BIOCHEMISTRY WEEK 1- 6 (MIDTERM PREP)

What is the ratio of protonated to unprotonated lactic acid in a 0.1 M sun of lactic acid at pH 5.86? (pKa of lactic acid is 3.86) a. 1:100 b. 1:10 c. 1:1 d. 10:1 e. 1:1

1:100

The nucleotide sequence 5'-ATTGCAG-3' should base pair with A. 5'-TAACGTC-3'. B. 5'-CTGCAAT-3'. C. 3'-ATTGCAG-5'. D. 3'-CTGCAAT-5'.

5'-CTGCAAT-3'

Heterochromatin is A. metabolically inactive regions of chromatin. B. found in the centromere region of the chromosome. C. DNA in the process of being replicated. D. A and B above. E. B and C above.

A and B above

All of the following statements about cells are correct except one: a. Cells are the basic units of any biological system. b. The main component of cells is water. c. Enzymes (which constitute a specific group of proteins) are in charge of anabolic and catabolic processes. d. All cells contain a well-defined nucleus containing circular molecules of DNA. e. All living organisms belong to one of those groups: archaea, eubacteria or eukaryotes.

All cells contain a well-defined nucleus containing circular molecules of DNA

Which of the following DNA replication enzymes has a major role in lagging strand synthesis, but only a minor role in leading strand synthesis? A. DNA gyrase B. DNA polymerase I C. DNA polymerase delta D. DNA polymerase III

DNA polymerase I

DNA and RNA are different because: a. DNA uses Thymine while RNA uses Uracil b. DNA is double stranded while RNA is triple stranded c. DNA is only found in the nucleus while RNA can travel anywhere in the cell d. B and C are correct

DNA uses thymine while RNA uses uracil

In the hormonal activation of adenylate cyclase, and the subsequent formation of cyclic AMP, which of the following components is NOT necessary? A. hormone receptor B. GTP C. ATP D. GDP E. guanyl nucleotide regulatory protein

GDP

Why are KD and EC50 usually not the same? A. Not all receptors are capable of activating cell response B. Not all receptors are capable of binding ligand C. Some receptors are inactive D. Some receptors bind more than one ligand E. The cell has �spare receptors�

The cell has �spare receptors�

Which of the following could be a positive allosteric effector of an enzyme? A. a competitive inhibitor B. a noncompetitive inhibitor C. a compound, other than the substrate, which binds to the active site D. a compound, other than the substrate, which binds to the enzyme but not to the active site E. a coenzyme which is essential for the activity of the enzyme

a compound, other than the substrate, which binds to the enzyme but not the active site

For Michaelis-Menten kinetics, Vmax is A. constant for any concentrations of enzyme. B. given in units of moles/liter. C. the velocity which is observed when the substrate concentration is one half of Km. D. a constant for a fixed concentration of enzyme. E. none of the above.

a constant for a fixed concentration of enzyme

Which is true about mRNA? A. It contains a _OH at the 5' carbon of its ribose moieties. B. A copy of its nucleotide sequence can be found in the genetic material C. Analysis of its nucleotide composition reveals that it obeys Chargaff's rules. D. It contains a hydrogen at the 2' carbon of its ribose moieties.

a copy of its nucleoside sequence can be found in the genetic material

Spontaneous conversion of adenine and cytosine from the amino to the amino forms of these bases within DNA results in A. cleavage of the glycosidic bond and loss of the base. B. cleavage of the 3', 5' phosphodiester DNA backbone. C. alteration of the hydrogen bonding of the bases. D. formation of guanine and thymine.

alteration of the hydrogen bonding of the bases

The primary structure of a protein refers to its A. ability to form intrachain hydrogen bonds. B. amino acid sequence. C. folding induced by disulfide linkages. D. ability to form subunit structures. E. ability to form interchain hydrogen bonds.

amino acid sequence

Phospholipids have the property of detergency. This is due primarily to A. polar head groups. B. a hydrocarbon tail. C. an amphipathic nature. D. solubility

an amphipathic nature

When a reaction reaches equilibrium, A. delta Go is equal to zero. B. delta G is equal to zero. C. no substrate is converted to product. D. no product can be converted back to substrate. E. the reaction becomes temperature independent.

delta G is equal to zero

What is an example of a lipid second messenger? A. Calcium B. cAMP C. cGMP D. Diacylglycerol E. Inositol phosphate

diacylglycerol

Hemoglobin A differs from hemoglobin S in having two more anionic groups (both hemoglobins have a molecular weight of approximately 67,000). Which one of the following separation methods is most likely to distinguish between these two A. Precipitation with ethanol B. Gel filtration C. Ultracentrifugation D. Electrophoresis

electrophoresis

At their isoelectric point proteins have A. no ionized groups. B. no positively charged groups. C. no negatively charged groups. D. equal numbers of positively and negatively charged groups. E. none of the above

equal numbers of positively and negatively charged groups

Which of the following reactions is catalyzed by a kinase? A. glycerol + ATP <===> glycerol phosphate + ADP B. lactate + NAD+ <===> pyruvate + NADH + H+ C. glucose 6-phosphate <===> fructose 6-phosphate D. UDP-galactose + glucose 1-phosphate <===> UDP-glucose + galactose 1-phosphate E. fructose 1,6-bisphosphate + H2O <===> fructose 6-phosphate + Pi

glycerol + ATP <===> glycerol phosphate + ADP

Which of the following amino acids predominates in the collagen molecule? A. Alanine B. Glycine C. Proline D. Lysine E. Tryptophan

glycine

In biological membranes the PREDOMINANT interaction between the proteins and phospholipids is probably A. hydrogen bonding. B. hydrophobic interaction. C. ionic interactions. D. covalent linkages.

hydrophobic interaction

which type of organelle is most likely to contain a set of enzymes devoted mainly to catabolism? a. rough endoplasmic reticulum b. smooth endoplasmic reticulum c. storage granule d. lysosome e. Golgi apparatus

lysosome

Which amino acid contains a sulfur atom? A. Arginine B. Aspartate C. Methionine D. Leucine E. Serine

methionine

If the mismatch repair machinery detects a mismatch soon after DNA replication, it can distinguish the parental strand from the newly synthesized strand by A. methylation B. the RNA primers C. the Okazaki fragments D. single stranded DNA binding protein E. the degree of supercoiling

methylation

Integral membrane proteins that exhibit an intrinsic activity of hydrolyzing ATP to ADP and Pi most likely participate in A. binding polypeptide hormones. B. generating intracellular messengers during signal transduction. C. initiating one or more steps in blood coagulation. D. moving cations against their concentration gradient. E. targeting proteins to different organelles.

moving cations against their concentration gradient

A frameshift or phase shift mutation A. can only affect one polypeptide chain made from a polycistronic mRNA. B. can usually be corrected by a missense mutation. C. has little effect on most proteins. D. could not occur in a regulatory gene. E. None of the other answers is correct.

none of the other answers is correct

The amount of phospahtidylinositol-4,5-bisphosphate in the membrane is too small to fill the need for prolonged signaling. What is an alternative source of diacylglycerol? A. Acetyl CoA B. Cardiolipin C. Intracellular IP2 D. Phosphatidyl choline and ethanolamine E. Triacylglycerols

phosphatidyl choline and ehtanolamine

Initiation of eukaryotic translation is directly inhibited by which of the following? A. acetylation of histone H1 B. phosphorylation of AP1 (activator protein-1) C. phosphorylation of eIF2 (eukaryotic initiation factor 2) D. acetylation of SRP (signal recognition particle)

phosphorylation of eIF2 (eukaryotic initiation factor 2)

What form does collagen IV in basal lamina take? A. Barrel B. Fibrils C. Globin fold D. Globular E. Sheet-like

sheet-like

Catabolite activator protein (CAP) increases transcription from the lactose operon by A. binding lactose which releases the repressor from the operator. B. directly increasing free cellular cAMP concentrations. C. binding the operator and competing for repressor binding. D. stabilizing the binding of RNA polymerase to the promoter. E. preventing the degradation of RNA polymerase.

stabilizing the binding of RNA polymerase to the promoter

Which of the following is NOT associated with transcription? a. tRNA b. mRNA c. RNA polymerase d. DNA e. a promoter

tRNA

Why does endocrine signaling result in a long-term response? A. The hormone is bound covalently to the receptor B. The hormone is metabolized slowly C. The receptor has a high affinity for hormone D. There is a high concentration of hormone in blood E. There is a rapid rate of synthesis of hormone

the receptor has a high affinity for hormone

Codons on mRNA may be accurately described by all of the following EXCEPT A. they are read in a non-overlapping fashion. B. they can form hydrogen bonds with tRNA. C. they may specify initiation points. D. different codons can specify for the same amino acid, due to the fact that the gentic code is degenerated. E. the same codon may specify more than one amino acid.

the same codon may specify more than one amino acid

To which of the following does protein tertiary structure refer? A. amino acid sequence B. amino acid composition C. helical structure in proteins D. the bonding of the protein to nonprotein components E. the three dimensional structure

the three dimensional structure

High concentrations of substrate overcome reversible inhibition by a transition-state analog because A. only the substrate has the inherent ability to bind at the active-site. B. the substrate has a greater inherent affinity for the active-site. C. transition-state analogs show noncompetitive kinetics. D. the substrate will react with the transition-state analog. E. The transition-state analog is a competitive inhibitor.

the transition-state analog is a competitive inhibitor

Laminin and fibronectin have which characteristic in common? A. they bind collagen B. they contain three polypeptide chains C. they undergo covalent modification outside of cells D. they contain a cell-binding domain characterized by an RDG sequence

they bind collagen

Which of the following is a general feature of both DNA and RNA? A. In vivo they are double helical structures formed from two separate chains. B. They are alkaline stable. C. They form complementary G-C base pairs. D. They contain small amounts of pseudouridine. E. They interact with histones to form nucleosomes.

they form complementary G-C base pairs

Characteristics of disulfide bonds in proteins include all of the following EXCEPT A. they are an example of a post-translational modification. B. they are common in proteins secreted from cells. C. they may cross-link two polypeptides in a globular protein. D. they may form with the assistance of a chaperone. E. they may stabilize the alpha-helix conformation.

they may stabilize the alpha-helix conformation

In the double helical structure of DNA, adenine is hydrogen bonded to A. uridine. B. cytosine. C. guanine. D. thymine.

thymine

Concerning the consensus sequences of EUKARYOTIC promoters... A. Those small stretches of DNA at the beginning of each promoter are all similar for all the genes. B. specific DNA sequences that are directly recognized by the RNA polymerase II. C. located downstream from the mRNA start site. D. variable sequences necessary for initiating the transcription of mRNA, from which the main consensus sequence is called "TATA box".

variable sequences necessary for initiating the transcriptions of mRNA, from which the main consensus sequence is called "TATA box"

To make an acetate buffer at pH 3.7, what is the required ratio of sodium acetate to acetic acid? (pKa of acetic acid is 4.7) a. 100:1 b. 10:1 c. 1:1 d. 1:10 e. 1:1

1:10

Use the Michaelis-Menten equation to calculate the initial velocity for an enzyme with Vmax = 3 micromole/min Km= 2 mM [S] = 4 mM A. 0.75 micromole/min B. 1.0 micromole/min C. 1.5 micromole/min D. 2 micromole/min E. 2.5 micromole/min

2 micromole/min

Listed are four enzymes involved in DNA replication1. DNA polymerase III 2. Primase 3. DNA ligase 4. DNA polymerase I. The correct order of action of these enzymes in lagging strand DNA synthesis is A. 4,2,1,3 B. 2,1,4,3 C. 4,3,2,1 D. 2,4,1,3 E. 4,1,2,3

2,1,4,3

Put the following events concerning Phosphatidylinositol-linked signal transduction in the appropriate order as regards the sequence of events. (l) PLC cleaves PIP2 to IP3 and DAG. (2) Hormone binds to a specific receptor. (3) There is a GTP for GDP exchange on a G protein. (4) The GTP-G protein moves to a PL-C and activates it. (5) IP3 binds to an intracellular receptor and induces calcium release. (6) DAG and calcium fully activate protein kinase C. A. 2, 3, 1, 4, 6, 5 B. 2, 3, 4, 1, 5, 6 C. 3, 2, 4, 1, 5, 6 D. 2, 4, 3, 1, 6, 5 E. 3, 4, 2, 1, 5, 6

2,3,4,1,5,6

Which is the complementary strand of this sequence: 3' AGTCAGACCAGAC 5'? A. 5' AGTCAGACCAGAC 3' B. 3' GTCTGGTCTGACT 5' C. 5' GTCTGGTCTGACT 3' D. 5' CAGACCAGACTGA 3'

3'-GTCTGGTCTGACT-5'

Glutamic acid (pK1 = 2.0, pK2 = 4.0, pK3 = 10.0) is dissolved in water. The isoelectric point (pI) of glutamic acid is A. 2.0 B. 3.0 C. 4.0 D. 7.0 E. 10.0

3.0

What are the complementary base pairs in DNA A. Adenine : Uracil and Guanine : Cytosine B. Adenine : Thymine and Guanine : Uracil C. Adenine : Guanine and Uracil : Cytosine D. Adenine : Thymine and Guanine : Cytosine E. Adenine : Cytosine and Guanine : Thymine

Adenine: thymine and guanine: cytosine

Which of the following groups of amino acid residues would be expected to have all of their side chains in a charged state at physiological pH? A. Glu, Tyr, Asn B. Met, Cys, Lys C. His, Ser, Arg D. Asp, His, Tyr E. Arg, Asp, Lys

Arg, Asp, Lys

Helicases A. cut one strand of the double helix. B. cut both strands of the double helix. C. require ATP. D. unwind the double helix. E. C and D

C and D

Which of the following is the anticodon for the initiator codon? (all written 5' to 3') A. TAC B. CTA C. UAC D. CAT E. CUI

CAT

Which of the following is NOT an intracellular mediator (second messenger) of hormone action? A. G protein B. cAMP C. calmodulin D. diacylglycerol (DG) E. inositol triphosphate (IP3)

G protein

Which form of anchoring proteins in the membrane allows for the easiest release and reattachment of a protein? A. Farnesyl B. Geranylgeranyl C. GPI D. Myristoyl E. Thioether

GPI

Which one of the following classes of histones is not a component of the core particle? A. H1 B. H2A C. H2B D. H. H4

H1

How does the cell maintain a higher level of K+ than of Na+? A. The Na+ leaks out into the surrounding extracellular fluid. B. K+ is bound to sites inside the cell. C. The body contains less total Na+ than K+, so Na+ is found at a low concentration inside the cell. D. Na+ is actively transported out of the cell and K+ actively transported in the cell. E. Much of the Na+ outside the cell is bound to protein, so that no Na+ gradient exists across the cell membrane.

Na+ is actively transported out of the cell and K+ actively transported in the cell.

In treating a patient with congestive heart failure, you have prescribed digoxin (a cardiac glycoside) to strengthen the heart's output and maintain a regular rate. The target of this drug is the A. ATP synthase. B. Na+, K+ - ATPase. C. ligand - gated Ca2+ channel. D. resting K+ channel. E. voltage - gated Na+ channel.

Na+, K+ - ATPase.

The nucleus... (Select the wrong answer) a. Contains the genetic information of each cell b. Is surrounded by a lipid membrane that restricts the shuttle of proteins from the cytoplasm to the nucleus c. Is absent in prokaryotes. d. Contains the nucleolus e. None of the above is wrong.

None of the above are wrong

Which of the following techniques is best suited for the determination of the molecular weight of protein? A. isoelectric focusing B. SDS polyacrylamide gel electrophoresis C. Capillary exlectrophoresis D. gel chromatography in dilute buffer E. B and C are correct

SDS polyacrylamide gel electrophoresis

Which of the following peptides would be least soluble in aqueous solution? A. Val - Arg - His - Ser - Glu - Arg - Tyr - Asp B. Val - Gly - Pro - Ser - Gly - Lys - Pro - Gly C. Val - Leu - Gly - Ser - Gly - Leu - Phe - Val D. Val - Arg - Cys - Ser - Glu - Glu - Cys - Glu

Val-Leu-Gly-Ser-Gly-Leu-Phe-Val

Polysomes are A. polycistronic messengers bound to RNA polymerase. B. polycistronic messengers bound to DNA polymerase. C. polycistronic messengers bound to a single ribosome. D. a group of ribosomes bound to different sections of the same mRNA with each ribosome engaged in the synthesis of the same kind of polypeptide chain. E. none of the above

a group of ribosomes bound to different sections of the same mRNA with each ribosome engaged in the synthesis of the same kind of polypeptide chain

An enzyme which removes groups (other than hydrogens) and leaves double bonds is called A. an isomerase. B. a lyase. C. a ligase. D. a transferase. E. none of the above

a lyase

The region of the DNA to which RNA polymerase binds prior to the synthesis of RNA is called A. a terminator. B. a repressor region. C. an operator. D. a promoter. E. a restriction site.

a promoter

DNA synthesis requires a primer. A primer is A. an available serine hydroxyl (-OH) group on DNA polymerase III for initiation of DNA synthesis. B. the complimentary strand of DNA. C. an available 5'-triphosphate on the nitrogenous bases used in synthesis. D. a short oligonucleotide with an available hydroxyl group on the ribose or deoxyribose. E. a short oligonucleotide with an available 2'-hydroxyl group on the ribose or deoxyribose.

a short oligonucleotide with an available hydroxyl group on the ribose or deoxyribose

Tetracycline is an antibiotic that binds to the 30S subunit of the bacterial ribosome. This information suggests that the most likely mechanism by which tetracycline blocks bacterial growth is to inhibit synthesis of: A. mRNA. B. rRNA. C. a specific bacterial protein. D. a specific class of bacterial proteins. E. all bacterial proteins.

all bacterial proteins

Chemicals that bind to DNA intercalating between the bases A. can cause frame shift mutations. B. can cause deletion mutations. C. can cause insertion mutations. D. are generally planar hydrophobic molecules. E. all of the above

all of the above

In the normal red blood cell, 2,3-BPG binds to alpha-amino groups of hemoglobin. What would happen to the O2-saturation curve of Hb in the presence of normal amounts of 2,3-BPG if a drug were administered that prevents the binding of 2,3-BPG to Hb? A. the curve would be shifted to the left from that of normal red cells B. the concentration of O2 necessary to saturate Hb would be lower than that normally required C. the amount of O2 delivered to the tissue for a given partial pressure of O2 (e.g., 40 mm Hg) would be lower than normal D. all of the above E. none of the above

all of the above

Which of the following properties is characteristic of an active transport system? A. carrier-mediated B. solute transported against a concentration gradient C. transport inhibited by compounds which are structurally similar to the normally transported solute D. stereospecificity E. all of the above

all of the above

Magnesium functions intracellularly as A. an activator for certain enzymes. B. an osmotic element. C. a structural part of mitochondria. D. a structural part of the cell membrane. E. a generalized enzyme inhibitor.

an activator for certain enzymes

Histones A. account for 1/4 the mass of the eukaryotic chromosome. B. complex with RNA to form spliceosomes. C. are bound to DNA in the transcriptional units of both active and inactive genes. D. are small Glu+Asp- rich proteins that facilitate compaction of eukaryotic DNA in the nucleus. E. are a highly conserved class of proteins with the most conserved being the linker histone Hl.

are bound to DNA in the transcriptional units of both active and inactive genes

Light chains of immunoglobulins A. are specific for each class of antibody B. are not specific for each class of antibody C. react with antigen D. have only a constant region E. consist only of carbohydrate

are not specific for each class of antibody

Which amino acid is modified when cholera toxin activates the G-protein cascade? A. Arginine in the a subunit B. Glutamate in the adenyl cyclase C. Histidine in protein kinase A D. Lysine in the ab complex E. Tyrosine in the receptor

arginine in the subunit

Which of the following statements about the composition of red cell membranes is correct? A. As with plant cell membranes, cholesterol is present only in traces. B. As a group, the glycerol phosphatides (PTC, PTE, PTS) are the quantitatively major lipid component. C. Proteins are found as extrinsic proteins on both the inner and outer surfaces of the lipid bilayer. D. Oligosaccharide chains of glycolipids project from both the inner and outer surfaces of the lipid bilayer. E. Sphingomyelins are uniformly distributed between the inner and outer layers of the lipid bilayer.

as a group, the glycerol phosphatides (PTC, PTE, PTS) are the quantitatively major lipid component.

One principal function of complement is to A. inactivate perforins. B. mediate the release of histamine. C. bind antibodies attached to cell surfaces and to lyse these cells. D. phagocytize antigen. E. cross-link allergens.

bind antibodies attached to cell surfaces and to lyse these cells

Repressors function in the regulation of gene expression by: A. altering the conformation of RNA polymerase. B. binding to the operator region of DNA. C. hybridizing to the promoter region of DNA. D. mediating removal of the sigma subunit of RNA polymerase. E. preventing translation of RNA.

binding in the operator region of DNA

Transcriptional control of gene expression can involve A. binding of hormone-receptor complexes to enhancers. B. repressor-mRNA binding. C. exon mutations. D. alternative polyadenylation and splicing pathways. E. hormone-RNA polymerase binding.

binding of hormone-receptor complexes to enhancers

Splicing of eukaryotic mRNA precursors involves all of the following EXCEPT A. binding of small nuclear RNAs. B. binding of poly(A) polymerase. C. assembly of spliceosome. D. RNA cleavage and ligation reactions.

binding of poly(A) polymerase

The dnaA protein A. is a single stranded DNA binding protein. B. binds to the origin of replication to prevent transcriptional initiation. C. binds to an alternative site for DNA replication. D. binds to the genomic DNA origin of replication to initiate DNA replication. E. binds to the dnaB-dnaC protein complex after initiation.

binds to the genomic DNA origin of replication to initiate DNA replication

The vitamin which functions as the coenzyme (or part of the coenzyme) for a variety of reactions of the type, RH + carbon dioxide --> R-COOH, is A. biotin. B. pyridoxine. C. pantothenate. D. B12. E. folate.

biotin

An alpha-helix conformation is favored in the transmembrane domain of a membrane protein because: A. Intramolecular H-bonding can occur, stabilizing the alphahelix. B. Within the core of the lipid bilayer, there are no other molecules which can form H-bonds and thus compete with the intramolecular H-bonds of the transmembrane peptide domain. C. Both D. Neither

both

Gap junctions, important for intercellular communication, can function as follows: A. They can be open or closed depending on the appropriate level of signal (e.g., Ca2+). B. They can allow molecules of up to 1,000 Daltons (molecular weight) pass from one to another of interconnected cells. C. Both D. Neither

both

Regarding RNA synthesis, which of the following statements is correct? A. In procaryotes, the rho subunit is required for chain initiation. B. Synthesis of mRNA from a DNA template strand occurs in a 5'-3' direction anti-parallel to the template. C. In eukaryotes, the RNA polymerase II synthesizes mRNA and acts in collaboration with different transcription factors to initiate RNA synthesis. D. Both A and B are correct. E. Both B and C are correct.

both B and C are correct

Peroxisomes produce much hydrogen peroxide. How are they protected from damage by this reactive oxygen species precursor? a. Catalase b. Glutathione peroxidase c. Rapid export from the peroxisome d. Rapid synthesis of new peroxisomes e. Superoxide dismutase

catalase

The lipoprotein with the highest content of triglycerides is A. LDL. B. VLDL. C. IDL. D. HDL. E. chylomicrons.

chylomicrons

Restriction endonuclease A. cleave single stranded DNA preferentially. B. cleave DNA at specific sequences only when those sequences are unmethylated. C. remove bases one at a time from the 5' end of the DNA only when the bases are incorrectly matched with the template strand. D. initiate the repair process by making a single endonucleolytic incision at the 5' end of the damaged DNA region. E. are required for the correct processing of tRNA in the cell.

cleave DNA at specific sequences only when those sequences are unmethylated

Genes containing intervening sequences (or introns) A. are rare in eukaryotic cells. B. code for mRNA precursors which must be spliced before translation. C. must undergo a DNA rearrangement before expression. D. do not code for proteins. E. are common in prokaryotes.

code for mRNA precursors which must be spliced before translation

The principal proteins of connective tissues are A. elastin and chondroitin. B. albumin and collagen. C. collagen and elastin. D. collagen and collagenase. E. hyaluronic acid and elastin.

collagen and elastin

Organization of multiple genes into operons in prokaryotes provides for: A. alternate gene expression B. global regulation C. DNA amplification D. coordinate expression of genes involved in a related process

coordinate expression of genes involved in a related process

Identify in the following list the covalent bond commonly found in proteins A. hydrogen bond. B. hydrophobic bond. C. pleated sheet. D. electrostatic bond. E. disulfide bond.

disulfide bond

In general, when the enzyme concentration is doubled the rate of an enzyme catalyzed reaction is A. unaffected. B. doubled. C. increased by a factor of four. D. halved. E. decreased by a factor of four.

doubled

Where is intracellular calcium stored that can rapidly released when needed? A. Endoplasmic reticulum B. Golgi C. Lysosomes D. Mitochondria E. Nucleus

endoplasmic reticulum

Which of the following membrane systems are responsible for the bulk of cellular protein and lipid synthesis? a. Plasma membrane b. Microbodies c. Lysosomes d. Endoplasmic reticulum e. Golgi complex

endoplasmic reticulum

At their isoelectric point proteins have: A. no ionized groups. B. no positively charged groups. C. no negatively charged groups. D. equal numbers of positively and negatively charged groups. E. an increased affinity for substrate.

equal numbers of positively and negatively charged groups

All of the following bond types are significant for the maintenance of the secondary, tertiary, and quaternary structure of enzymes or proteins EXCEPT A. hydrophobic interactions. B. disulfide bonds. C. ester bonds. D. hydrogen bonds. E. electrostatic interactions.

ester bonds

Each of the following are examples of post-translational modification of a protein EXCEPT which one? A. formylation of N-terminal methionine B. hydroxylation of proline in collagen C. specific cleavage of a site along the polypeptide chain D. formation of cystine E. phosphorylation of a serine residue

formulation of N-terminal methionine

The signal peptide is: A. found on precursors to plasma membrane, lysosomes and endosomes proteins. B. encoded nearer to the 3' end than the 5' end of mRNA. C. synthesized after the ribosome binds to the rough ER. D. found nearest the carboxyl terminus of proteins, rather than nearest the amino terminus. E. found nearest the amino terminus of soluble cytoplasmic proteins.

found on precursors to plasma membrane, lysosomes and endosomes proteins

During signal transduction, fluctuations in the concentration of cytosolic calcium are controlled by A. calmodulin and phospholipase C. B. gated Ca2+ channels and Ca2+-ATPase. C. parathyroid hormone and calcitonin. D. protein kinase and phosphoprotein phosphatase.

gated Ca2+ channels and Ca2+-ATPase

The following protein separation techniques take advantage of the charge differences between various proteins EXCEPT for: A. Diethylaminoethyl (DEAE) chromatography B. Two dimensional gel electrophoresis C. Isoelectric focusing D. Gel filtration chromatography

gel filtration chromatography

Lipid rafts tend to be thicker than the rest of the membrane. What causes this? A. High cholesterol B. High glycosphingolipids C. High plasmalogen D. High protein content E. High unsaturated fatty acids

high glycosphingolipids

amino acids are classified according to the nature of their side chain. All of the following amino acids are correctly classified EXCEPT A. Serine : polar, uncharged. B. Glutamic : polar, acidic. C. Arginine : polar, basic. D. Histidine : nonpolar, uncharged. E. Phenylalanine : nonpolar, uncharged.

histidine: non polar, uncharged

During vigorous physical activity, the Bohr effect would enhance the delivery of oxygen to the tissues of the body. All of the following are associated with this effect at the tissues EXCEPT A. a conformational change occurs that alters the pKa and hence the charge on the imidazole groups of the hemoglobin molecules. B. the oxygen-hemoglobin association curve shifts to the right. C. the tense form of hemoglobin is stabilized. D. hydrogen ions are released from the hemoglobin to the tissues. E. there are alterations in the salt linkages of the hemoglobin molecules.

hydrogen ions are released from the hemoglobin to the tissues

Activation of zymogens or proenzymes is often accomplished by A. aggregation of monomers to form the active oligomer. B. glycosylation reactions. C. formation of covalent crosslinks. D. hydrolysis of the peptide chain at a specific place. E. the addition of a coenzyme to the structure.

hydrolysis of the peptide chain at a specific place

Which of the following statements about protein structure is correct? A. Disulfide interactions are required for the stability of globular structures. B. Hydrophobic sidechains commonly occur clustered in interior areas of globular proteins. C. The alpha-helix is maintained chiefly by hydrophobic interactions. D. Covalent linkages between the protomeric chains are a common feature of globular oligomeric proteins such as hemoglobin and lactate dehydrogenase (LDH). E. Pleated-sheet structures are found only in fibrous proteins.

hydrophobic side chains commonly occur clustered in interior areas of globular proteins

Splicing occurs A. in the nucleus, by removing introns from DNA. B. in the nucleus, prior to transcription. C. in the nucleus, either during or subsequent to transcription. D. in the cytoplasm, prior to translation. E. in the cytoplasm, subsequent to translation.

in the nucleus, either during or subsequent to transcription

Increased [H+] in blood will most likely A. increase the pH. B. increase the P50 of hemoglobin. C. increase the [HCO3-]/[CO2] ratio. D. increase the oxygen affinity of hemoglobin. E. decrease buffering by hemoglobin.

increase the P50 of hemoglobin

Which of the following is NOT a property of catalysts? A. are unchanged by the net reaction B. facilitate both the forward and reverse reactions C. increase the equilibrium constant to favor products D. enhance the rate of the reactions E. are required in only trace amounts compared to the reactants

increase the equilibrium constant to favor products

Dimerization of transcription factor subunits accomplishes which of the following? A. Blocks their association with DNA B. Prevents their translocation to the nucleus C. Increases their binding affinity for DNA D. Targets them for degradation

increases their binding affinity for DNA

The difference in P50 values of fetal and adult hemoglobins is best explained by a difference in the A. binding of nitric oxide. B. extent of subunit cooperativity. C. interaction with an allosteric effector. D. number of alpha-globin subunits.

interaction with an allosteric effector

To what type of receptor do most neurotransmitters bind on the post-synaptic membrane? A. Adenyl cyclase-associated B. Autophosphorylating C. Ion channel D. PKC-associated E. Voltage-gated channel

ion channel

A polyribosome A. is a group of ribosomes bound to a single polypeptide chain. B. is an organized array of ribosomes on the surface of a membrane. C. is a number of ribosomes engaged in translating the same mRNA molecule. D. must be formed for protein synthesis to proceed. E. None of the above.

is a number of ribosome engaged in translating the same mRNA molecule

Eukaryotic chromatin replication: A. Is controlled by exactly the same enzymes as bacteria. B. Is characterized by conservative segregation of pre_existing H3_H4 tetramers at the replication fork. C. Requires the presence of a special enzyme, telomerase, which appends short oligonucleotide blocks to the overhanging S' ends of the newly replicated DNA strands. D. Is initiated by the formation of an Origin Recognition Complex (ORC) at a unique specific site of the genome. E. Both B and C.

is characterized by conservative segregation of preexisting H3_H4 tetramers at the replication fork

In mammalian cells, rRNA A. accounts for of the total cellular RNA content. B. is rapidly degraded during protein synthesis. C. is composed of only two types - 2and 16S. D. contains the codons for protein synthesis. E. is composed of at least 4 different size classes of RNA.

is composed of at lease 4 different size classes of RNA

Which of the following amino acid residues may participate in strong hydrophobic bonding? A. Glycine. B. Isoleucine. C. Lysine. D. Serine. E. Aspartate.

isoleucine

Which of the following statements are true about the small ribosomal subunit? A. It catalyzes peptide bond synthesis. B. It is responsible for proofreading of the amino acid incorporated in response to a given codon. C. It forms a complex with initiator tRNA and mRNA D. It contains both A and P sites for tRNA attachment. E. none is true

it forms a complex with initiator tRNA and mRNA

Which of the following statements uniquely applied to eukaryotic mRNA when compared to eukaryotic rRNA and tRNA? A. It is synthesized in the nucleus. B. It is modified after its transcription. C. It contains methylated bases. D. It usually contains a polyadenylic acid sequence at its terminus. E. It is always larger than any other RNA species.

it usually contains a polyadenylic acid sequence at its terminus

the enzymes responsible for the degradation of sphingolipids are localized in which sub cellular structure? a. Peroxisomes b. Mitochondria c. Lysosomes d. Smooth endoplasmic reticulum e. Rough endoplasmic reticulum

lysosomes

The quaternary structure of hemoglobin is A. not important for the functioning of this protein. B. rigid and is not affected by oxygen binding. C. maintained by hydrophobic bonds, salt bridges, and hydrogen bonds. D. stabilized by disulfide bridges. E. none of the above

maintained by hydrophobic bonds, salt bridges, and hydrogen bonds

Which of the following is true concerning the structure of tRNA? A. molecular weight greater than 10 million B. many modified bases C. anticodon loop near the amino acid binding site D. linear structure with no H-bonding between bases E. -CCA sequence at 5' end

many modified bases

Which one of the following membranes contains the highest percentage of lipid? A. Endoplasmic reticulum B. Erythrocyte plasma membrane C. Myelin sheath D. Inner mitochondrial membrane E. Outer mitochondrial membrane

myelin sheath

The conversion of B-DNA to Z-DNA is facilitated by A. sequences rich in A-T base pairs. B. increasing NaCl concentration. C. negative supercoiling. D. histone acetylation.

negative supercoiling

Regarding the Na+ - K+ ATPase pump: A. Na+ and Mg2+ are required for dephosphorylation of the phosphorylated enzyme. B. K+ is required for phosphorylation of the enzyme by ATP. C. Both D. Neither

neither

UAG is an example of A. redundant (degenerate) code. B. intra-allelic suppressor. C. nonsense codon. D. universality of the code. E. non-overlapping code.

nonsense codon

The following polynucleotide is being translated in a cell-free protein synthesis system. 5'-AUGUUUUCACUA-is mutated to5'-AUGUUUUAACUA- The result is a A. silent mutation. B. nonsense mutation. C. missense mutation. D. suppressor mutation. E. None of the other answers is correct.

nonsense mutation

Which of the following statement is wrong about nucleic acids? a. Nucleic acids are the support of genetic information and are only present in the nucleus in eukaryotic cells b. DNA and RNA are both different class of nucleic acids, but are both polymers of nucleotide units. c. DNA mutations can cause various diseases or be "silent" d. One copy of DNA can be duplicated through the mechanism of replication e. The structure of the DNA molecule has been elucidated by Watson and Crick

nucleic acids are the support of genetic information and are only present in the nucleus in eukaryotic cells

In what part of the mammalian cell is ribosomal RNA produced? A. Endoplasmic reticulum B. Mitochondrion C. Nucleolus D. Golgi apparatus

nucleolus

About nucleosomes and polynucleosomes... A. nucleosomes corresponds to an octamer of histone proteins. B. ionic charged forces are reponsible for histone-histone interactions C. the higher condensation process between nucleosomes and polynucleosomes is due to the cooperative binding of the histones H2B to one another. D. histone methylation results in a decrease of positive charges on the histones ad their relative dissociation from the DNA.

nucleosomes corresponds to an octamer of histone proteins

Protein synthesis: A. requires a preexisting copy of the protein that is to be synthesized. B. occurs at specialized ribosomes dedicated to synthesizing a single, specific protein. C. occurs in generalized ribosomes that can synthesize any protein. D. requires tRNA as the template containing the genetic information encoding the protein. E. requires rRNA as the template containing the genetic information encoding the protein.

occurs in generalized ribosomes that can synthesize any protein

Replication of the DNA in a human chromosome is similar to E. coli DNA replication in all of the following EXCEPT A. replication is semiconservative. B. the lagging strand is synthesized discontinuously. C. multiple DNA polymerases are involved. D. RNA is used as a primer. E. only one origin is involved per DNA molecule.

only one origin is involved per DNA molecule

An inducible enzyme is one that A. is produced only when it is needed. B. is always present. C. is always under allosteric regulation. D. none of the above.

only produced when it is needed

Which of the following is the name for a group of genes, the activity of which is expressed or repressed in a coordinated manner? A. operon B. structural genes C. regulator genes D. operator E. mutator genes

operon

All of the following enter or leave mitochondria via a specific transport protein EXCEPT A. ATP. B. inorganic phosphate. C. pyruvate. D. malate. E. oxygen.

oxygen

Which of the following statements regarding pH is NOT true? a. pH = log[H+] b. a ten fold change in [H+] alters the pH by 1 unit c. the pH of pure water is 7 d. many physiological reactions are sensitive to pH e. in a buffer the pH changes little with addition of small amounts of strong acid or base

pH= log[H+]

The 70S ribosome contains about 50 separate proteins and one clearly definable enzymatic activity in protein synthesis. The name of that activity is A. dependent ATPase. B. aminoacyl-tRNA synthetase. C. elongation factor G. D. peptidyl transferase. E. None of the other answers is correct.

peptide transferase

Which basal lamina component binds cations and water to form gels that can withstand compression? A. Collagen B. Entactin C. Laminin D. Nidogen E. Perlecan

perlecan

What is required for STAT (signal transducers and activators of transcription) to respond to a cytokine signal? A. Binding of cytokine to intracellular receptor B. Dissociation of the receptor subunits C. Dissociation of the STAT subunits D. Formation of cAMP E. Phosphorylation of the cytokine receptor

phosphorylation of the cytosine receptor

The purpose of the short RNA chains which are synthesized during DNA replication is to: A. code for genes necessary for replication. B. provide a primer for DNA synthesis. C. maintain DNA strands in an open (i.e., not base-paired) from so that polymerases can recognize the template strand. D. reduce superhelical density. E. provide a template for ligation of Okazaki fragments

prive a primer for DNA synthesis

An amino acid found in large amounts in collagen is A. proline. B. lysine. C. arginine. D. asparagine. E. histidine.

proline

Which of the following amino acids will terminate an alpha helical structure in globular proteins? A. Tryptophan B. Proline C. Tyrosine D. Histidine E. Isoleucine

proline

Which three amino acids are all known to undergo posttranslational modifications? A. glutamine, valine, isoleucine B. tyrosine, lysine, alanine C. proline, glutamic acid, serine D. aspartic acid, histidine, glycine E. methionine, threonine, phenylalanine

proline, glutamic acid, serine

Which of the following mutations would most likely alter the amount of a protein but not its primary structure? A. missense mutation B. splicing mutation D. nonsense mutation E. promoter mutation

promoter mutation

Chaperone proteins help nascent proteins achieve correct folding. What other function do they serve? A. Addition of prosthetic groups B. Cleavage of zymogens C. Protein refolding after crossing a membrane D. Stabilization of tetrameric conformation E. Targeting to organelles

protein refolding after crossing a membrane

About plasma membranes... Which is the correct term? a. Proteins bound to the plasma membranes and to the cytoskeleton are responsible for the shape of each cell b. Plasma membranes are similar in composition between all cell types in the organism c. The inner as well as the outer layers that composed the plasma membrane are exactly similar and contain both lipids and proteins d. Plasma membranes passively let ions and proteins in and out of the cells e. Plasma membranes are not involved in intercellular communication

proteins bound to the plasma membranes and to the cytoskeleton are responsible for the shape of each cell

How does the metabolism of rRNA differ from that of tRNA in eukaryotic cells? A. rRNA is cleaved from a larger precursor while tRNA is transcribed as such from the transfer RNA cistrons. B. rRNA is made in the nucleus while tRNA is synthesized in the cytoplasm. C. The methylated bases in rRNA are added at the polymer level while in tRNA these bases are incorporated as nucleoside triphosphates. D. rRNA forms specific complexes with proteins in the nucleus while tRNA does not.

rRNA forms specific complexes with proteins in the nucleus while tRNA does not

Which of the following mutations would you expect to cause the most drastic alteration in the functional performance of a polypeptide chain? (Assuming the replacement is not at the active site) A. Replacement of glutamate with lysine. B. Replacement of valine with alanine. C. Replacement of aspartic acid with glutamic acid. D. Replacement of lysine with arginine.

replacement of glutamate with lysine

DNA synthesis is called: A. replication B. transcription C. translation D. transformation E. polymerization

replication

All of the following statements concerning replication of E. coli DNA are true EXCEPT A. replication of the lagging DNA chain occurs in short discontinuous pieces. B. replication begins at multiple sites of origin. C. RNA-DNA hybrids are temporarily formed on the lagging strand. D. topoisomerases and single strand DNA binding proteins are required. E. DNA polymerase III is the primary polymerase involved.

replication begins at multiple sites of origin

Okazaki fragments are associated with A. resolution of recombination intermediates. B. splicing of transcripts. C. resolution of DNA replication at telomeres. D. replication of the leading strand. E. replication of the lagging strand.

replication of the lagging strand

Denaturation of protein A. produces a modification of the primary structure. B. always causes the protein to precipitate. C. causes unfolding of the secondary structure. D. results in irreversible inactivation. E. results from an unfolding of the conformation.

results from an unfolding of the conformation

The participation of nitric oxide in signal transduction A. depends upon interaction with a heterotrimeric guanine nucleotide-binding protein. B. is mediated by a receptor localized in the nucleus. C. requires the oxidation of lysine by nitric oxide synthase. D. results in the activation of guanylyl cyclase.

results in the activation of guanylyl cyclase

All of the following statements about coenzymes and vitamins are CORRECT EXCEPT A. thiamine deficiency affects carbohydrate metabolism. B. biotin is a cofactor for certain enzymatic carboxylations. C. pantothenic acid is a vitamin precursor for coenzyme A. D. riboflavin is a vitamin precursor for NAD+. E. pyridoxal phosphate is a coenzyme for transaminase reactions.

riboflavin is a vitamin precursor for NAD+

The beta-conformation structure of a protein can be considered an example of A. primary structure. B. secondary structure. C. tertiary structure. D. quaternary structure. E. none of the above

secondary structure

Primary sequences of proteins are determined mainly by A. sequential degradation. B. X-ray diffraction. C. ultracentrifugation. D. synthesis. E. amino acid analysis.

sequential degradation

Which of the following amino acids possesses an uncharged side-chain at pH 7.0? A. lysine B. aspartate C. arginine D. serine E. glutamate

serine

Which of the following participates in the reaction at the catalytic site of chymotrypsin? A. amino ethanol B. urea C. pyridoxal D. serine E. mercaptoethanol

serine

RNA polymerases and DNA polymerases have in common the property that they both A. require a primer for their activity. B. have proofreading activity. C. synthesize polynucleotides in a 5' to 3' direction. D. have exonuclease activity.

synthesize polynucleotides on a 5' to 3' direction

Which of the following enzymes is involved in extending the ends of linear chromosomal DNA? A. telomerase B. ligase C. primase D. RNA polymerase E. DNA polymerase a

telomerase

A key feature of regulatory systems involving deletion of a gene is: A. the DNA deletion event must be passed to progeny cells B. the cell can modulate the level of expression of this gene (one cell can express the gene at different levels) in response to different growth conditions C. the deletion event can occur in any cell type at any time D. the DNA deletion event must not be passed to progeny or germline cells E. the sigma factor of RNA polymerase is altered

the DNA deletion event must not be passed to progeny or germline cells

In considering the 'active site' of enzymes, a fair generalization is that A. nearly all the amino acid side-chains of the protein must directly participate in catalysis. B. all the amino acid residues which are involved in the active site are adjacent because they are located on the same short stretch of the polypeptide backbone. C. the conformation of the active site region does not exist at all until the substrate is bound. D. the amino acid residues which form the active site are in close proximity because of the specific three-dimensional conformation the protein has adopted. E. only one amino acid residue is involved in the active site.

the amino acid residues which form the active site are in close proximity because of the specific three- dimensional conformation the protein has adopted

When the oxygen-saturation curve of hemoglobin is analyzed by use of the Hill equation, a Hill constant of about 3 is found. This means that A. only 3 of the 4 hemes can bind O2. B. negative cooperativity causes hemoglobin to behave as if it had only 3 hemes that can bind O2. C. each of the 4 hemes can bond O2, but not as tightly as they would in the absence of cooperativity. D. the binding of O2 is highly, but not perfectly, cooperative. E. 3 of the heme groups bind O2 equally tightly, and the 4th heme binds O2 more tightly.

the binding of o2 is highly, but not perfectly, cooperative

Select the wrong statement about mitochondria: a. Mitochondria can vary in number depending on the need in energy of the cell b. Mitochondria host numerous important cell functions c. Mitochondria are called "the powerhouse of the cells", because they are the sites of production of ATP d. The electron transport chain complexes are mainly located in the outer membrane of mitochondria. e. Mitochondria contain genetic information inherited from the mother in Humans

the electron transport chain complexes are mainly located in the outer membrane of mitchondria

Which of the following statements about protein structure is correct? A. The alpha-helix conformation is stabilized by hydrophobic interactions. B. The beta-sheet conformation is rarely found in globular proteins. C. The folding of a polypeptide into a globular structure results in an interior enriched with hydrophobic amino acids. D. The primary structure does not influence the native tertiary structure. E. The subunits of proteins with quaternary structure associate through covalent bonds.

the folding of a polypeptide into a globular structure results in an interior enriched which hydrophobic amino acids

The effect of pH on enzyme-catalyzed reactions can be related to all of the following EXCEPT A. the influence of pH on the equilibrium. B. the need for certain forms of ionizable groups on the substrate. C. the need for certain forms of ionizable groups in the enzyme. D. the general effect of pH on protein structure. E. the influence of pH on the interaction of hydrophobic residues in the protein.

the influence of pH of the interaction of hydrophobic residues in the protein

About 2,3-bisphosphoglycerate in Red Blood cells... A. It is present in smaller amounts in Red Blood cells as compared with other cellular types. B. BPG binds to both (T) and (R) conformations of Hemoglobin. C. The levels of BPG are increased in smokers. D. Increased levels of BPG leads to a translation of the oxygen-hemoglobin saturation curve to lower P50 value. E. None of the previous answers is correct.

the levels of BPG are increased in smokers

Transposition is A. the inversion of a stretch of DNA B. the duplication of a stretch of DNA C. the movement of a stretch of DNA from one genetic locus to the other D. the movement of DNA Pol III along the template at l,000 nucleotides per second E. never responsible for oncogenesis

the movement of a stretch of DNA from one genetic locus to the other

The Hill relationship can be used to determine the A. reversibility of a reaction. B. number of independent binding sites on a protein for a ligand. C. the number of cooperative binding sites in a protein for a single ligand. D. whether an effector is homotropic or heterotropic. E. oxygen binding capacity of a protein.

the number of cooperative binding sites in a protein for a single ligand

The degeneracy of the genetic code refers to: A. the possibility of tolerated mispairing in the third position of the codon. B. the universal utilization of the same genetic code across all life forms on earth. C. the observation that multiple codons specify the same amino acid. D. the utilization of AUG for two functions (start and methionine). E. codon usage for both amino acid specification and punctuation (start and stop).

the observation that multiple codons specify the same amino acid

All of the following statements about facilitated diffusion are correct EXCEPT A. a plot of rate of uptake by cells of the pertinent substance would be expected to give a hyperbolic curve. B. depending on conditions, transport could occur in either direction across the membrane. C. the process can allow a substance in cells to be accumulated against a concentration gradient. D. an interaction between the substance transported and a membrane component is likely to occur. E. competitive inhibition of the transport of a substance by its chemical analogs is likely to occur.

the process can allow a substance in cells to be accumulated against a concentration gradient

All of the following statements concerning the lactose operon are true EXCEPT A. in the lactose operon of E. coli, TRANSCRIPTION is regulated by both positive and negative acting proteins. B. the mRNA transcribed from an operon may contain information for one or more enzymes on a single, long mRNA molecule. C. the cyclic AMP binding protein modulates transcription of the lac operon in response to the external glucose levels. D. the repressor is a negative effector which acts by specifically binding to DNA polymerase. E. induction of the lactose operon requires binding of a derivative of lactose to the repressor.

the repressor is a negative effector which acts by specifically binding to DNA polymerase

Chemical damage to nuclear DNA from exposure to a mutagenic agent is most dangerous when A. the resulting mutation is repaired prior to replication of the damaged DNA. B. the resulting mutation causes a permanent substitution of a single amino acid in an important protein with a chemically similar amino acid C. the mutagenic agent causes a frameshift mutation near the amino terminus of a protein which promotes spermatogenesis. D. the chemical change in the DNA results in a silent mutation which is fixed via DNA replication. E. the resulting mutation is fixed through DNA replication and leads to the activation of a cellular oncogene and malignant transformation in a liver cell.

the resulting mutation is fixed through DNA replication and leads to the activation of a cellular oncogene and malignant transformation in a liver cell

Semiconservative replication of DNA means that after two rounds of replication A. only one of the two parental strands is preserved intact in the progeny molecules of DNA. B. both parental strands remain intact in one of the progeny molecules of DNA. C. the two parental strands remain intact in different progeny molecules. D. one of the parental strands is broken down and dispersed in one of the progeny molecules of DNA, the other parental strand remains intact in one of the progeny molecules. E. neither of the parental strands appears in the progeny molecules of DNA.

the two parental strands remain intact in different progeny molecules

One of the following five statements describing the Watson-Crick model for double stranded DNA is incorrect. INDICATE THE INCORRECT STATEMENT A. The two strands of DNA are intertwined in such a way that they can be separated without unwinding the complementary strand. B. The paired chains have opposite polarity. C. The paired bases are located in the interior of the double helical structure. D. One turn of the double helix involves approximately 10 nucleotides and occurs every angstroms. E. The double helical structure has two grooves running helically along its length, one of which is considerably narrower than the other.

the two strands of DNA are intertwined in such a way that they can be separated without unwinding the complementary strand

All of the following are true of IgM antibodies, EXCEPT which one? A. They fix complement. B. They occur on the surface of B-lymphocytes. C. They predominate in the primary immune response to antigen. D. They are glycoproteins. E. They are a molecule with a single, defined amino acid sequence.

they are a molecule with a single, defined amino acid sequence

By which of the following means are the nucleosides linked to one another in RNA and DNA molecules? A. They are linked together by alpha-glycosidic bonds. B. They are linked together by beta-glycosidic bonds. C. They are linked together by 5' phosphodiester bridges. D. They are linked together by 2',5' phosphodiester bridges. E. None of the other answers is correct.

they are linked together by 5' phosphodiester bridges

Which is the correct answer about glucose transporters (GLUTs).... A. They share structural similarities and have 12 transmembrane segments B. They are all highly specific, allowing the translocation of D-Glucose only C. GLUT1 is mostly expressed in the liver. D. They are all located at the plasma membrane. E. their activity is downregulated in the muscle during exercise.

they share structural similarities and have 12 transmembrane segments

Sunlight is most likely to cause which of the following mutations? A. interstrand crosslink B. depurination C. deamination D. thymine dimmer

thymine dimmer

tRNA charging involves A. transfer of an amino acid from one adenosine residue to another adenosine residue. B. transfer of an AMP residue, which carries an amino acid, to the 3' end of tRNA. C. activation of tRNA by ATP hydrolysis followed by condensation with an amino acid. D. phosphorylation of the 3' end of tRNA followed by condensation with an amino acid.

transfer of an amino acid from one adenosine residue to another adenosine residue

A mutation in which an A-T base pair in DNA is replaced by a G-C base pair is referred to as a(an) mutation. A. Transition B. Transversion C. Insertion D. Inversion E. Deletion

transition

With respect to mutations A. transitions arise from the replacement of one purine to another purine or one pyrimidine to another pyrimidine. B. transversions arise from the replacement of one pyrimidine to another pyrimidine. C. transitions arise through deletions of a nucleotide in the DNA sequence. D. transversions arise through the insertion of a nucleotide in the DNA sequence. E. both transitions and transversions cause frameshift mutations.

transitions arise from the replacement of one price to another purine or one pyrimidine to another pyrimidine

Protein translocation across the endoplasmic reticulum (ER) membrane requires A. translational arrest by signal recognition particle (SRP). B. cleavage of the signal sequence by SRP. C. translocation of SRP across the ER membrane. D. secretion of SRP.

translational arrest by signal recognition particle (SRP)

Which of the following groups contains amino acids with sidechains that are all strong absorbers of ultraviolet (UV) radiation? A. Glycine and alanine B. Alanine and tyrosine C. Tyrosine and tryptophan D. Phenylalanine and lysine E. Glutamic acid and lysine

tyrosine and tryptophan

The antigen binding site of an immunoglobulin is located within the A. carbohydrate residues attached to the protein molecule. B. immunoglobulin domains of the light chains. C. hinge regions of the heavy chains. D. variable regions of the heavy and light chains. E. Fc fragment of the protein molecule.

variable resigns of the heavy and light chains