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Biochemistry MCQ Exam 1- PMU 2nd Year

Question 1 of 32

1

Which of the following amino acids have charge at ph 7.0?

Select one or more of the following:

  • alanine

  • arginine

  • lysine

  • cysteine

  • aspartic acid

Explanation

Question 2 of 32

1

Which of the following statements about noncompetitive inhibitors is TRUE:

Select one or more of the following:

  • the noncompetitive inhibitor can bind both the enzyme and the ES complex

  • the noncompetitive inhibitor decreases Vmax but does not change Km

  • the noncompetitive inhibitor binds the enzyme at site distinct from the active site

  • the noncompetitive inhibitor is it structural analog of the substrate

Explanation

Question 3 of 32

1

The consequences of folic acid deficiency is:

Select one or more of the following:

  • beri-beri

  • scurvy

  • pellagra

  • megaloblastic anemia

Explanation

Question 4 of 32

1

Vit. C is involved in:

Select one or more of the following:

  • the biosynthesis of noradrenaline and adrenaline

  • the postsynthetic modification of procollagen to collagen

  • the formation of Coenzyme A

  • the metabolism one-carbon fragments

  • the biosynthesis of bile acids

Explanation

Question 5 of 32

1

Which of the following amino-acids are sulphur-containing?

Select one or more of the following:

  • Histidine

  • Cysteine

  • Threonine

  • Methionine

Explanation

Question 6 of 32

1

Which of the following statements about nuclear DNA are TRUE?

Select one or more of the following:

  • It contains deoxyribose as pentose

  • It contains Uracil instead of Thymine

  • It is a double-stranded circular structure

  • It is double-stranded helix

Explanation

Question 7 of 32

1

Denaturation of proteins:

Select one or more of the following:

  • Can affect primary structure of proteins

  • Affect all the structures except the primary structure of proteins

  • Can be reversible and irreversible depending on the duration of the denaturating agent

  • Breaks down the covalent bonds within the polypeptide chain

Explanation

Question 8 of 32

1

Which of the following statements about competitive inhibitors are TRUE?

Select one or more of the following:

  • The competitive inhibitor can bind only with the active site of the enzyme

  • The competitive inhibitor can bind only with the ES complex

  • The competitive inhibitor can bind both with the active site of the enzyme and the ES complex

  • Vmax remains unchanged, Km rises

  • Km remains unchanged. Vmax decreases

  • The competitive inhibitor is a structural analog of the substrate

Explanation

Question 9 of 32

1

Which of the following amino acids are hydrophobic and are localized inside the globular protein molecule?

Select one or more of the following:

  • Lysine and Glutamate

  • Leucine and Isoleucine

  • Alanine and Valine

  • Serine and Cysteine

  • Tryptophan and Proline

Explanation

Question 10 of 32

1

Which of the following are not included in protein structures. but have important biological role?

Select one or more of the following:

  • Ornithine

  • β-alanine

  • Histidine

  • Homocysteine

  • Citrulline

  • Citrate

Explanation

Question 11 of 32

1

Which is the type of covalent bond between a-amino acid residues in polypeptide chain?

Select one or more of the following:

  • phosphoesteric bond

  • glycosidic bond

  • sulfur bridge

  • peptide bond

  • esteric bond

Explanation

Question 12 of 32

1

Polypeptide chains are consisted of:

Select one or more of the following:

  • α-amino acid residues

  • nucleotides

  • glycerol

  • free fatty acids

  • glucose or other monosaccharides

Explanation

Question 13 of 32

1

The collagen is:

Select one or more of the following:

  • fibrilar protein

  • globular protein

  • rich of Glycine residues

  • rich of Proline residues

  • rich of Glutamate and Glutamine residues

Explanation

Question 14 of 32

1

Vitamin B1:

Select one or more of the following:

  • Its deficiency causes pellagra

  • Its deficiency causes “beri-beri"

  • Its chemical name is riboflavin

  • Its chemical name is thiamine

Explanation

Question 15 of 32

1

Allosteric effectors:

Select one or more of the following:

  • Bind with the active site of the enzyme

  • Can change the total amount of the enzymes

  • Are Inducers and suppressors

  • Are activators and inhibitors

  • can cause negative or positive feedback

Explanation

Question 16 of 32

1

Km

Select one or more of the following:

  • is equal to (k-1+k2)/k1

  • is equal to (k1+k2)/k-1

  • Gives information for affinity between the active site of the enzyme and its substrate

  • The higher Km is, the greater affinity exists

Explanation

Question 17 of 32

1

Which of the following belong to the six classes of enzymes according to the enzyme classification:

Select one or more of the following:

  • hydrolases

  • transferases

  • esterases

  • oxidoreductases

  • peptidases

Explanation

Question 18 of 32

1

The consequences of niacine (Vit. PP) deficiency is

Select one or more of the following:

  • beri beri

  • scurvy

  • pellagra

  • rickets

Explanation

Question 19 of 32

1

Pyridoxal phosphate coenzyme is a:

Select one or more of the following:

  • derivative of Vit. B2

  • derivative of Vit. B3

  • derivative of Vit. B6

  • participates in oxidation and reduction

  • Participates in transfer of amine

Explanation

Question 20 of 32

1

Which of the following co-factor's participate in reactions catalyzed by oxidoreductases:

Select one or more of the following:

  • Biotin

  • Pyridoxal phosphate

  • NAD+

  • CoASH

  • FMN

Explanation

Question 21 of 32

1

In which enzymes participates thiamine diphosphate (TPP)- the active form of vitamin B1.

Select one or more of the following:

  • aminotransferases

  • decarboxylases

  • pyruvate dehydrogenase

  • α-ketoglutarate dehydrogenase

  • transketolase

Explanation

Question 22 of 32

1

What are the interactions that stabilize the tertiary and the quatemary structure of proteins:

Select one or more of the following:

  • hydrophobic interactions

  • hydrogen bonds

  • ion interactions

  • peptide bonds

  • disulfide bonds in oligomeric proteins

Explanation

Question 23 of 32

1

The reversible covalent Phosphorylation-dephosphorylation of the enzymes:

Select one or more of the following:

  • acts on the enzymes active site

  • acts on the enzymes allosteric sites

  • acts on a single enzyme

  • acts on several enzymes

  • is under direct neural and hormonal control

  • is a mechanism for quick enzyme regulation

Explanation

Question 24 of 32

1

Which is the vitamin in FMN and FAD:

Select one or more of the following:

  • folic acid

  • riboflavin

  • thiamin

  • biotin

  • niacin

Explanation

Question 25 of 32

1

In competitive inhibition:

Select one or more of the following:

  • Vmax remains unchanged, Km decreases

  • Vmax remains unchanged, Km increases

  • Vmax and Km remain unchanged

  • Vmax and Km decrease

Explanation

Question 26 of 32

1

The feedback inhibition:

Select one or more of the following:

  • is a mechanism of regulation of multistep metabolic pathways

  • is under direct neural and hormonal control

  • acts on early steps enzymes

  • acts on the enzymes active site

Explanation

Question 27 of 32

1

Which of the following statements about peptide bond are TRUE:

Select one or more of the following:

  • the peptide bonds maintain the primary structure of proteins

  • the peptide bonds maintain the secondary structure of proteins

  • the peptide bond is a non-covalent bond

  • the peptide bond has a partial double-bond character

Explanation

Question 28 of 32

1

The simultaneous increase in AST and ALT is diagnostic marker mostly for:

Select one or more of the following:

  • Muscle Dieseases

  • Cardiac Diseases

  • Liver Diseases

  • Brain Diseases

Explanation

Question 29 of 32

1

Vitamin C

Select one or more of the following:

  • It is a water-soluble vitamin

  • Its deficiency causes pellagra

  • Its deficiency causes scurvy

  • It participates as a cofactor in the posttranslational modification of collagen

Explanation

Question 30 of 32

1

Which of the following is TRUE?

Select one or more of the following:

  • some of proteins are enzymes

  • all of proteins are enzymes

  • some of proteins are hormones

  • all of proteins are hormone

  • some of proteins participate as transporting molecules

Explanation

Question 31 of 32

1

Nucleotides are derivatives consisted of:

Select one or more of the following:

  • heterocyclic ring consisted of C- and N- atoms named purine or pyrimidine monosaccaride- ribose or deoxyribose and phosphoric acid

  • heterocyclic ring consisted of C- and S- atoms, monosaccaride- an hexose and phosphoric acid

  • heterocyclic ring consisted of C- and N- atoms, named purine or pyrimidine- a disaccharide and phosphoric acid

  • heterocyclic ring consisted of C- and N- atoms named purine or pyrimidines, monosaccaride- ribose deoxyribose and nitric acid

Explanation

Question 32 of 32

1

Protein denaturation is a process that:

Select one or more of the following:

  • amino acids composition is changed

  • its primary structure is disrupted

  • its biological activity is lost

  • chemical and physical feature are changed

  • its conformation is disrupted

Explanation

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