77 Questions
What is the effect of binding of dTTP on the ribonucleotide reductase enzyme?
It allows the reduction of GDP to dGDP at the catalytic site
What is the role of 5´-nucleotidase in purine degradation?
It converts IMP to inosine
What is the end product of dietary purine degradation?
Uric acid
What is the effect of hydroxyurea on ribonucleotide reductase?
It inhibits the enzyme
What is the primary level of regulation of genes in both prokaryotes and eukaryotes?
Transcription
What is the role of nucleotidases in nucleic acid degradation?
They remove phosphate groups from nucleotides
What is the function of the lacY gene in the lac operon?
Facilitates movement of lactose into the cell
What is the role of purine nucleoside phosphorylase in purine degradation?
It converts inosine and guanosine to their respective purine bases
What is the role of the repressor protein in the lac operon?
It binds to the operator, preventing transcription when glucose is available
What is required for the induction of the lac operon?
The presence of lactose and the absence of glucose
What is the role of cAMP in the lac operon?
It binds to the CAP site, inducing transcription of the lac operon
What is the term for genes that are expressed under certain conditions in all cells or in a subset of cells?
Regulated genes
What is a primary difference between prokaryotic and eukaryotic protein synthesis?
Eukaryotes use a different set of initiation factors than prokaryotes
What is the primary source of nitrogen in the body?
Dietary protein
What is the role of EF-1 and EF-2 in eukaryotic protein synthesis?
They are involved in the elongation step of protein synthesis
What is the result of an imbalance in the amino acid pool?
A disruption in the balance of nitrogen input and output
What is the primary fate of nitrogen in the body?
It is excreted as urea, ammonia, and other products
What is the purpose of the SD-sequence in prokaryotic protein synthesis?
It helps to initiate translation
What is the result of Crigler-Najjar I and II gene mutation?
Unconjugated hyperbilirubinemia
What is the effect of hemolytic jaundice?
Production of bilirubin is faster than its conjugation
What is the characteristic of Dubin-Johnson syndrome?
Liver cells are not pigmented
What is the effect of obstructive jaundice?
Conjugated hyperbilirubinemia
What is the characteristic of Rotor syndrome?
Impaired hepatocellular storage of conjugated bilirubin
What is the effect of hepatocellular jaundice?
Unconjugated hyperbilirubinemia
What is the purpose of DNA repair systems?
To prevent mutations and potential cancer
What is the role of Mut proteins in DNA repair?
To identify mispaired nucleotides
Why is the parental strand assumed to be correct during mismatch repair?
Because it is methylated
What is the function of DNA adenine methylase (DAM) in DNA repair?
To methylate GATC sequences
What is the role of the exonuclease in DNA repair?
To remove mismatched nucleotides
What is the function of DNA polymerase III in DNA repair?
To fill the gap with new nucleotides
In which pathway are fatty acids in enterocytes converted into triacylglycerol?
Monoacylglycerol pathway via 1,3
Which of the following compounds is NOT a component of sphingomyeline?
Cephaline
What is the function of phosphatidylinositol 4,5-bisphosphate?
Source of second messengers
What is a characteristic of lysophospholipids?
Contain only one acyl residue in the C1 position
Which of the following statements is true about arachidonic acid?
May be a substrate in prostaglandins biosynthesis
What is the byproduct of polyamine oxidase?
Putrescine
What is the substrate for dopa decarboxylase?
Phenylalanine
What is the role of glycine in the synthesis of?
Purines
What is required by dopamine β-oxidase?
All of the above
What is the structural formula of?
Creatinine
Which of the following statements about unsaturated fatty acids is true?
The acyl chains are at the opposite sides of double bonds
What is synthesized from glyoxylate and glutamate?
Glycine
Which of the following lipids are present in nervous tissue in high concentration?
Gangliosides, Glucosylcermide, and Sphingomyelins
What is the function of phosphatidylinositol 4,5-bisphosphate?
It is a source of second messengers
Which of the following is a characteristic of sphingosine?
It is the alcoholic component of sphingomyelins
What is the function of intestinal lipase?
It cleaves triacylglycerol into diacylglycerol and fatty acid
Which of the following statements about linoleic acid is true?
It contains 3 double bonds
Which amino acid exists in anion form?
Aspartic acid
What is a characteristic of collagen?
Undergoes post-translational modification
Which amino acid can disrupt the conformation of alpha helix?
Glycine and Proline
What is a characteristic of pathologic prion-related proteins (PrPsc)?
All of the above
Which of the following bonds are non-covalent?
Salt bridges and Hydrophobic interactions
What is a characteristic of all amino acids in proteins?
All of the above
What is the correct statement about phosphorylation-dephosphorylation?
Phosphorylation-dephosphorylation is mainly associated with serine, threonine or tyrosine residues of enzymes
What is the characteristic of acetyl-CoA carboxylase?
It is the rate-limiting enzyme for fatty acid biosynthesis
What is the role of ubiquitin in proteasome pathway?
It is attached covalently to target proteins by E3 ligases
What is the characteristic of rate-limiting reaction?
It is the slowest reaction in biochemical pathways
What is the characteristic of aspartate transcarbamoylase (ATCase)?
It is regulated by allosteric mechanism
What can affect the catalytic efficiency of an enzyme?
All of the above
What is the derivative of purine nucleotide?
S-adenosylethionine
Which of the following amino acids is involved in the biosynthesis of both glutamine and proline?
Glutamate
What is the principal source of methyl groups?
S-adenosylmethionine
Which of the following is a component of anserine?
Β-alanine
What is the cofactor required for the action of phenylalanine hydroxylase?
Dihydrobiopterin
Which of the following amino acids are involved in the Urea Cycle?
Ornithine and N-Acetylglutamate
What is the main characteristic of Wilson disease?
Low level of ceruloplasmin in plasma
What is the function of IgM?
It is the main antibody in primary response
What is the concentration of total plasma protein in human plasma?
70-75 g/dL
What is the advantage of electrophoresis of cellulose acetate?
It can determine proportions between fractions of plasma proteins
What is the characteristic of albumin?
It possesses three domains with different functions
What is the characteristic of IgM molecule?
It possesses four constant regions on heavy chain
What is the correct primer required for glycogen formation?
1,2
Which of the following statements is correct regarding galactose?
All of the above
Which of the following biochemical symptoms are characteristic of glycogen synthase deficiency?
Ketosis, hypoglycemia, lactic acidemia, hyperlipidemia
What is the role of glucagon in glycolysis?
It inhibits glycolysis by dephosphorylating pyruvate kinase
What is the role of glucokinase?
It is activated indirectly by glucose
What is the role of fructose 1,6-biphosphate?
It is converted to fructose 2,6-biphosphate by phosphofructokinase-2
Learn about the mechanism of ribonucleotide reductase, an enzyme that converts ribonucleotides to deoxyribonucleotides. Understand how ATP and nucleoside triphosphates regulate substrate specificity and how the enzyme is inhibited by hydroxyurea.
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