Cell Bio Exam 2

Which of the following statements about the genetic code is CORRECT?

The genetic code is redundant.

The Na+-K+ ATPase is also known as the Na+-K+ pump. It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens immediately after the pump hydrolyzes ATP?

The pump is phosphorylated.

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are

hypertonic to fresh water but hypotonic to the salt solution.

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found?

in the interior of the membrane

The plasma membrane Na+/K+-ATPase pump

is used to generate sodium and potassium gradients across the membrane.

RNA in cells differs from DNA in that

it is single-stranded and can fold up into a variety of structures

Which of the following statements about miRNAs is FALSE?

miRNAs are produced from rRNAs.

Which of the following statements is TRUE?

A ribosome is a large rRNA and protein complex

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane.

Genes in eukaryotic cells often have intronic sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why?

Introns are removed from RNA molecules by the spliceosome, which works in the nucleus.

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

It exhibits a specificity for a particular type of molecule

What is meant by the term "fluid mosaic model"?

It is the movement of lipids and integral proteins within the lipid bilayer.

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?

Membrane carbohydrates function primarily in cell-cell recognition.

Which of the following statements is TRUE?

Membrane lipids frequently diffuse within the plane of the membrane.

Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because

RNA allow for the formation of polyribosomes, increasing the efficiency of protein synthesis.

In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?

RNA polymerase II

Ribozymes are known to catalyze which of the following reactions in cells?

RNA splicing

What is the role of the promoter region in the regulation of gene expression?

Recruit RNA polymerase and transcription factors to DNA

Which of the following statements about prokaryotic mRNA molecules is FALSE?

Ribosomes must bind to the 5′ cap before initiating translation.

Sodium concentrations are higher outside and glucose concentrations are higher inside the cell. Using the same membrane protein for Na+ and glucose transport, what is it called when a Na+ electrochemical gradient is used to drive glucose transport into the cell against its concentration gradient?

Secondary active transport

The movement of sucrose and H+ into the cell by the same membrane protein reflects the actions of what type of transporter?

Symporter

The ribosome is important for catalyzing the formation of peptide bonds. Which of the following statements is TRUE?

The enzyme that catalyzes peptide bond formation is a ribosomal RNA

Which membrane component is most important for allowing large, charged molecules to pass through the membrane?

Transmembrane proteins

The glycocalyx is

a carbohydrate coat covering the cell

Passive diffusion

is a spontaneous process that does not need input of energy

Total nucleic acids are extracted from a culture of yeast cells and are then mixed with resin beads to which the polynucleotide 5′-TTTTTTTTTTTTTTTTTTTTTTTTT-3′ has been covalently attached. After a short incubation, the beads are then extracted from the mixture. When you analyze the cellular nucleic acids that have stuck to the beads, which of the following is most abundant?

mRNA

Which of the following functions of the plasma membrane is possible without membrane proteins?

selective permeability

Ion channels

selectively allow passage of certain ions.

Which of the following RNA serves the regulatory functions including splicing and gene expression?

small RNA

Which of the following examples does NOT describe a mechanism of post-transcriptional control of gene expression?

the action of protein that blocks TATA box binding protein function

The distinct characteristics of different cell types in a multicellular organism result mainly from the differential regulation of the

transcription of genes transcribed by RNA polymerase II.

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant outside a typical mammalian cell?

Na+

Which of the following is most likely to occur after the lipid bilayer is pierced?

The membrane reseals.

Which of the following statements is false?

The only known function of RNA molecules is their involvement in translation

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

The ribosome binds to the mRNA

Which of the following might decrease the transcription of only one specific gene in a bacterial cell?

a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site

Which of the following substances does not require a protein carrier in order to cross a membrane?

carbon dioxide

Which of the following membrane lipids does not contain a fatty acid tail?

cholesterol

Which of the following statements about RNAi is true?

destroys double-stranded viral RNA as a cellular defense system

Osmosis is a special case of

diffusion

Which of the following processes includes all others?

passive transport

Introns are significant to biological evolution because

their presence allows exons to be alternatively spliced

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'

RNA polymerase moves in which direction along the DNA?

3' → 5' along the template strand

Which of the following help(s) to stabilize mRNA by inhibiting its degradation?

5' cap and poly (A) tail

Which of the following molecules of RNA would you predict to be the most likely to fold into a specific structure as a result of intramolecular base-pairing?

5'- CCCUAAAAAUUUUUAGGG- 3'

You have a piece of DNA that includes the following sequence: 5'-ATAGGCATTCGATCCGGATAGCAT-3' 3'-TATCCGTAAGCTAGGCCTATCGTA-5' Which of the following RNA molecules could be transcribed from this piece of DNA?

5'-AUAGGCAUUCGAUCCGGAUAGCAU-3'

Which is a property of integral membrane proteins?

All integral membrane proteins contain hydrophobic regions.

In eukaryotic cells, internal membranes

All of the choices are correct

Scientists unearth a Wooly Mammoth from the Siberian Ice Sheath and discover that a eukaryotic "amoeba"-like cell is still alive. Which component of the cell membrane might contribute to maintaining the fluidity of plasma membranes under freezing conditions?

High levels of unsaturated fatty acyl tails within the lipid bilayer

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

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

Water diffuses through certain organs such as the kidneys and bladder much faster than would occur by passive diffusion through a lipid bilayer alone. What accounts for this more rapid rate of water transport in these organs?

Presence of aquaporin channels for facilitated diffusion of water.

Cell surface molecules are labeled with a fluorescent tag and then a portion of them are bleached with a laser beam. What would one observe after the cell is incubated for a few minutes?

The bleached molecules would diffuse laterally through the membrane and intermix with unbleached molecules.

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.

The TATA box

acts to position RNA polymerase for transcription initiation

Cholesterol is an essential component of biological membranes. Although it is much smaller than the typical phospholipids and glycolipids in the membrane, it is a/an____________ molecule.

amphipathic

What is a ribozyme?

an RNA with enzymatic activity

Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found?

an aquaporin

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of transla-tion, is likely to have the most serious effect on the polypeptide product?

an insertion of a codon

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

different copies DNA can be replicated according to different physiological processes

When does translation begin in prokaryotic cells?

as soon as transcription has begun

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the

attachment of amino acids to tRNAs.

Transcription is similar to DNA replication in that

both follow base-pair rule during synthesis

The functions of the plasma membrane include

cell-cell communication, membrane transport, and intercellular joining

All carrier proteins on the membrane critically depend on which of the following for their function?

conformational change

Transepithelial glucose transport uses a symport to transport glucose up a concentration gradient by

coupling glucose transport to Na+ movement

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

embedded in a lipid bilayer

Following a meal, glucose must move from the gut lumen where there is a high glucose concentration into the intestinal cell where there is a relatively low level of glucose. This movement is called

facilitated diffusion

What are polyribosomes?

groups of ribosomes reading a single mRNA simultaneously

How is the head and the tail part WITHIN a phospholipid molecule held together?

none of the above

Which type of lipids are the most abundant in the plasma membrane?

phospholipids

According to the fluid mosaic model of cell membranes, which type of molecule spans the membrane, from its inner to outer surface?

protein

Lipid-anchored proteins (also known as lipid-linked proteins) are

proteins located on the surface of the cell membrane that are covalently attached to membrane lipids

The sigma subunit of bacterial RNA polymerase

recognizes promoter sites in the DNA

Transporters, in contrast to channels, work by

specific binding with the substance to be transported

A neuron and a white blood cell have very different functions. For example, a neuron can receive and respond to electrical signals, while a white blood cell defends the body against infection. This is because

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

There are 61 mRNA codons that specify amino acids, but only 45 tRNAs. This is best explained by the fact that

the rules for base pairing between the third base of a codon and tRNA are flexible.

From the following list, which is the first event in translation in eukaryotes?

the small subunit of ribosome is assembled at the start codon AUG of mRNA with the initiator tRNA, Met-tRNA.

The cell has highly regulated mechanisms to control gene expression. A reason for gene regulation is

to do all of the above.

Transcription in eukaryotes requires which of the following in addition to RNA polymerase?

transcription factors