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Codons & Genetic code

Codons and genetic codes

Q. 1

A codon in the genetic code consists of:

 A

One molecule of charged-tRNA

 B

A Shine-Dalgarno sequence

 C

Three consecutive nucleotides

 D

Two complementary base pairs

Q. 1

A codon in the genetic code consists of:

 A

One molecule of charged-tRNA

 B

A Shine-Dalgarno sequence

 C

Three consecutive nucleotides

 D

Two complementary base pairs

Ans. C

Explanation:

A codon is a triplet sequence of bases. The tRNA molecule contains an anticodon.

The Shine-Dalgarno sequence is found in the 23S prokaryotic ribosomal RNA. A codon is on the same strand of DNA or mRNA.


Q. 2

Which of the following is the CORRECT explanation for ‘degeneracy of codon’?

 A

More than one codon for a single amino acid

 B

More than one amino acid for a single codon

 C

No punctuation in codons

 D

Termination of protein synthesis

Q. 2

Which of the following is the CORRECT explanation for ‘degeneracy of codon’?

 A

More than one codon for a single amino acid

 B

More than one amino acid for a single codon

 C

No punctuation in codons

 D

Termination of protein synthesis

Ans. A

Explanation:

Three of the 64 possible codons do not code for specific amino acids; these have been termed nonsense codons. These nonsense codons are utilized in the cell as termination signals; they specify where the polymerization of amino acids into a protein molecule is to stop. The remaining 61 codons code for the 20 naturally occurring amino acids. Thus, there is “degeneracy” in the genetic code—that is, multiple codons decode the same amino acid.

 
Ref: Weil P. (2011). Chapter 37. Protein Synthesis & the Genetic Code. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper’s Illustrated Biochemistry, 29e.

Q. 3

Amino acids not coded by triplet codon:

 A

Lysine

 B

Hydroxyproline

 C

Selenocysteine

 D

Pyrrolysine

Q. 3

Amino acids not coded by triplet codon:

 A

Lysine

 B

Hydroxyproline

 C

Selenocysteine

 D

Pyrrolysine

Ans. B

Explanation:

B i.e. Hydroxyproline

Quiz In Between


Q. 4

Stop codons are:

 A

UAA

 B

UAG

 C

UGA

 D

All

Q. 4

Stop codons are:

 A

UAA

 B

UAG

 C

UGA

 D

All

Ans. D

Explanation:

A, B, C i.e. UAA, UAG, UGA


Q. 5

If there are 4 nucleotides instead of 3 in codon, how many amino acids may be formed?

 A

16

 B

21

 C

256

 D

64

Q. 5

If there are 4 nucleotides instead of 3 in codon, how many amino acids may be formed?

 A

16

 B

21

 C

256

 D

64

Ans. C

Explanation:

C i.e. 256


Q. 6

Stop codon:

 A

UAG

 B

UCA

 C

UAC

 D

AUG

Q. 6

Stop codon:

 A

UAG

 B

UCA

 C

UAC

 D

AUG

Ans. A

Explanation:

A i.e. UAG

Quiz In Between


Q. 7

A codon consists of –

 A

One molecule of amono acyl-t RNA

 B

Two complementary base pairs

 C

3 consecutive nucleotide units

 D

4 individual nucleotides

Q. 7

A codon consists of –

 A

One molecule of amono acyl-t RNA

 B

Two complementary base pairs

 C

3 consecutive nucleotide units

 D

4 individual nucleotides

Ans. C

Explanation:

C i.e. 3 consecutive nucleotide units


Q. 8

Nonsense codons bring about-

 A

Elongation of polypeptide chain

 B

Pre-translational modificastion of protein

 C

Initiation of protein synthesis

 D

Termination of protein synthesis

Q. 8

Nonsense codons bring about-

 A

Elongation of polypeptide chain

 B

Pre-translational modificastion of protein

 C

Initiation of protein synthesis

 D

Termination of protein synthesis

Ans. D

Explanation:

D i.e. Termination of protein synthesis


Q. 9

Same aminoacid is coded by multiple codons d/t following :

 A

Degeneracy

 B

Frame-shift mutation

 C

Transcription

 D

Mutation

Q. 9

Same aminoacid is coded by multiple codons d/t following :

 A

Degeneracy

 B

Frame-shift mutation

 C

Transcription

 D

Mutation

Ans. A

Explanation:

A i.e. Degeneracy

Quiz In Between


Q. 10

The anticodon region is an important part of the

 A

r-RNA

 B

m-RNa

 C

t-RNa

 D

hn-RNa

Q. 10

The anticodon region is an important part of the

 A

r-RNA

 B

m-RNa

 C

t-RNa

 D

hn-RNa

Ans. C

Explanation:

C i.e. t – RNA


Q. 11

In transcription anticodon is seen in ‑

 A

t-RNA

 B

m-RNA

 C

r-RNA

 D

None

Q. 11

In transcription anticodon is seen in ‑

 A

t-RNA

 B

m-RNA

 C

r-RNA

 D

None

Ans. A

Explanation:

 A i.e. t – RNA


Q. 12

Amber codon refers to

 A

Mutant codon

 B

Stop codon

 C

Initiating codon

 D

Codon for more than one amino acids

Q. 12

Amber codon refers to

 A

Mutant codon

 B

Stop codon

 C

Initiating codon

 D

Codon for more than one amino acids

Ans. B

Explanation:

B i.e Stop Codon

Quiz In Between


Q. 13

A mutation in the codon which causes a change in the coded amino acid, is known as:

 A

Mitogenesis

 B

Somatic mutation

 C

Missense mutation

 D

Recombination

Q. 13

A mutation in the codon which causes a change in the coded amino acid, is known as:

 A

Mitogenesis

 B

Somatic mutation

 C

Missense mutation

 D

Recombination

Ans. C

Explanation:

C i.e. Missense mutation


Q. 14

A codon codes for a single amino acid. This characteristic is called ‑

 A

Non-overlapping

 B

Unambiguous

 C

Non-punctate

 D

Degeneracy

Q. 14

A codon codes for a single amino acid. This characteristic is called ‑

 A

Non-overlapping

 B

Unambiguous

 C

Non-punctate

 D

Degeneracy

Ans. B

Explanation:

Ans. is ‘b’ i.e., Unambiguous

Characteristics of genetic codes

Genetic codes have following characteristics ‑

1) Universal :- Each codon specifically codes for same amino acid in all species, e.g. UCA codes for serine and CCA codes for proline in all organisms. That means specificity of codon has been conserved from very early stages of evolution. Exception to the universality of genetic coder are found in human mitochondria, where the code :-

α UGA codes for tryptophan instead of serving as a stop codon.

AUA codes for methionine instead of isoleucine.

CUA codes for threonine instead of leucine.

LI AGA and AGG serve as stop codon instead of coding for arginine.

2) Unambiguous/Specific :- A particular codon always codes for the same amino acid. For example CCU always codes for proline and UGG always codes for tryptophan.

3)  Degeneracy/Redundancy :- A given amino acid may have more than one codon. For example, CCU, CCC, CCA and CCG all four codons code for proline. Therefore, there are 61 codons for 20 amino acids.

4) Stop or termination or nonsense codons:- Three of the 64 possible nucleotide triplets UAA (amber), UAG (Ochre) and UGA (opal) do not code for any amino acid. They are called nonsense codons that normally signal termination of polypeptide chains. Thus, though there are 64 possible triplet codons, only 61 codes for 20 amino acids (as remaining three are non-sense codons).

5) Non overlapping and nonpuntate (Comma less) :- During translation, the code is read sequentially, without spacer bases, from a fixed starting point, as a continuous sequence of bases, taken 3 at a time, e.g. AUGCUA GACUUU is read as AUG/CUA/GAC/UUU without “ponctation” (coma) between codons.


Q. 15

Multiple codons code for same amino acid ‑

 A

Ambiguity

 B

Wobble phenomenon

 C

Degeneracy

 D

Mutation

Q. 15

Multiple codons code for same amino acid ‑

 A

Ambiguity

 B

Wobble phenomenon

 C

Degeneracy

 D

Mutation

Ans. C

Explanation:

Quiz In Between


Q. 16

RNA which contains codon for speicific amino acid ‑

 A

tRNA

 B

rRNA

 C

mRNA

 D

None

Q. 16

RNA which contains codon for speicific amino acid ‑

 A

tRNA

 B

rRNA

 C

mRNA

 D

None

Ans. C

Explanation:

Ans. is ‘c’ i.e., m RNA

The m RNA carries genetic information in the form of codons.

  • Codons are a group of three adjacent nucleotides that code for the amino acids of protein.
  • Each mRNA molecule is a transcript of antisense or template strand of a particular gene.
  • Its nucleotide sequence is complementary to that of antisense or template strand of the gene, i.e. adenine for thyamine, guanine for cytosine, uracil for adenine (as RNA does not contain thymine) and cytosine for guanine.
  • For example, if antisense strand of DNA has a gene with sequence 5′-TTACGTAC-3′, its complementary RNA transcript will be 5 ‘-GUACGUAA-3’.

Q. 17

Total mubers of codons are ‑

 A

60

 B

61

 C

62

 D

64

Q. 17

Total mubers of codons are ‑

 A

60

 B

61

 C

62

 D

64

Ans. D

Explanation:

Ans. is ‘d’ i.e., 64 

  • The information needed to direct the synthesis of protein is contained in the mRNA in the form of a genetic code, which inturn is transcribed from template strand of DNA and is therefore complementary to it.
  • The genetic code is the system of nucleotide sequences of mRNA that determines the sequence of amino acids in protein.
  • Codon is a sequence of three adjacent bases that corresponds to one amino acid.
  • There are 64 possible codom sequences.
  • Because four nucleotide bases A,G, C and U are used to produce the three base codons, there are therefore 64(43) possible codon sequences.

Q. 18

Which is non-sense codon –

 A

UGG

 B

AUG

 C

UGA

 D

CCA

Q. 18

Which is non-sense codon –

 A

UGG

 B

AUG

 C

UGA

 D

CCA

Ans. C

Explanation:

Ans. is ‘c’ i.e., UGA 

Stop codons or nonsense codons or termination codons

  • Three of the 64 possible nucleotide triplets UAA (amber), UAG (Ochre) and UGA (opal) do not code for any amino acid.
  • They are called nonsense codons that normally signal termination of polypeptide chains.
  • Thus, though there are 64 possible triplet codons, only 61 codes for 20 amino acids (as remaining three are non­sense codons).

Quiz In Between



Codons & Genetic code

Codons & Genetic code


CODON &GENETIC CODE

  • Codon- is a sequence of three adjacent bases that corresponds to one of the amino acid.
  • There are 64 possible codon of sequence.
  • Four nucleotide bases A, G, C and U.
  • If 4 bases 44 = 256 amino acids.
  • Methionine has only 1 codon.
  • Genetic code is the system of nucleotide sequences of mRNA that determines the sequence of amino acids in protein.
  • Characteristics of genetic codes-

1.  Triplet codon– each amino acid has triplet sequence.

2. Degenerate (Redundant)

  • A given amino acid may have more than one codon.
  • Degeneracy of the codon lies in the 3rd base.

3. Universal– a specific codon represent a specific amino acid in all the  species.

  • Genetic coder are found in human mitochondria, code is-
  1. AUA codes for methionine instead of isoleucine.
  2. AGA and AGG serve as as stop codon.
  3. UGA also codes for Selenocysteine, a mechanism called translational recording.

4.Unambiguous/ Specific– a particular codon always codes for the same amino acid

5. Non overlapping and nonpuntate (comma less)– reading of genetic code does not involve overlapping sequence.

  • E.g.- AUGCUA GACUUU reads as AUG/CUA/GAC/UUU without punctuation (comma) between codons.

6. Stop or termination or nonsense codons

  • The three nucleotide triplets do not code for any amino acid are- UAA (amber), UAG (ochre), UGA (opal) called as nonsense codons that normally signal termination of polypeptide chains.
  • Wobble Hypothesis- states that a single tRNA can recognise more than one codon.
  • Base pairing of 3rd base of codon (at 31 end) often fails to recognize the specific complementary base codon (at 51 end at tRNA)
  • Wobble explains the degeneracy of genetic code.
  • A minimum of 31 tRNAs are required to translate all 61 different codons for the amino acids.
  • Gene- is the smallest functional unit of genome. 2 types
  1. Inducible gene
  2. Constitutive gene (housekeeping genes)- genes whose expression is not regulated
  • Cistron- is the smallest unit of genetic expression.
  • The codons that designate the same amino acid are called synonyms.

 Exam Important

  • Information for synthesis of protein is contained in the mRNA.
  • Thymine is not involved in codons.
  • 64 (43) possible codon sequences.
  • tRNA acts as the adapter molecule between the codon and specific amino acid.
  • UUU is the codon for phenylalanine.
  • Degeneracy of the codon lies in the 3rd base.
  • Amino acid with maximum number codons are Serine, Arginine, Leucine.
  • Monocistronic- e.g. eukaryotic mRNA
  • Polycistronic- e.g. Prokaryotic mRNA
Don’t Forget to Solve all the previous Year Question asked on Codons & Genetic code

Module Below Start Quiz

Phospholipids

Phopholipids

Q. 1 Glycerol  is  the  backbone  of  all  of  the following phospholipids EXCEPT
 A Phosphatidylethanolamine
 B Cardiolipin
 C Phosphatidylcholine
 D Sphingomyelin
Q. 1 Glycerol  is  the  backbone  of  all  of  the following phospholipids EXCEPT
 A Phosphatidylethanolamine
 B Cardiolipin
 C Phosphatidylcholine
 D Sphingomyelin
Ans. D

Explanation:

Sphingomyelin   = phosphorylcholine + ceramide

Ceramide            = fatty acid + sphingosine

Sphingosine        = condensing palmitic acid with a decarboxylated   serine   and   then   reducing   the product

Glycerol  never  is  involved  in  the  structure  of sphingomyelin. Phosphatidylethanolamine, cardiolipin, phosphatidylcholine, and phosphatidylinositol are synthesized using phosphatidic acid as the basic building block  Phosphatic acid  is  diacylglycerol with a phosphate  ester on carbon three; therefore, glycerol is the backbone of all of these compounds. FAQ Sphingomyelin :-

–  Membranous myelin sheath that surrounds nerve cell axons.

–    It is the only sphingolipid NOT derived from Glycerol.

–       Associated  with  increased  accumulation  in Niemann-Pick  Disease.


Q. 2

Function of phospholipid in cell membrance is:

 A

Cell to cell variation

 B

Transduction of Signals

 C

Transmembrane preparation of protein

 D

DNA replication

Q. 2

Function of phospholipid in cell membrance is:

 A

Cell to cell variation

 B

Transduction of Signals

 C

Transmembrane preparation of protein

 D

DNA replication

Ans. B

Explanation:

B i.e. Transduction of signals


Q. 3

Which of the following phospholipid has antigenic acitivity ‑

 A

Plasmalogen

 B

Cardiolipin

 C

Phosphatidylcholine

 D

Sphingomyelin

Q. 3

Which of the following phospholipid has antigenic acitivity ‑

 A

Plasmalogen

 B

Cardiolipin

 C

Phosphatidylcholine

 D

Sphingomyelin

Ans. B

Explanation:

Ans. is ‘b i.e., Cardiolipin 

  • Cardiolipin is the only human glycerophospholipid that possess antigenic properties”
  • Cardiolipin is the major lipid of inner mitochondrial membrane.

Q. 4

Which of the following is not a phospholipid ‑

 A

Lecithine

 B

Plasmalogen

 C

Cardiolipin

 D

Ganglioside

Q. 4

Which of the following is not a phospholipid ‑

 A

Lecithine

 B

Plasmalogen

 C

Cardiolipin

 D

Ganglioside

Ans. D

Explanation:

Ans. is ‘d’ i.e., Ganglioside

Phospholipids are :

  1. Glycerophospholipids (glycerol containing) :- Phosphatidylcholine (lecithin), phosphatidylethanolamine (cephaline), phosphatidylserine, phosphatidylinositol, plasmalogens, lysophospholipids, cardiolipin.
  2. Sphingophospholipids (sphingosine containing) :- Sphingomyeline

Quiz In Between



Phospholipids

PHOSPHOLIPIDS


PHOSPHOLIPIDS

  • Phospholipid= Fatty acid+ Glycerol+Phosphoric acid+ nitrogenous base
  • Function is transduction of signals in cell membrane.

2 types-

  1. Glycerophospholipids
  2. Sphingophospholipids

1. Glycerophospholipids (phosphoglycerides)- that contains glycerol as alcohol. They are-

a) Phosphatidylcholine (lecithin)

  • Most abundant phospholipids in cell membrane.
  • Dipalmitoyl lecithin in lungs
  • Insufficient production of Dipalmitoyl lecithin- acute pulmonary distress syndrome in premature infants.

b) Phosphatidylethanolamine (Cephalin)- contains ethanolamine.

c) Plasmogens- platelet activating factor

d) Cardiolipin (Diphosphatidylglycerol) – is a major lipid of inner mitochondrial membrane.

  • It has antigenic properties (only humans).
  • Deficiency causes- Barth syndrome.

Exam Important

1.Glycerophospholipids (phosphoglycerides)- that contains glycerol as alcohol. They are-

a) Phosphatidylcholine (lecithin)

  • Most abundant phospholipids in cell membrane.
  • Dipalmitoyl lecithin in lungs
  • Insufficient production of Dipalmitoyl lecithin- acute pulmonary distress syndrome in premature infants.

 b) Phosphatidylethanolamine (Cephalin)- contains ethanolamine.

c) Plasmogens- platelet activating factor

d) Cardiolipin (Diphosphatidylglycerol) – is a major lipid of inner mitochondrial membrane.

  • It has antigenic properties (only humans).
  • Deficiency causes- Barth syndrome.
Don’t Forget to Solve all the previous Year Question asked on PHOSPHOLIPIDS

Module Below Start Quiz

Severe Combined Immunodeficiency (Scid)

Severe combined immunodeficiency

Q. 1

SCID which is true –

 A

Adenosine deaminase deficiency

 B

Decreased circulating lymphocytes

 C

NADPH oxidase deficiency

 D

CI esterase dificiency

Q. 1

SCID which is true –

 A

Adenosine deaminase deficiency

 B

Decreased circulating lymphocytes

 C

NADPH oxidase deficiency

 D

CI esterase dificiency

Ans. A

Explanation:

Ans. is ‘a’ i.e., Adenosine deaminase deficiency


Q. 2

Which of the following about SCID is false ‑

 A

Failure of descent of thymus

 B

Peyer’s patches are present and normal

 C

X-linked type is the most common

 D

Gene therapy can be used

Q. 2

Which of the following about SCID is false ‑

 A

Failure of descent of thymus

 B

Peyer’s patches are present and normal

 C

X-linked type is the most common

 D

Gene therapy can be used

Ans. B

Explanation:

Ans. is ‘b’ i.e., Peyer’s patches are present and normal

Quiz In Between



Severe Combined Immunodeficiency (Scid)

SEVERE COMBINED IMMUNODEFICIENCY (SCID)


SEVERE COMBINED IMMUNODEFICIENCY (SCID)

It is caused due to –

  • Deficiency of Adenosine Deaminase (ADA)
  • Adenosine accumulates and converted to ribonucleotides and deoxyribonucleotides (dATP).
  • dATP inhibits ribonucleotidereductase which decreases production of deoxyribose nucleotides.
  • There is decrease in T and B cells leading to immunodeficiency.
  • X Linked Type is the Most Common Pattern of Inheritance

Clinical features-

  •  Chronic diarrhea
  •   failure to thrive.

Treatment-

  • Gene therapy is the first order to be treated.
  • Enzyme Replacement Therapy with Polyethyleneglycol modified bovine adenosine deaminase (PEGADA).

Exam Important

  • There is a decrease in T and B cells.
  • Adenosine accumulation is seen in SCID.
  • DNA synthesis decreases.
  • X Linked Pattren of Inheritance is most common
Don’t Forget to Solve all the previous Year Question asked on SEVERE COMBINED IMMUNODEFICIENCY (SCID)

Module Below Start Quiz

Lesch- Nyhan Syndrome

LESCH-NYHAN SYNDROME

Q. 1

Lesch Nyhan syndrome is associated with deficiency of?

 A

HPRT(partial)

 B

HPRT(total)

 C

PRPP(partial)

 D

PRPP(total)

Q. 1

Lesch Nyhan syndrome is associated with deficiency of?

 A

HPRT(partial)

 B

HPRT(total)

 C

PRPP(partial)

 D

PRPP(total)

Ans. B

Explanation:

A complete deficiency of HPRT, the Lesch-Nyhan syndrome, is characterized by hyperuricemia, self-mutilative behavior, choreoathetosis, spasticity, and mental retardation. A partial deficiency of HPRT, the Kelley-Seegmiller syndrome, is associated with hyperuricemia but no central nervous system manifestations. In both disorders, the hyperuricemia results from urate overproduction and can cause uric acid crystalluria, nephrolithiasis, obstructive uropathy, and gouty arthritis. Early diagnosis and appropriate therapy with allopurinol can prevent or eliminate all the problems attributable to hyperuricemia but have no effect on the behavioral or neurologic abnormalities.

Ref: Burns C.M., Wortmann R.L. (2012). Chapter 359. Disorders of Purine and Pyrimidine Metabolism. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison’s Principles of Internal Medicine, 18e.

 


Q. 2

Lesch Nyhan syndrome is due to deficiency of:

 A

Hypoxanthine phosphoribosyl transferase

 B

Xanthine oxidase

 C

Purine phosphorylase

 D

Adenosine deaminase

Q. 2

Lesch Nyhan syndrome is due to deficiency of:

 A

Hypoxanthine phosphoribosyl transferase

 B

Xanthine oxidase

 C

Purine phosphorylase

 D

Adenosine deaminase

Ans. A

Explanation:

A i.e. Hypoxanthine phosphoribosyl transferase

Quiz In Between



Metabolism of Triacylglycerol

Metabolism of triacylglycerides

Q. 1

In the liver cells, triglycerides are formed primarily in the following organelle:

 A

Rough endoplasmic reticulum

 B

Smooth endoplasmic reticulum

 C

Golgi apparatus

 D

Ribosomes

Q. 1

In the liver cells, triglycerides are formed primarily in the following organelle:

 A

Rough endoplasmic reticulum

 B

Smooth endoplasmic reticulum

 C

Golgi apparatus

 D

Ribosomes

Ans. B

Explanation:

Synthesis of triacylglycerols mainly takes place on the smooth endoplasmic reticulum of the liver but can also be generated in adipose cells.

 
Regardless of the location of synthesis, the starting molecule is glycerol-3-phosphate produced in liver from glycerol stores or in adipose cells from dihydroxyacetone phosphate, the product of the fourth step of glycolysis.
 
Ref: Janson L.W., Tischler M.E. (2012). Chapter 7. Lipid Metabolism. In L.W. Janson, M.E. Tischler (Eds), The Big Picture: Medical Biochemistry.

 


Q. 2

A 32-year-old woman who has been on oral contraceptive pills for 5 years, developed symptoms of depression, irritability, nervousness and mental confusion. Her hemoglobin level was 8g/dl. Biochemical investigations revealed that she was excreting highly elevated concentrations of xanthurenic acid in urine. She also showed high levels of triglycerides and cholesterol in serum. All of the above are most probably related to a vitamin B6 deficiency caused by prolonged oral contraceptive use except:

 A

Increased urinary xanthurenic acid excretion

 B

Neurological symptoms by decreased synthesis of biogenic amines

 C

Decreased hemoglobin level

 D

Increased triglyceride and cholesterol levels

Q. 2

A 32-year-old woman who has been on oral contraceptive pills for 5 years, developed symptoms of depression, irritability, nervousness and mental confusion. Her hemoglobin level was 8g/dl. Biochemical investigations revealed that she was excreting highly elevated concentrations of xanthurenic acid in urine. She also showed high levels of triglycerides and cholesterol in serum. All of the above are most probably related to a vitamin B6 deficiency caused by prolonged oral contraceptive use except:

 A

Increased urinary xanthurenic acid excretion

 B

Neurological symptoms by decreased synthesis of biogenic amines

 C

Decreased hemoglobin level

 D

Increased triglyceride and cholesterol levels

Ans. D

Explanation:

Vit B6 deficiency will not cause increased triglyceride and cholesterol levels in serum.

It is best attributed to the metabolic effects of steroidal contraceptives.

Pyridoxal phosphate is a coenzyme involved in the metabolism of protein, carbohydrates and fat. In protein metabolism, Vit B6 participates in the decarboxylation of amino acids and the conversion of tryptophan to niacin or serotonin.

Ref: Harper’s Biochemistry Pages 258, 491 ; Textbook of Therapeutics: Drug and Disease Management By Richard A. Helms, David J. Quan, 2006, Page 737 ; Psychology and Schizophrenia By Janet E. Pletson, 2007, Page 110


Q. 3

Not true about eukaryotic gene:

 A

Polycistronic mRNA

 B

Noncoding intron

 C

Contain nuclear gene & pseudogene

 D

Modification of mRNA before transportation from nucleus

Q. 3

Not true about eukaryotic gene:

 A

Polycistronic mRNA

 B

Noncoding intron

 C

Contain nuclear gene & pseudogene

 D

Modification of mRNA before transportation from nucleus

Ans. A

Explanation:

A i.e. Polycistronic mRNA

Quiz In Between


Q. 4

Triglycerides synthesis is increased by:    

 A

Growth hormone

 B

Insulin

 C

Cortisol

 D

Glucagons

Q. 4

Triglycerides synthesis is increased by:    

 A

Growth hormone

 B

Insulin

 C

Cortisol

 D

Glucagons

Ans. B

Explanation:

Q. 5

Where is the triglycerides stored in the human body?

 A

Nerve cells

 B

Adipose tissues

 C

Both 

 D

None

Q. 5

Where is the triglycerides stored in the human body?

 A

Nerve cells

 B

Adipose tissues

 C

Both 

 D

None

Ans. B

Explanation:

Triglycerides are stored in adipose tissues.

Quiz In Between



Metabolism of Triacylglycerol

Metabolism of Triacylglycerol


METABOLISM OF TRIACYLGLYCEROL

  • Triacylglycerol contains one molecule of glycerol and 3 molecules of fatty acid.
  • Occurs in liver, adipose tissue, intestinal mucosal cells.
  • Organelle- endoplasmic reticulum.

3 steps-

  1. Fatty acid to acyl CoA by Acyl CoA synthase (thiokinase)
  2. Glycerol to glycerol-3-phosphate (formed from glucose-3- phosphate dehydrogenase in adipose tissue) by glucose kinase.
  3. Phosphatidate undergoes hydrolytic dephosphorylation which is esterified to form triacylglycerol.
  • In adipose tissues- insulin enhances triacylglycerol synthesis.
  • In Diabetes, glycerol-3-phosphate is hampered leading to decrease triglyceride synthesis.
  • Triglyceride is the major lipid for adipose tissues.

Triacylglycerol hydrolysis (lipolysis)-

  • Triacylglycerol (stored fat) is degraded.
  • Enzyme- hormone sensitive lipase.
  • Lipolysis refers to hydrolysis of triacylglycerol in adipose tissues.

Regulation of lipolysis-

  1. Hormone sensitive lipase activated by-
  2. Epinephrine
  3. Catecholamines
  4. Thyroid hormones
  5. Growth hormone
  6. ACTH
  7. Glucocorticoids

Hormone sensitive lipase inactivated by-

  1. Insulin
  2. Prostaglandin

Exam Important

  • Triacylglycerol contains one molecule of glycerol and 3 molecules of fatty acid.
  • Occurs in liver, adipose tissue, intestinal mucosal cells.
  • Organelle- endoplasmic reticulum.

3 steps-

  1. Fatty acid to acyl CoA by Acyl CoA synthase (thiokinase)
  2. Glycerol to glycerol-3-phosphate (formed from glucose-3- phosphate dehydrogenase in adipose tissue) by glucose kinase.
  3. Phosphatidate undergoes hydrolytic dephosphorylation which is esterified to form triacylglycerol.
  • In adipose tissues- insulin enhances triacylglycerol synthesis.
  • In Diabetes, glycerol-3-phosphate is hampered leading to decrease triglyceride synthesis.
  • Triglyceride is the major lipid for adipose tissues.
  • Triacylglycerol hydrolysis (lipolysis)-
  • Triacylglycerol (stored fat) is degraded.
  • Enzyme- hormone sensitive lipase.
  • Lipolysis refers to hydrolysis of triacylglycerol in adipose tissues.

Regulation of lipolysis-

Hormone sensitive lipase activated by-

  1. Epinephrine
  2. Catecholamines
  3. Thyroid hormones
  4. Growth hormone
  5. ACTH
  6. Glucocorticoids

Hormone sensitive lipase inactivated by-

  1. Insulin
  2. Prostaglandin
Don’t Forget to Solve all the previous Year Question asked on Metabolism of Triacylglycerol

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Lesch- Nyhan Syndrome

LESCH- NYHAN SYNDROME


LESCH- NYHAN SYNDROME

Main Features

  • It is X-linked Recessive disorder.
  • It is caused due to complete deficiency of Hypoxanthine guanine phosphoribosyl transferase (HGPRT deficiency).
  • It affects only males.
  • Increased production of purine nucleotide from PRPP via De Novo pathway.
  • Purine degraded into uric acid and its level increases.

Clinical features

  • Hyperuricemia
  • Gouty arithritis
  • Urinary stones
  • Intellectual disability
  • Dystonic movement
  • Dysarthric speech
  • Self mutilation (irresistible urge to bite the fingers and lips)
  • Megaloblastic anaemia

Diagnosis

  • Hyperuricemia
  • HGPRTase enzyme acitivity in RBCs is deficient

Treatment

  • Allopurinol
  • Alkalanization of urine
  • High fluid intake

Exam Important

  • It is a sex linked disorder. (X Linked Recessive Disorder)
  • The structural gene of HGPRT is located on X-chromosome.
  • There is a complete deficiancy of HGPRT 
  • Self mutilation is one of the characteristic feature of the syndrome.
  • Allopurinol is used in the treatment.
Don’t Forget to Solve all the previous Year Question asked on LESCH- NYHAN SYNDROME

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