Q&A Hero

Q: The presence of enzymes to catalyze bioreactions in our bodies allows A) us to eat non-nutritious substances without consequence. B) the activation energy of a reaction to be raised. C) the rate of a desired chemical reaction to slow down. D) bioreactions to occur under extreme conditions of temperature and pH. E) bioreactions to take place under mild conditions.

Q: Urease catalyzes only the hydrolysis of urea, and no other substrates. This limited activity is called A) absolute specificity. B) extreme specificity. C) rigid specificity. D) noncompetitive specificity. E) hyperspecificity.

Q: Substances that react under the influence of an enzyme are usually held to the enzyme by A) peptide bonds. B) side chains of amino acids in the enzyme protein. C) ester bonds. D) pH changes. E) competitive inhibition.

Q: When a substance bonds to an enzyme for reaction, its place of binding is the A) allosteric site. B) primary pocket. C) end pocket. D) primary site. E) active site.

Q: In any reaction catalyzed by an enzyme, the reacting molecule is called the A) substrate. B) cofactor. C) coenzyme. D) isozyme. E) allostere.

Q: Most enzymes are A) fluid-mosaic proteins. B) induced proteins. C) substrate proteins. D) fibrous proteins. E) globular proteins.

Q: The general function of an enzyme in the body is to A) catalyze chemical reactions. B) maintain a neutral pH. C) act as a reactant in carbohydrate storage. D) maintain homeostasis. E) eliminate waste products from the blood.

Q: The active site of an enzyme A) is remote from the site of substrate attachment. B) is converted to a product. C) catalyzes the reaction. D) increases the energy of reaction. E) includes the entire enzyme.

Q: The formation of an enzyme-substrate complex is the ________ step in enzyme action. A) first B) second C) third D) fourth E) last

Q: Which of the following is NOT a step in the enzyme-catalyzed conversion of a substrate to product? A) The substrate binds to the enzyme away from the active site. B) The substrate binds in the active site to form the E-S complex. C) The enzyme assists in the conversion of the substrate to product. D) The product is released from the active site. E) A new substrate molecule binds to the enzyme for a new cycle.

Q: Compared to an uncatalyzed reaction, an enzyme-catalyzed reaction A) uses less substrate. B) produces different products. C) occurs at a faster rate. D) requires more energy. E) requires a higher temperature.

Q: Would an amino acid with the given R group be most likely to be found in the hydrophobic or hydrophilic region of a protein?A) bothB) hydrophilicC) hydrophobic

Q: Classify each protein by function. A) contractile B) structural C) catalytic D) protection E) transport 1> trypsin for the hydrolysis of protein 2> lipoproteins in the blood 3> collagen in tendons and cartilage 4> antibodies 5> actin in muscle

Q: Identify the structural level in each protein. A) quaternary B) tertiary C) secondary structure D) primary structure 1> The protein folds into a compact structure stabilized by interactions between R groups. 2> the combination of two or more protein molecules to form an active protein 3> pleated sheet 4> the peptide bonds between the amino acids 5> the structural level achieved when hydrogen bonds form between the carboxyl group of one amino acid and the amino group of a different amino acid

Q: Lead ions disrupt hydrophobic interactions.

Q: Upon hydrolysis the dipeptide abbreviated as Gly-Lys will yield the same products as the dipeptide abbreviated as Lys-Gly.

Q: Lysine and glutamic acid form hydrophobic interactions.

Q: Disulfide bonds stabilize the tertiary structure of a protein.

Q: The peptide sequence Gly-Gly-Gly gives the primary structure of a tripeptide.

Q: Sickle-cell anemia is caused by a change in the primary structure of a subunit of the hemoglobin protein.

Q: The dipeptide abbreviated as Gly-Lys is the same as the dipeptide abbreviated as Lys-Gly.

Q: Zwitterions have an overall positive charge.

Q: Insulin is a transport protein.

Q: Hemoglobin is a transport protein.

Q: Circle the peptide bond in this structure.

Q: Write the zwitterion of glycine.

Q: Electrophoresis is a laboratory technique for separating amino acids using their different ________.

Q: The isoelectric point for any amino acid is the pH at which the amino acid has a net charge of ________.

Q: A zwitterion of any amino acid has a net charge of ________.

Q: Amino acids that are not synthesized in the body but must be ingested with the diet are called ________ amino acids.

Q: Proteins that stimulate immune response are known as ________.

Q: The protein that transports oxygen in the blood is ________.

Q: Collagen can be classified as a ________ protein.

Q: In digestion, proteins are broken down into amino acids by a(n) ________ reaction. A) saponification B) reduction C) hydrolysis D) oxidation E) denaturation

Q: What process occurs when heat, acids, bases, and heavy metal ions cause a loss of biological function of a protein? A) denaturation B) saponification C) hydrogenation D) amidation E) esterification

Q: Hydrophobic interactions help to stabilize the ________ structure(s) of a protein. A) primary B) secondary C) secondary and tertiary D) tertiary and quaternary E) secondary and quaternary

Q: When two protein chains combine to form an active protein, the structural level is ________. A) pleated B) primary C) secondary D) tertiary E) quaternary

Q: In an enzyme, the polypeptide chain folds into a compact shape known as the ________ structure. A) pleated B) primary C) secondary D) tertiary E) quaternary

Q: The peptide hormone that regulates uterine contractions during labor is ________. A) oxytocin B) vasopressin C) myoglobin D) an endorphin E) an enkephalin

Q: Consider the R groups of the following amino acids:cysteine: -CH2SH; alanine: -CH3; serine: -CH2OHThe name for the dipeptide shown below is ________.A) alanyl-cysteineB) alanyl-serineC) seryl-alanineD) seryl-cysteineE) serine-alanine

Q: At what pH would you expect valine, an amino acid with a neutral R group, to be in the zwitterionic form? A) 1 B) 4 C) 6 D) 10 E) 14

Q: What amino acids have polar R groups that are attracted to water? A) hydrophilic B) hydrophobic C) nonpolar D) aromatic E) hydrocarbon

Q: Immunoglobulin, a protein that stimulates immune responses, would be classified as a ________ protein. A) transport B) structural C) storage D) protection E) catalytic

Q: An acid can denature a protein by A) agitating the protein chains. B) disrupting hydrogen bonds between R groups chains. C) disrupting hydrophobic interactions within a protein chain. D) removing helping molecules such as heme. E) breaking disulfide bridges.

Q: Heavy metals denature proteins by A) releasing amino acids. B) disrupting hydrophobic interactions. C) changing the pH of the protein solution. D) changing the temperature of the protein solution. E) disrupting disulfide bonds.

Q: One heavy metal that can cause denaturation of a protein is A) silver. B) sodium. C) barium. D) iron. E) calcium.

Q: Denaturation of a protein A) changes the primary structure of a protein. B) disrupts the secondary, tertiary, or quaternary structure of a protein. C) is always irreversible. D) hydrolyzes peptide bonds. E) can only occur in a protein with quaternary structure.

Q: Heat denatures a protein by disrupting A) ionic bonds and peptide bonds. B) hydrophobic bonds and hydrogen bonds. C) peptide bonds and hydrophobic bonds. D) disulfide bonds and peptide bonds. E) hydrogen bonds and disulfide bonds.

Q: Acids and bases denature a protein by disrupting A) peptide bonds and ionic bonds. B) amide bonds and alkene bonds. C) hydrophobic interactions and peptide bonds. D) ionic bonds and hydrophobic interactions. E) ionic bonds and hydrogen bonds.

Q: In sickle-cell anemia, the hemoglobin molecules A) come apart into separate chains. B) enlarge to twice normal size. C) clump together into insoluble fibers. D) dissolve in the plasma. E) undergo crenation.

Q: The function of myoglobin is to A) carry vitamins in the blood. B) carry oxygen in the blood. C) support the skeletal muscles. D) carry oxygen in the muscle. E) provide strength in cartilage.

Q: What kinds of interactions are NOT part of tertiary protein structure? A) peptide bonds B) disulfide bonds C) hydrophilic interactions D) salt bridges E) hydrophobic interactions

Q: Disulfide bonds in a protein chain connect A) an amine and a carboxylic acid group. B) an alcohol and a carboxylic acid group. C) tryptophan and alanine residues. D) two cysteine residues. E) two asparagine residues.

Q: What type of interaction would you expect between the following R groups in the tertiary structure of a protein?A) disulfide bondsB) salt bridgesC) hydrogen bondsD) hydrophobic interactionsE) peptide bonds

Q: Which R group would most likely be found in a hydrophobic area of the tertiary structure of a globular protein?

Q: The fibrous protein responsible for the structure of hair and wool is A) keratin. B) collagen. C) endorphin. D) myosin. E) casein.

Q: Hemoglobin has a total of ________ protein chains in its quaternary structure. A) one B) two C) three D) four E) five

Q: Within hemoglobin, the heme functions asA) a disulfide bridge.B) an oxygen carrier.C) a reducing agent.D) an subunit.E) one of the four protein subunits.

Q: The heme in hemoglobin is a(n) A) protein chain. B) small molecule within a protein. C) helix area in the hemoglobin molecule. D) pleated sheet area in the hemoglobin molecule. E) oxygen molecule within the hemoglobin molecule.

Q: Hemoglobin is an example of a protein withA) primary structure only.B) two protein chains held together.C) a globular structure.D) primarily a -pleated sheet structure.E) primarily an helix structure.

Q: In insulin, two peptide chains are held together in a single unit byA) disulfide bridges.B) hydrogen bonds.C) salt bridges.D) a prosthetic group.E) a -pleated sheet.

Q: The secondary structure of collagen is distinguished by A) single α helix strands. B) double α helix strands. C) many α helixes wound into fibrils. D) a braided triple helix. E) many glycoside links.

Q: Which of the following is a secondary protein structure? A) α helix B) Ser-Met-Ala-Gly-Ile C) disulfide bond D) salt bridges E) hydrophobic interactions

Q: The interactions that are important in the secondary structure of a protein are A) hydrogen bonds. B) hydrophobic interactions. C) disulfide bonds. D) salt bridges. E) peptide bonds.

Q: Enkephalins, naturally produced opiates in the body, are found in A) muscles and bone tissue. B) brain and kidney tissue. C) thalamus and spinal cord tissue. D) heart and lung tissue. E) pancreas and liver tissue.

Q: Enkephalins are polypeptides that have A) a sweet taste. B) a bitter taste. C) extra caloric value. D) pain-killing properties. E) hormone activity.

Q: In the β-pleated sheet secondary structure of a protein, two or more amino acid sequences in separate parts of the protein are held together A) in a coil, by hydrogen bonding. B) in random order, due to hydrophobic interactions. C) in a triple helix. D) in a double helix. E) in a zig-zag conformation, by hydrogen bonding.

Q: The α helix of the secondary structure of a protein is held together by ________ between two widely separated parts of a protein chain. A) hydrogen bonds B) disulfide bridges C) salt bridges D) hydrophilic interactions E) hydrophobic interactions

Q: Which of the following is an example of a secondary protein structure? A) dipeptide B) triglyceride C) a helix D) amino acid E) fatty acid

Q: A chain made of more than 50 amino acids is usually referred to as a(n) A) peptide. B) protein. C) enzyme. D) globulin. E) hormone.

Q: A peptide bond contains which kind of functional group? A) alcohol B) amine C) amide D) carboxylic acid E) ketone

Q: Which of the following shows all of the tripeptides that can be formed from one molecule each of lysine (Lys), threonine (Thr), and histidine (His)? A) Lys-Thr-His B) Lys-Thr-His, Lys-His-Thr, His-Thr-Lys, His-Lys-Thr, Thr-Lys-His, Thr-His-Lys C) Lys-Thr-His, Lys-His-Thr, His-Lys-Thr, Thr-His-Lys D) Lys-Thr-His, Lys-His-Thr, His-Lys-Thr E) Lys-Thr-His, Lys-His-Thr

Q: Which of the following shows all of the tripeptides that can be formed from one molecule each of glycine (Gly), valine (Val), and leucine (Leu)? A) Gly-Val-Leu, Gly-Leu-Val, Val-Leu-Gly, Val-Gly-Leu, Leu-Gly-Val, Leu-Val-Gly B) Gly-Val-Leu, Gly-Leu-Val, Leu-Gly-Val C) Val-Gly-Leu, Gly-Val-Leu, Gly-Leu-Val, Leu-Gly-Val D) Val-Gly-Leu, Gly-Leu-Val E) Gly-Val-Leu

Q: In the peptide Ser-Cys-Ala-Gly, the C-terminal end is A) serine. B) serotonin. C) glycine. D) glycerine. E) alanine.

Q: In the peptide Ala-Try-Gly-Phe, the N-terminal amino acid is A) alanine. B) phenylalanine. C) tryptophan. D) aspartic acid. E) glycine.

Q: The peptide bonds that combine amino acids in a protein are A) ester bonds. B) ether bonds. C) amide bonds. D) glycosidic bonds. E) sulfide bonds.

Q: Which of the following is the correct structure for Ser-Ala-Asp? The appropriate side chains look like this.

Q: Which of the following functional groups of an amino acid would be in the ionized state at high pH?

Q: The R group for serine is - CH2OH. As a zwitterion, serine has the structural formula

Q: In a typical amino acid zwitterion, the carboxylate end is A) positively charged. B) negatively charged. C) neutral. D) soluble in a nonpolar solvent. E) attached to an amine.