CH385 TEE

In one catalytic cycle, the Na +/K + ATPase transporter transports:

3 Na + out, 2 K + in, and converts 1 ATP to ADP + P i.

What is the CORRECT order for the following members of the MAP Kinase cascade? 1) MEK 2) ERK 3) Raf 4) RTK

4, 3, 1, 2

On the ribosome, the mRNA is read from ..., and the polypeptide chain is synthesized from...

5' to 3'; N- to C-terminus.

Comparing mRNA molecules from human and Escherichia coli cells, which of the following is typically NOT true?

A human mRNA contains noncoding sequences, while a bacterial mRNA does not.

Which of the following scenarios does NOT normally occur on a nuclear pore complex?

A. A protein complex is imported into the nucleus, with ONLY one of its subunits containing a nuclear localization signal (NLS). B. In a single pore, an NLS-containing protein is imported, while at the same time a nuclear export signal (NES)-containing protein is exported. C. A nuclear import receptor is exported from the nucleus through the pore. D. A protein is imported on its own through the pore, without the need for a separate import receptor.

Which of the following drugs is toxic for our cells?

A. Cytochalasin B, which caps the plus end of actin filaments and prevents actin polymerization. B. Phalloidin, which binds along actin filaments and stabilizes them. C. Nocodazole, which binds to tubulin subunits and prevents microtubule polymerization. D. Colchicine, which caps microtubule ends and leads to their depolymerization.

An ion channel ...

A. always mediates passive transport. B. is ion-selective. C. is typically several orders of magnitude faster than a transporter. D. is usually gated.

Which of the following is a function of membranes?

A. compartmentalization B. selectively permeable barrier C. mediates intercellular interactions D. helps cells respond to external stimuli

To ensure the fidelity of splicing, the spliceosome...

A. hydrolyzes ATP to undergo complex rearrangements. B. examines the splicing signals on the pre-mRNA several times. C. assembles on the pre-mRNA co-transcriptionally. D. takes advantage of "exon definition."

Several mechanisms contribute to the diversity of the mRNAs and proteins encoded by a single gene in our genome. Which of the following is normally NOT one of them?

Alternative choice of the reading frames

Why do cells not have membrane transport proteins for O 2?

Because oxygen can dissolve in the lipid bilayer and diffuse in and out rapidly without the need for a transporter.

In neurons, the synaptotagmin-1 protein is localized to presynaptic axon terminals. When activated, it facilitates the fusion of neurotransmitter-containing synaptic vesicles to the plasma membrane, leading to neurotransmitter release into the synaptic cleft. Which of the following would you expect to directly activate synaptotagmin-1 for this function?

Binding to Ca 2+

Which coated vesicles move materials in a retrograde direction from the Golgi stack backwards toward the ER?

COPI-coated vesicles

How does a eukaryotic cell deal with the superhelical tension in its genomic DNA resulting from the activity of RNA polymerases?

DNA topoisomerases rapidly remove the superhelical tension caused by transcription.

Once the kinase domain of receptor protein-tyrosine kinase has been activated, what does the activated receptor protein-tyrosine kinase do?

Each receptor subunit phosphorylates its partner on tyrosine residues found in regions adjacent to the kinase domain.

Which of the following is not true regarding the regulation of transcription in prokaryotes by RNA?

Each riboswitch can bind an assortment of small metabolites.

Which statement about the chemiosmotic theory is CORRECT?

Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane.

This family of ATPases is structurally related to the turbine-like pumps that acidify lysosomes and vesicles; however, they usually function in reverse, generating ATP from ADP and P i using proton gradients across membranes. What are they called?

F-type pumps

Which heterotrimeric G proteins function by inhibiting adenylyl cyclase?

Gi family

A neuron's repetitive firing rate is limited by an absolute refractory period, during which a new action potential cannot be generated. Which event is chiefly responsible for this limit?

Inactivation of voltage-gated Na + channels.

Consider an actin subunit that has just been incorporated into an actin filament at the leading edge of a lamellipodium. Before its ATP is hydrolyzed, how does its distance from the leading front edge of the plasma membrane change over time? How does its distance from the F-actin minus end change over time?

Increases; decreases

Which of these is a general feature of the lipid bilayer in all biological membranes?

Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.

Which of the following cytoskeletal filaments are abundant in an animal cell nucleus?

Intermediate filaments

Which of the following is true regarding genomic imprinting?

It is an epigenetic phenomenon.

What is usually the retrieval signal for ER integral membrane proteins, like the SRP receptor?

KKXX at the C-terminus of the protein

Under which of the following conditions is the Lac operon in Escherichia coli fully turned on?

Low glucose but high lactose levels

What is the effect of defective or missing N-acetylglucosamine phosphotransferase on lysosomal protein sorting?

Lysosomal proteins are secreted from the cell.

Which of the following would most reliably suggest that a genomic sequence is functionally important?

Multispecies conservation of the sequence

What evidence would suggest that histone acetylation provides a recognizable surface to recruit proteins that bind to acetylated histones?

Mutation of a lysine in the tail of histone H3 to an alanine, which cannot be acetylated, prevents the binding of transcription factors that normally bind to that promoter.

In the Na+/glucose cotransporter, _____ moving down its gradient drives the transport of _____ against its gradient.

Na+ ions, glucose

Which atom is the MOST electronegative?

O

Cyclin B1, a key cell cycle regulatory protein in vertebrates, is mostly cytosolic before mitosis. Early in mitosis, however, the protein is phosphorylated by certain protein kinases and consequently accumulates in the nucleus. How can phosphorylation bring about nuclear accumulation of this protein?

Phosphorylation within the nuclear export signal interferes with the function of the signal.

For which of the following ions is the intracellular concentration typically higher than the extracellular concentration?

Potassium

What molecule is TFIIH known to phosphorylate?

RNA polymerase II

The interaction between the membranes of vesicles and their target compartment is mediated by which proteins below?

SNAREs

Which of the following proteins or protein complexes is directly required for the targeting of mitochondrial inner membrane multipass proteins, such as metabolite transporters, whose signal sequence is normally not cleaved after import?

TIM22

Why did Kornberg initially think that the exonuclease activity he found in his DNA polymerase preparations was a contaminating enzyme?

The action of exonucleases is so dramatically opposed to the activity of DNA polymerases, the synthesis of DNA.

An elongating ribosome is bound to appropriate tRNAs in both the A and the P sites and is ready for peptidyl transfer. What happens next?

The carboxyl end of the polypeptide chain is released from the P-site tRNA and joined to the free amino group of the amino acid linked to the A-site tRNA.

What is the major microtubule-organizing center in animal cells?

The centrosome

The electron-transport chain and ATP synthase are effectively coupled. Which statement BEST describes how this occurs?

The electron-transport chain generates an electrochemical gradient that provides energy for the production of ATP.

After an animal dies, its muscles start to stiffen before the decomposition of tissues relaxes the muscles again. Which of the following would you expect to explain this muscle stiffening (i.e. rigor mortis)?

The myosin II heads in muscle cells remain attached to actin filaments due to the elevated Ca2+ in the muscle fibers.

Which of these statements is generally true of integral membrane proteins?

The secondary structure in the transmembrane region consists solely of α-helices or β-sheets.

What are the differences between ribosomes that make secretory proteins and those that make proteins intended for the cytosol?

There are no differences between them.

Which of the following features is common between the bacterial and eukaryotic ribosomes in translation initiation?

They both interact with various translation initiation factors.

Which of the following is NOT correct regarding M6P receptors and KDEL receptors?

They both release their soluble binding targets at lower

Whereas the cholera toxin ADP-ribosylates the alpha subunit of stimulatory G protein (Gs), thereby blocking GTP hydrolysis, pertussis toxin ADP-ribosylates the alpha subunit of inhibitory G protein (Gi) and prevents interaction with the receptor. What is the effect of these toxins on the concentration of intracellular cAMP?

They both tend to increase cAMP concentration.

When Rabs have bound to GTP, what do they do?

They recruit specific cytosolic tethering proteins to specific membrane surfaces.

The genetic information carried by a cell is passed on, generation after generation, with astonishing fidelity. However, genomes are still altered over evolutionary time scales, and even their overall size can change significantly. Which of the following genome-altering events has increased the size of the mammalian genome the most?

Transposition

What kind of enzyme is the RAS gene product, the Ras protein?

a GTPase

Which carbon atom is in the MOST reduced state?

a carbon in an alkyl group

Which carbon atom is in the MOST oxidized state?

a carbon in carbon dioxide

Triacylglycerols are composed of:

a glycerol backbone three fatty acids

In the presence of an ATP analog that can bind myosin normally but cannot be hydrolyzed, ...

a myosin cannot bind tightly to an actin filament and cannot move on it.

An integral membrane protein can be extracted with:

a solution containing detergent.

On average, how many amino acids engaged in predominantly hydrophobic α- helices does it take to cross the hydrophobic part of the membrane?

about 20 amino acids

What word describes a molecule that contains both hydrophilic and hydrophobic portions?

amphipathic

Consider a signaling protein that is only made up of one SH2 domain and two SH3 domains. This protein is most likely ...

an adaptor protein.

Transmembrane proteins ...

are sometimes covalently attached to a fatty acid chain that inserts into the membrane.

The interactions of ligands with proteins:

are usually transient.

G protein-coupled activation of phospholipase C directly generates which second messenger?

both diacylglycerol and inositol-1,4,5-trisphosphate

In contrast to transporters, the channel proteins in cellular membranes ...

can only mediate passive transport.

Polysomes...

can take advantage of the circularization of eukaryotic mRNA (by interactions between the 5' and 3' ends of the mRNA) to further speed up the rate of protein synthesis.

Lysosomal enzymes are transported from the TGN in vesicles coated with what protein?

clathrin

What are the two sites within a cell at which protein synthesis is generally thought to occur?

cytosolic surface of RER and free ribosomes

Gene silencing by RNA interference acts by ____________ of the target gene.

degradation of the mRNA

Protein subunits that interact specifically with DNA sequences ...

do so via hydrogen bonds, ionic bonds, and hydrophobic interactions.

Facilitated diffusion through a biological membrane is:

driven by a difference of solute concentration.

Why does it make sense that cells would be able to recognize dsRNAs as undesirable using a mechanism such as RNAi?

dsRNAs are not produced by the cell's normal genetic activities.

Which of the following molecular motors is known to travel in a retrograde direction along microtubules?

dyneins

What are the building blocks of a phosphoglyceride, specifically phosphatidic acid?

glycerol + 1 phosphate group + 2 fatty acids

What enzymes are responsible for determining the sequence of sugars added to growing oligosaccharide chains of membrane proteins or secretory proteins as they travel through the Golgi complex?

glycosyltransferase

In contrast to growing microtubules, shrinking microtubules ...

have curved protofilaments at their plus ends.

If the extracellular concentration of sodium ions is artificially decreased for a neuron, ...

he resting potential hardly changes but the action potential peak is lowered.

The fluidity of a lipid bilayer will be increased by:

increasing the temperature.

The lac operon is an example of a(n) _______ operon.

inducible

Enzymes are potent catalysts because they:

lower the activation energy for the reactions they catalyze

Along which structure do membranous vesicles and organelles typically move long distances in an animal cell?

microtubules

What is thought to direct the movement of vesicles through the cytoplasm to their final destination?

microtubules

What kinds of forces are thought to hold microtubular structure together?

noncovalent interactions

The formation of a stable ternary complex involving Ran GTPase, a nuclear transport receptor, and a cargo protein occurs in ...

nuclear export, but not import

The fundamental repeating unit of organization in a eukaryotic chromosome is the:

nucleosome.

All of the following are considered "weak" interactions in proteins except:

peptide bonds

Which of the proteins below is(are) not made on the membrane-bound ribosomes of the RER?

peripheral proteins of the inner surface of the plasma membrane

In an aqueous solution, protein conformation is determined by two major factors. One is the formation of the maximum number of hydrogen bonds. The other is the:

placement of hydrophobic amino acid residues within the interior of the protein.

A hydropathy plot is used to:

predict whether a given protein sequence contains membrane-spanning segments.

What enzyme does diacylglycerol (DAG) recruit and activate?

protein kinase C

Calmodulin is a(n):

regulatory subunit of calcium-dependent enzymes

Which amino acids are known to be phosphorylated by protein kinases?

serine, threonine, tyrosine

What end of a microtubule is associated with the centrosome?

the minus end

What is the name of the site where RNA polymerase binds to the DNA prior to the beginning of transcription?

the promoter

Consider a transcription regulatory protein that has both a nuclear localization and a nuclear export signal and is normally found both in the nucleus and in the cytosol at comparable concentrations. This protein has a high-affinity binding partner in the nucleus. Upon activation of a certain signaling pathway, the binding protein is ubiquitylated and degraded. As a result of this, ...

the transcription regulatory protein accumulates in the cytosol.

The Trp operon in Escherichia coli encodes the components necessary for tryptophan biosynthesis. In the presence of the amino acid in a bacterium, ...

the tryptophan operator is bound to the tryptophan repressor.

DNA and RNA polymerase differ in all of the following EXCEPT...

the type of chemical reaction they catalyze.

The accumulation of misfolded proteins in the ER is a potentially lethal situation and thus causes the triggering of what process?

the unfolded protein response (UPR)

Actin filaments that are held together by the cross-linking protein fimbrin are not contractile. This is probably because ...

the very tight packing of actin filaments by this small protein excludes myosin II filaments and other large proteins.

Almost all of the oxygen (O 2) one consumes in breathing is converted to:

water