Biology 302 Final Exam

For an uncharged molecule, the direction of passive transport across a membrane is determined solely by ______. For a charged molecule the ____ must also be considered. The net driving force for a charged molecule across a membrane therefore has two components referred to as the _______. Concentration Membrane Potential The electrochemical gradient

1. Concentration 2. Membrane Potential 3. The electrochemical gradient

There are two properties of phospholipids that affect how tightly they pack together: the length of the hydrocarbon chain and the number of double bonds. The degree of packing, in turn, influences the relative mobility of these molecules in the membrane. Which of the following would yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)?

15 carbons and 2 double bonds

A nucleosome core particle contains a core of histone with DNA wrapped around it approximately ____.

2 times

You have a segment of mRNA that contains the following sequence 5'-AUAGGCAUUCGAUCCGGAUAGCAU-3' Which of the following DNA molecules would be the coding strand from which this segment of mRNA was arranged? Using the transcript information from above, which of the following DNA molecules would be the template strand from which this segment of mRNA was produced? 5'-ATAGGCATTCGATCCGGATAGCAT-3'

3'-TATCCGTAAGCTAAGCTAGGCCTATCGTA-5'

Which diagram accurately represents the directionality of DNA strands at one side of a replication fork?

5' 3' ------- 5' ------- 3' ------- 5' 3' ------- 3' 5'

Homologous recombination is an important mechanism in which organisms use a homologous copy of the DNA as a template to fix double-strand breaks without loss of genetic information. Which of the following is not necessary for homologous recombination to occur?

5' DNA stran overhands

The human genome encodes about 24,000 genes. Approximately how many genes does the typical differentiated human cell express at any one time?

5,000-15,000

Which of the following statements about endoplasmic reticulum (ER) is true?

A and B (The ER is the major site of new membrane synthesiss in the cell/Proteins to be delivered to the ER are synthesized on the rib of the rough ER

Besides the distortion in the DNA backbone caused by a mismatched base pair, what additional mark may also be found on eukaryotic DNA to indicate which strand needs to be repaired?

A nick in the new strand

MicroRNA's _____. A: Are produced from a precursor miRNA transcript B: Can degrade RNAs by using their intrinsic catalytic activity C: Control gene expression by base-pairing with DNA sequences D: None of the above

A: Are produced from a precursor miRNA transcript

Which of the following statements about vesicle budding from Golgi Apparatus is false? A: Clathrin molecules are important for binding to and selecting cargoes for transport. B: Adaptins interact with clathrin. C: Once vesicle budding occurs and the vesicle comes into close proximity with the target membrane, clathrin molecules are released from the vesicle. D: Clathrin molecules act at the cytosolic surface of the Golgi membrane.

A: Clathrin molecules are important for binding to and selecting cargoes for transport.

Cells can signal to each other in various ways. A signal that must be relayed to the entire body is most efficiently sent by (A) ______ cells, which produce hormones that are carried throughout the body through the blood stream. Conversely, (B) ________ methods of cell signaling do not require the release of a secreted molecule and are used for very localized signaling events. During (C) _____ signaling, the signal remains in the neighborhood of the secreting cell and thus acts as a local mediator on nearby cells. Finally, (D) _____ signaling converts electrical impulses into a chemical signal. Cells receive signals through a (E) _____, which can be an integral membrane protein or can reside inside the cell. Contact-Dependent Receptor Neuronal Endocrine Paracrine

A: Endocrine B: Contact-dependent C: Paracrine D: Neuronal E: Receptor

Membrane lipids are capable of many different types of movement. Which of these occurs most rarely in biological membranes? A: Flip-flopping between lipid layers B: Lateral movement C: Rotation D: Flexing of hydrocarbon chains

A: Flip-flopping between lipid layers

What is the role of the nuclear localization sequence in a nuclear protein? A: It is bound by cytoplasmic nuclear receptor proteins that direct the nuclear protein to the nuclear pore. B: It is a hydrophobic sequence that enables the protein to enter the nuclear membranes. C: It aids in protein unfolding so that the protein can thread through nuclear pores. D: It prevents the protein from diffusing out of the nucleus through nuclear pores.

A: It is bound by cytoplasmic nuclear receptor proteins that direct the nuclear protein to the nuclear pore.

Which of the following is not part of the process known as oxidative phosphorylation?

ATP molecules are produced in cytosol as glucose is converted into pyruvate

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called ____.

Active transport

Membrane proteins can move laterally. Which type of protein is expected to be the least movable?

Anchors

Combinatorial control of gene expression ____. A: Involves every gene using a different combination of transcriptional regulators for its proper expression B: Involves groups of transcriptional regulators working together to determine the expression of a gene C: Involves only the use of gene activators used together to regulate genes appropriately D: Is seen only when genes are arranged in operons

B. Involves groups of transcriptional regulators working together to determine the expression of genes

Which of the following statements about RNA splicing is false? A: Conventional introns are not found in bacterial genes B: For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene C: Small RNA molecules in the nucleus perform the splicing reactions D: Splicing usually occurs after the 5′ cap has been added to the 5' end of the primary transcript

B: For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene

One method of establishing cell memory is through the faithful propagation of the DNA methylation patterns on CpG dinucleotides during DNA replication. The enzymes that guarantee that a pattern of DNA methylation is inherited by progeny DNA are ____ and this process is typically referred to as ____. A: Epigentic transferases; inherited methylation B: Maintenance methyltransferases; epigenetic inheritance C: Maintenance demethylase; DNA methylated mutations D: None of the above

B: Maintenance methyltransferases; epigenetic inheritance

The distinct characteristics of different cell types is a multicellular organism result mainly from the differential regulation of the ____. A: Replication of genes B: Transcription of genes transcribed by RNA polymerase II C: Transcription of housekeeping genes D: Translation of housekeeping genes

B: Transcription of genes transcribed by RNA polymerase II

After isolating the rough ER, you purify. Which protein would you expect from rough ER?

Both a and b - soluble secreted proteins and ER membrane proteins

Your friend has just joined a lab and wants to start designing experiment. Too embarrassed to ask. He recalls that this cell line forms coated pits, but vesicle budding and the removal of coat proteins doesn't happen. Which of the following proteins might be lacking in this cell line? A: Clathrin B: Rab C: Dynamin D: Adpatin

C. Dynamin

Figure 5 shows how normal signaling works with a Ras protein acting downstream of an RTK. While performing your lab research, however, you examine a cell line with a constitutively active Ras protein. Which of the following conditions will turn off signaling in this cell line? A: Addition of a drug that prevents protein X from activating Ras B: Addition of a drug that increase the affinity of protein Y and Ras C: Addition of a drug that blocks protein Y from interacting with its target D: Addition of a drug that increases the activity protein Y

C: Addition of a drug that blocks protein Y from interacting with its target

Which of the following statements is true? A: The signal sequences on mitochondrial proteins are usually C-terminal. B: Most mitochondrial proteins are not imported from the cytosol but are synthesized inside the mitochondria. C: Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes. D: Mitochondrial proteins cross the membrane in their native, folded state.

C: Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes.

Which of the following happens when a cell-surface receptor activates a G protein? A: The Beta subunit exchanges its bound GDP for GTP. B: The GDP bound to the Alpha subunit is phosphorylated to form bound GTP. C: The Alpha subunit exchanges its bound GDP for GTP. D: It activates the Alpha subunit and inactivates the Beta-Gamma complex

C: The Alpha subunit exchanges its bound GDP for GTP.

N-linked oligosaccharides on secreted glycoproteins are attached to ____. A: The cytosolic face of the ER. B: The serine or threonine residue in the growing polypeptide chain. C: The NH2 of an asparagine residue in the growing polypeptide chain. D: None of the above

C: The NH2 of an asparagine residue in the growing polypeptide chain.

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the ____.

Cell cortex

Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules. In the extracellular case, what is the principal anion?

Cl-

Operons ______.

Contain a cluster of genes transcribed as a single mRNA

The figure above shows that intracellular signaling pathways can be highly interconnected, which of the following statements is false?

Cyclic AMP is activated only when the RTK is active and not when the GPCR is active

Which component of the electron-transport chain is required to combine the electrons with molecular oxygen?

Cytochrome C oxidase

New membrane phospholipids are synthesized by enzymes bound to the_____ side of the _____ membrane.

Cytosolic, endoplasmic reticulum

Pyruvate is an important metabolic intermediate that can be converted into several other compounds, depending on which enzyme is catalyzing the reaction. Which of the following cannot be produced from pyruvate in a single enzyme-catalyzed reaction? A: Lactate B: Oxaloacetate C: Alanine D: All of the above E: None of the above

D. All of the above

The core histones are proteins that have a globular domain at the C-terminus and a long, extended "tail" at the N-terminus. Which of the following is/are true of the N-terminal "tail" of these histones? A: It is subject to covalent modifications B: It helps DNA pack tightly C: It binds to DNA by electrostatic interactions D: All of the above

D. All of the above

Which of the following is involved in post-transcriptional control? A: the splicesome B: dicer C: RISC D: All of the above

D. All of the above

Which of the following statements concerning the ER signal sequence and/or the SRP is true? A: The SRP binds to the exposed ER signal sequence and to the ribosome, thereby slowing protein synthesis by the ribosome. B: The SRP-ribosome complex binds to an SRP receptor in the ER membrane. C: The SRP gets released, passing the ribosome to a translocation channel in the ER membrane. D: All of the above

D. All of the above

Which of the following protein families are involved in directing transport vesicles to the target membrane? A. Snares B. Rabs C. Tehetering proteins D. All the above

D. All the above

Which of the following statements about the carbohydrate coating of the cell is false? A: It is not usually found on the cytosolic side of the membrane. B: It can play a role in cell-cell adhesion. C: Specific oligosaccharides can be involved in cell-cell recognition. D: None of the above

D. None of the Above

Which of the following statements about the unfolded protein response (UPR) is false? A. Misfolded proteins bind to receptors that stimulate the production of a transcriptional regulator B. Activation of UPR results in chaperon production of more chaperon proteins C. Activations of the UPR results in the transcript. Regulator translocation to nucleus D. None of the above

D. None of the above

Which of the following statements is false in regards to transcription? A: A new RNA molecule can begin to be synthesized from a gene before the previous RNA molecule's synthesis is completed. B: If two genes are to be expressed in a cell, these two genes can be transcribed with different efficiencies. C: RNA polymerase is responsible for both unwinding the DNA helix and catalyzing the formation of the phosphodiester bonds between nucleotides. D: None of the above

D. None of the above

Which of the following statement about a newly synthesized strand of DNA is true? A: It was synthesized from a single origin solely by continuous DNA synthesis B: It was synthesized from a single origin by a mixture of continuous and discontinuous DNA synthesis C: It was synthesized from multiple origins solely by discontinuous DNA synthesis D: It was synthesized from multiple origins by a mixture of continuous and discontinuous DNA synthesis

D: It was synthesized from multiple origins by a mixture of continuous and discontinuous DNA synthesis

The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation?

Decrease in gene expression

Which of the following statements is true? A: Ribosomes have large complex of 4 RNAs and more than 80 proteins B: Ribosomes have binding sites from mRNA and 3 binding sites for tRNA C: rRNA contains the catalytic activity that joins amino acids together D: Ribosomes bind multiple tRNAs at a time E. All of the above

E. All the above

Which of the following choices reflects the appropriate order through which a protein destined for the plasma membrane travels?

ER > Golgi > plasma membrane

DNA replication is considered semiconservative because ____.

Each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand

True or False: A mature miRNA assembles with a set of proteins to form a RISC complex. RISC stands for RNA-insctructed screening complex.

False

True or False: A repressor protein binds to a regulatory sequence on the DNA and then interacts with the RNA polymerase to help in initiate transcription.

False

True or False: If the concentration of solutes inside a cell is higher than that outside, water will in by osmosis, causing the cell to undergo crenation.

False

True or False: In secretory cells, the regulated and constitutive pathways of exocytosis diverge in the trans Golgi network. A constitutive secretory pathway is one that operates only when an extracellular signal stimulates their secretion.

False

True or False: Proteins that span the plasma membrane can also be referred to as peripheral membrane proteins, while proteins that associate with, but do not transverse the plasma membrane, are referred to as integral membrane proteins.

False

True or False: The enzyme that catalyzes the last irreversible reaction in glycolysis (step 10), yielding a molecule each of ATP and pyruvate, is called a hexokinase.

False

What is the three letter abbreviation for the amino acid Glutamine?

Gln

A nucleosome contains two molecules each of histones ____ as well as histones H3 and H4.

H2A and H2B

Although all protein structures are unique, there are common structural building blocks that are referred to as regular secondary structures. Some have alpha helices, some have beta sheets, and still others have a combination of both. What makes it possible for proteins to contain these common structural elements?

Hydrogen bonds along the protein backbone

Proteins bind selectively to small-molecule targets called ligands. The selection of one ligand out of a mixture of possible ligands depends on a number of weak, noncovalent interactions in the protein's ligand-binding site. Where is the binding site typically located in the protein structure?

Inside a cavity on the protein

Single-particle Tracking?

Limited mobility protein = least movement

Using the table below, translate the following eukaryotic messenger RNA sequence.

Met-Phe-Asp-Pro-Asp

Which amino acid will be on the tRNA that is the first to bind to the P-site of the ribosome?

Methionine

Which of the following statements about DNA methylation in eukaryotes is false?

Methylation of DNA attracts proteins that initiate gene expressions

Identify the membrane-enclosed compartments in a eukaryotic cell where each one listed takes place. Modification of Secreted Proteins: Steroid Hormone Synthesis: Degradation of Worn-Out Organelles:

Modification of Secreted Proteins: Golgi Steroid Hormone Synthesis: ER Degradation of Worn-Out Organelles: Lysosome

Acetylcholine binds to a GPCR on heart muscle, making the heart beat more slowly. The activated receptor stimulates a G protein, which opens a K+ channel in the plasma membrane. Would the following enhance or diminish the effect of acetylcholine?

Mutations in the acetylcholine receptor that weaken the interaction between the receptor and acetylcholine

NADH contains a high energy bond that, when cleaves, donates a pair of electrons to the electron transport chain. What are the immediate products of this bond cleavage?

NAD+ and H-

Which of the following methods is not used by cells to regulate the amount of a protein in a cell?

Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.

Transcription is similar to DNA replication in that ___________?

Nucleotide polymerization occurs only in the 5'-3' direction

Nucleosomes are aided in their formation by the high proportion of____________?

Positively charged amino acids in histone proteins

Because all DNA polymerases synthesize DNA in a specific direction, and the parent strands are antiparallel, DNA replication is accomplished with the use of two diff mechanisms: continuous and discontinuous. A=continuous, B=discontinuous, C=both. Primase Single-strand binding protein Sliding clamp RNA primers DNA helicase

Primase- C Single Strand Binding protein-B Sliding Clamp - C RNA Primers - C DNA Helicase - C

Which of the following is NOT a general mechanism that cells use to maintain stable patterns of gene expression as cells divide?

Proper segregation of the house keeping proteins when cells divide

Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of 3D shapes. This is largely because ___________?

RNA is single stranded

Transcription in bacteria differs from transcription in a eukaryotic cell because ______?

RNA polymerase (along with its sigma subunit) can initiate transcription on its own

Match the general type of biochemical reaction catalyzed in the left column with the class of enzyme listed in the column on the right. A. Removes a phosphate group from a molecule B. Adds phosphate groups to molecules C. Joins two ends of DNA together Catalyzes the synthesis of polymers such as RNA and DNA Nuclease, Polymerase, Ligase, Phosphatase, Kinase

Removes a phosphate group from a molecule - (Phosphatase) Adds phosphate groups to molecules - (Kinase) Joins two ends of DNA together - (Ligase) Catalyzes the synthesis of polymers such as RNA and DNA - (Polymerase

Some cells have aquaporins to facilitate the flow of water. What regulates the rate and direction of water diffusion across the membrane?

Solute concentrations on either side of the membrane

Which of the following statements about differentiated cells is true?

Some of the proteins found in differenciated cells are found in all cells of a multicellular organism

Transporters in contrast to channel work by ______.

Specific binding to solutes

The stimulation of auditory nerves depends on the opening and closing of channels in the auditory hair cells. Which type of gating mechanism do these cells use?

Stress-gated

Both ions move in same/opposite direction:

Symport/antiport

Sometimes, chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the adenosine in the sequence TCAT is depurinated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two rounds of DNA replication?

TCT

If the cytosine in the sequence TCAT is deaminated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two round of DNA replication?

TTAT

In the photosynthetic archean halobacterium, a membrane transport protein celled bacteriohodopsin captures energy from sunglight and pumps protons out of the cell→ trapped to generate ATP:

The absorption of sunglight triggers a shift in the conformation of the proteins seven membrane, spanning alpha helices, allowing a proton to leave a cell

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in Figure 4A. Which type of defect is most likely to cause the redistribution of that protein around the entire cell, show in Figure 4B? A: A nonfunctional protein glycosylase B: The deletion of a junctional protein C: The truncation of a protein found in the extracellular matrix D: A nonfunctional flippase

The deletion of junctional protein

Which of the following statements about the lac operon is false?

The lac repressor binds when lactose is present in the cell

Telomeres serve as caps at the end of linear chromosomes. Which of the following is false regarding the replication of telomere sequences during lagging strands synthesis?

The leading strand doubles back on itself to form a primer for the lagging strand

Which of the following does not occur before a Eukaryotic mRNA is exported from the nucleus?

The ribosome must bind to the mRNA

Porin proteins from large, barrel-like channels in the membrane. Which is NOT true about their channels:

They are made primarily of alpha helices

The correct folding of proteins is necessary to maintain healthy cells and tissues. Unfolded proteins are responsible for such neurodegenerative disorders as Alzheimer's, Huntington's, and Creutzfeld-Jacob disease (the specific faulty protein is different for each disease). What is the ultimate fate of these disease-causing, unfolded proteins?

They form protein aggregates called amyloid fibrils

Which of the following statements about transcriptional regulators is false?

Transcriptional regulators usually interact with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix

True or False: A riboswitch is a short sequence in a number of mRNAs that change their conformation when bound to small molecules to regulate their own transcription and translation.

True

True or False: Photobleaching techniques, such as FRAP, can be used to measure the rate of lateral diffusion of a membrane protein

True

True or False: The trypotophan operator binds to the tryptophan repressor when the repressor is bound to tryptophan

True

True or False: When studying signal transduction pathways in a laboratory-based setting, mutant transmembrane protein receptors can be synthesized to help determine exactly where an intracellular signaling molecule binds

True

True or false: Alternative splicing is a process that allows many different proteins to be produced from the same gene.

True

Although the chromatin structure of interphase and mitotic chromosomes is very compact, DNA-binding proteins and protein complexes must be able to gain access to the DNA molecule. Chromatin-remodeling complexes provide this access by?

Using energy of ATP hydrolysis to loosen the DNA from the nucleosomes

What is the one letter abbreviation of the amino acid tryptophan?

W

The extent of complementary of miRNA with its target mRNA determines: __________.

Whether or not the mRNA will be degraded

The drug dinitrophenol (DNP) makes the inner mitochondrial membrane permeable to hydrogen ions. When added to mitochondria, DNP _____.

Will both decrease the production of ATP and affect the PH gradient across the membrane

Match the following structures with their names. a. Uracil b. Deoxyribose c. Ribose d. Adenine

a. Uracil b. Deoxyribose c. Ribose d. Adenine http://www.scielo.br/img/revistas/babt/v50n3/11f3.gif

A neuron and white blood cell have different functions because:

the neuron expresses some mRNAs that the white blood cell does not