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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5337_Библиотеки_им_академика_М_И_Перельмана.pdf
Non-essential amino acids are produced from
transamination.
Characteristic features of deamination
Phospholipase is mandatory
No release of NH3, only the transfer of amino group.
Reversible process.
Deamination
It is a process of removal of the amine group in the form
of ammonia (NH3) for the synthesis of urea.
The carbon skeleton of amino acids is converted into
keto acids.
It may be oxidative or non-oxidative.
Liver mitochondria have glutamate dehydrogenase.
Glutamate dehydrogenase (GDH)— deaminates
glutamate into α-ketoglutarate and ammonia.
MULTIPLE CHOICE QUESTIONS
This process requires NAD+ as a coenzyme (allosteric
enzyme).
Its activation is done by ADP
Its inhibition is done by GTP
Site: Mostly in liver and kidney.
Deamination of cytosine to uracil
The main disadvantage of deamination is that produced
ammonia is too much toxic and causes hyperammonemia.
1. Which of the following is an example of nano
peptide?
A. Oxytocin B. Vasopressin
C. Bradykinin D. All of these
2. Oxidative deamination is the process in which an
amino acid converts into:
A. Group of an amino acid to a keto acid
B. A carboxylic acid + ammonia
C. A keto acid + ammonia
D. Group of an amino acid to a carboxylic acid
3. All of the below mentioned amino acids can
participate in hydrogen bonding, except one:
A. Serine B. Cysteine
C. Threonine D. Valine
4. The process of breakdown of amino acids to α-keto
acids is called:
A. Cisamination B. Amination
C. Transamination D. Racemisation
5. Glycogen is converted to glucose-1- phosphate by:
A. UDPG transferase B. Branching enzyme
C. Phosphorylase D. Phosphatase
6. Choose one correct statement about the genetic
code.
A. All genetic codons are identified by a given
tRNA which encodes different amino acids.
B. Genetic code is identical in all living organisms.
C. Various genetic codons may encode the same
amino acid.
D. None of the above
7. Transamination is catalysed by:
A. Transferases B. Aminotransferases
C. Hydrogenases D. Dehydrogenases
8. Intermediates of the following metabolic pathway
have not been used in the synthesis of amino
acids?
A. Glycolysis
B. Fatty acid biosynthesis
C. Citric acid cycle
D. Pentose phosphate pathway
9. The number of water-soluble molecules ketone
bodies include are:
A. 1 B. 2
C. 3 D. 4
10. Blood is an example of connective tissue, needed
for the transport of all absorbed products in the gut
after digestion processes. The function of blood
as described above is:
A. Body temperature regulatory function
B. Transport of hormones
C. Nutrition function
D. The maintenance of acid–base balance in the
organism
11. Which of these amino acids is/are essential for
infants?
A. Methionine
B. Arginine and histidine
C. Valine
D. Lysine and leucine
12. For determination of protein’s isoelectric point,
rst establish that a gel:
A. Having a denaturing detergent that distributes
negative charges over the protein’s surface
uniformly
B. Exhibits a stable pH gradient on the distribution
of ampholytes in an electric field
Section 3 Biochemistry
389388
C. neutralises all ionic groups on a protein through
titration
D. Both A and C
13. Name the amino acid which does not take part in
transamination during amino acid catabolism.
A. Proline B. Threonine
C. Lysine D. Serine
14. Name of amino acid which acts as a precursor of
niacin.
A. Tyrosine B. Threonine
C. Tryptophan D. Phenylalanine
15. Out of the following which one is a function of
aminoacyl-tRNA synthetases?
A. Identify specific t-RNA and specific amino acids
B. Catalyses the esterification of a specific cognate
amino acid
C. Both A and B
D. None of the above
16. A compound serving a link between citric acid
cycle and urea cycle is:
A. Malate B. Citrate
C. Succinate D. Fumarate
17. In deamination, an amino acid is changed into:
A. Aldol acid B. Keto acid
C. Hydrochloric acid D. Carboxylic acid
18. All amino acids are glucogenic as well as ketogenic
except one. Choose that amino acid from the
following.
A. Isoleucine B. Leucine
C. Tyrosine D. Phenylalanine
19. Which are two amino acids from following that
have sulphur atoms in their structure?
A. Cysteine and serine
B. Cysteine and threonine
C. Methionine and cysteine
D. Threonine and serine
20. _____________ cell in which synthesis of urea cycle
takes place.
A. Pancreatic
B. Hepatocyte
C. Bowman’s gland
D. Urinary epithelium
21. All of the amino acids that are found in proteins,
except for proline, contain a/an _____________
A. Amino group B. Carbonyl group
C. Carboxyl group D. Ester group
22. Amino acids are ampholytes in nature so that they
can function as either:
A. Acid or a base
B. Neutral molecule
C. A nonpolar molecule
D. A polar compound
23. In which form, the nitrogen is incorporated into
Section 3 Biochemistry
an amino acid?
A. Nitrite B. Glutamate
C. Nitrate D. Ammonium ion
24. A glutamic acid converted into γ-carboxyglutamate
at pH 7.0, will have what type of effect on the
overall charge of the protein containing it?
A. Have more negative charge
B. Have more positive charge
C. Same as previous
D. The final charge depends on the concentration
of salt
25. When a peptide bond is formed between two
amino acids? This shows a/an ______________
reaction.
A. Cleavage B. Condensation
C. Group transfer D. Isomerization
26. The peptide alanyl, glutamyl, glycyl, alanyl, and
leucine have:
A. A disulphide bridge
B. Four peptide bonds
C. Two carboxyl groups
D. Five free amino groups
27. Which one is an example of a peptide antibiotic?
A. Erythromycin B. Gramicidin
C. Ciprofloxacin D. Sulphonamide
28. In a conjugated protein, a prosthetic group is a:
A. Non-amino part
B. A non-identical subunit of a protein with many
identical subunits
C. A part of the protein that is not composed of
amino acids
D. Both A and C
29. In glycoproteins, prosthetic group is composed of:
A. Carbohydrates B. Nucleic acid
C. Lipids D. Iron
30. Which of the following is/are feature(s) of the
wobble hypothesis?
A. A naturally occurring tRNA which is found in
yeast that can read both arginine and lysine
codons
B. One tRNA able to recognize only one genetic
codon
C. Some tRNAs can identify genetic codons that
specify two dissimilar amino acids, if both are
non-polar
D. The wobble form only in the first base of the
anticodon
31. Choose one correct statement about ribosomes.
A. Only a large subunit of ribosomes contains
rRNA molecules, the small subunit does not
B. The RNA in ribosomes does not perform
catalytic role
C. There are two major subunits, each with
multiple proteins
D. All of the above
32. Tryptophan could be considered as a starting
material of:
A. Melatonin B. TSH
C. Melanin D. Norepinephrine
33. Transamination reaction in amino acid synthesis
is catalyzed by enzyme _________.
A. Nitric oxide synthase
B. Decarboxylase
C. Aminotransferase
D. Glutamate decarboxylase
34. In bacterial protein synthesis, ribosomal initiation
complex formation does not require ___________.
A. EF-Tu
B. Formyl methionyl tRNA
C. GTP
D. Initiation factor 2
35. The highest concentration of cystine can be found
in:
A. Melanin B. Keratin
C. Collagen D. Myosin
36. The elongation stage of protein synthesis of
bacteria does not require?
A. Aminoacyl-tRNAs B. EF-Tu
C. GTP D. IF-2
37. Which statement is correct about the elongation
phase of protein synthesis?
A. Six high-energy phosphoryl groups are
mandatory for the expedition of each peptide
bond formed
B. Amino acylated tRNAs are first bound to the P
site
C. Peptidyl transferase is an example of ribozyme
D. None of the above
38. Approximately how many NTPs must be
converted to NDPs to incorporate one amino acid
into a protein?
A. 0 B. 2
C. 4 D. 8
39. Which of the following peptides is cyclic in
nature?
A. Glutathione B. Gramicidin
C. Metencephalin D. Leuenkephalin
40. During electrophoresis of proteins, by adding
sodium dodecyl sulphate, we can perform which
of the following functions?
A. Isoelectric point determination of a protein
B. An enzyme’s specific activity determination
C. Preservation of a protein’s native structure and
its activity
D. Separation of proteins exclusively on the basis
of their molecular weight
41. Apolipoprotein A-I acts as:
A. Enzyme activator B. Ligand for receptor
C. Both A and B D. None of these
42. Which out of the following is not a brous protein?
A. Carbonic anhydrase B. Collagen
C. Fibrinogen D. Keratin
43. An example of polar amino acid is:
A. Alanine B. Leucine
C. Arginine D. Valine
44. A coagulated protein is:
A. Insoluble
B. Biologically inactive
C. Unfolded in structure
D. All of the above
45. Which structure of protein gives overall threedimensional folding of a polypeptide?
A. Primary structure
B. Secondary structure
C. Tertiary structure
D. Quaternary structure
46. One method used to prevent disulphide bond
interference with protein sequencing procedures
is:
A. Cleaving proteins with proteases that especially
identify disulphide bonds
B. Protecting the disulphide bridge against
spontaneous reduction
C. Reducing disulphide bridges and preventing
their re-formation by making further
modifications in -SH groups
D. Eliminate cystines groups from protein
sequences via proteolytic cleavage
47. Function of proteins is to:
A. Transport oxygen to haemoglobin
B. Catalyse biochemical reactions
C. Regulate reactions
D. All of the above
48. The term “proteome” has been used to describe:
A. Proteins domains
B. Protein structures regularities
C. The complement of proteins which are encoded
by an organism’s DNA
D. The structure of a protein-synthesising ribosome
49. In scurvy, which amino acid that is normally a part
of collagen is not synthesized?
A. Hydroxytryptophan
B. Hydroxytyrosine
C. Hydroxyalanine
D. Hydroxyproline
50. During the rst 6 months of lactation, the following
increment in energy intake is recommended?
A. 200 kcal/day B. 300 kcal/day
C. 550 kcal/day D. 1,000 kcal/day
51. Which of the following activity is related to amino
acid glycine?
A. Optically inactive
B. Hydrophilic, basic in nature
C. Hydrophobic, basic in nature
D. Hydrophilic, acidic in nature
Section 3 Biochemistry
391390
52. __________ amino acids of myoglobin, type of
globular protein, is highly likely to be localized
within the molecule?
A. Arginine B. Valine
C. Aspartic acid D. Lysine
53. In metabolic point of view, we can classied amino
acids as:
A. Glycogenic
B. Ketogenic
C. Glycogenic or ketogenic
D. All of the above
54. If the following enzyme activity increases in
the blood plasma 10 times or more— it indicates
myocardium damage.
A. Alkaline phosphatase
B. Aspartate transaminase
C. Glutamate dehydrogenase
D. All of the above
55. Choose a false statement about tRNA molecules.
A. A, C, G, and U are the only bases present in the
tRNA molecule
B. Has a single strand of RNA
C. Any tRNA will be able to accept only one
specific amino acid
D. The amino acid attachment is always occurring
to an A nucleotide at the 3’ end of the molecule.
56. The name of nucleoproteins that is found in sperm
is:
A. Prolamine B. Protamine
C. Albumin D. Globulin
57. Which of the following amino acids is considered
as both ketogenic and glucogenic?
A. Valine B. Tryptophan
C. Lysine D. None of these
58. In the total proteins, the percentage of albumin is
about:
A. 10–40 B. 30–50
C. 84–98 D. 50–70
59. A glucogenic amino acid is one that is degraded to:
A. Keto sugars
B. Either acetyl CoA or acetoacetyl CoA
C. Pyruvate or citric acid cycle intermediates
D. None of the above
60. Trypsinogen is converted to active trypsin by:
A. Enterokinase B. Bile salts
C. HCl D. Mg
++
61. If an average amino acid residue contributes 110
to the peptide molecular weight, what will be the
minimum length of the mRNA that encoded a
protein of molecular weight 50,000?
A. 138 nucleotides B. 550 nucleotides
C. 1,400 nucleotides D. 7,000 nucleotides
Section 3 Biochemistry
62. An –OH group is present in the side chain of:
A. Serine B. Arginine
C. Lysine D. Proline
63. The nature of anabolism reaction is:
A. Exergonic B. Endergonic
C. Spontaneous D. Non-spontaneous
64. Which of the following is correct with respect to
the amino acid composition of proteins?
A. Larger proteins have a more uniform distribution
of amino acids as compared to smaller proteins
B. Proteins have at least one each of the 20 different
standard amino acids
C. Those proteins which have different functions
generally vary significantly in their amino acid
composition
D. If two proteins have same molecular weight
then they must have the same amino acid
composition
65. The largest alpolipoprotein is:
A. Apo E B. Apo B-48
C. Apo B-100 D. Apo A-I
66. Which of the following is the best described
glucogenic amino acid?
A. Lysine B. Tryptophan
C. Valine D. None of these
67. Recognition of antigen is the function of:
A. Variable region of light chains
B. Variable regions of light and heavy chains
C. Constant region of heavy chains
D. Constant regions of light and heavy chains
68. Transamination is the process where:
A. Carboxyl group is transferred from amino acid
B. α-amino group is removed from amino acid
C. Polymerisation of amino acid takes place
D. None of the above
69. All the following statements about pepsin are
correct except:
A. It is smaller than pepsinogen
B. It is synthesised by the action of HCl on its
precursor
C. Its optimum pH is 1.0–2.0
D. It hydrolyses the C-terminal and N-terminal
peptide bonds of proteins
70. Glucose and fructose are examples of
A. Double sugars B. Disaccharides
C. Single sugars D. Polysaccharides
71. Glycine is not required for the formation of:
A. Taurocholic acid B. Creatine
C. Purines D. Pyrimidines
72. When gamma-aminobutyric acid binds to its
receptors (found in the brain), it increases the
permeability of cell membrane towards:
A. Cl– B. Na
+
C. K+ D. Ca++
73. Which of the following is a polymer?
A. Nucleic acid B. Fatty acid
C. Amino acid D. Glycerol
74. The term “salting in” refers to:
A. Changes in an amino acid’s isoelectric point.
B. Increasing the solubility of a protein in solution
by adding ions.
C. The ionisation of a strong acid
D. All of the above
75. Required for synthesis of alanine:
A. Pyruvate B. Glutamate
C. Pyridoxal phosphate D. All of the above
76. The procedure in which the three-dimensional
shape of a protein is disrupted is known as
A. Dehydration B. Denaturation
C. Deamination D. Hydrolysis
77. The α-helix of proteins is:
A. A pleated structure
B. Made periodic by disulphide bridges
C. A non-periodic structure
D. Stabilised by hydrogen bonds
78. Example of sulphur containing amino acid is:
A. Methionine B. Leucine
C. Valine D. Asparagine
79. Non-essential amino acids:
A. May not be formed in the body from essential
amino acids
B. It may be formed in the body from essential
amino acids
C. Have no role in the metabolism
D. It may be synthesised in the body in diseased
state
80. Michaelis-Menten equation is used to explain the
effect of substrate concentration on:
A. Carbohydrate B. Enzyme
C. Lipid D. Protein
81. Stability of parallel β-stranded protein structures
is less as compared to antiparallel β-stranded.
Reason behind that is:
A. Having less extended configuration as compared
to antiparallel strands
B. Do not held in sheets as well as antiparallel
strands
C. Having a smaller number of lateral hydrogen
bonds as compared to antiparallel strands
D. Having weaker hydrogen bonds laterally
between adjacent strands
82. A tripeptide functioning as an important reducing
agent in the tissues is:
A. Bradykinin B. Kallidin
C. Tyrocidin D. Glutathione
83. Name those living organisms which secrete
nitrogen in the form of urea?
A. Ureotelic B. Uricotelic
C. Ammonotelic D. Nitroso compounds
84. Milk is decient in:
A. Calcium B. Iron
C. Sodium D. Potassium
85. _____________ is an example of chromoprotein.
A. Haemoglobin B. Sturine
C. Nuclein D. All of these
86. The alpha-helix found in myoglobin can best be
described as:
A. Primary structure
B. Secondary structure
C. Tertiary structure
D. Motif structure
87. What is the reason behind chirality of an amino
acid regarding its α-carbon?
A. Has no charge
B. Is a type of carboxylic acid
C. It attached with four different chemical groups
D. It is found in L absolute configuration in
naturally occurring proteins
88. Bacterial ribosomes:
A. Formed polysomes by binding tightly to specific
regions of DNA
B. Has at least one ribozyme
C. Have special, different binding sites for each of
the 20 tRNAs
D. Both A and B
89. The milk protein infant’s stomach is digested
through:
A. Pepsin B. Trypsinogen
C. Chymotrypsin D. Rennin
90. Name the excretory enzyme of the blood plasma.
A. Alkaline phosphatase
B. Malate dehydrogenase
C. Glutamate dehydrogenase
D. Alanine transaminase
91. Active immunity can be produced by the
administration of:
A. Killed bacteria or viruses
B. Live attenuated bacteria or viruses
C. Toxoids
D. All of the above
92. Ceruloplasmin is:
A. α1-globulin B. α2-globulin
C. β-globulin D. None of these
93. A lipoprotein inversely related to the incidence of
coronary atherosclerosis is:
A. VLDL B. IDL
C. LDL D. HDL
94. Point out the most probable location of the plasma
proteins synthesis:
A. Kidneys B. Muscle tissue
C. Liver D. Lungs
95. The optically inactive amino acid is:
A. Glycine B. Serine
C. Threonine D. Valine
Section 3 Biochemistry
393392
96. Familial hypertriaacylglycerolemia is associated
with:
A. Over-production of VLDL
B. Increased LDL concentration
C. Increased HDL concentration
D. Slow clearance of chylomicrons
97. Point out the main blood plasma protein,
participating in the blood oncotic pressure
maintaining:
A. Globulin B. Lipoprotein
C. Haemoglobin D. Albumin
98. The end-product of protein digestion in GIT is:
A. Dipeptide B. Tripeptide
C. Polypeptide D. Amino acid
99. At physiological pH of 7.4, out of the following
amino acids may be referred to as a hydrophobic
amino acid?
A. Isoleucine B. Arginine
C. Aspartate D. Threonine
100. The main site of urea synthesis in mammals is:
A. Liver B. Skin
C. Intestine D. Kidney
101. ____________ is an example of amino acids which
is most likely to be altered in mutations that distort
collagen molecules.
A. Glycine B. Tyrosine
C. Tryptophan D. Uracil
102. Choose correct statement regarding peptide bond:
A. It is a carbon–carbon bond
B. It has cis hydrogen and oxygen groups
C. It is planar
D. It has rotational freedom
103. Name the blood plasma protein used as an
inhibitor of some proteolytic enzymes.
A. Albumin B. Immunoglobulin G
C. C-reactive protein D. Alpha1-antitrypsin
104. The movement of charged particles towards one
of the electrodes under the inuence of electrical
current is:
A. Gel filtration
B. Molecular sieving
C. Gas liquid chromatography
D. Electrophoresis
105. Which one is a rate limiting step in the biosynthesis
of catecholamines?
A. Decarboxylation of dihydroxyphenylalanine
B. Hydroxylation of phenylalanine
C. Hydroxylation of tyrosine
D. Oxidation of dopamine
106. Histidine is degraded to α-ketoglutarate and is
described as a:
Section 3 Biochemistry
A. Gluco amino acid
B. Glucogenic amino acid
C. Ketogenic amino acid
D. Keto-gluco amino acid
107. At isoelectric pH, an amino acid exists as:
A. Anion B. Cation
C. Zwitterion D. None of these
108. Apolipoproteins C-I, C-II and C-III are present in:
A. Chylomicrons B. VLDL
C. HDL D. All of these
109. A person with phenylketonuria cannot convert:
A. Phenylalanine to tyrosine
B. Phenylalanine to isoleucine
C. Phenol into ketones
D. Phenylalanine to lysine
110. An expopeptidase is:
A. Trypsin B. Chymotrypsin
C. Elastase D. Elastalase
111. A person with phenylketonuria is advised not to
consume which of the following products?
A. Glycine containing foods
B. Fat containing food
C. Glucose
D. Aspartame
112. Positive nitrogen balance is seen in:
A. Starvation
B. Wasting diseases
C. Growing age
D. Intestinal malabsorption
113. Which of the following amino acids is a limiting
amino acid in pulses?
A. Leucine B. Lysine
C. Methionine D. Glutamine
114. Choose the correct category for milk protein casein
out of the following:
A. Nucleoprotein B. Phosphoprotein
C. Lipoprotein D. Glycoprotein
115. Hydroxyproline rich in:
A. Prolamin B. Procollagen
C. Collagen D. Proinsulin
116. All the below mentioned proteins are metalloproteins except:
A. Carbonic anhydrase
B. Xanthine oxidase
C. Lactate dehydrogenase
D. Superoxide dismutase
117. Plasma proteins act as:
A. Buffers B. Immunoglobulins
C. Reserve proteins D. All of these
118. Gamma heavy chains are present in:
A. IgA B. IgG
C. IgM D. IgD
119. Two types of β-pleated sheets can be called:
A. Parallel and antiparallel
B. Left-handed and right-handed
C. Φ and ψ
D. Both Α and B
120. Choose a correct statement about hydrophobic
interactions from following:
A. They are responsible for the development of
amphipathic compound micelles in water
B. They do not take part in the structure of water-
soluble proteins.
C. Their bonding energies per mole are around
20–40 kilojoule
D. They involve the ability of water to denature
proteins.
121. MHC class I proteins, in conjunction with antigens
are recognised by:
A. Cytotoxic T cells B. Helper T cells
C. Suppressor T cells D. Memory T cells
122. (CH2O)n is the molecular formula for which type
of macromolecules?
A. Proteins B. Lipids
C. Carbohydrates D. Nucleic acid
123. CD3 complex and p56lck proteins are present in:
A. Cytotoxic T cells B. Helper T cells
C. Both A and B D. None of these
124. What is described as the “building blocks of
protein”?
A. Fibre B. Lipids
C. Amino acids D. Nutrients
125. In allergic diseases, the concentration which of
the following is increased in plasma?
A. IgA B. IgG
C. IgD D. IgE
126. The pH of an amino acid depends on:
A. Optical rotation B. Dissociation constant
C. Diffusion coefficient D. Chain length
127. In hypoparathyroidism
A. Calcium and inorganic phosphorus levels in the
plasma are low
B. Calcium and inorganic phosphorus levels in the
plasma are high
C. Calcium levels in the plasma are low, whereas
inorganic phosphorus levels are high
D. Calcium levels in the plasma are high, but
inorganic phosphorus levels are low
128. Which amino acids are most suitable with an αhelical structure of a protein?
A. Tryptophan B. Alanine
C. Leucine D. Proline
129. Out of the following which protein is rich in
cysteine amino acid?
A. Elastine B. Collagen
C. Fibrin D. Keratin
130. Which of the following is NOT true about a
globular protein?
A. Polypeptide chain in extended, long sheets
B. Polypeptide chains are folded in a spherical
shape
C. Contains several types of secondary structure
D. Typical for regulatory proteins
131. Serum amylase is increased in:
A. Acute parotitis B. Acute pancreatitis
C. Pancreatic cancer D. All of these
132. One of the following has a phenolic group:
A. Histidine B. Hydroxy lysine
C. Serotonin D. Hydroxy proline
133. Choose correct statement(s) for bacterial mRNA.
A. Translation starts near the end of the mRNA
which is synthesised last and this translation
initiates by the ribosome
B. An mRNA is never destroyed and passed on to
the daughter cells at the time of cell division
C. Ribosomes always move 5’–3’ direction during
polypeptide synthesis, along the mRNA
D. The genetic codon responsible for termination
is located in the mRNA near its 5’ end
134. In one of the following, the quality of the protein
synthesised is affected:
A. Diabetes mellitus
B. Gout
C. Multiple myeloma
D. Primaquine sensitivity
135. There are 5 proteins in a mixture as listed
below, which one is elute in second place while
performing size-exclusion chromatography?
A. Cytochrome C Mr = 13,000
B. Immunoglobulin G Mr = 145,000
C. Ribonuclease A Mr = 13,700
D. RNA polymerase Mr = 450,000
136. Transamination is a:
A. Irreversible process
B. Reversible process
C. Both A and B
D. None of the above
137. The rst step in 2D gel electrophoresis produces
a series of bands of a protein through isoelectric
focusing. In the next step, a strip of this gel is turned
90° then placed on another gel containing SDS, and an
electric current is again applied. In this step:
A. Proteins have similar isoelectric points further
separated on the basis of their molecular
weights
B. The individual bands can be stained separately
so that the isoelectric focus pattern can be
visualised
Section 3 Biochemistry
395394
C. The individual bands become visualised
due to their interaction with protein-specific
antibodies present in the second gel
D. All of the above
138. All of the following are ketogenic amino, acids
except:
A. Leucine B. Isoleucine
C. Phenylalanine D. Glycine
139. Tyrosine is degraded to acetoacetyl-CoA and
fumarate and is described as:
A. Glucogenic amino acid
B. Ketogenic amino acid
C. Ketogenic and glucogenic amino acid
D. Keto-gluco amino acid
140. Proteins are _____________ made of amino acid
_____________
A. Monomers; polymers
B. Polymers; polypeptides
C. Polymers; monomers
D. Monomers; molecules
141. The metabolism of all proteins ingested over and
above the essential requirements is called:
A. Exogenous metabolism
B. Endogenous metabolism
C. Both A and B
D. None of the above
142. Systematic name of lysine is:
A. Amino acetic acid
B. 2,6-diaminohexanoic acid
C. Amino succinic acid
D. 2-aminopropanoic acid
143. Which one is an example of an anticancer peptide?
A. Bleomycin
B. Methotrexate
C. Cytosine arabinoside
D. Dideoxy inosine
144. Platelets contain an enzyme that has an important
role in the clotting in blood. This enzyme is known
as:
A. Cholinesterase B. Transaminase
C. Decarboxylase D. Thrombokinase
145. A zwitterion is a:
A. Positive ion B. Negative ion
C. Both A and B D. None of these
146. Which would be the best to separate a protein that
binds strongly to its substrate?
A. Gel filtration
B. Affinity chromatography
C. Cation exchange
D. Cation or anion exchange
ANSWER KEY
1. D 2. C 3. D 4. C 5. C 6. C 7. B 8. B 9. C 10. C 11. B 12. B 13. D 14. C
15. C 16. D 17. B 18. B 19. C 20. B 21. A 22. A 23. D 24. A 25. B 26. B 27. B 28. D
29. A 30. D 31. C 32. A 33. A 34. A 35. B 36. D 37. C 38. C 39. B 40. D 41. C 42. A
43. C 44. D 45. D 46. C 47. D 48. C 49. D 50. C 51. A 52. B 53. D 54. B 55. A 56. B
57. B 58. D 59. C 60. A 61. C 62. A 63. B 64. C 65. C 66. C 67. B 68. B 69. D 70. C
71. A 72. A 73. A 74. B 75. D 76. B 77. C 78. A 79. B 80. B 81. D 82. D 83. A 84. B
85. A 86. B 87. C 88. B 89. D 90. A 91. D 92. A 93. D 94. C 95. A 96. A 97. D 98. D
99. A 100. A 101. A 102. B 103. D 104. D 105. C 106. B 107. C 108. D 109. A 110. D 111. D 112. C
113. C 114. B 115. C 116. C 117. D 118. B 119. A 120. A 121. A 122. C 123. D 124. C 125. D 126. B
127. C 128. B 129. D 130. A 131. B 132. C 133. C 134. C 135. B 136. B 137. A 138. D 139. C 140. C
141. A 142. B 143. A 144. D 145. C 146. B
Section 3 Biochemistry
4. Lipids
Lipids are organic compounds that are relatively insoluble
in water but soluble in organic solvents (alcohol, ether, etc.),
are associated to fatty acids that are used by living cells.
Lipids include large a vast group of compounds like oils,
fats, and fate like substances which are generally nonpolar/
hydrophobic in nature (soluble in organic solvents):
Cells store fats for the long-term and use them for energy
as needed by the body
They protect plants and animals from environment by
insulating them
Chief cellular storage form of energy
Role in cellular structure and biochemical functions
The liver has a central role in the control of various
aspects of lipid metabolism.
Functions of Lipids
Lipids serve a variety of roles.
They are the body’s concentrated fuel store
(triacylglycerols).
Lipids (phospholipids and cholesterol) are components of
membrane structure and control membrane permeability.
They are high in fat-soluble vitamins (A, D, E, and K).
Lipids are important metabolic regulators in cells (steroid
hormones and prostaglandins).
Lipids protect internal organs, act as insulators, and give the
body its shape and smooth surface.
Digestion
Digestion of triacylglycerols and phospholipids begins
when lipids mix with saliva in mouth during mastication.
Breakdown of triacylglycerols starts by the action of
lingual lipase, phospholipid act as an emulsifier.
Lingual lipase secreted by Ebner’s gland.
These actions make fats, easily accessible to the digestive
enzymes. The end of this process resulted in fats into
very small droplets and separate fats molecules from
the watery components.
In the stomach, enzymatic action continues gastric
lipase (secreted by chief cells) starts to breakdown
triacylglycerols into diglycerides and fatty acids.
Effective digestion of lipids is done by pancreatic juice
in the small intestine.
Emulsification: Breakdown of large fat molecules into
small tiny molecules it is done by bile salts. It decreases
surface tension and increases the surface area of fat
globules.
Lipids Classification
Simple lipid includes fats, oils, wax, derived from lipidlike substances, e.g. fatty acids (have long chains of
carboxylic acid in their structure). Generally, have an
even number of carbon atoms (C-14–20) in their structure.
The chain may have one or more double bonds or have
no double bond.
Complex lipid: It contains groups in addition to alcohol
and a fatty acid. Depending upon that extra groups
we can classify them into (a) phospholipids (b) non
phosphorylated.
Derived lipid: They derived from simple and compound
lipids by the process of hydrolysis.
Sphingophospholipids are present in large amount in
the brain and nervous tissue.
Ceramide: Sphingosine + fatty acid
Oils: A mixture of triglycerols that is liquid because it
contains a high proportion of unsaturated fatty acids.
Fats: A mixture of triglycerols that is solid because it
contains a high proportion of saturated fatty acids.
Bile salts formed from bile acids like chenodeoxycholic
acid.
Fatty Acids
Are simpler form of lipids
Amphipathic in nature
They may be saturated or unsaturated
Classification
z
Very long-chain
z
Long-chain
z
Medium-chain
z
Short-chain.
Pancreatic juice contents:
Pancreatic lipase
Phospholipase A2
Cholesterol esterase.
Gastrointestinal secretion
Secretin
Pancreozymin of CCK
Cholecystokinin of CCK
Hepatocrinin.
Ketone Bodies
When the breakdown of fatty acids occurs excessively
then ketone bodies are produced as metabolic products,
acetoacetate, acetone (true ketone bodies) and
β-hydroxybutyrate.
Section 3 Biochemistry
397396
Ketone bodies are utilised to get energy in the brain,
heart, skeletal muscle and kidney cells.
In peripheral tissues, acetoacetate and β-hydroxybutyrate
serve as important sources of energy.
Normal concentration:≤ 3 mg/100 ml
Disorder: Ketosis (excessive production of ketone bodies)
Ketonuria: The presence of ketone bodies in urine.
Significance of ketone bodies
Alternate option in place of glucose for energy needs
Ketone bodies produced when cellular energy deprived.
Ketogenesis
It is a process in which ketone bodies are generated.
Occurs in the liver.
Enzymes responsible for ketogenesis are found in
mitochondria so all synthetic reactions occur in
mitochondria.
Step I: Formation of acetoacetyl-CoA from the
condensation of two molecules of acetyl-CoA with the
help of thiolase
Step II: β-hydroxy β-methyl glutaryl-CoA also known as
HMG CoA is formed from the combination of one acetyl
CoA to acetoacetyl-CoA in presence of HMG-CoA synthase.
Step III: HMG-CoA lyase breakdown HMG-CoA
converted into acetoacetate and acetyl-CoA.
Step IV: β-hydroxybutyrate is produced.
Step V: Formation of acetone.
Regulation of ketogenesis
Occurs when carbohydrate is not available for energy
to tissues
Glucagon- increases ketogenesis
Insulin- inhibit ketogenesis
The ratio of glucagon/insulin—increased ketogenesis
Disorder of Lipid Metabolism
Chylomicron syndrome—an autosomal recessive
disorder occurs due to familial lipoprotein lipase
deficiency
Familial hypercholesterolaemia—in this condition
plasma cholesterol concentrations increased very high
from early childhood; it is independent of environmental
factors.
Familial combined hyperlipidaemia
Polygenic hypercholesterolaemia
Familial hypertriglyceridaemia
Type III hyperlipoproteinaemia
Steroids
Have cyclic steroid nucleus
List of various steroids which are present in biological
systems:
z
Cholesterol
z
Bile acids
z
Adrenocortical hormones
z
Cardiac glycosides
Section 3 Biochemistry
z
Vitamin D
z
Sex hormone
z
Alkaloids.
Cholesterol
Major steroid of animal cells.
In plasma, both free and stored cholesterol are transported
with lipoproteins.
LDL is responsible for the uptake of cholesterol and
cholesteryl ester into various cells.
HDL is responsible for the removal of free cholesterol
from tissues and transport to the liver, from here is
cholesterol removed from the body.
Structure of cholesterol
Cholesterol is a white crystalline, odourless, tasteless
wax-like substance found in plasma and all animal cells
mainly synthesised in liver cells.
Cholesterol has 4 rings fused together, all rings are
denoted by A,B,C,D.
The molecular formula of cholesterol is C27H46O.
Cholesterol has 2 methyl groups one methyl present on
C-19, it is attached to C-10, and the methyl group which
is present on C-18 is attached to C-13.
Functions of cholesterol
It is an essential constituent of the plasma membrane.
It is starting substance for bile salts.
Cholesterol is used as a precursor in the synthesis of
steroid hormone, adrenocortical hormones, testosterone
and progesterone, placental hormones vitamin D, cardiac
glycosides, Sitosterol and some AST alkaloids.
An important source of energy- triglycerides
Cholesterol is commonly distributed in nervous tissue.
Five steps of cholesterol biosynthesis:
Step I: Acetyl-CoA acts as a starting material for
cholesterol (27 carbon structure) synthesis. In the
first step, acetyl-CoAs are changed into 3-hydroxy-3-
methylglutaryl-CoA also known as (HMG-CoA).
Step II: 3-hydroxy-3-methylglutaryl-CoA, then converted
into mevalonate
Step III: By loss of CO2-activated isoprenoid units
(isopentenyl pyrophosphate) formed from mevalonate
by loss of CO
Step IV: Squalene is formed from the condensation of
six isoprenoid units.
Step V: Cyclisation reaction of squalene give rise to
lanosterol (tetracyclic product) and lanosterol converted
into cholesterol.
Regulation of cholesterol biosynthesis
Mevalonate and cholesterol inhibited the activity of
HMG-CoA reductase.
Phosphorylation reactions suppress the activity of the
reductase enzyme.
The immediate product of pathway— mevalonate
The ultimate end-product of the pathway—cholesterol
The amount of cholesterol taken up by the cells also
regulates the biosynthesis of cholesterol.
Glucagon hormone increases the formation of
phosphorylated form of HMG-CoA reductase, hence
slowing down the rate of cholesterol synthesis.
.
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