Biochemistry final

Which of the following are true regarding nucleotides?

-they are made by de novo and salvage pathways.

Which of the following is true regarding purine synthesis?

ALL ANSWERS ARE TRUE

-It consumes ATP.

-PRPP synthetase catalyzes the process that

-It includes the intermediate known as IMP.

-It begins with ribose-5-phosphate.

-It consumes ATP.

Which of the following is NOT correctly associated regarding ATP and GTP synthesis?

N10-formyl-THF — source of N atoms in purine synthesis

Which of the following is true regarding purine synthesis?

IMP is the branch point for synthesis of AMP and GMP

Which of the following enzymes control the amount of ATP to be synthesized in the cell?

Adenylosuccinate synthetase

Which of the following is true regarding the regulation of purine metabolism? Select all that apply.

-IMP dehydrogenase is inhibited by GMP.

-Both of the enzymes acting on IMP are feedback inhibited.

The amount of pyrimidine is controlled by which enzyme?

ATCase

The ATCase enzyme is activated due to an excess of which of the following?

ATP and aspartate

How do the higher concentrations of CTP affect the production of pyrimidine?

The higher concentrations of CTP inhibit the ATCase enzyme and therefore stop the further synthesis of pyrimidine nucleotides.

Which of the following is true regarding de novo synthesis of pyrimidines? Select all options that apply.

-The second step is catalyzed by a regulatory enzyme.

-UMP is the first pyrimidine synthesized.

Which of the following is true regarding the synthesis of UTP from UMP?

ALL answers are true.

• Two kinases are involved.

• no regulation occurs

• Two ATPs are required.

• Two sequential reactions are required.

Which of the following occurs during the breakdown of nucleotides

Nucleases break down nucleic acids into nucleotides.

Which of the following reactions is paired with the correct enzyme?

AMP → Inosinic acid (IMP) : AMP deaminase

Which of the following occurs in the catabolism of hypoxanthine?

Allopurinol inhibitsanthine oxidase.

Which of the following is true regarding gout?

It is caused by crystals of uric acid.

Which of the following is true regarding the salvage synthesis of purine nucleotides?

It results in Lesch-Nyhan syndrome if HGPRT is absent.

Which statement is true regarding Lesch-Nyhan syndrome?

Lesch-Nyhan syndrome occurs due to a deficiency of hypoxanthine-guanine phosphoribosyltransferase enzyme

Which statement is true regarding allopurinol?

Allopurinol is used in the treatment of gout because of its ability to inhibit uric acid production.

Pyrimidine nucleosidases require which of the following molecules and reactions?

Water is needed to hydrolyze the base from the sugar.

Which of the following is true regarding deoxyribonucleotide de novo synthesis?

It requires ribonucleotide reductase.

Which of the following is true regarding ribonucleotide reductase (RNR)?

It has allosteric sites on the large subunit.

Which of the following assists with the conversion of oxidized ribonucleotide reductase enzyme back into a reduced form?

Reduced thioredoxin

Which of the following occurs in allosteric control of ribonucleotide reductase?

The binding of dGTP at the allosteric site favors the binding of ADP at the active site.

An abundance of the dATP in the cell leads to what?

It transfers a carbon from a folate to make dTMP.

Which of the following is true regarding dihydrofolate reductase?

It is necessary for folate recycling.

Which of the following is true regarding methotrexate?

All of the answers are true:

• It is an inhibitor of dihydrofolate reductase.

• it is used in chemotherapy.

• it resembles dihydrofolate.

Which of the following is not true regarding suicide inhibitor?

The suicide inhibitor causes the activation of cancer-causing enzymes and leads to the formation of malignant tissues

Which of the following descriptions is correct?

5,10-Methylenetetrahydrofolate - donates a methyl group to convert dUMP to dTMP

Which of the following is true regarding nucleoside analogs used in therapeutics?

They are commonly competitive inhibitors of nucleotides when present in cells.

Nucleoside and nucleotide analogs commonly used as anti-viral therapeutic drugs to prevent what?

Viral replication in the infected cells

What is a benefit of nucleoside analogs?

they readily cross the cell membrane

Which of the following statement regarding DNA replication is FALSE?

It requires an RNA polymerase.

Which of the following is true regarding polymerase proofreading?

It comes from the 3’ to 5’ exonuclease activity of some DNA polymerases.

Which of the following is true regarding arginine?

It is an important precursor of urea.

What is the most abundant amino acid in collagen?

Glycine

Which statement regarding hydroxylation of proline is true?

It gives collagen more thermal stability.

What does the gene lacZ express?

β-galactosidase

Which statement regarding collagen is true?

It is an important part of the clotting system.

Which enzyme helps in the conversion between euchromatin and heterochromatin?

Histone deacetylase

Which of the following is true regarding the amino acids in the pyruvate family?

They all have non-polar R groups.

Which statement regarding lysine is true?

Cross-linking is important for strengthening collagen.

Which of the following statements is correct regarding the lac operon in E. coli bacterium?

LacZ cleaves lactose into glucose and galactose.

The conversion of glutamate to glutamine catalyzed by glutamine synthetase results in which of the following?

Removal of ammonia

Which of the following is true regarding an operon?

It contains multiple genes under the control of a single promoter.

The deficiency of which enzyme leads to phenylketonuria?

Phenylalanine hydroxylase

Which statement regarding collagen in the human body is true?

It is found in skin, tendons, and cartilage.

Which of the following is true regarding RNA interference?

It relies on formation of duplex RNA sequences in cells.

Which of the following is true of insulator sequences?

They are bound by a protein called CTCF.

Which of the following is true regarding phenylalanine?

Phenylalanine can cause brain damage in high amounts.

Methionine is produced from homocysteine by...

...adding a methyl group.

Which statement regarding hydroxylation of collagen is true?

It occurs in the endoplasmic reticulum.

Which of the following is true regarding the acetylation of histones?

It causes them to be less positively charged

Epigenetics explains which type of changes?

Heritable changes in the gene expressions which do not change the underlying DNA sequence.

The TFIID factor, which helps in the transcription of eukaryotic genes, recognizes which sequences in the promoter region?

AT-rich sequences

Which of the following occurs in the lac operon?

The CAP protein binds to DNA when it binds to cAMP.

RNA polymerase I in eukaryotes primarily makes which of the following?

rRNAs

Which of the following is true regarding RNA?

RNA is made by transcribing DNA.

Which statement regarding lysyl hydroxylase is true?

It ultimately requires vitamin C to function.

Which part of the amino acid gives it unique characteristics, structure, function, and chemistry?

R group

Which of the following statements is correct regarding glutamate?

In transamination, glutamate is produced when alpha-ketoglutarate accepts an amine group from another molecule.

Which of the following statements about tRNA is not true?

tRNA contains codons. 

How does the aminoacyl-tRNA synthetase enzyme help to improve the accuracy of the translation process?

The aminoacyl-tRNA synthetase ensures the attachment of the correct amino acid to the corresponding tRNA molecule.

Methionine is produced from homocysteine by...?

...adding a methyl group.

Which of the following statements about RNase P is true?

RNase P is a ribozyme.

Essential amino acids are amino acids that must be...?

in an organism’s diet.

Which of the following glycolysis intermediates is the closest precursor to serine?

3-phosphoglycerate

Enhancer sequences in the eukaryotic DNA help in doing what?

Binding and set-up of the transcriptional machinery.

Which amino acid is NOT part of the aspartate family?

cysteine

Which statement regarding prolyl hydroxylase is true?

It requires molecular oxygen for the reaction

Which statement is true regarding the RNA splicing process?

The removal of introns produces a lariat structure

What molecular change occurs during transamination?

An amine group and a carbonyl group are exchanged.

The first 3 steps in the synthesis of threonine are the same as the first 3 steps in the synthesis of...?

...methionine.

Which protein associates with the RISC complex and assists with target mRNA cleavage?

Argonaute

What will happen to the lac operon in the presence of high levels of glucose and lactose?

Very low basal levels of lac operon gene expressions will be observed in the cell.

Which enzyme breaks the dsRNA in the RNAi pathway?

Dicer

Which molecule controls the binding of regulatory proteins to the control sites of the lac operon?

cAMP

Which type of linkage occurs with the addition of 7-methylguanosine to mRNA?

5’ to 5’ linkage

 

Which of the following is true regarding thyroid hormones?

Thyroid hormones include thyroxine and triiodothyronine

The hydroxylation of which amino acid is important for making strong collagen?

lysine

Which is true of the aromatic amino acid family?

they occasionally under got splicing

Transamination of glutamate and pyruvate could yield...?

.α-ketoglutarate and alanine.

Which of the following does not fall under the category of catecholamines?

S-adenosylmethionine

Which of the following amino acids is serine most closely linked through folate metabolism?

glyceine

Which amino acid is the main precursor of thyroid hormones?

tyrosine

What is the unusual phosphodiester bond linkage within a lariat structure?

2’ to 5’ bond

Which of the following is true regarding aminoacyl tRNA synthetase?

It reads the anticodon in the tRNA to put the right amino acid on the tRNA.

What will happen to the lac operon if there is no cellular glucose or lactose?

The binding of the lac repressor protein to O-site will oppose the action of CAP protein present on CAP site, and hence the lac operon will not be expressed.

Which enzyme converts thyroxine into triiodothyronine?

deiodiase

The deficiency of which enzyme leads to homocystinuria?

Cystathionine β-synthase

Which of the following is true regarding the structure of RNA?

It has more possibilities than DNA due to G-U base pairs

What is a characteristic of tRNAs?

They have many chemically modified bases.

Which statement regarding collagen is true?

Collagen is the most abundant protein in the body.

Where do type-1 and type-2 aminoacyl-tRNA synthetase enzymes attach amino acids?

Amino acids are attached to the 2’OH and 3’OH of terminal A of the tRNA, respectively.

Which statement regarding scurvy is true?

It is caused by vitamin C deficiency.

Which of the following inhibits eukaryotic RNA polymerase?

α-amanitin