Ionic bonding = Aspartate c.# Van der Waals interactions = Valine d.# None of these options = Glycine END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 06 06) Which of the following statements best describes an induced fit? Feedback: An induced fit refers to the way the binding site changes shape as a result of the binding interactions formed between it and the chemical messenger. An induced fit cannot take place before the chemical messenger binds. The chemical messenger must be in the correct conformation to bind effectively, but this is a process which is not controlled by the binding site. The likelihood of a molecule being in the active conformation will depend on how stable the active conformation is relative to other inactive conformations. incorrect a.# The process by which a binding site alters shape such that it is ready to accept a chemical messenger. incorrect b.# The process by which a chemical messenger adopts the correct binding conformation before entering a binding site. Correct c.# The process by which binding of a chemical messenger to a binding site alters the shape of the binding site. incorrect d.# The process by which a binding site alters the shape of the chemical messenger into the binding conformation before binding. END OF QUESTION Type: matching Title: Chapter 04 - Question 07 07) Which of the following amino acid residues is likely to form its strongest binding interaction by means of: Feedback: Alanine has an alkyl side chain capable of forming van der Waals interactions. Glycine has no side chain or residue. Threonine has an alcohol functional group capable of hydrogen bonding. Lysine has an amino group which could be protonated to form an ionised centre capable of ionic bonding. It is also possible for this group to interact by hydrogen bonding, either in the ionised or non-ionised forms, but this will be weaker than an ionic bond. a.# Hydrogen bonding = Threonine b.# Ionic bonding = Lysine c.# Van der Waals interactions = Alanine d.# None of the answers = Glycine END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 08 08) There is a fine balance required for the binding interactions of a neurotransmitter with its receptor. Which of the following statements best expands on this statement? Feedback: All the statements are accurate, but the following statement best describes the importance of having an equilibrium between the bound and unbound states of the chemical messenger: ‘The binding interactions must be sufficiently strong that the neurotransmitter binds long enough to have an effect, but not too strong in case the neurotransmitter remains permanently bound.’ If the interaction was too weak, the messenger would not be bound long enough to have an effect. If too strong, the receptor would be continually activated. incorrect a.# It is important that the binding interactions involve a mixture of van der Waals interactions, hydrogen bonds and ionic bonds since neurotransmitters have different functional groups. incorrect b.# The binding interactions must be of the correct nature to match the functional groups of the neurotransmitter and the functional groups in the binding site. Correct c.# The binding interactions must be sufficiently strong that the neurotransmitter binds long enough to have an effect, but not too strong in case the neurotransmitter remains permanently bound. incorrect d.# There must be the correct balance of hydrophilic and hydrophobic interactions to ensure that the chemical messenger can enter a hydrophobic binding site. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 09 09) When a membrane-bound receptor binds its chemical messenger, an induced fit takes place which leads to secondary effects, allowing a chemical message to be received within the cell. Which of the following mechanisms is not involved in this process? Feedback: Transport proteins are involved in transporting molecules across cell membranes, and are not receptors. If a receptor is present in the cell membrane, there is no need for a chemical messenger to enter the cell. If the receptor is within the cell, the chemical messengers are generally hydrophobic and can pass through the cell membrane on their own account. Correct a.# The transport of the chemical messenger into the cell. incorrect b.# The opening or closing of an ion channel. incorrect c.# The activation of a signal protein. incorrect d.# The activation of a membrane-bound enzyme. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 10 10) Which of the following statements is not true about a ligand-gated ion channel receptor? Feedback: Ligand-gated ion channels consist of five glycoproteins and not six. The other statements are correct. Receptors that are controlled by the membrane potential are known as voltage-gated ion channels. incorrect a.# Ligand-gated ion channel receptors are present in the cell membrane. incorrect b.# Neurotransmitters can act as the chemical messengers for ligand-gated ion channels. Correct c.# Ligand-gated ion channels consist of six glycoproteins. incorrect d.# Some ion channel receptors are controlled by differences in membrane potential rather than by ligands. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 11 11) Which of the following statements is not true about ligand-gated ion channels? Feedback: The response time of ligand-gated ion channels to neurotransmitters is fast rather than slow. The other statements are correct. incorrect a.# There are different ligand-gated ion channels for specific ions. Correct b.# The response time to a neurotransmitter is slow. incorrect c.# The process by which an ion channel opens as a result of receptor-ligand binding is known as gating. incorrect d.# The opening of cationic ion channels generally leads to depolarisation of the cell. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 12 12) Which of the following statements is true about the ion channel controlled by the nicotinic receptor? Feedback: Three of the options are wrong for the following reasons: Each protein subunit of the ion channel contains four hydrophobic regions which traverse the cell membrane Two of the protein subunits are identical (the -subunits) The binding site for the nicotinic receptor is shared between the -protein subunit and a neighbouring protein subunit. There are two binding sites per ion channel. Therefore the following option is correct: ‘Each protein subunit of the ion channel has a lengthy N-terminal extracellular chain.’ incorrect a.# Each protein subunit of the ion channel contains three hydrophobic regions which traverse the cell membrane. incorrect b.# Three of the protein subunits are identical (the -subunits). incorrect c.# The binding site for the nicotinic receptor is located solely on the -subunit which means that there are two binding sites per ion channel. Correct d.# Each protein subunit of the ion channel has a lengthy N- terminal extracellular chain. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 13 13) The nicotinic receptor controls an ion channel. Which of the following statements is true about the -subunit of this ion channel? Feedback: The N-terminal and C-terminal chains are both extracellular. There are two intracellular loops and only one extracellular loop. incorrect a.# The N-terminal and C-terminal chains are both intracellular. incorrect b.# There is one intracellular loop. Correct c.# The binding site for the neurotransmitter resides solely on the N-terminal chain. incorrect d.# There are two extracellular loops END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 14 14) The mechanism of gating involves the rotation of five kinked -helices which traverse the cell membrane. Which of the following statements is untrue? Feedback: It is the -helix of the second transmembrane section that is involved and not the first. The other statements are correct. incorrect a.# Each protein subunit making up the ion channel contributes one of the kinked -helices. Correct b.# It is the -helix of the first transmembrane section that is involved. incorrect c.# Rotation of the helices opens up a central channel to allow the flow of ions. incorrect d.# The neurotransmitter binds to the N-terminal chain to produce a rapid response. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 15 15) Which of the following statements is true about a G-protein coupled receptor? Feedback: There are seven transmembrane hydrophobic regions. The number of intracellular and extracellular loops is the same. The N-terminal chain is extracellular and the C-terminal chain is intracellular. The binding region for the G-protein involves one of the intracellular loops and the C-terminal chain, as stated. incorrect a.# It contains five transmembrane hydrophobic sections. Incorrect b.# There are more extracellular loops than intracellular loops. Correct c.# The binding region for the G-protein involves one of the intracellular loops and the C-terminal chain. Incorrect d.# The N-terminal chain is intracellular and the C-terminal chain is extracellular. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 16 16) Which of the following is not a G-protein coupled receptor? Feedback: The nicotinic receptor is an ion channel. incorrect a.# The histamine receptor. Correct b.# The nicotinic receptor. incorrect c.# The dopaminergic receptor. incorrect d.# The adrenergic receptor. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 17 17) Which of the following statements is not true about G-protein coupled receptors? Feedback: Growth factors are ligands for kinase-linked receptors. incorrect a.# They contain seven transmembrane sections. incorrect b.# They mediate the action of some hormones. incorrect c.# They activate signal proteins called G-proteins. Correct d.# Growth factors can act as ligands for some G-protein coupled receptors. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 18 18) Which of the following pairs of receptors illustrates convergent evolution? Feedback: Both the H1 and H2 receptors bind histamine, but they have evolved from different branches of the evolutionary tree. The other pairings are examples of divergent evolution since they have evolved from the same branch. incorrect a.# The D1B and D1A dopaminergic receptor subtypes. Correct b.# The H1 and H2 receptor subtypes. incorrect c.# The 2a and 2b adrenoceptor subtypes. incorrect d.# The M2 and M4 muscarinic receptor subtypes. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 19 19) Which of the following statements is true about a tyrosine kinase linked receptor? Feedback: The receptor is situated in the cell membrane. The N-terminal chain is extracellular and this is where the ligand binding site is. The receptor has one hydrophobic transmembrane region as stated. incorrect a.# It is situated in the cytoplasm. incorrect b.# The N-terminal chain is intracellular. incorrect c.# The ligand binding site is in the C-terminal chain. Correct d.# It has one hydrophobic transmembrane region. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 20 20) Which of the following is a messenger for a tyrosine kinase linked receptor? Feedback: Adrenaline, dopamine, and histidine are neurotransmitters that activate G- protein coupled receptors. The epidermal growth factor activates a tyrosine kinase linked receptor. incorrect a.# Adrenaline. incorrect b.# Dopamine. Correct c.# Epidermal growth factor. incorrect d.# Histidine. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 21 21) Which of the following statements is untrue regarding the epidermal growth factor receptor? Feedback: Activation of the kinase results in the phosphorylation of tyrosine residues and not serine residues. It is a tyrosine kinase and not a serine-threonine kinase. incorrect a.# Binding of epidermal growth factor results in dimerisation of the receptor. incorrect b.# Dimerisation activates the kinase active site. Correct c.# Activation of the kinase results in phosphorylation of serine residues. incorrect d.# One half of the receptor dimer catalyses reactions on residues present on the other half. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 22 22) Which of the following statements is true regarding intracellular receptors? Feedback: Intracellular receptors are single proteins. They contain a ligand binding site near the C-terminal end. They contain a binding region for DNA near the middle of the protein and they are activated by hydrophobic molecules which are extracellular messengers and cross the cell membrane to reach their target. incorrect a.# They consist of three protein subunits. incorrect b.# They contain a ligand binding site near the N-terminal end. Correct c.# They contain a binding region for DNA near the middle of the protein. incorrect d.# They are activated by hydrophobic molecules which are synthesised within the cell. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 23 23) Which of the following statements is true regarding the DNA binding region of intracellular receptors? Feedback: The DNA binding region of intracellular receptors contains nine cysteine residues, eight of which are involved in binding two zinc ions. The receptor does not contain nucleotides. The DNA binding region is known as the zinc finger domains. Correct a.# It contains nine cysteine residues. incorrect b.# Four cysteine residues are involved in binding two zinc ions. incorrect c.# It contains particular nucleotide sequences that can base pair to DNA. incorrect d.# The DNA binding region is known as having 'thiol fingers'. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 24 24) Which of the following statements is not true about a ligand-gated ion channel receptor? Feedback: Ligand-gated ion channels are controlled by ligands and not by the membrane potential. Voltage-gated ion channels are controlled by membrane potential. incorrect a.# Ligand-gated ion channel receptors are present in the cell membrane. incorrect b.# Neurotransmitters can act as the chemical messengers for ligand-gated ion channels. incorrect c.# Ligand-gated ion channels consist of five glycoproteins. Correct d.# Differences in membrane potential affect whether ligand-gated ion channel receptors open or close. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 25 25) Which of the following statements is not true about ligand-gated ion channels? Feedback: The opening of cationic ion channels generally leads to depolarisation of the cell. incorrect a.# There are different ligand-gated ion channels for specific ions. incorrect b.# The response time to a neurotransmitter is extremely fast. incorrect c.# The process by which an ion channel opens as a result of receptor-ligand binding is known as gating. Correct d.# The opening of cationic ion channels generally leads to polarisation of the cell. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 26 26) Which of the following statements is true about the ion channel controlled by the nicotinic receptor? Feedback: There are four hydrophobic regions for each protein subunit. The binding site is shared between the -protein subunit and a neighbouring protein subunit. However, there are two binding sites per ion channel. The N-terminal chain is extracellular and not intracellular. incorrect a.# Each protein subunit of the ion channel contains three hydrophobic regions which traverse the cell membrane. Correct b.# Two of the protein subunits are identical (the -subunit). incorrect c.# The binding site for the nicotinic receptor is located solely on the -subunit which means that there are two binding sites per ion channel. incorrect d.# Each protein subunit of the ion channel has a lengthy N- terminal intracellular chain. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 27 27) The nicotinic receptor controls an ion channel. Which of the following statements is true about the -subunit of this ion channel? Feedback: There are two intracellular loops. The binding site for the neurotransmitter resides solely on the N-terminal chain. There is only one extracellular loop. Correct a.# The N-terminal and C-terminal chains are both extracellular. incorrect b.# There is one intracellular loop. incorrect c.# The binding site for the neurotransmitter resides solely on the C-terminal chain. incorrect d.# There are two extracellular loops. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 28 28) The mechanism of gating involves the rotation of five kinked -helices which traverse the cell membrane. Which of the following statements is untrue? Feedback: The neurotransmitter produces a rapid response but it binds to the N- terminal chain. incorrect a.# Each protein subunit making up the ion channel contributes one of the kinked -helices. incorrect b.# It is the -helix of the second transmembrane section that is involved. incorrect c.# Rotation of the helices opens up a central channel to allow the flow of ions. Correct d.# The neurotransmitter binds directly to the TM2 section to produce a rapid response. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 29 29) How many transmembrane sections are there in a G-protein coupled receptor? Feedback: G-Protein coupled receptors are also known as 7-TM receptors, where TM stands for transmembrane. incorrect a.# 1 incorrect b.# 3 incorrect c.# 5 Correct d.# 7 END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 30 30) Which of the following statements is true about a G-protein coupled receptor? Feedback: The N-terminal chain is extracellular and the C-terminal chain is intracellular. However, there are seven transmembrane hydrophobic regions. There are the same number of intracellular and extracellular loops. The binding region of the G-protein involves one of the intracellular loops and the C- terminal chain. incorrect a.# It contains five transmembrane hydrophobic sections. incorrect b.# There are more extracellular loops than intracellular loops. incorrect c.# The binding region for the G-protein involves two extracellular loops. Correct d.# The N-terminal chain is extracellular and the C-terminal chain is intracellular. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 31 31) Which of the following is not a G-protein coupled receptor? Feedback: The glycine receptor is an ion channel. incorrect a.# The muscarinic receptor. Correct b.# The glycine receptor. incorrect c.# The adrenergic receptor. incorrect d.# The glutamate receptor. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 32 32) Which of the following statements is not true about G-protein coupled receptors? Feedback: Fast-acting neurotransmitters generally activate ion channels since the secondary effect is faster than that of G-protein coupled receptors. Correct a.# They generally mediate the action of fast acting neurotransmitters. incorrect b.# They mediate the action of some hormones. incorrect c.# They activate signal proteins called G-proteins. incorrect d.# Calcium ions can act as a ligand for some G-protein coupled receptors. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 33 33) Which of the following pairs of receptors are likely to show the greatest structural similarity? Feedback: These receptors are closely related on the evolutionary tree of G-protein coupled receptors. The other pairings are more distantly related. incorrect a.# The dopamine receptor subtypes D3 and D5. incorrect b.# The muscarinic receptor M2 and the -adrenergic receptor 2. Correct c.# The histamine H2 receptor and the 1 adrenoceptor. incorrect d.# The histamine H1 receptor and the 2 adrenergic receptor. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 34 34) Which of the following statements is true about a tyrosine kinase linked receptor? Feedback: The ligand binding site is in the N-terminal chain is a true statement. The receptor is situated in the cell membrane. The N-terminal chain is extracellular and this is where the ligand binding site is. There is only one hydrophobic transmembrane region. incorrect a.# It is situated in the cytoplasm. incorrect b.# The N-terminal chain is intracellular. Correct c.# The ligand binding site is in the N-terminal chain. incorrect d.# It has two hydrophobic transmembrane regions. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 35 35) Which of the following reactions is catalysed by a tyrosine kinase? Feedback: Esterifications are catalysed by esterases. A tyrosine kinase phosphorylates the phenol functional group present on the side chain of the amino acid tyrosine. incorrect a.# The phosphorylation of an alcohol functional group. incorrect b.# The esterification of an alcohol functional group. Correct c.# The phosphorylation of a phenol functional group. incorrect d.# The esterification of a phenol functional group. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 36 36) Which of the following terms describes the epidermal growth factor? Feedback: The epidermal growth factor is a bivalent ligand which can bind to two binding sites on different proteins allowing dimerisation and activation of the protein receptor. incorrect a.# Divalent ligand. incorrect b.# Heterovalent ligand. incorrect c.# Covalent ligand. Correct d.# Bivalent ligand. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 37 37) Which of the following statements is untrue regarding the epidermal growth factor receptor? Feedback: ATP and not GTP is required for phosphorylation. The other statements are accurate. incorrect a.# Binding of epidermal growth factor results in dimerisation of the receptor. incorrect b.# Dimerisation activates the tyrosine kinase active site. incorrect c.# Activation of tyrosine kinase results in phosphorylation of tyrosine residues on the other half of the dimer. Correct d.# GTP is required for phosphorylation. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 38 38) In what way does the insulin receptor differ from the EGF receptor? Feedback: The insulin receptor is preformed before the ligand binds whereas the EGF receptor requires the presence of its ligand to dimerise. All the other statements are true for both kinds of receptor. Correct a.# The receptor is preformed prior to ligand binding. incorrect b.# A tyrosine kinase active site is activated. incorrect c.# Phosphorylation of one half of the receptor complex is catalysed by enzyme active sites on the other half. incorrect d.# ATP is required for phosphorylation. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 39 39) In what way does the growth hormone receptor differ from the EGF receptor? Feedback: The growth hormone receptor is formed as a result of ligand binding. Unlike the EGF-receptor, four protein subunits are assembled where the kinase enzymes are separate protein subunits from the protein subunits acting as receptors. incorrect a.# The receptor is formed as a result of ligand binding. Correct b.# The kinase enzyme is a separate protein from the receptor protein. incorrect c.# Phosphorylation of one half of the complex is catalysed by active sites on the other half. incorrect d.# ATP is required for phosphorylation. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 40 40) What major role do intracellular receptors play? Feedback: The major role for intracellular receptors is to trigger transcription through the formation of a nuclear transcription factor. Correct a.# They trigger transcription. incorrect b.# They trigger replication. incorrect c.# They trigger translation. incorrect d.# They trigger reproduction. END OF QUESTION Type: multiple choice Title: Chapter 04 - Question 41 41) Which of the following statements is generally true regarding the chemical messengers for intracellular receptors? Feedback: Since the chemical messengers for intracellular receptors are extracellular, they have to be hydrophobic in order to cross the cell membrane. incorrect a.# They are hydrophilic in order to bind to zinc atoms. incorrect b.# They are hydrophilic in order to dissolve in the cell's cytoplasm. incorrect c.# They are hydrophobic in order to enter the nucleus of the cell. Correct d.# They are hydrophobic in order to cross the cell membrane. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 01 01) What is the name of the substrate in the following reaction? Feedback: This reaction is the conversion of ATP to ADP, catalysed by the membrane- bound enzyme adenylate cyclase. Correct a.# ATP. incorrect b.# CTP. incorrect c.# GTP. incorrect d.# UTP. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 02 02) What is the name of the product in the following reaction? Feedback: This reaction is the conversion of ATP to ADP, catalysed by the membrane bound enzyme adenylate cyclase. Correct a.# Cyclic AMP. incorrect b.# Cyclic CMP. incorrect c.# Cyclic GMP. incorrect d.# Cyclic UMP. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 03 03) What is the name of the enzyme in the following reaction? Feedback: This reaction is the conversion of ATP to ADP, catalysed by the membrane bound enzyme adenylate cyclase. incorrect a.# Phosphorylase a. incorrect b.# Esterase. Correct c.# Adenylate cyclase. incorrect d.# Guanylate cyclase. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 04 04) What structure activates the enzyme that catalyses the following reaction? Feedback: The enzyme catalysing this reaction is adenylate cyclase which is activated by the s-subunit of a G-protein. incorrect a.# The -dimer of a Gs-protein. Correct b.# The s subunit of a Gs-protein. incorrect c.# A Gs-protein. incorrect d.# The -subunit of a Gs-protein. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 05 05) What structure deactivates the enzyme that catalyses the following reaction? Feedback: The enzyme catalysing this reaction is adenylate cyclase which is activated by the s-subunit of a G-protein and deactivated by the i-subunit incorrect a.# The -dimer of a Gi-protein. Correct b.# The i-subunit of a Gi-protein. incorrect c.# A Gi-protein. incorrect d.# The -subunit of a Gi-protein. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 06 06) Which of the following enzymes catalyses a phosphorylation reaction? Feedback: Protein kinase enzymes are responsible for catalysing phosphorylations of alcohol or phenol groups on protein substrates. The hydrolysis of phosphates is catalysed by phosphorylases and not by kinases. Esterases catalyse the hydrolysis of esters. Ligases catalyse the linking together of two substrates. Correct a.# Protein kinases. incorrect b.# Phosphorylases. incorrect c.# Esterases. incorrect d.# Ligases. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 07 07) Which of the following amino acids is phosphorylated by a protein kinase? Feedback: Protein kinases catalyse phenol or hydroxyl groups on the amino acid side chains of proteins. Tyrosine has a phenolic group which can be phosphorylated by such enzymes. The side chain of cysteine contains a thiol group which is not phosphorylated by protein kinases. Phenylalanine has an aromatic ring on its side chain and lysine has a primary amino group on its side chain. Neither of these groups is phosphorylated by protein kinases. Correct a.# Tyrosine. incorrect b.# Cysteine. incorrect c.# Phenylalanine. incorrect d.# Lysine. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 08 08) Which of the following statements is true regarding protein kinase A? Feedback: Protein kinase A is an intracellular enzyme that contains four protein subunits in the resting state. It is a serine-threonine kinase and not a tyrosine kinase. incorrect a.# It is an extracellular enzyme. incorrect b.# It is a tyrosine kinase. incorrect c.# It contains two protein subunits in the resting state. Correct d.# It is activated by cyclic AMP. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 09 09) Phospholipase catalyses the formation of two products from phosphatidylinositol diposphate. Which of the following structures is one of these products? Feedback: The reaction splits diacylglycerol from the substrate leaving all three phosphate groups unaffected. The product is inositol triphosphate. incorrect a.# Structure A. Correct b.# Structure B. incorrect c.# Structure C. incorrect d.# Structure D. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 10 10) Which of the following statements is true for diacylglycerol? Feedback: Diacylglycerol is a hydrophobic molecule that does act as a secondary messenger. It remains in the cell membrane and activates protein kinase C. incorrect a.# It is a hydrophilic molecule. incorrect b.# It moves into the cytoplasm. Correct c.# It activates an enzyme called protein kinase C. incorrect d.# It is not a secondary messenger. END OF QUESTION Type: matching Title: Chapter 05 - Question 11 11) Match the following secondary messengers to their actions. Feedback: Different secondary messengers trigger different signal transduction pathways a.# Activation of protein kinase A = Cyclic AMP. b.# Activation of calcium ion = Inositol triphosphate. release in the cell c.# Activation of protein kinase C = Diacylglycerol. d.# Activation of protein kinase G = Cyclic GMP. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 12 12) Which of the following statements is true regarding small G-proteins? Feedback: Small G proteins are single proteins and are not typical G-proteins (the latter are made up of three protein subunits). They are not directly activated by receptors, but are activated 'downstream' of activated receptors. They bind GDP in the resting state and GTP in the active state, just like the -subunits of G-proteins. incorrect a.# Ras is an example of a typical G-protein. incorrect b.# Small G-proteins have two subunits rather than three. incorrect c.# Small G-proteins are directly activated by receptors. Correct d.# Small G-proteins bind GDP in the resting state and GTP in the active state. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 13 13) How many subunits make up a G-protein? Feedback: The three subunits of a G-protein are labelled ,  and  incorrect a.# 2 Correct b.# 3 incorrect c.# 4 incorrect d.# 5 END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 14 14) Which of the following molecules is bound to a G-protein in the inactivated state? Feedback: The G-protein binds GDP when it is in the resting, inactivated state. It binds GTP in the active state. GMP is not bound at all. incorrect a.# GMP Correct b.# GDP incorrect c.# GTP incorrect d.# None of these. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 15 15) Which of the following molecules binds to the G-protein when the G- protein binds to the G-protein coupled receptor and is activated? Feedback: The G-protein binds GDP when it is in the resting, inactivated state. It binds GTP in the active state. GMP is not bound at all. incorrect a.# GMP incorrect b.# GDP Correct c.# GTP incorrect d.# None of these. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 16 16) Activation of the G-protein results in fragmentation of the G-protein. What does the G-protein fragment to? Feedback: Feedback: The -dimer and the -subunit depart the G-protein binding site once fragmentation has taken place. Correct a.# A -dimer and an -subunit linked to GTP. incorrect b.# A -subunit, a -subunit, and an -subunit linked to GTP. incorrect c.# A -subunit and a -dimer linked to GTP. incorrect d.# A -subunit and a -dimer linked to GTP. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 17 17) Which of the following explanations best describes the mechanism by which the G-protein fragments? Feedback: Binding of the G-protein to the G-protein binding site does not in itself destabilise the G-protein. Binding alters the relative affinity of a binding site on the G- protein for GDP and GTP such that the latter is preferred over the former. Once GTP is bound, a further conformational change destabilises the G-protein leading to fragmentation. No phosphorylation reactions are involved in this process. incorrect a.# Binding of the G-protein to the receptor results in a conformational change which destabilises the G-protein. Correct b.# Binding of the G-protein to the receptor results in a conformational change which leads to the exchange of GDP for GTP, resulting in a further conformational change which destabilises the G-protein. incorrect c.# Binding of the G-protein to the receptor results in a conformational change which leads to the exchange of GDP for GTP. GTP then phosphorylates tyrosine residues destabilising the G-protein. incorrect d.# Binding of the G-protein to the receptor results in a conformational change which stabilises the  dimer leading to dissociation of the -subunit. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 18 18) Which of the following statements describes the signal amplification that results from activation of the G-protein coupled receptor? Feedback: All the statements are true, but only the correct answer explains how an amplification of the signal is achieved. incorrect a.# The binding of a ligand to the receptor increases the chances of the receptor binding a G-protein. incorrect b.# The binding of a G-protein to the receptor increases the chances of it exchanging GDP for GTP. Correct c.# The ligand is bound to the receptor sufficiently long such that the receptor can fragment several G-proteins. incorrect d.# Fragmentation of the G-protein leads to an increase in entropy. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 19 19) Which of the following statements describes how signal amplification takes place with respect to the enzyme adenylate cyclase? Feedback: The s subunit binds to an allosteric binding site on adenylate cyclase and activates it. Several enzyme-catalysed reactions occur during the time that the subunit is bound, resulting in a signal amplification. incorrect a.# The s subunit of a G-protein binds to the enzyme and increases the chances of the enzyme catalysing a reaction. Correct b.# Several enzyme-catalysed reactions are carried out during the period of time that the s subunit is bound to the enzyme. incorrect c.# Each s subunit activates several different adenylate cyclase enzymes. incorrect d.# Each -dimer and s-subunit activates different adenylate cyclase enzymes. END OF QUESTION Type: multiple choice Title: Chapter 05 - Question 20 20) What term is used to describe the process by which an activated membrane-bound receptor passes a message in

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