Week 1 practice exam

If two heterozygotes (Aa) for a given gene had children, what would be the expected ratios of their offspring?

25% AA, 50% Aa, and 25% aa

The RNA codon for methionine is 5′-AUG-3′. Which is the anticodon in the correct methionyl-tRNA?

5′-CAU-3′ or 3'-UAC-5'

A decrease of blood pH from 7.5 to 6.5 would be accompanied by which of the following changes in ion concentration? A 10-fold increase in hydrogen ion concentration A 10-fold increase in hydroxyl ion concentration An increase in hydrogen ion concentration by a factor of 7.5/6.5 A decrease in hydrogen ion concentration by a factor of 6.5/7.5 A shift in concentration of buffer anions, with no change in hydrogen ion concentration

A 10-fold increase in hydrogen ion concentration

With respect to gene mutations, what is a substitution?

A base pair is replaced with another in the coding sequence

Autopsies of patients with Alzheimer disease show protein aggregates called neurofibrillary tangles and neuritic plaques in various regions of the brain. These plaques exhibit the characteristic staining of amyloid. Which of the following structural features is the most likely characteristic of at least one protein in these plaques? A high content of β-pleated sheet structure A high content of α-helical structure A high content of random coils Disulfide bond cross-links between polypeptide chains A low-energy native conformation

A high content of β-pleated sheet structure The characteristic staining of amyloid arises from fibrils ofβ-pleated sheet structure perpendicular to the axis of the fiber. The native conformation of a protein is generally the most stable and lowest energy conformation, and the lower its energy state, the more readily a protein folds into its native conformation and the less likely it will assume the insoluble β-pleated sheet structure of amyloid.

If the DNA strand shown below is used as a template for RNA polymerase, what would be the sequence of the resultant mRNA following transcription? 5′-CATTCCATAGCATGT-3′ A. 5′-ACAUGCUAUGGAAUG-3′ B. 5′-CAUUCCAUAGCAUGU-3′ C. 5′-GUAAGGUAUCGUACA-3′ D. 5′-UGUACGAUACCUUAC-3′

A. 5′-ACAUGCUAUGGAAUG-3′

What do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments? A. Actin filaments would grow longer, because the monomer interactions would be stabilized. B. Actin filaments would shorten because depolymerization would be enhanced. C. Actin filaments would shorten because new monomers could not be added to the filaments. D. No change, as addition of monomers binding nonhydrolyzable ATP would not affect actin filament length.

A. Actin filaments would grow longer, because the monomer interactions would be stabilized.

On which cellular component is protein synthesis initiated? A. Free ribosomes B. Golgi complex C. Rough ER D. Smooth ER E. Lysosomes

A. Free ribosomes

Which of the following are true for all Gram negative bacteria but not all Gram positive bacteria? A. Shed lipopolysaccharide B. Have a thick peptidoglycan layer C. Have teichoic acid in the cell wall D. Have a Cell wall E. Have two lipid bilayers

A. Shed lipopolysaccharide E. Have two lipid bilayers

A 7-month-old girl exhibits an exaggerated startle response, has decreased muscle tone, and demonstrates a loss of hearing. Previously attained developmental milestones appear to be disappearing in this infant. Physical and biochemical examinations show cherry-red spots on the retinas of both eyes and a significant reduction in hexosaminidase A activity. A diagnosis of Tay-Sachs disease is made. Which of the following properties of the lipid substrate for the deficient enzyme is the most likely cause of these symptoms? A. accumulation in cells B. failure to enter cells C. failure to form a physiologically required product D. failure to interact with a cell membrane receptor E. shunting via minor metabolic pathways

A. accumulation in cells

The aldehyde and ketone moieties of the carbohydrates with 5 and 6 carbons will spontaneously react with alcohol groups present in neighboring carbons to produce ring structures. The rings can open and close allowing for different configurations of the atoms in the ring. Which of the following represents the carbon about which this rotation occurs? A. anomeric B. chiral C. glycosidic D. hydroxy E. terminal

A. anomeric

Peripheral membrane proteins: A. are generally noncovalently bound to membrane lipids. B. are usually denatured when released from membranes C. can be released from membranes only by treatment with detergent(s). D. may have functional units on both sides of the membrane. E. penetrate deeply into the lipid bilayer.

A. are generally noncovalently bound to membrane lipids.

You are carrying out experiments to study DNA replication in a cell line derived from a breast cancer tumor. You discover that the replication process does not completely copy all of each chromosome. Examination of the process using electron microscopy indicates that replication ceases near to where the DNA strands are attached to the chromatin scaffold. Given these observations, which of the following activities is most likely to be defective in these cells? A. topoisomerase B. single-stranded binding proteins C. polymerase-α D. DNA ligase E. helicase

A. topoisomerase

Actin subunits bind ____, while ____ subunits bind GTP.

ATP; microtubule

In an enzyme with a critical glutamic acid residue (Glu, E) in the active site, which of the following amino acid substitutions would be expected to have the least effect on enzyme activity? R D K H Y

Aspartic acid; Since glutamic acid is a negatively charged amino acid at physiological pH, any other negatively charged amino acid, such as aspartic acid, could potentially be substituted without significant loss of enzyme activity.

The final step in the maturation of the newly synthesized lagging strand of DNA is the formation of phosphodiester bonds between the Okazaki fragments. What enzymes catalyzes this reaction?

DNA Ligase

A 10-year-old male presents with severe obesity, hypotonia, and hypogonadism. Suspecting a genetic disorder, karyotype analysis is performed. Which chromosome(s) will most likely be abnormal and what is the chromosomal abnormality? A. X, fragile site amplification B. 5, deletion C. 15, microdeletion D. 14 and 21, translocation E. 17, duplication

C. 15, microdeletion (PW)

Which of the following best describes the role of lysosomes? A. The storage of macromolecules B. Sorting of transport vesicles C. Clean-up, recycling, and disposal D. Transport of material to the Golgi E. Facilitate nuclear import

C. Clean-up, recycling, and disposal

If a genetic mutation leads to the development of a non-functional retinoblastoma (RB) gene, which of the following actions will be inhibited? A. Activation of DNA synthesis B. Arrest of the cell cycle in G1 C. Binding of cyclins to CDKs D. Completion of nuclear division during mitosis E. Removal of inhibitory phosphorylations from CDKs

B. Arrest of the cell cycle in G1

Which of the following structures is present in a primordial follicle? A. Antrum B. Follicular cells C. Secondary oocyte D. Zona pellucida E. Granulosa cells

B. Follicular cells

Heavy metal salts are commonly used in transmission electron microscopy (TEM). Which statement best describes the functionality of these metal salts in respect to cellular components? A. Does not affect the density of the labeled components and makes then appear lighter in a TEM image. B. Increase the density of the labeled component and makes then appear darker in a TEM image. C. Increase the density of the labeled component and makes then appear lighter in a TEM image. D. Decrease the density of the labeled component and makes then appear lighter in a TEM image. D. Decrease the density of the labeled component and makes then appear darker in a TEM image.

B. Increase the density of the labeled component and makes then appear darker in a TEM image.

Adenylyl cyclase is activated by a G protein. Which of the following second messengers will be generated? A. ATP B. cAMP C. Calcium D. DAG E. IP

B. cAMP

Which of the following molecule would be the least soluble in aqueous solution? hydroxybutyrate Glycerol Acetoacetic acid Glucose 6-phosphate Benzene

Benzene

A patient was diagnosed with a deficiency of the lysosomal enzyme α-glycosidase. The name of the deficient enzyme suggests that it hydrolyzes a glycosidic bond, which is best described as a bond formed via which of the following? Through multiple hydrogen bonds between two sugar molecules Between the anomeric carbon of a sugar and an O-H (or N) of another molecule Between two anomeric carbons in polysaccharides Internal bond formation between the anomeric carbon of a monosaccharide and its own fifth carbon hydroxyl group Between the carbon containing the aldol or keto group and the α-carbon of the sugar

Between the anomeric carbon of a sugar and an O-H (or N) of another molecule The term "glycosidic bond" refers to a covalent bond formed between the anomeric carbon of one sugar, when it is in a ring form, and a hydroxyl group or nitrogen of another compound. Disaccharides can be linked through their anomeric carbons, but not polysaccharides, because there would be no anomeric carbon left to form a link with the next sugar in the chain.

Steroid hormones usually act on receptors that________?

Bind DNA

Which statement best describes why Cdk activity levels fluctuate with the cell cycle? A. The Cdks activate cyclins. B. Cyclins levels remain constant throughout the cycle. C. Cyclin levels change during the cycle. D. Cyclins phosphorylate each other. E. Cdk degradation precedes entry into the next phase of the cell cycle.

C. Cyclin levels change during the cycle.

Most genetic syndromes that result from duplications or deletions occur during which event? A. Separation of sister chromatids during meiosis II B. Formation of the polar body during meiosis I C. Homologous recombination D. Separation of homologous chromosomes during meiosis I E. Independent assortment during metaphase I

C. Homologous recombination

Under which one of the following conditions would the carboxyl group on a side chain of an amino acid in a polypeptide be predominantly in the unprotonated form? A. In a solution at pH 1 B. Associated with other proteins C. In a solution at pH 7 D. Next to a proline residue E. In a solution of hydrochloric acid

C. In a solution at pH 7

A membrane-enclosed intracellular structure is observed to release a protein through a pore into the cytosol. Following this release, biochemical reactions take place and result in the cell's death by apoptosis. The most likely identity of this intracellular structure is A. Golgi complex B. Lysosome C. Mitochondria D. Nucleus E. Peroxisome

C. Mitochondria

What of the following statements correctly represents a major difference between spermatogenesis and oogenesis? A. Polar bodies are produced during spermatogenesis, but not oogenesis. B. Spermatogenesis begins while the male fetus is in the uterus; while oogenesis does not start until puberty C. Oogenesis results in the formation of only one viable oocyte; while spermatogenesis results in the formation of four viable sperm cells. D. Females are born with oogonia still present in the ovary; while males are born with only primary spermatocytes present in the testes. E. Folliculogenesis occurs only during spermatogenesis, as a stage of spermiogenesis.

C. Oogenesis results in the formation of only one viable oocyte; while spermatogenesis results in the formation of four viable sperm cells

In an experiment, a researcher treats cultured cells overnight with a CDK1 inhibitor, and then in the morning removes the inhibitor and treats the cells with a second drug that is known to depolymerize microtubules. That afternoon the researcher decides to look at the cells under a microscope, what phase of the cell cycle would you expect to find the cells? A. Anaphase B. Interphase C. Prometaphase D. Telophase E. Interphase

C. Prometaphase

The following happens when a G-protein-coupled receptor activates a G protein. A. The β subunit exchanges its bound GDP for GTP. B. The GDP bound to the α subunit is phosphorylated to form bound GTP. C. The α subunit exchanges its bound GDP for GTP. D. It activates the α subunit and inactivates the βγ complex.

C. The α subunit exchanges its bound GDP for GTP.

Which one of the following amino acids may be considered a hydrophobic amino acid at physiological pH of 7.4? A. aspartic acid B. arginine C. isoleucine D. glycine E. threonine

C. isoleucine

In a membrane, which of the following is most likely to be found in the interior of the bilayer, away from water? Carbon chains of fatty acid Glutamic acid-containing portions of intrinsic proteins Phosphate portions of amphipathic lipids The portion of a hormone receptor that binds the hormone The sugar moiety of a glycolipid

Carbon chains of fatty acid

What occurs during interphase?

Cells grow in size

A patient was diagnosed with one of the types of sphingolipidoses, which are congenital diseases involving the inability to degrade sphingolipids. All sphingolipids have in common which one of the following? A glycerol backbone Ceramide Phosphorylcholine N-acetylneuraminic acid (NANA) A steroid ring structure to which sphingosine is attached

Ceramide

Raising the membrane content of which ONE of the following can increase membrane fluidity? Stearic acid Transmembrane proteins Saturated fatty acids Glycosylated proteins Cholesterol

Cholesterol; Cholesterol, as a small, rigid, hydrophobic molecule, increases the disorder in the membrane bilayer, blocking the strong hydrophobic interactions which can occur with unsaturated fatty acid chains, and stabilizing the disorder brought about by unsaturated fatty acid chains. Proteins in the membrane do nto affect the fluidity since the sugars face the outside of the cell, and are not a ppart of the membrane bilayer. Steric acid is a saturated fatty acid and would decrease the fluidity, not increase it.

An insoluble form of a prion protein accumulates in the brains of patients who have which of the following dieases? Alzheimers Alpers sickle cell Creutzfeldt-Jakob disease, CJD Parkinsons

Creutzfeldt-Jakob disease, CJD The α-helix and β-sheet structures in proteins result from the formation of hydrogen bonds between the amide hydrogen of one peptide bond and an adjacent carbonyl oxygen in another peptide bond. For an α-helix to convert into a β-sheet it is required that the hydrogen bonds holding the structure together be broken and then a different series of hydrogen bonds need to form to generate the β-sheet structure

Cytosine in DNA can spontaneously deaminate generating uracil. This spontaneous deamination is corrected for by the removal of uracil by uracil-DNA glycosylase. Spontaneous deamination of 5-methylcytosine generates which of the following nitrogen bases? A T G C U

Cytosine in DNA can spontaneously deaminate generating uracil. This spontaneous deamination is corrected for by the removal of uracil by uracil-DNA glycosylase. Spontaneous deamination of 5-methylcytosine generates thymine.

For which of the following organs would a reticulin stain be most useful to visualize the tissue structure? A. Heart B. Stomach C. Thyroid gland D. Lymph node E. Skin

D. Lymph node

A cell expresses a transmembrane protein that is transported to the plasma membrane and cleaved. The fragment facing the extracellular space is released and binds to receptors on neighboring cells, resulting in activation of intracellular signaling pathways. What form of signaling does this represent? A. Autocrine signaling B. Contact-dependent signaling C. Endocrine signaling D. Paracrine signaling

D. Paracrine signaling

The sodium-proton exchanger is an antiporter. Therefore, it transports A. Both sodium ions and protons against their concentration gradients. B. By hydrolyzing ATP to power movement of both substrates. C. Individual substrates one at a time across the plasma membrane. D. Sodium ions and protons in opposite directions across a membrane. E. Sodium into the cell against its concentration gradient

D. Sodium ions and protons in opposite directions across a membrane.

Which of the following is a correct pairing of clinical syndrome to likely chromosomal cause? A. Turner Syndrome - Translocation B. Edward Syndrome - Fragile site replication C. Angelman Syndrome - Inversion D. Robertsonian Trisomy 21 - Nondisjunction E. Charcot Marie Tooth - Duplication

E. Charcot Marie Tooth - Duplication

A precursor protein intended to function within a lysosome fails to receive a proper lysosomal tag while it is being processed. The protein will therefore be sent to A. Peroxisomes B. Mitochondria C. Cytosol D. Nucleus E. Outside the cell

E. Outside the cell

STATs function in signal transduction by A. Activating GTP binding to the α subunits of G proteins. B. Binding receptors phosphorylated on serine/threonine residues. C. Linking to G protein-coupled transmem- brane receptors. D. Phosphorylating substrates on Tyr residues. E. Stimulating transcription of responsive genes.

E. Stimulating transcription of responsive genes.

Transmembrane proteins can best be described by which one of the following? A. They can usually be dissociated from membranes without disrupting the lipid bilayer. B. They are classified as peripheral membrane proteins. C. They contain hydrophobic amino acid residues at their carboxy terminus. D. They contain hydrophilic amino acid residues extending into the lipid bilayer. E. They contain membrane-spanning regions that are α-helices.

E. They contain membrane-spanning regions that are α-helices. The transmembrane regions are α-helices with hydrophobic amino acid side chains binding to membrane lipids. The hydrophobic interactions hinder their extraction (thus, A and D are incorrect). Because they are not easily extracted, they are classified as integral proteins (thus, B is incorrect). The carboxy and amino terminals of transmembrane proteins extend into the aqueous intracellular and extracellular medium and thus need to contain many hydrophilic residues (thus, C is incorrect).

____ will accumulate in the patients suffering from Tay-Sacs disease?

GM2 Ganglioside

Tay-Sachs disease is caused by elevated intracellular levels of ____

GM2 ganglioside; In the genetic disorder known as Tay-Sachs disease, ganglioside GM2 is not catabolized. As a consequence, the ganglioside concentration is elevated many times higher than normal. The functionally absent lysosomal enzyme is β-N-acetyl hexosaminidase (more commonly called hexosaminidase A). The elevated GM2 results in irreversible brain damage to infants, who usually die before the age of 3 years. Under normal conditions, this enzyme cleaves N-acetylgalactosamine from the oligosaccharide chain of this complex sphingolipid, allowing further catabolism to occur.

A single-nucleotide mutation has converted an "Isoleucine" amino acid to an "Aspergine" within a protein. Surprisingly, the protein lost activity. This could have occurred due to which ONE of the following? Loss of hydrogen bonding capabilities Gain of hydrogen bonding capabilities Gain of hydrophobic interactions Loss of van der Waals interactions Loss of ionic interactions

Gain of hydrogen bonding capabilities Asperagine, contains a carbonyl carbon linked to an amide group on its side chain, and , as such, can participate in hydrogen bonding with other amino acid side chains.

A 42-year-old man presents with hepatomegaly, jaundice, refractory ascites, and renal insufficiency. Peripheral leukocytes exhibit only 20% of normal glucocerebrosidase activity. Which of the following would explain his symptoms? Fabry disease Gaucher disease Krabbe disease Niemann-Pick disease type C2 Tay-Sachs disease

Gaucher disease; Gaucher disease is characterized by the lysosomal accumulation of glucosylceramide (glucocerebroside) which is a normal intermediate in the catabolism of globosides and gangliosides. Gaucher disease results from defects in the gene encoding the lysosomal hydrolase: acid β-glucosidase, also called glucocerebrosidase The hallmark feature of Gaucher disease is the presence of lipid-engorged cells of the monocyte/macrophage lineage with a characteristic appearance in a variety of tissues. These distinctive cells contain one or more nuclei and their cytoplasm contains a striated tubular pattern described as "wrinkled tissue paper." These cells are called Gaucher cells.

Phospholipids generally have which of the following molecules as their major back bone? Glycerol Peptide bond Sphingomyelin Cholesterol cis-Fatty acid

Glycerol

What is the basic amino acid group from the following groups? Lys, His, Arg Asp, Glu Ser, Thr Cys, Met Asn, Gln

Lys, His, Arg

A 4-week-old female with a 2-day history of umbilical bleeding, poor feeding, increased irritability, and vomiting is brought to a pediatric emergency ward. Upon further examination, it is determined that she has "hemorrhagic disease of the newborn," a rare and often fatal disease that usually develops shortly after a baby is born. Although rare, it is generally preventable because it occurs as a result of a deficiency of which vitamin?

K

Which one of the following amino acid substitution would you expect to have the least effect upon secondary and tertiary structure formation whithin a protein? D to V G to K V to R L to I K to E

L to I

The structure of soluble proteins is held together by hydrophobic interactions between amino acids in the core, whereas hydrophilic amino acids on the surface allow interactions with the environment. Which of the following amino acids would you expect to find in the core of a protein? Lysine Arginine Glutamine Leucine Aspartate

Leucine; The side chain in leucine is a branched hydrocarbon without polar groups. The e-amino group of lysine is positively charged at neutral pH and hence is hydrophilic. The guanidine-group of arginine is positively charged at neutral pH and hence is hydrophilic. The carboxylic acid group of glutamate has a negative charge at neutral pH and hence is hydrophilic. The carboxylic acid group of aspartate has a negative charge at neutral pH and hence is hydrophili

Which of the following best describes enzyme histochemistry?

Localizes cellular structures based on specific enzymatic activities

Lysine and amino acids with similer characterstics in histones most likely promot the interactions of histones with which DAN component? Purine Pyrimidines Deoxyribose Phosphate group Nitrogen base

Phosphate group

Rifampicin inhibits which of the following in prokaryotes - DNA doulble helix - RNA polymerase (elongation blocker) - Splicesome - mRNA splicing - helicase activity - tata binding protein

RNA polymerase (elongation blocker)

Which of the following recognizes nascent polypeptides as they emerge from ribosomes?

Signal recognition particle (SRP)

A pateint with a β - thalassemia had their β-globin gene sequenced, and there were no mutations found within the exons of the gene. A mutation was found, however, in the second intron of the gene. Such a mutation could lead to a β-thalassemia due to alterations in which one of the following processes? Capping Transcription Translation Polyadenylation Splicing

Splicing

The backbone of a DNA strand is composed of ___

The backbone is composed of the phosphates and deoxyribose in phosphodiester linkages. The bases are internal to the backbone, base-paired to bases in the complementary strand, and forming stacking interactions within the double helix.

You are examining a patient complaining of cramping in the lower belly, bloating, gas, and diarrhea. These symptoms appear within 30 minutes to 2 hours after the ingestion of dairy products. You advise your patient to avoid foods that contain a particular sugar. Which of the following is the sugar this patient should avoid? glucose lactose sucrose fructose galactose

The patient is most likely deficient in intestinal lactase and is thus, lactose intolerant. The signs and symptoms of lactose intolerance usually begin 30 minutes to 2 hours after eating or drinking foods that contain lactose and include nausea, vomiting, diarrhea, bloating, gas, and painful abdominal cramping.

A patient was diagnosed with a hypertriglyceridemia. This condition is named for the high blood levels of lipids composed of which one of the following? Three fatty acyl groups attached to a glycerol backbone A glycerol lipid containing a phosphorylcholine group A sphingolipid containing three fatty acyl groups Three glycerol moieties attached to a fatty acid Three glyceraldehyde moieties attached to a fatty acid

Three fatty acyl groups attached to a glycerol backbone

An integral membrane protein can be extracted with ___

a solution containing detergent.

The fluidity of the lipid side chains in the interior of a bilayer is generally increased by: - a decrease in temperature. - an increase in fatty acyl chain length. - an increase in the number of double bonds in fatty acids. - an increase in the percentage of phosphatidyl ethanolamine - the binding of water to the fatty acyl side chains.

an increase in the number of double bonds in fatty acids

A 47-year-old man is delivered to the hospital for malaise, jaun- dice, edema, and ascites. On physical exam he had 2 cm hard hepatomegaly and 5 to 6 cm splenomegaly. His bloodwork revealed acanthocytosis (spur cells) and severe liver disease. Liver ultrasound showed nodular hepatomegaly, and biopsy showed advanced cirrhosis with iron accumulation. His bone marrow was hypercellular. While waiting for a liver transplant, the patient was treated with diuretics but progressed to grade IV hepatic encephalopathy and died. If you analyzed the lipid composition of the patient's red blood cells, you would find a relative increased concentration of _____

cholesterol

Patients suffering from spur cell anemial have rough or thorny projections (acanthocytes) on their erythrocytes and also have decreased membrane fluidity. Accumulation of which of the following lipid in their erythroctes mainly causes these symptoms? - triglyceride - lipoprotein - cholesterol - saturated fatty acid - ceramide

cholesterol

A 12-year-old boy has suffered from chronic sinopulmonary disease including persistent infection of the airway with Pseudomonas aeruginosa. He has constant and chronic sputum production because of the airway infection. Additionally, he suffers from gastrointestinal (GI) and nutritional abnormalities that include biliary cirrhosis, meconium ileus, and pancreatic insufficiency. The symptoms are classical for which of the following disorders? congenital adrenal hyperplasia cystic fibrosis renal Fanconi syndrome sickle cell anemia Tay-Sachs disease

cystic fibrosis; Cystic fibrosis results from mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). The disease is characterized by abnormal transport of chloride and sodium across an epithelium, leading to thick, viscous mucus secretions. This mucus builds up in the breathing passages of the lungs, as well as in the pancreas and intestines. Difficulty breathing is the most serious symptom and results from frequent lung infections, particularly with P. aeruginosa. The secretions in the pancreas block the exocrine movement of the digestive enzymes into the duodenum and result in irreversible damage to the pancreas. The lack of digestive enzymes leads to difficulty in absorbing nutrients with their subsequent excretion in the feces resulting in a malabsorption disorder.

During the normal processes of the cell cycle, specific types of DNA-protein complexes form and dissociate which allow condensation and decondensation of the chromosomes. What is the major attractive force between the DNA and the proteins, allowing these complexes to form?

electrostatic interactions

Signaling by a molecule that is carried through circulation to act on target cells at a distance site is an example of which type of signaling?

endocrine

You are studying RNA processing in a cell-free system. You find that incomplete RNA processing is occurring in your system and that the failure is most likely due to incomplete assembly of the splicesome complex. Which of the following RNA-processing events is most likely defective in your assay system? - addition of poly(A) tail - guiding ribosomes to the endoplasmic reticulum - modification of the 5′ end of hnRNA - removal of introns in hnRNA - transport of mRNA to the cytoplasm

removal of introns in hnRNA

Vitamin K serves as a coenzyme in reactions that result in the modified activity of several enzymes of the blood coagulation cascade. Which amino acid modifications requires the activity of vitamin K?

glutamate to γ-carboxyglutamate

Mutational studies on collagen proteins demonstrate that substitution of one particular amino acid significantly affects the normal structure of the collagen molecules. Which of the following amino acids is absolutely required for the stable formation of the collagen triple helix? alanine cysteine glycine phenylalanine tryptophan

glycine All collagens contain 3-stranded helical segments of similar structure. The unique properties of each type of collagen are due mainly to segments that interrupt the triple helix and that fold into other kinds of 3-dimensional structures. The triple-helical structure of collagen arises from an unusual abundance of 3 amino acids: glycine, proline, and hydroxyproline. These amino acids make up the characteristic repeating motif Gly-Pro-X, where X can be any amino acid. Each amino acid has a precise function. The side chain of glycine, an H atom, is the only one that can fit into the crowded center of a 3-stranded helix. Hydrogen bonds linking the peptide bond nitrogen of a glycine residue with a peptide carbonyl group in an adjacent polypeptide help hold the 3 chains together. It is because of this role of glycine in collagen that it is indispensable for normal collagen structure and function.

Mutational studies on collagen proteins demonstrate that substitution of one particular amino acid significantly affects the normal structure of the collagen molecules. Which amino acids are absolutely required for the stable formation of the collagen triple helix?

glycine-x-y, where X is proline and Y is hydroxy-proline or -lysine

A transcriptional promoter is required for which of the following processes? - cleavage and polyadenylation of mRNA - initiation of RNA synthesis - recognition of the 3′ boundary for mRNA splicing - recognition of the 5′ boundary for mRNA splicing - termination of RNA synthesis

initiation of RNA synthesis

Which of the following represents a characteristic feature of the cap structure on the 5′ end of most eukaryotic mRNAs before maturation? - it is a methylated adenine - it is a methylated cytidine - it is a methylated guanine - it is an adenine found attached to a cytidine dinucleotide in the context A-C-C - it is a guanine found attached to a cytidine dinucleotide in the context G-C-C

it is a methylated guanine The 5′ end of all eukaryotic mRNAs are capped with a unique 5′→5′ linkage to a 7-methylguanosine residue. The capped end of the mRNA is thus protected from exonucleases and more importantly is recognized by specific proteins of the translational machinery.

Acid hydrolases fuse with ____

late endosomes

Hydroxylation of what amino acids are required for collagen tensile strength?

lysine or proline

Which of the following determines the sequence of a polypeptide synthesized by the polyribosome complex? aminoacyl-tRNA aminoacyl-tRNA synthetase elongation factor 1 (eEF-1) mRNA peptidyltransferase

mRNA

What is made up of two concentric membranes and is continuous with the endoplasmic reticulum?

nuclear envelope

What defines the isoelectric point (pI) of an amino acid or protein?

pH at which a molecule is electrically neutral

During translation, which of the following enzymes form peptide bonds between adjacent amino acids?

peptidyltransferase

In light microscopy motor neurons (N), basophilic clumps are seen in the cytoplasm are associated with ____

protein signaling molecule production

You are studying the effects of a novel compound on the processes of protein synthesis using a cell culture system. You find that addition of your compound results in premature termination of protein synthesis. Analysis of the compound reveals that it has structural characteristics of an aminoacyl-tRNA. Which of the following protein-synthesis inhibitors is most similar to your test compound? erythromycin puromycin ricin streptomycin tetracyclin

puromycin

You are examining the thermodynamically stable structures of proteins. In particular you are studying the α-helix and β-sheet conformations that form in the study proteins. These conformations correspond to which of the following? native conformation primary structure secondary structure tertiary structure quaternary structure

secondary structure

Neimann Pick disease caused due to the accumulation of what?

sphingomyelin

Sickel cell anemia results from a single nucleotide mutations in which of the the following α-globin locus β-globin locus β-globin genes α- globin genes gaama globin genes

β-globin genes Sickle cell anemia results from a single nucleotide mutation in the β-globin gene resulting in a single amino acid change in the protein. There is no effect of this mutation on the amount (quantitative) of the mutant β-globin protein. The defect is manifest in a change in the character (qualitative) of the resultant β-globin protein. When in the deoxy state, this hemoglobin sticks together resulting in long polymers that distort the shape of the erythrocyte.