Biochem

Which of the following components of fish oil is an omega-3 fatty acid?

A. Palmitoleic acid or hexadecenoic acid

B. Oleic acid or octadecenoic acid

C. Timnodonic acid or eicosapentaenoic acid

D. Arachidonic acid or eicosatetraenoic acid

Which of the following serves as the main storage form of fatty acids?

A. triacylglycerol

B. Cholesterol ester

C. phosphoglyceride

D. glycosphingolipid

What will be the effect of biotin deficiency on the controlling step of lipogenesis?

A. There will be no carbon dioxide fixation because of lack of CO2.

B. Malonyl even if present will not be incorporated to acyl carrier protein.

C. Decarboxylation reaction will not take place.

D. Malonyl CoA will not be produced.

Which of the following reactions in beta oxidation of fatty acids is true?

A. Activation of fatty acids takes place in the mitochondrial matrix.

B. Long-chain fatty acids penetrate the inner mitochondrial membrane as acylcarnitine.

C. Per cycle of beta oxidation involves repetitive steps of oxidation, hydration and reduction.

D. Beta oxidation involves successive cleavage of two carbons which is released as propionyl CoA

Prostaglandin, thromboxane and leukotriene cannot be formed if this essential fatty acid is missing from the diet.

A. Oleic acid

B. Arachidonic acid

C. Palmitoleic acid

D. Palmitic acid

The plasma concentration of this subfraction of HDL is inversely proportional to the incidence of coronary atherosclerosis.

HDL1

HDL2

HDL 3

HDLc

Which of the following phospholipases play a key role in producing second messengers of hormones?

Phospholipase A2

Phospholipase B

Phospholipase C

Phospholipase D

Which one of the following amino acids play a key role in enzymatic catalysis?

Asparagine

Histidine

Glutamic acid

Threonine

Reductive amination of alpha-ketoglutarate will convert it to this amino acid

Glutamic acid

Glutamine

Aspartic acid

Asparagines

Which chemical reaction interconverts pairs of alpha-amino acids and alpha- keto acids?

Oxidative deamination

Transamidination

Non-oxidative deamination

Transamination

Catabolism of the carbon skeletons of all the following amino acids will form pyruvic acid, EXCEPT:

Glycine

Tyrosine

Serine

Alanine

What is the significance of phosphorylation or dephosphorylation of serine and threonine residues in an enzyme molecule?

A. It regulates the activity of covalently modulated enzymes

B. Zymogens are converted to active enzymes.

C. Enzymes become more susceptible to degradation

D. Isoenzymes are released from the cell

All of the following amino acids are needed for the synthesis of creatine phosphate, EXCEPT

Arginine

Glycine

Methionine

Cysteine

Synthetic nucleotide analogs like 5-fluorouracil are used as:

Chemotherapeutic agents

Amoebicidal agents

Antibiotics

Antifungal

Which enzyme of the de novo synthesis of pyrimidine nucleotide is controlled by allosteric regulation?

Carbamyl phosphate synthase

Ribonucleotide reductase

Aspartate transcarbamylase

Thymidylate synthase

Which of the following about transfer RNA is correct?

Double stranded

Has unique or peculiar bases

Contains the codon

Associated with ribosomal proteins

Which form of mammalian RNA polymerase is responsible for synthesizing messenger RNA?

RNAP I

RNAP II

RNAP III

RNAP IV

The genetic code is degenerate which means that

A. It applies to both animal and plant species.

B. Each codon specifies only one amino acid.

C. There is no signal that denotes the end of one codon and beginning of another.

D. There are more than one codons for most amino acids.

Which of these enzymes use hydrogen peroxide as electron donor and electron acceptor?

Peroxidase

Dehydrogenase

Catalase

Oxygenase

Complex IV of the respiratory chain is inhibited by all of the following, EXCEPT:

Hydrogen sulfide

Cyanide

Carbon monoxide

Amobarbital

A very anxious student hyperventilates an hour before the biochemistry board exam. What is the effect of hyperventilation on his Pco2 and blood pH?

Pco2 decreases and pH increases

Pco2 decreases and pH decreases

Pco2 increases and pH decreases

Pco2 increases and pH increases.

Which of the following statements regarding a double-helical molecule of DNA is TRUE?

All hydroxyl groups of pentoses are involved in linkages

Bases are perpendicular to the axis

Each strand is identical.

Each strand replicates itself

A newborn baby has a sibling with sickle cell anemia and is at risk for this disease. The appropriate diagnostic test for sickle cell anemia in this baby would include which of the following?

A. DNA amplification

B. Hemoglobin antibodies

C. Red cell counting

D. DNA fingerprinting

Which of the following laboratory results would best indicate metabolic alkalosis?

A. Increased Pco2, increased pH, increased HCO3.

B. Normal Pco2, increased pH, decreased HCO3.

C. Increased Pco2, increased pH, normal HCO3.

D. Decreased Pco2, increased pH, normal HCO3.

What is that process that occurs at the 5-position of Cytidine and is often correlated with gene inactivation?

A. Gene conversion

B. Sister chromatid exchange

C. Gene rearrangement

D. DNA methylation

A child’s developmental progress is noted to stop at 2 years old. The following year, skeletal deformities appear. The child regresses to a vegetative state at 10 years old. Urine examination tests positive for glucosaminoglycans that include most likely which of the following?

A. Collagen

B. Glycogen

C. GABA

D. Heparan sulfate

DNA polymerases synthesize DNA only in the 5’ to 3’ direction. However, at the replication fork, both parentral strands of DNA are being replicated with the synthesis of new DNA. How is it possible that while one strand is being synthesized in the 5’ to 3’ direction, the other strand appears to be synthesized in the 3’ to 5’ direction? This is best explained by

A. 3’ to 5’ DNA repair enzymes

B. 3’ to 5’ DNA polymerase

C. Okazaki fragments

D. Lack of RNA primer on one of the strands.

Sickle cell anemia is the manifestation of homozygous genes for an abnormal hemoglobin molecule. The mutation in the beta-chain is known to produce a single amino acid change. The most likely mechanism for this mutation is:

A. Two base insertion

B. Three base deletion

C. Nondysjunction

D. Point mutation

Following ultraviolet damage to DNA in the skin, which of the following is MOST likely to occur?

A. A specific nuclease detects damaged areas.

B. Purine dimmers are formed.

C. Both strands are cleaved.

D. Endonuclease removes the damaged strand.

Which of the following is provided by the Northern Blot Analysis?

A. Detection of specific base pairs.

B. Detection of DNA molecules.

C. Detection of RNA molecules.

D. Detection of proteins.

The removal of introns and subsequent self-splicing of adjacent exons occurs in some portions of primary ribosomal RNA transcripts. The splicing of introns in mRNA precursors is:

A. RNA-catalyzed in the absence of protein.

B. Carried out by spliceosomes.

C. Controlled by RNA polymerase.

D. Regulated by RNA helicase.

The “sigma factor” found in many bacteria is best described as a:

A. Subunit of RNA polymerase responsible for the specificity of the initiation of transcription.

B. Subunit of DNA polymerase that allows for the synthesis in both 5’ to 3’ and 3’ to 5’ directions.

C. Subunit of the 50S ribosome that catalyzes peptide bond synthesis.

D. Subunit of the 30S ribosome to which mRNA binds.

The consensus sequence 5’-TATAAAA-3’ found ineukaryotic genes is almost similar to a consensus sequence observed in prokaryotes. The consensus sequence is important as the:

A. Only site of binding of RNA polymerase II.

B. Promoter site for all RNA polymerases.

C. Termination site for RNA polymerase II.

D. First site of binding of a transcription factor for RNA polymerase II.

In bacterial RNA synthesis, what is the function of the “rho” factor?

A. It binds catabolite repressor to the promoter region.

B. It increases the rate of RNA synthesis.

C. It eliminates the binding of RNA polymerase to the promoter.

D. It participates in the proper termination of transcription.

Which of the following statements correctly describes the synthesis of mammalian mRNA?

A. Each mRNA often encodes several different proteins.

B. Several different genes may produce identical mRNA molecules.

C. Mammalian mRNA undergoes minimal modification during its maturation.

D. The RNA sequence transcribed from a gene is identical to the mRNA that exits from nucleus to cytoplasm.

Immunoglobulin G (IgG) molecules can be characterized by which of the following statements?

A. They are maintained at a constant level in the serum.

B. They contain nucleic acids.

C. They contain mostly carbohydrates.

D. They can be separated into subunits with a reducing agent and urea.

Which of the following amino acids is ionizable in proteins?

A. Leucine

B. Histidine

C. Valine

D. Alanine

Which of the following statements concerning immunoglobulins is most accurate?

A. IgE is the principal antibody in the serum.

B. The heavy chains are similar in each class of immunoglobulin.

C. The constant regions of the heavy chains are the same in each class of immunoglobulin.

D. IgE is the major immunoglobulin found in external secretions.

A child develops chronic diarrhea and liver inflammation in early infancy when the mother begins using formula that includes corn syrup. Evaluation of the child demonstrates sensitivity to fructose in the diet. Which of the following glycosides contains fructose and therefore should be avoided when feeding or treating this infant?

A. Sucrose

B. Oaubain

C. Lactose

D. Maltose

The major metabolic product under normal circumstances by erythrocytes and by muscle cells during intense exercise is recycled through the liver in the Cori cycle. The metabolite is:

A. Oxaloacetate

B. Glycerol

C. Alanine

D. Lactate

The Michaelis constant, Km is:

A. Numerically equal to ½ V max

B. Dependent on the enzyme concentration

C. Independent pH

D. Numerically equal to the substrate concentration that gives half-maximal velocity.

Which of the following statements is NOT characteristic of allosteric enzymes?

A. They frequently catalyze a committed step early in a metabolic pathway

B. They are often composed of subunits

C. They frequently show cooperativity for substrate binding

D. They follow Michaelis-Menten kinetics

The property of an enzyme to catalyze a given chemical reaction is an intrinsic function of its

A. concentration

B. conformation

C. Amphoteric nature

D. Electrophoretic mobility

Plotting initial velocity against various pH values in an enzyme-catalyzed reaction gives:

A. A hyperbolic curve

B. A bell-shaped curve

C. A linear plot

D. A sigmoid curve

Isoenzymes are utilized as markers in the diagnosis of certain clinical conditions because:

A. Of their high catalytic activity

B. Of the unique combination of their subunits in forming the active polymeric especies

C. They are present in significant concentration in specific cells

D. They exhibit optimum activity within a very narrow pH range

The chief constituent of fibrous part of plants, is:

A. Starch

B. Cellulose

C. Chitin

D. Peptidoglycan

Not true about a glycosidic bond:

A. Acted upon by specific glucosidases

B. May either be in L or D form

C. Broken down by boiling with acids

D. Is stable in an alkaline medium

True regarding sucrose:

A. It has a free carboxyl group

B. It is a non-reducing sugar

C. It is also known as sucrase

D. All of the above

Not true of Lactose:

A. A reducing sugar

B. Hydrolyzed by beta-glycosidase

C. Not fermentable by yeast

D. Has free carbonyl group at the galaxies moiety

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