laboursonline – MCQs, Mock Tests | Biochemistry Biochemistry MCQ Set 3

How many amino acid residues are there in ubiquitin?

1. 70
2. 72
3. 74
4. 75

✅ Correct Answer: 4

Which of the following are the structural motifs that mediate protein-protein interactions?

1. Zinc finger
2. Helix-turn-helix
3. Homeodomain
4. Leucine zipper and basic helix-loop-helix

✅ Correct Answer: 4

Which of the following are the structural motifs that mediate protein-protein interactions?

1. Zinc finger
2. Helix-turn-helix
3. Homeodomain
4. Leucine zipper and basic helix-loop-helix

✅ Correct Answer: 4

Which of the following bacterial operon is not controlled by attenuation?

1. Histidine
2. Leucine
3. Arabinose
4. Tryptophan

✅ Correct Answer: 3

Which of the following regulatory sequence allows transcription to continue?

1. Sequence 4
2. Sequence 1
3. Sequence 2
4. Sequence 3

✅ Correct Answer: 3

Which of the following enzyme is secreted by the pancreas?

1. Myoglobin
2. Cytochrome c
3. Ribonuclease
4. Lysozyme

✅ Correct Answer: 3

Which of the following is a hypertonic solution?

1. 0.45% sodium chloride
2. Oceans
3. Red blood cells placed in fresh water
4. Freshwater habitats

✅ Correct Answer: 2

Which of the following is not an example of housekeeping genes?

1. RNA polymerase
2. r-RNA genes
3. Beta galactosidase
4. Enzymes required for basic metabolic pathways common to most cells

✅ Correct Answer: 3

Lactose utilization by E. coli requires ____________

1. Lac-Z
2. Lac-A
3. Lac-Y
4. Lac-l

✅ Correct Answer: 3

The lactose repressor is encoded by ____________

1. Lac-l
2. Lac-A
3. Lac-Y
4. Lac-Z

✅ Correct Answer: 1

Where does a repressor bind an operon?

1. Operator
2. Promoter
3. Inducer
4. Catabolite activator site

✅ Correct Answer: 1

Lac repressor dissociates from its operator when the repressor binds to ____________

1. Heat shock module
2. Promoter
3. Inducer
4. Catabolite activator site

✅ Correct Answer: 3

The lac repressor has which of the following DNA-binding motif?

1. Helix-turn-helix
2. Zinc finger
3. Homeodomain
4. Leucine zipper

✅ Correct Answer: 1

Which of the following are the structural motifs that mediate protein-protein interactions?

1. Leucine zipper and basic helix-loop-helix
2. Homeodomain
3. Zinc finger
4. Helix-turn-helix

✅ Correct Answer: 1

If lactose and glucose are provided in the growth medium of a culture of E. coli ____________

1. Lactose operon is not transcribed
2. Lactose metabolism is favored
3. Both lactose and glucose are metabolized at same rate
4. Adenylate cyclase is activated

✅ Correct Answer: 1

Which of the following is not required for the expression of genes in the lactose operon?

1. lacl gene product
2. cAMP
3. Allolactose
4. Adenylate cyclase

✅ Correct Answer: 1

Which out of the following is not an example of an inducible operon?

1. Lactose operon
2. Galactose operon
3. Maltose operon
4. Tryptophan operon

✅ Correct Answer: 4

Which of the following statements is not correct?

1. Bacteria possess only one type of RNA polymerase
2. Attenuation is a regulatory process used by bacteria to control the initiation of transcription
3. Repressor binds to operator
4. Bacterial genes are polycistronic

✅ Correct Answer: 2

Which of the following bacterial operon is not controlled by attenuation?

1. Arabinose
2. Tryptophan
3. Leucine
4. Histidine

✅ Correct Answer: 1

Which of the following is the most appropriate definition of an operator?

1. A non-coding, regulatory DNA sequence that is bound by RNA polymerase
2. A non-coding, regulatory DNA sequence that is bound by a repressor protein
3. A DNA-binding protein that regulates gene expression
4. A cluster of genes that are regulated by a single promoter

✅ Correct Answer: 2

To which class of transcription factor do nuclear receptors belong?

1. Zinc finger proteins
2. Leucine zipper proteins
3. Helix-turn-helix proteins
4. Helix-loop-helix proteins

✅ Correct Answer: 1

Which of the following statements about lac operon in e.coli is true?

1. Promoter is the binding site for the lac repressor
2. Operon is only switched on in the absence of lactose in the growth medium
3. β-galactosidase is only produced in large quantities when the lac repressor is bound to the operator
4. Lac operon mRNA is a polycistronic mRNA

✅ Correct Answer: 4

Which of the following statements regarding the regulation of trp operon expression by attenuation is correct?

1. Rapid translation of the leader peptide prevents completion of mRNA transcript
2. Rapid translation of the leader peptide allows completion of mRNA transcript
3. The leader peptide sequence encodes enzymes required for tryptophan synthesis
4. The leader peptide sequence contains no tryptophan residues

✅ Correct Answer: 1

Which of the following increases gene expression as much as 200-fold?

1. TATA box
2. Insulator
3. Enhancer
4. CAAT box

✅ Correct Answer: 3

The mechanism by which CBP activates transcription is?

1. CBP has DNA methyl transferase activity
2. CBP has histone acetyl transferase activity
3. CBP interacts with the basal transcription complex
4. CBP interacts with the basal transcription complex and has histone acetyl transferase activity

✅ Correct Answer: 3

RNAi stands for ____________

1. RNA inducer
2. RNA interference
3. RNA intron
4. RNA insertion

✅ Correct Answer: 2

Which of the following about mRNA stability is not correct?

1. Regulation of mRNA stability is a way of regulating gene expression b) c) d)
2. Prokaryotic mRNAs have a half-life of only a few minutes
3. Histone mRNAs have especially long poly-A tails and are stable
4. It is thought that poly-A tails stabilize eukaryotic mRNAs

✅ Correct Answer: 3

Which of the following about mRNA stability is not correct?

1. Regulation of mRNA stability is a way of regulating gene expression
2. Prokaryotic mRNAs have a half-life of only a few minutes
3. Histone mRNAs have especially long poly-A tails and are stable
4. It is thought that poly-A tails stabilize eukaryotic mRNAs

✅ Correct Answer: 3

CAP is ____________

1. Catabolite gene activator protein
2. Catabolite gene repressor protein
3. Anabolite gene activator protein
4. Anabolite gene repressor protein

✅ Correct Answer: 1

Trp repressor is a ____________

1. Homodimer
2. Homotrimer
3. Heterodimer
4. Heterotrimer

✅ Correct Answer: 1

Attenuator sequences base-pair to form a stem-and-loop structure rich in ____________

1. A = T
2. G ≡ C
3. A = C
4. G = C

✅ Correct Answer: 2

Formation of the attenuator stem-and-loop structure depends on the events that occur during translation of ____________

1. Sequence 1
2. Regulatory sequence 2
3. Regulatory sequence 3
4. Regulatory sequence 4

✅ Correct Answer: 2

Which of the following takes place when tryptophan levels are low?

1. Ribosomes quickly translates sequence 1
2. Sequence 2 is blocked before sequence 3 is transcribed
3. Ribosomes pauses at the Try codons in sequence 1
4. Attenuation at the attenuator structure formed by sequences of 3 and 4

✅ Correct Answer: 3

Which of the following takes place when tryptophan levels are high?

1. Attenuation at the attenuator structure formed by sequences of 3 and 4
2. Ribosomes pauses at the Try codons in sequence 1
3. Formation of paired structure between 2 and 3 sequences prevents attenuation
4. 2:3 structures, unlike the 3:4 attenuator, does not prevent transcription

✅ Correct Answer: 1

Whose interaction with Lex-A facilitates the repressor’s self-cleavage reaction?

1. Rec-A
2. Rec-B
3. Rec-C
4. Rec-D

✅ Correct Answer: 1

When DNA segment is in one orientation ____________

1. The gene for FljB and gene encoding FljA are expressed
2. The gene for FliC are expressed
3. The gene for FljB and gene encoding FljA are not expressed
4. The gene for FljB and gene encoding FljC are not expressed

✅ Correct Answer: 1

When DNA segment is in one orientation ____________

1. The gene for FljB and gene encoding FljA are expressed
2. The gene for FliC are expressed
3. The gene for FljB and gene encoding FljA are not expressed
4. The gene for FljB and gene encoding FljC are not expressed

✅ Correct Answer: 1

When DNA segment is in one orientation ____________

1. The gene for FljB and gene encoding FljA are expressed
2. The gene for FliC are expressed
3. The gene for FljB and gene encoding FljA are not expressed
4. The gene for FljB and gene encoding FljC are not expressed

✅ Correct Answer: 1

Which of the following encodes recombinase?

1. fliC
2. fljB
3. hin
4. fljA

✅ Correct Answer: 3

Which of the following is not true about secondary protein structure?

1. The hydrophilic/hydrophobic character of amino acid residues is important to secondary structure
2. The ability of peptide bonds to form intramolecular hydrogen bonds is important to secondary structure
3. The alpha helix, beta pleated sheet and beta turns are examples of protein secondary structure
4. The steric influence of amino acid residues is important to secondary structure

✅ Correct Answer: 1

A structure that has hydrogen bonds between polypeptide chains arranged side by side is ____________

1. Primary structure
2. α-helix
3. β-pleated sheets
4. Tertiary structure

✅ Correct Answer: 3

The enzyme of E.coli is a nuclease that initiates the repair of double stranded DNA breaks by homologous recombination is?

1. DNA glycosylase
2. DNA ligase
3. DNA polymerase
4. RNA polymerase

✅ Correct Answer: 1

Which of the statements is false about multiple sequence alignment?

1. Both protein and nucleic acid secondary structures can be used
2. More useful in RNA
3. These alignments can be made more accurate by the inclusion of secondary structure information
4. A significant increase in accuracy

✅ Correct Answer: 2

Which of the statements is false about multiple sequence alignment?

1. Both protein and nucleic acid secondary structures can be used
2. More useful in RNA
3. These alignments can be made more accurate by the inclusion of secondary structure information
4. A significant increase in accuracy

✅ Correct Answer: 2

Which of the following serves as a bactericidal agent?

1. Ribonuclease
2. Lysozyme
3. Cytochrome c
4. Myoglobin

✅ Correct Answer: 2

Which of the following enzyme is secreted by the pancreas?

1. Ribonuclease
2. Lysozyme
3. Cytochrome c
4. Myoglobin

✅ Correct Answer: 1

Which of the following statement is false?

1. Lysozyme has S-S linkage
2. Ribonuclease has S-S linkage
3. Heme group in cytochrome c is covalently linked to the protein on two sides
4. Ribonuclease has SH-SH linkage

✅ Correct Answer: 4

Which of the following is first determined as oligomer?

1. Myoglobin
2. Collagen
3. Keratin
4. Hemoglobin

✅ Correct Answer: 4

Which of the following is abundantly found in collagen?

1. Glycine
2. Serine
3. Alanine
4. Tryptophan

✅ Correct Answer: 1

Which of the following are important for white blood cell recognition?

1. Glycosaminoglycans
2. Proteoglycans
3. Glycoproteins
4. Glycolipids

✅ Correct Answer: 3

Which of the following is a hypertonic solution?

1. Oceans
2. Freshwater habitats
3. 0.45% sodium chloride
4. Red blood cells placed in fresh water

✅ Correct Answer: 1

If pH of solution of NaOH is 12.0 the pH of H2SO4 solution of same molarity will be ____________

1. a) 2.0
2. 12.0
3. 1.7
4. 10.0387

✅ Correct Answer: 3

1M NaCl and 1M HCl are present in an aqueous solution. What is the solution?

1. Not a buffer solution with pH < 7
2. Not a buffer solution with pH > 7
3. A buffer solution with pH < 7
4. A buffer solution with pH > 7

✅ Correct Answer: 1

What does it mean when we say that water acts as a “heat buffer”?

1. It keeps the temperature of an organism relatively constant as the temperature of the surroundings fluctuates
2. It increases the temperature of an organism as the temperature of the surroundings increases
3. It decreases the temperature of an organism as the temperature of the surroundings increases
4. It increases the temperature of an organism as the temperature of the surroundings decreases

✅ Correct Answer: 1

What trend does the reactivity of group II elements follow with water?

1. Increases down the group
2. Decreases down the group
3. Does not follow any particular trend
4. No reaction

✅ Correct Answer: 1

Which of the following is not the classified form of conjugated proteins?

1. Lipoproteins
2. Glycoproteins
3. Metalloproteins
4. Complete proteins

✅ Correct Answer: 4

Tertiary conformation of proteins is maintained by 3 types of bonds namely ionic, hydrogen and ____________

1. Sulfide
2. Disulfide
3. Covalent
4. Peptide

✅ Correct Answer: 2

Which of the following is true?

1. The disulfide bridges formed by reduction of the sulfhydryl groups on cysteine stabilizes protein tertiary structure
2. The disulfide bridges formed by oxidation of the sulfhydryl groups on cysteine destabilize protein tertiary structure c) d)
3. The disulfide bridges formed by oxidation of the sulfhydryl groups on cysteine stabilizes protein tertiary structure
4. The disulfide bridges formed by reduction of the sulfhydryl groups on cysteine destabilize protein tertiary structure

✅ Correct Answer: 3

In 3° structure of proteins, folding and shaping is done by ____________

1. Hydrophobic interactions
2. Polar interactions
3. Hydrogen bonding
4. None of the mentioned

✅ Correct Answer: 1

Which of the following glycoprotein functions as a lubricant and protective agent?

1. Collagens
2. Mucins
3. Transferrins
4. Immunoglobulins

✅ Correct Answer: 2

Which of the following is a hydroxyl fatty acid?

1. Linoleic acid
2. Palmitic acid
3. Linolenic acid
4. Cerebronic acid

✅ Correct Answer: 4

Which of the following is false about fatty acids?

1. Melting point of fatty acids decreases with increase in the degree of saturation
2. Lipids in tissues that are subjected to cooling are more unsaturated
3. Naturally occurring unsaturated long-chain fatty acids are nearly Trans-configuration
4. The membrane lipids contain mostly unsaturated fatty acids

✅ Correct Answer: 3

The binding of ligands to many GPCRs leads to ____________

1. Decrease in concentration of second messengers
2. Increase in concentration of second messengers
3. Decrease in concentration of first messengers
4. Increase in concentration of first messengers

✅ Correct Answer: 1

Which of the following are included in the types of glycolipids?

1. N-acetylgalactosamine
2. N-acetylglucosamine
3. Xylose
4. Cerebrosides

✅ Correct Answer: 4

Which of the following catalyzes the cutting of PIP2 into 2 moles of IP3 and diacylglycerol in cell signaling?

1. Phosphokinase C
2. Phospholipase C
3. Lipokinase
4. Phosphodiesterase C

✅ Correct Answer: 2

Site directed mutagenesis facilitated research on ____________

1. Carbohydrates
2. Proteins
3. Lipids
4. Fats

✅ Correct Answer: 2

Which product formed in the isomerization of mannose 6-phosphate?

1. Fructose 6-phosphate
2. Glucose 6-phosphate
3. 2-phosphoglycerate
4. 3-phosphoglycerate

✅ Correct Answer: 1

Which is the first reaction of the pentose phosphate pathway?

1. Oxidation of glucose 6-phosphate to 6-phosphoglucono-δ-lactone
2. Oxidation of 6-phosphogluconate to ketopentose ribulose 5-phosphate
3. Reduction of 6-phosphoglucono-δ-lactone to glucose 6-phosphate d)
4. Reduction of ketopentose ribulose 5-phosphate to 6-phosphogluconate

✅ Correct Answer: 1