Biochemistry 1 Questions - PDF

Biochemistry 1 – questions PROTEINS 1. The image below is the general structure of amino acids. Indicate the name of the structure indicated by arrows. 2. The amino acid molecules are amphoteric molecules. Depending on the pH, amino acids will be present in an aqueous solution in...

Biochemistry 1 – questions PROTEINS 1. The image below is the general structure of amino acids. Indicate the name of the structure indicated by arrows. 2. The amino acid molecules are amphoteric molecules. Depending on the pH, amino acids will be present in an aqueous solution in different forms: positively charged (cation), negatively charged (anion) or Amphion (zwitterion). Draw the indicated structure and name them. 3. All amino acids are optically active, except for: a. Glycine b. Arginine c. Glutamine d. Tyrosine e. Cysteine 4. Peptide bond is a _________ a) Covalent bond b) Ionic bond c) Metallic bond d) Hydrogen bond 5. Which part of the amino acid gives it uniqueness? a) Amino group b) Carboxyl group c) Side chain d) None of the mentioned 6. Unfolding of a protein can be termed as _________ a) Renaturation b) Denaturation c) Oxidation d) Reduction 7. What are the following is not a factor responsible for the denaturation of proteins? a) pH change b) Organic solvents c) Heat d) Charge 8. Which of the following statements is true about size-exclusion chromatography? a) During the separation of a mixture of proteins, protein with smallest molecular weight is eluted first b) During the separation of a mixture of proteins, protein with largest molecular weight is eluted first c) During the separation of a mixture of proteins, protein with largest molecular weight is eluted last d) During the separation of a mixture of proteins, protein with largest molecular weight flow around the beads 9. Two chains of amino acids in an insulin molecule are held together by __________ a) Sulfide bridges b) Disulfide bridges c) Peptide bond d) Covalent linkage 10. Who deduced the double-helical structure of DNA? a) Frederick Sanger b) Mendel c) Watson and Francis Crick d) Anton van Leeuwenhoek 11. Hemoglobin is a __________ a) Monomer b) Dimer c) Trimer d) Tetramer 12. β-pleated sheets are the examples of _________ a) Primary structure b) Secondary structure c) Tertiary structure d) Quaternary structure 13. Which of the following are known as helix breakers? a) Proline and glycine b) Isoleucine and leucine c) Valine d) Threonine 14. Which of the following is a false statement? a) α-Keratin is α helical b) Collagen is α helical c) Hemoglobin has a quaternary structure d) α-Keratin is β pleated structure 15. Which of the following is abundantly found in collagen? a) Glycine b) Serine c) Alanine d) Tryptophan 16. Which of the following is false about fibrous protein? a) It is in rod or wire like shape b) Keratin and collagen are the best examples c) Hemoglobin is the best example d) It provides structural support for cells and tissues 17. Myoglobin is particularly abundant in ________ a) Nerves b) Muscles c) Blood cells d) Skin 18. Contractile protein of a muscle is __________ a) Troponin b) Myosin c) Tubulin d) Tropomyosin 19. During the formation of the peptide bond which of the following takes place? a) Hydroxyl group is lost from its carboxyl group of one amino acid and a hydrogen atom is lost from its amino group of another amino acid b) Hydrogen atom is lost from its carboxyl group of one amino acid and a hydroxyl group is lost from its amino group of another amino acid c) Hydroxyl group is lost from its carboxyl group of one amino acid and a hydroxyl group is lost from its amino group of another amino acid d) Hydrogen atom is lost from its carboxyl group of one amino acid and a hydrogen atom is lost from its amino group of another amino acid 20. Two amino acids cysteine and serine, form by condensation reaction dipeptides: a. How many different dipeptides are formed? b. Draw structural formulae of the dipeptides formed. 21. Give the structural formulae of two possible compounds formed by a condensation reaction between alanine and phenylalanine. 22. Indicate the peptide bond; then give the structural formulae of amino acids formed by hydrolysis of dipeptide: 23. Which of the following 2 Fischer projections represents the natural form of alanine? 24. Mark the asymmetric (chiral) carbon atoms in the next amino acids and calculate the number of optical isomers for each amino acid. 25. In the presence of enzymes called amino acid decarboxylases, amino acids eliminate a carbon dioxide molecule from COOH bound to alpha carbon and form a. biogenic amines b. ammonia c. amines d. salts e. sarcosine 26. Indicate the peptide bond(s), the number of amino acids, the N-terminus amino acid, and the C-terminus amino acid of the next oligopeptide. 27. Glutathione is a. a cellular tripeptide b. formed by the condensation of glutamic acid, cysteine and glycine c. carried a thiol group (SH) which gives its reducing properties. d. a, b and c are correct answers e. only a is the correct answer 28. Draw the general structure of an α amino acid? 29. Identify the amino acids that fit each description: a. Does not have a chiral carbon b. Has at the side chain a phenol – OH c. Has at the side chain a disulphide bridge 30. Define the term isoelectric point (pI). 31. Draw the oxidation reaction of cysteine (to form cystine) 32. Draw the phosphorylation reaction of serine. 33. How many amino acids are found in an oligopeptide? a) 2 to 10 b) 1 to 5 c) 10 to 50 d)> 50 34. How many amino acids are found in a polypeptide? a) 5 to 10 b) 1 to 5 c) 11 to 50 d)> 50 35. How many peptide bonds are found in a tetrapeptide? But in a hexapeptide? 36. How many peptide bonds and amino acids are found in the next oligopeptide? 37. Glutathione is a cellular peptide formed by glutamic acid, cysteine, and glycine condensation. Write its structure of reduced glutathione. 38. Oxytocin and vasopressin are ………………………………………… synthesized in the hypothalamus and secreted from the posterior pituitary gland. These molecules differ only by …………………………………………………………………, at positions 3 and 8 (isoleucine and leucine in oxytocin are replaced respectively by phenylalanine and arginine in vasopressin). 39. Insulin is a a. polypeptide hormone  b. oligopeptide c. carbohydrate d. complex lipid e. nonapeptide 40. Chain A of insulin is linked to chain B by a. 2 disulfide bridges b. 7 disulfide bridges c. 20 disulfide bridges d. 1 disulfide bridge e. 0 disulfide bridges 41. Promote the uptake of glucose from the blood to the tissues a. Insulin b. Glucagon c. Oxytocin d. Vasopressin e. Prostaglandine 42. Diabetes mellitus is a disease of a. disturbed insulin secretion b. disturbed glucagon secretion c. disturbed vasopressin secretion d. disturbed oxytocin secretion e. disturbed cholesterol secretion 43. Its effect is opposite to that of insulin: a. Cholesterol b. Glucagon c. Oxytocin d. Vasopressin e. Prostaglandine 44. Who fits the description? It is established between amino acids to form a chain; is planar, rigid, and polar; the C, H, O, and N atoms and the two adjacent carbons (Cα) are in the same plane; Cα atoms are Trans oriented. a. peptide bond b. glycosidic bond c. 45. Primary structure of proteins is represented by the …………………… and …………………………… of amino acids in the polypeptide chain of a protein. 46. The secondary structure of proteins is dictated by the primary structure and is stabilized by: a. hydrogen bonds 47. The 100% α-helix structure or α-keratin contains a. hair, wool, b. horns, c. nails, d. claws e. all the answers are correct 48. The tertiary structure is maintained by different interactions:  a. Covalent interactions b. Ionic interactions c. Hydrogen bonds d. van der Waals interactions e. all the answers are correct 49. Describe the structures of reduced and oxidized glutathione. 50. Describe the structure and function of insulin. 51. Describe what happens during diabetes mellitus. 52. Indicate the role of insulin and glucagon in the organism. 53. Oxitocine is: a. an amino acid b. a sugar c. a dipeptide d. a nanopeptide 54. Mark the incorrect answer about insulin: a. It is a polypeptide with 2 chains; b. it is a dimer with 2 chains linked together by ionic interactions; c. it is a polypeptide with 51 amino acid residues; d. it increases glycogen synthesis; e. It is a polypeptide with 1 chain 55. Vasopressin produces: a. the retaining of water in the body; b. the retaining of glucose in the body; c. atherosclerosis; d. vasoconstriction e. the answers a. and d. are correct 56. Name the three different protein types based on morphology. 57. Heme in haemoglobin binds O2: a. reversibly with oxidation of Fe2+ b. irreversibly without oxidation of Fe2+ c. irreversibly with oxidation of Fe2+ d. reversibly without oxidation of Fe2+ 58. Hemoglobin has: a. 2 O2 binding sites per molecule b. 1 O2 binding site per molecule c. 3 O2 binding sites per molecule d. 4 O2 binding sites per molecule 59. Hemoglobin transports CO2 from tissues to lungs in the form of: a. Carboxyl at Fe2+ b. Carbamate at amino termini of chains c. Carbamate at carboxyl termini of chains d. Carboxyl at amino termini of chains 60. Heme in myoglobin binds O2: a. reversibly with oxidation of Fe2+ b. irreversibly without oxidation of Fe2+ c. irreversibly with oxidation of Fe2+ d. reversibly without oxidation of Fe2+ 61. Myoglobin has: a. 2 O2 binding sites per molecule b. 1 O2 binding site per molecule c. 3 O2 binding sites per molecule d. 4 O2 binding sites per molecule 62. Myoglobin, in meat, after several days of exposure to air : a. ferrous ion of Mb is oxidized to ferric b. ferric ion is reduced to ferrous c. meat turns into a brown colour  d. meat turns into a cherry red colour. 63. Glucagon is released from ___________ a) Muscle b) Pancreas c) Kidneys d) Epithelial tissues 64. A structure that has hydrogen bonds between polypeptide chains arranged side by side is ____________ a) Primary structure b) α-helix c) β-pleated sheets d) Tertiary structure 65. CARBOHYDRATES 1. What is the difference between glucose and fructose structure? Draw the Haworth projections for α and β anomers of those compounds. 2. The most abundant disaccharides are sucrose, lactose, and maltose. a. What monosaccharides enter the structure of each disaccharide? b. What kind of reaction occurs to form a disaccharide? Give an example! c. Which of the above disaccharides give a positive Fehling test? d. What specific enzyme allows their hydrolysis? 3. Melibiose is a disaccharide with the following structure: a. Which are the monosaccharides incorporated in melibiose? b. What type of linkage (α or β) joins the two monosaccharides in melibiose? c. Circle the anomeric carbon and indicate whether the -OH group is α or β. d. Is melobiose a reducing sugar or a non-reducing sugar? 4. Glycogen: a. Describe its structure!  b. What color generates in the presence of iodine? c. Describe its solubility in water. d. In which tissues or organs is a significant amount of glycogen? 5. Name the dextrins that result during starch hydrolysis and the colours formed with iodine solution. 6. Write the condensed structural formula for: a. Palmitic acid (16C) b. Arachidonic acid (20CΔ5,8,11,14). What family of PUFA (ω3, ω6, ω7, ω9) it belongs? c. Linoleic acid (18CΔ9,12). What family of PUFA (ω3, ω6, ω7, ω9) it belongs? 1. What are the functions of starch and cellulose in plants? 2. What role does glycogen play in animals? 3. What are the structural characteristics of starch, glycogen and cellulose? 4. What is formed during the hydrolysis of starch and glycogen in acid catalysis? 5. Name the branched polysaccharides? 6. Identify the differences between amylopectin and amylose. 7. Identify the differences between cellulose and amylose. 8. Identify the differences between enzymatic hydrolysis and acid-catalysed hydrolysis of polysaccharides. 9. Why can't cellulose be digested by humans? 10. What are the dextrins resulting from the hydrolysis of starch and what colours are formed with the iodine solution? 11. The carbohydrate unit that makes up cellulose is: β-D-galactose b) lactose c) α-D-glucose d) β-D-glucose 12. Glycogen is a) fat b) protein c) carbohydrate d) enzyme 13. People cannot digest: a) cellulose b) sucrose c) glycogen d) amylose e) amylopetin 14. What is the carbohydrate in the muscle cell: a) amylose b) cellulose c) glycogen d) amylodextrins 15. Which substance has a branched structure: a) amylose b) glycogen c) cellulose d) amylase 16. What is the dark red carbohydrate with the iodine solution: a) starch b) glycogen c) cellulose d) maltose 17. The β-glycoside bond (1 → 4) exists in: a) amylodextrins b) acrodextrins c) cellodesxtrins d) amylose 18. In the animal body, glucose is stored in the form of a) maltose b) lactase c) glycogen d) sucrose e) starch 13. Which of the following is an example of monosaccharide? a) Galactose b) Sucrose c) Lactose d) Maltose 14. Which of the following is an example of disaccharide? a) Glucose b) Fructose c) Galactose d) Maltose 15. Which of the following carbohydrates is a triose? a) Glucose b) Ribose c) Ribulose d) Glyceraldehyde 16.Lactose is a disaccharide of which of the following sugar units? a) Glucose and fructose b) Glucose and galactose c) Glucose and sucrose d) Glucose and ribose 17.When all the monosaccharides in a polysaccharide are same type, such type of a polysaccharide is called a ___________ a) Glycogen b) Homoglycan c) Heteroglycan d) Oligosaccharide 18.In which of the following forms, glucose is stored in the liver? a) Glycogen b) Starch c) Dextrin d) Cellulose ENZYME 1. Heavy metal ions are poison compounds that bind to the –SH groups in the polypeptide chain and change the conformation of the whole enzyme, including the active site, altering the rate of the enzymatic reaction, but Km remains unchanged. Which type of inhibition does this represent? A competitive inhibition B Reversible inhibition C noncompetitive inhibition  2. Malonic acid is a compound that binds to the succinate dehydrogenase (SDH) to prevent the binding of fumaric acid to the enzyme and increases the Km, but the speed of the enzymatic reaction (Vmax) remains unchanged. Which type of inhibition does this represent? A competitive inhibition B Reversible inhibition C noncompetitive inhibition 3. Which of the following is true of enzymes? I. They increase the rate of reaction by stabilizing the transition state II. They raise activation energy to shift the equilibrium to favor the products III. They lower activation energy by altering the products of a reaction A I only B II +III C I + III D III only 4. In the first step of cascade reactions, the allosteric enzyme (E1) produces an intermediate A compound which is the E2 substrate. The last reaction results in an intermediate B compound, which is the substrate for E3. This reaction results in the final product of the chain. The final product achieves a certain concentration and can bind to E1 at the active site, stopping the chain reaction. This is an example: A. Allosteric inhibition B. Feedback inhibition C. Non-competitive inhibition D. Uncompetitive inhibition 5. Which of the following will be true regarding enzymes saturated with substrate? a. At saturating levels of substrate, a competitive inhibitor will affect the reaction rate more than a non-competitive inhibitor b. An enzyme with lower Km is more easily saturated than an enzyme with high Km c. Any excess substrate will shift the equilibrium towards the product end of the reaction d. Increasing the substrate concentration will appreciably increase the reaction rate 6. If the red curve indicates the normal reaction, which of the curve on the following graph is an example of noncompetitive inhibition. A (green curve) B (blue curve) C (pink curve) d. Not enough information was provided. 8. Which of the following enzyme classes catalyse reactions in which two molecules are covalently connected to each other? A. Ligase b. Kinase c. Isomerase d. Lyase 7. With regards to the Michaelis-Menten equation, a molecule that has the effect of increasing the Vmax of a reaction upon binding to an enzyme would be called what? a. Uncompetitive inhibitor b. Activator c. Non-competitive inhibitor d. Competitive inhibitor 9. What effect does extremely high pH have on enzymes? a. Denatures them b. Kills them c. Activate them 10. What does the term optimum mean for enzyme temperature? a. The lowest temperature at which the enzyme works b. The temperature which gives the highest enzyme activity c. The highest temperature before denaturing occurs 11. What type of enzymes break down carbohydrates? a. Protease b. Lipase c. Carbohydrase 12. What type of enzymes break down fats?  a. Lipase b. Carbohydrase c. Protease 13. What type of enzymes break down proteins? a. Lipase b. Protease c. Carbohydrase 14. What type of enzyme is amylase? a. Lipase b. Protease c. Carbohydrase 15. Which of these statements about enzymes is true? a. They work best at low pH b. Temperature does not affect their activity c. They can be reused 16. What is the correct calculation for the rate of an enzyme reaction? a. Amount of substrate used ÷ time taken b. Amount of substrate used + time taken c. Amount of substrate used × time taken 17. What is the general mechanism of an enzyme? a) It acts by reducing the activation energy b) It acts by increasing the activation energy c) It acts by decreasing the pH d) It acts by increasing the pH 18. Which one out of the following is not a NAD+ requiring enzyme? a) Lactate dehydrogenase b) Pyruvate dehydrogenase complex c) Maltate dehydrogenase d) Acyl co-A dehydrogenase 19. Which of the following enzyme catalyses the direct transfer and incorporation of O 2 into a substrate molecule is a) Reductase b) Oxidase c) Oxygenase d) Peroxidase 20. Loss of electrons can be termed as ______________ a) Metabolism b) Anabolism c) Oxidation d) Reduction 21. Which of the following enzyme is present in saliva? a) Hexokinase b) Alpha amylase c) Fructokinase d) Triose kinase 22. Hydrolysis of lactose yields ___________ a) D-galactose and D-glucose b) D-glucose and D-glucose c) D-galactose and D-fructose d) D-fructose and D-glucose 23. Hydrolysis of sucrose yields ___________ a) D-galactose and D-glucose b) D-glucose and D-glucose c) D-galactose and D-fructose d) D-fructose and D-glucose 24 Pyridoxal phosphate and its aminate form, pyridoxamine phosphate are tightly bound coenzymes of ___________ a) Amino transferases b) Glutaminase c) Glutamine synthase d) Glutamate dehydrogenase 25. What is the necessary coenzyme for transamination reactions? a) Pyridoxal phosphate b) Thiamine pyrophosphate c) NAD d) Coenzyme A Nucleotides & Nucleic Acids 1. Identify the purine base of nucleic acids in the following. a) Cytosine b) Thymine c) Uracil d) Adenine 2. Which of the following are not the components of RNA? a) Thymine b) Adenine c) Guanine d) Cytosine 3. What is the composition of nucleotide? a) a sugar + a phosphate b) a base + a sugar c) a base + a phosphate d) a base + a sugar + phosphate 4. What is the composition of nucleoside? a) a sugar + a phosphate b) a base + a sugar  c) a base + a phosphate d) a base + a sugar + phosphate 5. The sugar molecule in a nucleotide is ____________ a) Pentose b) Hexose c) Tetrose d) Triose 6. Building blocks of nucleic acids are ____________ a) Nucleotides b) Nucleosides c) Amino acids d) Histones 7. Number of hydrogen bonds between adenine and thymine? a) 1 b) 2 c) 3 d) 4 8. Number of hydrogen bonds between guanine and cytosine? a) 1 b) 2 c) 3 d) 4 9. Which ratio is constant for DNA? a) A + G / T + C b) A + T / G + C c) A + C / U + G d) A + U / G + C 10. Which of the following statements is not true about RNA? a) Does not have a double stranded structure b) Thymine is present c) Adenine is present d) The sugar contained in RNA is a ribose 11. Which of the following nucleotides is not present in RNA? a) AMP b) GMP c) CMP d) TMP 12. Which of the following nucleotides is not present in DNA? a) AMP b) GMP c) CMP d) UMP 13. The extra chromosomal, self-replicating, closed, double stranded and circular DNA molecule is generally termed as __________ a) Chromosome b) Plasmid c) Genomic DNA d) Bacteriophage LIPIDS 1. Which of the following is an essential fatty acid? a) Linolenic b) Palmitic c) Oleic d) Stearic 2. Which of the following is a polar derivative of cholesterol? a) Bile salt b) Oestrogen c) Vitamin D d) Progesterone 3. Which of the following is false about fatty acids? a) Melting point of fatty acids decreases with increase in degree of saturation b) Lipids in tissues that are subjected to cooling are more unsaturated c) Naturally occurring unsaturated long-chain fatty acids are nearly Trans- configuration d) The membrane lipids contain mostly unsaturated fatty acids 4. Which of the following fatty acid has 16 carbon atoms? a) Linolenic acid b) Oleic acid c) Palmitic acid d) Stearic acid 5. Out of the following, which is not an essential amino acid? a) Linoleic acid b) Linolenic acid c) Arachidic acid d) Arachidonic acid 6. Which of the following is a storage form of lipid? a) Glycolipid b) Phospholipid c) Sufolipid d) Triacyl glycerol 7. Out of the following, cholesterol does not serve as a precursor for which compounds? a) Vitamin D b) Sex hormones c) Bile salts d) red pigments 8. Which of the following vitamin is derived from cholesterol? a) A b) B c) C d) D 9. Which of the following is false about lipids? a) They are either strongly hydrophobic or amphipathic b) They are more soluble in water c) Extraction of lipids from tissues require organic solvents d) They are insoluble in water 10. Which of the following is not a phospholipase? a) A  b) C c) D d) K 11. Which of the following is choline containing lipid? a) Sphingomyelin b) Phosphatidylserine c) Phosphatidylglycerol d) Phosphatidylethanolamine 12. Maximum energy per gram on oxidation is yielded from ____________ a) Starch b) Fat c) Glycogen d) Protein PW EXERCISE 1. Circle the correct answer: a. Compounds containing at least three peptide bonds react with the biuret reagent forming a purple-colored complex b. Compounds containing at least ten peptide bonds react with the biuret reagent forming a purple-colored complex c. Compounds containing at least two peptide bonds react with the biuret reagent forming a purple-colored complex d. Compounds containing at least one peptide bond react with the biuret reagent forming a purple-colored complex e. Compounds containing at least four peptide bonds react with the biuret reagent forming a purple-colored complex 2. The Biuret method is based on the complexation of: a. Na+ to functional groups in the protein’s peptide bond b. Cu+ to functional groups in the protein’s peptide bond c. Cu2+ to functional groups in the protein’s peptide bond d. Co2+ to functional groups in the protein’s peptide bond e. Pb2+ to functional groups in the protein’s peptide bond 3. According to the Biuret method, the intensity of the color is directly proportional to: a. the amount of starch present in the sample b. the amount of cellobiose present in the sample a. the amount of cholesterol present in the sample b. the amount of protein present in the sample c. the amount of glucose present in the sample 4. The final product(s) of starch enzyme hydrolysis is a. Maltose and glucose b. Maltose and isomaltose c. Lactose d. Glucose e. Dextrin 5. During the starch hydrolysis, partial hydrolysis products of intermediate size are obtained, called: a. Maltose  b. Isomaltose c. Dextrins d. Glucose e. Cellobiose 6. The final product(s) of starch hydrolysis in the presence of hydrochloric acid are: a. Maltose and glucose b. Maltose and isomaltose c. Lactose d. Glucose e. Dextrin 7. Compare the enzyme hydrolysis of starch and starch hydrolysis in the presence of hydrochloric acid. Find at least one similarity and one difference between the reactions. 8. Which of the following does not act as a restriction enzyme? a) EcorI b) BamHI c) HindIII d) polydeoxyribonucleotide synthase 9. E.cor1 is a __________ a) DNA ligase enzyme b) Restriction endonuclease c) A vector used for insulin synthesis d) A plasmid used as a vector 10. Electrophoresis helps to separate ____________ a) DNA segments b) Cells from DNA c) Tissues d) RNA from DNA 11. The number of milligrams of KOH required to neutralize the free and combined fatty acid in one gram of a given fat is called __________ a) Saponification number b) Iodine number c) Acid number d) Polenske number