Biomolecules: Amino Acids and Peptides Lecture 4, Medical Biochemistry.
4) Biomolecules - Solutions
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1. On prolonged heating with HI, glucose given n-hexane which suggest that all the six carbon atoms in glucose are linked linearly. 2. Hydrolysis of sucrose brings about a changes in sign of rotation from dextro (+) to laevo (-) and hence, it is known as invert sugar. 3. (i) (ii) 4. Simplest carbohydrates that cannot be hydrolysed to smaller molecules are known as monosaccharides e.g., glucose,frucrose etc. 5. The sugars which reduce Tollen’s reagent, Fehling’s Solutions etc. are called reducing sugars. e.g., all monosaccharides, disaccharides except sucrose. 6. The reducing sugars have free aldehydeic or ketonic group. 7. Due to the presence of chiral or asymmetric carbon atoms and absence of plane of symmetry carbohydrates are generally optically active. 8. (i) Carbohydrates are used as storage molecules as starch in plants. (ii) Cell wall of bacteria and plants is made up of cellulose. 9. Monosaccharides Ribose, 2-deoxyribose, galacrose and fructose. Disaccharides Maltose and lactose. 10. 11. Amylose and amylopectin are the components of starch. Amylose is a long unbranched chain polymer of D-glucose while amylopecting is a branched chain polymer of D - glucose. 12. Liver and adipose tissue are the two fat storing tissues in human body. 13. Self (teacher) 14. Self (teacher) 15. Self (teacher) 16. The polymers of amino acids are known as polypeptides. 17. During denaturation, the protein molecule uncoils from an ordered and specific conformations into more random conformations. The primary structure does not change. 18. The structure of proteins is stabilized by intermolecular H-bonding between C == O of on amino acid residue and the N - H of the fourth amino acid residue in the chain. 19. When the egg is boiled, the proteins first undergo denaturation and then coagulation, and the water gets absorbed in the coagulated proteins. 20. Self (teacher) 21. Self (teacher) 22. Self (teacher) 23. Self (teacher) 24. Vitamin-B 12 25. Vitamin K is responsible for coagulations of blood. 26. Because vitamin C is soluble in water, it excreted readily in urine and hence cannot be stored in the body. 27. (i) Thymine is present in DNA. (ii) Uracil is present in RNA. 28. There are three types of RNA s (i) Ribosomal (r-RNA) (ii) Messenger (m-RNA) (iii) Transfer (t-RNA) 29. Thymine, 2-dcosy-D-ribose and phosphoric acid. 30. Common bases are adenine,guanine and cytosine. 31. Self (teacher) 32. Why must vitamin C be supplied regularly in the diet. 33. Self (teacher) 34. Self (teacher) 35. Self (teacher) 36. Self (teacher) 37. They are single carbohydrates, i.e., polyhydroxy aldehydes (aldoses) or polyhydroxy ketones (ketonses) which can not be broken into lower sugars upon hydrolysis. They have the general formula, C n H 2n O n , where n varies form 3 to 9 carbon atoms. The common monosaccharides are glucose, fructose and ribose, etc. 38. Sucrose, Generated From SaraNextGen App SaraNextGen.Com 3 4 2 3 4 2 CH ) CH ( CH HI CHO ) CHOH ( HOCH ¾® ¾ + D - a - a helix - a Fructose 6 12 6 e cos Glu 6 12 6 H 11 22 12 O H C O H C HOH O H C + ¾® ¾ + +
Transcript of 4) Biomolecules - Solutions
1. On prolonged heating with HI, glucose given n-hexanewhich suggest that all the six carbon atoms in glucoseare linked linearly.
2. Hydrolysis of sucrose brings about a changes in sign ofrotation from dextro (+) to laevo (-) and hence, it isknown as invert sugar.
3. (i)
(ii)
4. Simplest carbohydrates that cannot be hydrolysed tosmaller molecules are known as monosaccharides e.g.,glucose,frucrose etc.
5. The sugars which reduce Tollen’s reagent, Fehling’sSolutions etc. are called reducing sugars. e.g., allmonosaccharides, disaccharides except sucrose.
6. The reducing sugars have free aldehydeic or ketonicgroup.
7. Due to the presence of chiral or asymmetric carbonatoms and absence of plane of symmetrycarbohydrates are generally optically active.
8. (i) Carbohydrates are used as storage molecules asstarch in plants.(ii) Cell wall of bacteria and plants is made up ofcellulose.
9. Monosaccharides Ribose, 2-deoxyribose, galacrose andfructose.Disaccharides Maltose and lactose.
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11. Amylose and amylopectin are the components of starch.Amylose is a long unbranched chain polymer of
D-glucose while amylopecting is a branched chainpolymer of D - glucose.
12. Liver and adipose tissue are the two fat storing tissues inhuman body.
13. Self (teacher)14. Self (teacher)15. Self (teacher)16. The polymers of amino acids are known as polypeptides.17. During denaturation, the protein molecule uncoils from
an ordered and specific conformations into morerandom conformations. The primary structure does notchange.
18. The structure of proteins is stabilized byintermolecular H-bonding between C == O of on aminoacid residue and the N - H of the fourth amino acidresidue in the chain.
19. When the egg is boiled, the proteins first undergodenaturation and then coagulation, and the water getsabsorbed in the coagulated proteins.
20. Self (teacher)21. Self (teacher)22. Self (teacher)23. Self (teacher)24. Vitamin-B12
25. Vitamin K is responsible for coagulations of blood.26. Because vitamin C is soluble in water, it excreted readily
in urine and hence cannot be stored in the body.27. (i) Thymine is present in DNA.
(ii) Uracil is present in RNA.28. There are three types of RNAs
(i) Ribosomal (r-RNA)(ii) Messenger (m-RNA)(iii) Transfer (t-RNA)
29. Thymine, 2-dcosy-D-ribose and phosphoric acid.30. Common bases are adenine,guanine and cytosine.31. Self (teacher)32. Why must vitamin C be supplied regularly in the diet.33. Self (teacher)34. Self (teacher)35. Self (teacher)36. Self (teacher)37. They are single carbohydrates, i.e., polyhydroxy
aldehydes (aldoses) or polyhydroxy ketones (ketonses)which can not be broken into lower sugars uponhydrolysis. They have the general formula, CnH2nOn,where n varies form 3 to 9 carbon atoms. The commonmonosaccharides are glucose, fructose and ribose, etc.
38. Sucrose,
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39.Raffinose,
40. Equimolar mixture of
41. Starch and cellulose, (C6H10O5)n.42. Two to nine.43. Glycogen.44. The two monosaccharide units are joined together
through an oxide (ethereal) linkage formed by the lossof a molecule of H2O. Such a linkage between towmonosaccharide units through oxygen atom of amolecule of disaccharide is called glycosidic linkage. Forexample, a glucosidic linkage is present in sucrose,maltose, lactose, etc.
45. Carbohydrates are optically active as they providepolyhydroxy aldehydes or ketones on hydrolysis. Theirmolecules are chiral because of the presence of manyasymmetric carbon atoms.
46. Polysaccharides.47. Reducing - maltose or lactose ; Non-reducing-sucrose.48. Osazone formation (Glucosazone or Fructosazone).49. They are epimers.
50. Peptide bond .
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52. Amylases.53. Open chain structure of D-glucose could not explain the
following reactions.(i) Despite having the aldehyde group. glucose doesnot give Schiff’s test and 2,4-DNP test.(ii) Glucose does not react with sodium hydrogensulphide to from addition product.(iii) The penta-acetate of glucose does not reacts withhydroxyl amine showing the absence of free -CHO anytow reactions.
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76.
77. (i) Structural meterials for plant cell walls and (ii)Reserve food material.
78. Sucrose, maltose, lactose.79. Sugars : they are monosaccharides and disaccharides,
sweet in taste, soluble in water and are crystallinesolid.Non-sugars : They are polysaccharides which are notsweet in taste, insoluble in cold water and areamorphous powder.80. Reducing sugars reduces Tollen’s reagent to metallicsilver or Fehling’s solutions to red ppt. Of Cu2O orBenedict’s solutions. Examples are glucose, mannose,galactose, fructose, etc. (all monosaccharides) and alsodisaccharides such as maltose, lactose, etc. (exceptsucrose) are reducing sugars.
81. Amylose and amylopectin.82. Oxygen is replenished in out atmosphere through
photosynthesis in plants. During photosynthesis, the CO2
and air (produced as a result of combustion of fuels andbreathing of animals and human beings) is consumedand O2 is generated.
83. The first asymmetric carbon atom in cyclic compoundson which the configurations of H - and OH - groups aredifferent is called anomeric C - atom. For example,
glucose and glucose (they are anomers).
84. The process which involves the change in opticalrotation of either from of glucose (or fructose) inaqueous solutions to that of equilibrium mixture iscalled mutarotation.
85. The six membered cyclic structure of glucose (i.e., thering is formed between C1 and C5) is called pyranosestructure in analogy with pyran heterocyclic compoundor structure.
86. Essential amino acids : They can not be synthesised inthe body and must be obtained through diet are knownas essential amino acids, e.g., Valine.Non-essntial amino acids : They can be synthesised inthe body and are known as non-essential amino acids,e.g., Glycine.
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88. Most of the reactions in living system proceeds at veryhigh rate under physiological pH of 7.4 and temperatureof 310 K under one atmosphere. All these reaction arecatalysed by a group of biomolecules called enzymes.Thus, enzymes are biocatalyst and are highly specific intheir actions. Chemically, they are globular (watersoluble) proteins which have high molecular massranging from 15,000 to 1,000,000 g mol-1 . Thay aregenerally named after the class of compounds uponwhich they act, e.g., maltase.
89. Haemoglobin.90. The intermediate pH at which the amino acid shows no
tendency to migrate towards any of the electrodes andexists in the equilibrium when placed in an electric fieldis known as isoelectric points.
91. (i) Fibrous protein : Examples are : Keratin, Myosin.Fibroin, Collagen. Etc.(ii) Globular proteins : Examples are : Haemoglobin,Insulin, Enzymes, Antibodies, etc.
92. Intramolecular H-bonding, disulphide bridgine, dipolarinteractions (ionic) hydrophobic interactions.
93. Further folding, twisting and bending of secondarystructure of protein in the three dimensional space togive a different specific compact shape is called tertiarystructure of proteins.
94. Nucleoside is a combinations of base and sugar.Nucleosides are obtained when a nitrogenous base(purine or pyrimidine) is attached to C1 of a sugar (riboseor deoxyribose) by a linkage.
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95. Nucleotides are nucleosides phosphate. Nucleotides areobtained when mainly C5 - OH group of sugar (2’.3.’5’ inribose or 3’, 5’ in deoxyribose) or a nucleoside isesterifies with phosphoric acid.
96. Purine base are :(i) Adenine and(ii) Guanine, they are present in both RNA and DNA.Pyrimidine bases are :(i) Uracil and cytosine in RNA and(ii) thymine and cytosine in DNA.
97. ATP (Adenosine triphosphate).98. Water soluble vitamins are : B group (such as B1, B6, B12)
and C and water insoluble vitamins are : A, D,E and K.99.
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143. There are three types of RNA :(i) Messenger RNA (mRNA)(ii) Ribosomal RNA (r RNA)(iii) Transfer RNA (tRNA)
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154. Self (teacher)155. Self (teacher)156. Self (teacher)157. Self (teacher)158. In RNA, the sugar is D-ribose while in DNA, it is D-2-
deoxyribose, RNA is a single stranded structure whileDNA exist as double stranded (helical) structure.The common bases present in both RNA and DNA are :Adenine (A) Guanine (G) and Cytosine (C).
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173. The main structural differences between DNA andRNA are :(i) In DNA, sugar is deoxyribose while in RNA it is ribose.(ii) Pyrimidine base thymine is present in DNA only whileuracil is present in RNA only.(iii) DNA exists as double helix whereas RNA exists assingle strand.
174. On heating, the two strands of DNA eparate fromeach other. This is known as melting of DNA. Thetemperature at which the two strands of DNA separatecompletely is known melting temperature (Tm) of DNA.A DNA molecule with more number of GC base pairsthan AT base pairs has higher Tm than the one with lessnumber of GC base pairs than AT base pairs becausebetween G and C these are three hydrogen bonds ascompared to two hydrogen bonds between A and T.Thus, GC linkage is stronger than AT linkage.
175. The products of hydrolysis would be(i) (D)-2-deoxyribose(ii) Thymine(iii) Phosphoric acid (or phosphate).
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181. DNA is a double helix in which the two strands ofDNA are held by the hydrogen bonds between the baseson the two strands. Thymine (T) pairs with adeninethrough two hydrogen bonds and cytosine (C) pairs withguanine (G) through three hydrogen bonds.
So opposite each adenine (A) onone strand there is always a thymine on the other strandand opposite guanine, there is cytosine. This means thatthe two strands of DNA are complementary to eachother.182. 1. Inspite of the presence of an aldehydic group,glucose does not restore the pink colour of Schiff’sreagent and does not form addition products withsodium bisulphate and ammonia.2. Glucose pentaacetate does not react with hydroxylamine thus indicating the absence of aldehydic group.3. When dry hydrogen chloride gas is passed through asolution of glucose in methyl alcohol, a reaction takesplace and a mixture of methyland methyl is formed. Theseglucosides do not reduce Fehling’s solution and also donot react with HCN and hydroxylamine. This indicatesthat glucosides do not have free-CHO-group.
During the formation of glucosides only onemolecule of combines with a molecule ofglucose.
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186. (a) Glucose on reaction with hydrogen cyanide givescyanohydrins. Hydrolysis of the cyanohydrins andreduction of the acid obtained with hydrogen iodideyields heptanoic acid.
(b) (i)
When glucose is heated with concentrated solution ofsodium hydroxide it first turns yellow then brown andfinally resinifies.(ii) When glucose is treated with dilute sodiumhydroxide solution, it undergoes a reversibleisomerication resulting in the formation of a mixture ofD-glucose, D-fructose and D-mannose.
This reaction is known as Lobry de Bruyn vanEkenstein rearrangement.
It is because of this isomerication that D-fructosereduces Tollen’s reagent and Fehling’s solution inalkaline medium although it does contain any aldehydegroup.
187. Peptides are the products formed by thecondensation of two or more amino acids through theiramino and carboxylic groups involving elimination ofwater molecules. They may be classified as dipeptides,tripeptides and polypeptides, depending upon whetherthe number of amino acid molecules taking part incondensation is two, three or more than threerespectively. The linkage which unitesvarious amino acid units in a peptide molecule is calledpeptide linkage or peptide bond.
188. (i) Native protein is the protein found in a biologicalsystem with definite configuration and biologicalactivity.(ii) When a protein is subjected to some physical orchemical treatment which disrupts its higher structureswithout affecting its primary structure, the process iscalled denaturation. The denatured protein loses itsbiological activity. For example, boiling of an egg. Thedenaturation may be reversible or irreversible.(iii) Renaturation. In many cases a denatured proteinrecovers its physical and chemical properties andbiological activity when the disruptive agent is removed.This process, which is reverse of denaturation, is knownas renaturation.
189. The amino acids which cannot be synthesized in ourbody but must be supplied through our diet are knownas essential amino acids. There are about 10 essentialamino acids. For example, valine, leucine and lysine.The amino acids which can be synthesized in the humanbody are known as non-essential amino acids. There areabout 10 non-essential amino acids. For example,glycine, alalnine, serine.
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191. The N-glycosides of purine or pyrimidine bases withpentose sugars are known as nucleosides.
The pentose sugar present in RNA is ribose while in DNAis 2-deoxyribose.The nucleoside formed by combination of uracil and
ribose is present only in RNA.
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233. (i) Glucose decolouriese red colour of brominewater. It is oxididsed to gluconic acid. Fructose does notreacts with bromine water.Fructose gives a red colour with resorcinol and conc. HClwhile glucose does not give any colour.(b) Glucose on heating with Tollen’s reagent gives silivermirror while sucrose does not. Glucose given red ppt.With Fehling’s solutions while sucrose does not.(c) Glucose’s give positive tests with Tollen’s reagentand Fehling’s solutions while starch does not. Starch giveblue colour with iodine solutions while glucose does not.
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246. Self (teacher)247. Self (teacher)248. If three amino acids viz., glycine, alanine and
phenylalanine react together, how many possibletripeptides can be formed. Write down the structuresand names of each one. Also write their names usingthree and one letter abbreviations for each amino acid.
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249. (i) Glycine(ii) Cytosine and uracil(iii) Phenyl ketone urea(iv) Helix and sheet structures(v) Fructose(vi) Glucose is a reducing sugar while sucrose is anon-reducing sugar.
250. The hydrogen bonding between bases of the twostrands of DNA is highly specific. Thymine (T) pairs withadenine (A) through two hydrogen bonds and cytosine(C) pairs with guanine (G) through three hydrogen bonds,the above combination is energetically most favoured.The other combination and hence do not occur innormal DNA.Thus, complimentary base of adenine is thymine whilethat of guanine is cytosine. The hydrogen bondingbetween adenine and thymine and cytosine andguanine.
251. (a) (i) Vitamin C(ii) Vitamin D(iii) Vitamin H(iv) Beriberi(v) Scurvy.(b) Avitaminosis is the conditions caused by lack of morethan one vitamins in the human beings.
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