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WorksheetsBIOCHEM END-TERM EXAM
Total questions: 131
Worksheet time: 1hrs 6mins
All of the following are considered "weak" interactions in proteins, except:
hydrogen bonds
hydrophobic interactions
ionic bonds
peptide bonds
In an aqueous solution, protein conformation is determined by two major factors. One is the formation of the maximum number of hydrogen bonds. The other is the:
placement of hydrophobic amino acid residues within the interior of the protein.
formation of the maximum number of hydrophillic interactions
maximazation of ionic reactions
minization of entropy by the entropy by the formation of a water solvent shell around the protein
Enzymes differ from other catalysts in that only enzymes:
are not consumed in the reaction.
display specificity toward a single reactant.
fail to influence the equilibrium point of the reaction.
form an activated complex with the reactants.
Which of the following statements is false?
A reaction may not occur at a detectable rate even though it has a favorable equilibrium.
After a reaction, the enzyme involved becomes available to catalyze the reaction again.
For S-->P, a catalyst shifts the reaction equilibrium to the right.
Lowering the temperature of a reaction will lower the reaction rate.
Which one of the following statements is true of enzyme catalysts?
They bind to substrates, but are never covalently attached to substrate or product.
They increase the equilibrium constant for a reaction, thus favoring product formation.
They increase the stability of the product of a desired reaction by allowing ionizations, resonance, and isomerizations not normally available to substrates.
They lower the activation energy for the conversion of substrate to product.
Which one of the following statements is true of enzyme catalysts?
Their catalytic activity is independent of pH.
They are generally equally active on D and L isomers of a given substrate.
They can increase the equilibrium constant for a given reaction by a thousand fold or more.
They can increase the reaction rate for a given reaction by a thousand fold or more.
The role of an enzyme in an enzyme-catalyzed reaction is to:
bind a transition state intermediate, such that it cannot be converted back to substrate.
ensure that all of the substrate is converted to product.
ensure that the product is more stable than the substrate.
increase the rate at which substrate is converted into product.
Enzymes are potent catalysts because they:
are very specific and can prevent the conversion of products back to substrates.
drive reactions to completion while other catalysts drive reactions to equilibrium.
increase the equilibrium constants for the reactions they catalyze.
lower the activation energy for the reactions they catalyze
Which one of the following is not among the six internationally accepted classes of enzymes?
Hydrolases
Ligases
Oxidoreductases
Polymerases
One of the enzymes involved in glycolysis, aldolase, requires Zn2+ for catalysis. Under conditions of zinc deficiency, when the enzyme may lack zinc, it would be referred to as the:
apoenzyme.
coenzyme.
holoenzyme.
prosthetic group.
The major site of formation of acetoacetate from fatty acids is the;
liver
muscle
adipose tissue
kidney
Ketone bodies are formed in the liver and transported to the extrahepatic tissues mainly as:
beta-hydroxybutyric acid
beta-hydroxybutyric CoA
acetone
acetoacetyl-CoA
When comparing the B-oxidation and W-oxidation pathways, which one of the following statements is correct?
B oxidation occurs at the carboxyl end of the fatty acid whereas W oxidation occurs at the methyl end.
B oxidation and w-oxidation occur in the cytoplasm
B oxidation occurs at the methyl end of the fatty acid whereas w oxidation occurs mainly in the mitochondria
B oxidation occurs mainly in the mitochondria whereas w oxidation occurs mainly in the cytoplasm
During B oxidation of fatty acids,___________ is produced in peroxisomes but not in mitochondria
H₂O₂
FADH2
H2O
NADH
In the disease sprue, vitamin B₁₂ (cobalamin) is poorly absorbed in the intestine, resulting in B₁₂ deficiency. If each of the following fatty acids were in the diet, for which one would the process of fatty acid oxidation be most affected in a patient with sprue?
CH₃(CH₂)12COOH
CH₃(CH₂)11COOH
CH₃(CH₂)14COOH
CH₃(CH₂)18COOH
The carbon atoms from a fatty acid with an odd number of carbons will enter the citric acid cycle as acetyl-CoA and:
succinyl-CoA
butyrate
citrate
malate
The following fatty acids, in which the indicated carbons is labeled with 14 C, is fed to an animal ¹⁴CH₃(CH₂)₉COOH. After allowing 30 minutes for fatty acid B oxidation, the label would most likely be recovered in:
propionyl-CoA
palmitoyl-CoA
acetyl-CoA
both acetyl-CoA and propionyl-CoA
If an aerobic organism were fed each of the following four compounds as a source of energy, the energy yield per from these molecules would be in the order?
palmitate > glucose> alanine
glucose > alanine > palmitate
glucose > palmitate > alanine
palmitate > alanine > glucose
The conversion of palmiatoyl-CoA (16:0) to nyristoyl-CoA (14:0) and 1 mol of acetyl CoA by the B-oxidation pathway?
8 mol of FADH₂ are formed.
1 mol of ATP is needed
8 mol of acetyl-CoA are formed
AMP and PPi are formed
The conversion of palmitoyl-CoA (16:0) to myristoyl-CoA (14:0) and 1 mol of acetyl-CoA by the B-oxidation pathway reults in the net formation of
1 FADH2 and 1 NADH
1 FADH2 and 1 NADPH
1 FADH2, 1 NADH, and 1 ATP
2 FADH2 and 2 NADH
Which compound is an intermediate to the B-oxidation of fatty acids?
CH3-CO-CH2-CO-S-CoA
CH₃-CH2-CO-CH2-CO-OPO32-
CH3-CH2-CO-CH2-OH
CH3-CO-CH2-CO-S-CoA
Which of the following statements concerning the B-oxidation of fatty acids is true?
The free fatty acids must be converted to a thioester before the process of B-oxidation commences.
About 1,200 ATP molecules are ultimately produced per 20-carbon fatty acid oxidized
One FADH2 and two NADH are produced for each acetyl CoA
Two NADH are produced for each acetyl-CoA
Saturated fatty acids are degraded by the stepwise reactions of B-oxidation, producing acetyl-CoA under aerobic conditions, how many ATP molecules would be produced as a consequence of removal of each acetyl-CoA?
4
2
3
5
If the 16-carbon saturated fatty acids palmitate is oxidized completely to carbon dioxide and water via the B-oxidation pathway and the citric acid cycle and all of the energy-conserving products are used to drive ATP synthesis in the mitochondrion, the net yield of ATP per molecule of palmitate is?
108
3
10
25
Which of these is able to cross the inner mitochondrial membrane?
Fatty Acyl-carnitine
Acetyle-CoA
Fatty acyl-CoA
Malonyl-CoA
Carnitine is?
essential for intracellular transport of fatty acids
a 15-carbon fatty acid
an essential cofactor for the citric acid cycle
one of the amino acids commonly found in protein
Fatty acids are activated to actyl-CoA(s) and the acyl group is further transferred to carnitine because?
acyl-carnitines readily across the mitochondrial but acyl-CoA(s) do not
acyl-CoAs easily cross the mitochondrial membrane, but the fatty acid themselves will not
carnitine is required to oxidize NAD+ to NADH
fatty acids cannot be ozidized by FAD unless they are in the acyl-carnitine form
Transport of fatty acids from the cytoplasm to the mitochondrial matrix requires?
ATP, Carnitine, and coenzyme A
ATP, cartinine, and coenzyme A
ATP, coenzyme A, and hexokinase
ATP, coenxyme A, and pyruvate dehydrogenase
The role of hormone sensitive triacylgycerol lipase is to?
Hydrolyze triacylgycerol stored in adipose tissue.
Hydrolyze lipids stored in the liver
Hydrolyze membrane phospholipids in hormone-producing cell
Synthesize lipids in adipose tissue
Free fatty acids in the blood stream are?
Carried by the protein serum albumin
Bound to hemoglobin
Freely soluble in the aqueous phase of the blood
Nonexistent; the blood does not contain free fatty acids
Lipoprotein lipase acts in?
Hydrolysis of triacyclgerols of plasma lipoproteins to supply fatty acids to various tissues.
Intestinal uptake of dietary fat
intracellular lipid breakdown of lipoprotein
lipoprotein breakdown to supply needed amino acids
Identify the molecule(s) derived from
arachidonic acid
gangliosides
phosphatidylglycerol
vitamin D
Which vitamin is derived from cholesterol
A
B12
D
E
Which of the following is not a fat-soluble vitamin
A
C
D
E
In the human genetic disease maple urine disease, the metabolic defect involves
a deficiency of the vitamin niacin
oxidative decarboxylation
synthesis of branched chain amino acids
transamination of an amino acid
The human genetic disease phenylketonuria (PKU) can result from:
deficiency of protein in the diet
inability to catabolize ketone bodies
inability to convert phenylalanine
inability to synthesize phenylalanine
Serine or cysteine may enter the citric acid cycle as acetyl-CoA after conversion to:
oxaloacetate.
propionate.
pyruvate
succinate.
The amino acids serine, alanine, and cysteine can be catabolized to yield:
fumarate.
pyruvate.
succinate.
α-ketoglutarate.
If a person's urine contains unusually high concentrations of urea, which one of the following diets has he or she probably been eating recently?
Very low carbohydrate, very high protein
Very high carbohydrate, no protein, no fat
Very very high fat, high carbohydrate, no protein
Very high fat, very low protein
Which of the following statements is false in reference to the mammalian synthesis of urea?
The amino acid arginine is the immediate precursor to urea.
The carbon atom of urea is derived from mitochondrial HCO3-
The precursor to one of the nitrogens of urea is aspartate.
The process of urea production is an energy-yielding series of reactions.
In the urea cycle, ornithine transcarbamoylase catalyzes:
cleavage of urea to ammonia.
formation of citrulline from ornithine and another reactant.
formation of ornithine from citrulline and another reactant.
formation of urea from arginine.
Conversion of ornithine to citrulline is a step in the synthesis of:
carnitine.
pyruvate.
tyrosine.
urea
Which of these directly donates a nitrogen atom for the formation of urea during the urea cycle?
Adenine
Aspartate
Creatine
Glutamate
Which substance is not involved in the production of urea via the urea cycle
Aspartate
ATP
Carbamoyl phosphate
Malate
Urea synthesis in mammals takes place primarily in tissues of the:
brain.
kidney
liver.
skeletal muscle.
The conversion of glutamate to an α-ketoacid and NH4
does not require any cofactors.
is a reductive deamination.
is accompanied by ATP hydrolysis catalyzed by the same enzyme.
is catalyzed by glutamate dehydrogenase.
Glutamate is metabolically converted to α-ketoglutarate and NH4
deamination.
hydrolysis
oxidative deamination
reductive deamination.
Which of the following is not true of the reaction catalyzed by glutamate dehydrogenase?
transamination in that it involves the coenzyme pyridoxal phosphate (PLP)
NH4+ is produced.
The enzyme can use either NAD+or NADP+ as a cofactor.
The enzyme is glutamate-specific, but the reaction is involved in oxidizing other amino acids.
Pyridoxal phosphate is a cofactor in this class of reactions:
desulfuration.
methylation
reduction
transamination.
Transamination from alanine to α-ketoglutarate requires the coenzyme:
biotin.
NADH.
No coenzyme is involved.
pyridoxal phosphate (PLP).
The coenzyme involved in a transaminase reaction is:
biotin phosphate.
lipoic acid.
nicotinamide adenine dinucleotide phosphate (NADP+)
pyridoxal phosphate (PLP).
The coenzyme required for all transaminations is derived from:
niacin.
pyridoxine (vitamin B6)
riboflavin
thiamin.
In amino acid catabolism, the first reaction for many amino acids is a(n):
hydroxylation requiring NADPH and O2.
oxidative deamination requiring NAD+.
reduction requiring pyridoxal phosphate (PLP).
transamination requiring pyridoxal phosphate (PLP).
Which of the following is a zymogen that can be converted to an endopeptidase that hydrolyzes peptide bonds adjacent to Lys and Arg residues?
Pepsin
Pepsinogen
Trypsin
Trypsinogen
In the digestion of protein that occurs in the small intestine, which enzyme is critical in the activation of zymogens?
Enteropeptidase
Hexokinase
Papain
Pepsin
Which of these is not a protease that acts in the small intestine?
Chymotrypsin
Elastase
Enteropeptidase
Secretin
During muscle contraction, hydrolysis of ATP results in a change in the:
conformation of actin
conformation of myosin
structure of the myofibrils
structre of the sacroplasmic
The energy that is released by the hydrolysis of ATP by actin is used for:
actin filament assembly.
actin filament disassembly.
actin-myosin assembly.
actin-myosin disassembly.
The predominant structural feature in myosin molecules is:
a β structure
an α helix.
the Fab domain.
the light chain.
Which of the following generalizations concerning motor proteins is correct?
They convert chemical energy into kinetic energy.
They convert chemical energy into potential energy.
They convert kinetic energy into chemical energy.
They convert kinetic energy into rotational energy.
The fundamental cause of sickle-cell disease is a change in the structure of
blood.
capillaries.
hemoglobin.
red cells.
The amino acid substitution of Val for Glu in Hemoglobin S results in aggregation of the protein because of ___________ interactions between molecules.
covalent
disulfide
hydrogen bonding
hydrophobic
Which of the following is not correct concerning cooperative binding of a ligand to a protein?
It is usually a form of allosteric interaction.
It is usually associated with proteins with multiple subunits.
It rarely occurs in enzymes.
It results in a nonlinear Hill Plot.
Which of the following is not correct concerning 2,3-bisphosphoglycerate (BPG)?
It binds at a distance from the heme groups of hemoglobin.
It binds with lower affinity to fetal hemoglobin than to adult hemoglobin.
It increases the affinity of hemoglobin for oxygen.
It is an allosteric modulator.
In hemoglobin, the transition from T state to R state (low to high affinity) is triggered by:
Fe2+ binding.
heme binding.
oxygen binding.
subunit association.
An allosteric interaction between a ligand and a protein is one in which:
binding of a molecule to a binding site affects binding of additional molecules to the same site
binding of a molecule to a binding site affects binding properties of another site on the protein.
binding of the ligand to the protein is covalent.
multiple molecules of the same ligand can bind to the same binding site.
Myoglobin and the subunits of hemoglobin have:
very different primary and tertiary structures.
very similar primary and tertiary structures.
very similar primary structures, but different tertiary structures.
very similar tertiary structures, but different primary structures.
Which of the following statements about protein-ligand binding is correct?
The Ka is independent of such conditions as salt concentration and pH.
The larger the Ka (association constant), the weaker the affinity.
The larger the Ka, the faster is the binding.
The larger the Ka, the smaller the Kd (dissociation constant).
In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as:
hyperbolic.
linear with a negative slope.
linear with a positive slope.
random.
When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe2+ are occupied by:
one O atom and one amino acid atom.
one O2 molecule and one amino acid atom.
one O2 molecule and one heme atom.
two O atoms.
A prosthetic group of a protein is a non-protein structure that is:
a ligand of the protein.
a part of the secondary structure of the protein.
a substrate of the protein.
permanently associated with the protein.
The interactions of ligands with proteins:
are relatively nonspecific.
are relatively rare in biological systems.
are usually irreversible.
are usually transient.
Protein S will fold into its native conformation only when protein Q is also present in the solution. However, protein Q can fold into its native conformation without protein S. Protein Q, therefore, may function as a ____________ for protein S.
ligand
molecular chaperone
protein precursor
structural motif
Which of the following is least likely to result in protein denaturation?
Altering net charge by changing pH
Changing the salt concentration
Disruption of weak interactions by boiling
Exposure to detergents
A repeating structural unit in a multimeric protein is known as a(n):
domain.
motif.
oligomer.
protomer.
Which of the following statements about oligomeric proteins is false?
A subunit may be similar to other proteins.
All subunits must be identical.
Many have regulatory roles.
Some oligomeric proteins can further associate into large fibers.
Proteins are classified within families or superfamilies based on similarities in:
evolutionary origin.
physico-chemical properties.
structure and/or function.
subcellular location.
Proteins often have regions that show specific, coherent patterns of folding or function. These regions are called:
domains.
oligomers.
peptides
sites.
Determining the precise arrangement of atoms within a large protein is possible only through the use of:
light microscopy.
molecular model building.
Ramachandran plots.
x-ray diffraction.
Which of the following statements is false?
Collagen is a protein in which the polypeptides are mainly in the α-helix conformation
Disulfide linkages are important for keratin structure
Gly residues are particularly abundant in collagen.
Silk fibroin is a protein in which the polypeptide is almost entirely in the α conformation.
The three-dimensional conformation of a protein may be strongly influenced by amino acid residues that are very far apart in sequence. This relationship is in contrast to secondary structure, where the amino acid residues are:
always side by side.
generally near each other in sequence.
invariably restricted to about 7 of the 20 standard amino acids.
often on different polypeptide strands.
Amino acid residues commonly found in the middle of β turn are:
Ala and Gly.
hydrophobic.
Pro and Gly.
those with ionized R-groups.
The major reason that antiparallel β-stranded protein structures are more stable than parallel β-stranded structures is that the latter:
do not have as many disulfide crosslinks between adjacent strands.
do not stack in sheets as well as antiparallel strands.
have fewer lateral hydrogen bonds than antiparallel strands
have weaker hydrogen bonds laterally between adjacent strands.
A D-amino acid would interrupt an α helix made of L-amino acids. Another naturally occurring hindrance to the formation of an α helix is the presence of:
a negatively charged Arg residue.
a nonpolar residue near the carboxyl terminus.
a positively charged Lys residue.
a Pro residue.
In the alpha helix the hydrogen bonds:
are roughly parallel to the axis of the helix
are roughly perpendicular to the axis of the helix.
occur mainly between electronegative atoms of the R groups.
occur only between some of the amino acids of the helix.
Which of the following pairs of bonds within a peptide backbone show free rotation around both bonds?
Cα—C and N—Cα
C=O and N—C
C=O and N—Cα
N—C and Cα—C
Which of the following best represents the backbone arrangement of two peptide bonds?
Cα—N—Cα—C—Cα—N—Cα—C
Cα—N—C—C—N—Cα
C—N—Cα—Cα—C—N
Cα—C—N—Cα—C—N
Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase complex?
Biotin participates in the decarboxylation.
Both NAD+ and a flavin nucleotide act as electron carriers.
The reaction occurs in the mitochondrial matrix.
The substrate is held by the lipoyl-lysine "swinging arm."
Which of the below is not required for the oxidative decarboxylation of pyruvate to form acetyl-CoA?
ATP
CoA-SH
FAD
Lipoic acid
Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?
Biotin, NAD+, and FAD
NAD+, biotin, and TPP
Pyridoxal phosphate, FAD, and lipoic acid
TPP, lipoic acid, and NAD+
Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic conditions in animal cells is correct?
The methyl (—CH3) group is eliminated as CO2.
The process occurs in the cytosolic compartment of the cell.
The pyruvate dehydrogenase complex uses all of the following as cofactors: NAD+, lipoic acid, pyridoxal phosphate (PLP), and FAD.
The reaction is so important to energy production that pyruvate dehydrogenase operates at full speed under all conditions.
Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate, which of the following compounds would you expect to decrease in concentration?
Citrate
Fumarate
Isocitrate
Pyruvate
Which of the following is not an intermediate of the citric acid cycle?
Acetyl-CoA
Citrate
Oxaloacetate
Succinyl-CoA
In mammals, each of the following occurs during the citric acid cycle except:
formation of α-ketoglutarate.
generation of NADH and FADH2.
metabolism of acetate to carbon dioxide and water.
net synthesis of oxaloacetate from acetyl-CoA.
xaloacetate uniformly labeled with 14C (i.e., with equal amounts of 14C in each of its carbon atoms) is condensed with unlabeled acetyl-CoA. After a single pass through the citric acid cycle back to oxaloacetate, what fraction of the original radioactivity will be found in the oxaloacetate?
All
1/2
1/3
1/4
Conversion of 1 mol of acetyl-CoA to 2 mol of CO2 and CoA via the citric acid cycle results in the net production of:
1 mol of citrate.
1 mol of FADH2.
1 mol of NADH.
1 mol of oxaloacetate.
Which one of the following is not associated with the oxidation of substrates by the citric acid cycle?
All of the below are involved.
CO2 production x
Flavin reduction
Pyridine nucleotide oxidation
The oxidative decarboxylation of α-ketoglutarate proceeds by means of multistep reactions in which all but one of the following cofactors are required. Which one is not required?
ATP
Coenzyme A
Lipoic acid D
NAD+
The reaction of the citric acid cycle that is most similar to the pyruvate dehydrogenase complex-catalyzed conversion of pyruvate to acetyl-CoA is the conversion of:
fumarate to malate.
malate to oxaloacetate.
succinyl-CoA to succinate.
α-ketoglutarate to succinyl-CoA.
Which one of the following enzymatic activities would be decreased by thiamine deficiency?
Isocitrate dehydrogenase
Malate dehydrogenase
Succinate dehydrogenase
α-Ketoglutarate dehydrogenase complex
The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) by substrate level phosphorylation is the conversion of:
fumarate to malate.
malate to oxaloacetate.
succinate to fumarate
succinyl-CoA to succinate
21. All of the oxidative steps of the citric acid cycle are linked to the reduction of NAD+ except the reaction catalyzed by:
isocitrate dehydrogenase.
malate dehydrogenase.
pyruvate dehydrogenase
succinate dehydrogenase.
Which of the following cofactors is required for the conversion of succinate to fumarate in the citric acid cycle?
ATP
Biotin
FAD
NAD+
In the citric acid cycle, a flavin coenzyme is required for:
oxidation of fumarate.
oxidation of isocitrate.
oxidation of malate.
oxidation of succinate.
Which of the following intermediates of the citric acid cycle is prochiral?
Citrate
Isocitrate
Malate
Oxaloacetate
Entry of acetyl-CoA into the citric acid cycle is decreased when: B)
NADH is rapidly oxidized through the respiratory chain.
the ratio of [ATP]/[ADP is low
the ratio of [ATP]/[ADP] is high.
the ratio of [NAD+]/[NADH] is high.
Citrate synthase and the NAD+-specific isocitrate dehydrogenase are two key regulatory enzymes of the citric acid cycle. These enzymes are inhibited by: AMP and/or NAD+. C) AMP and/or NADH. D) ATP and/or NAD+. E) ATP and/or NADH.
AMP and/or NAD+.
AMP and/or NADH.
ATP and/or NAD+.
ATP and/or NADH.
During seed germination, the glyoxylate pathway is important to plants because it enables them to:
carry out the net synthesis of glucose from acetyl-CoA.
form acetyl-CoA from malate.
get rid of isocitrate formed from the aconitase reaction.
obtain glyoxylate for cholesterol biosynthesis.
The glyoxylate cycle is:
a means of using acetate for both energy and biosynthetic precursors.
an alternative path of glucose metabolism in cells that do not have enough O2.
defective in people with phenylketonuria.
is not active in a mammalian liver.
A certain bacterial mRNA is known to represent only one gene and to contain about 800 nucleotides. If you assume that the average amino acid residue contributes 110 to the peptide molecular weight, the largest polypeptide that this mRNA could code for would have a molecular weight of about:
800.
5,000.
30,000.
80,000.
Which one of the following statements about ribosomes is true?
The large subunit contains rRNA molecules; the small subunit does not.
The RNA in ribosomes plays a structural, not catalytic, role.
There are about 25 ribosomes in an E. coli cell.
There are two major ribosomal subunits, each with multiple proteins.
Which of the following statements about tRNA molecules is false?
A, C, G, and U are the only bases present in the molecule.
Although composed of a single strand of RNA, each molecule contains several short, double-helical regions.
Any given tRNA will accept only one specific amino acid.
The amino acid attachment is always to an A nucleotide at the 3' end of the molecule.
Which of the following statements about the tRNA that normally accepts phenylalanine is false? (mRNA codons for phenylalanine are UUU and UUC.)
It will accept only the amino acid phenylalanine.
Its molecular weight is about 25,000.
Phenylalanine can be specifically attached to an —OH group at the 3' end.
The tRNA must contain the sequence UUU.
Which of the following is not true of tRNA molecules?
Their anticodons are complementary to the triplet codon in the mRNA.
They contain more than four different bases.
They contain several short regions of double helix.
With the right enzyme, any given tRNA molecule will accept any of the 20 amino acids.
In E. coli, aminoacyl-tRNA synthetases:
activate amino acids in 12 steps.
are amino acid-specific; there is at least one enzyme specific for each amino acid.
fall into two classes, each of which attaches amino acids to different ends of the tRNA.
have no proofreading activities.
Which of the following statements about aminoacyl-tRNA synthetases is false?
Some of the enzymes have an editing/proofreading capability.
The enzyme attaches an amino acid to the 3' end of a tRNA.
The enzyme splits ATP to AMP + PPi.
The enzyme will use any tRNA species but is highly specific for a given amino acid.
The enzyme that attaches an amino acid to a tRNA (aminoacyl-tRNA synthetase):
always recognizes only one specific tRNA.
attaches a specific amino acid to any available tRNA species.
attaches the amino acid at the 5' end of the tRNA.
catalyzes formation of an ester bond.
Which of the following statements about bacterial mRNA is true?
A ribosome usually initiates translation near the end of the mRNA that is synthesized last.
An mRNA is never degraded but is passed on to the daughter cells at cell division.
During polypeptide synthesis, ribosomes move along the mRNA in the direction 5' 3'.
Ribosomes cannot initiate internally in a polycistronic transcript.
Bacterial ribosomes:
bind tightly to specific regions of DNA, forming polysomes.
contain at least one catalytic RNA molecule (ribozyme).
contain three species of RNA and five different proteins.
have specific, different binding sites for each of the 20 tRNAs.
The large structure consisting of a mRNA molecule being translated by multiple copies of the macromolecular complexes that carry out protein synthesis is called a:
lysosome.
polysome
proteosome
ribosome.
Which one of the following antibiotics does not function by interfering with the translational process?
Chloramphenicol
Cycloheximide
Penicillin
Puromycin
Haemopoiesis is a process of the production of
Blood plasma
Erythrocytes
Bone marrow
Haemoglobin
What happens to the iron (Fe) that is released during the breakdown of damaged RBCs?
It is used to synthesize protein
It is transport to the liver where it becomes part of the bile
It is converted into urobilin and excreted in urine
It attaches to transferrin and is transported to bone marrow for use in hemoglobin synthesis
Which of the following is a mismatch between blood cells and their description?
Neutrophils - respond to tissue destruction by bacteria; release lysozyme, strong oxidants and defensins
Lymphocyte - occur as B-cells, T-cells and natural killer cells
Eosinophils - WBC showing a kidney-shape nucleus; capable of phagocytosis
Basophil - involved in inflammatory and allergic reaction; are involved in hypersensitivity reactions
The main function of erythrocytes
Aggregate and prevent bleeding
Defends the body against bacteria
Transport nutrients
Transport oxygen
If tests reveals high levels if cosinophils what may this indicate
A fungal infection
Leukaemia
A viral infection
An allergy
Definition of haemostats is
The formation of blood cells
The pooling of blood
The prevention of bleeding
The destruction of RBC
What is blood is responsible for fighting infections
RBC
WBC
Platelets
Plasma
What part of blood is responsible for carrying wastes, nutrients, and minerals?
RBC
WBC
Platelets
Plasma
A person has bloos group B means he/she has
an antigen in RBC
an antigen in plasma
b antigen in in RBC
b antigen in plasma
For blood clotting fibrinogen is changed into fibrin with the help of
thrombin
platelets
vitamin K
antithrombin
