Quiz Questions Cell Bio

A folded protein structure with which free-energy (G) value would likely have the most stable conformation?

1

Which of the following junctions binds a cell to another cell and is linked to keratin intermediate filaments?

desmosome

A stretch of amino acids in a polypeptide chain that is capable of independently folding into a defined structure is called a

domain

Which of the following types of cell signaling is long range and uses hormones as signals?

endocrine

Covalent bonds in macromolecules are primarily important for

linking together monomers.

The reading frame to use for translating an mRNA into functional protein is determined by the

location of an AUG.

A cell membrane made up primarily of lipids with which characteristics would be the least fluid (i.e., most stiff)?

long, saturated fatty acid tails

In the cell, enhancer sequence functions are limited in their range of action by the formation of ___________ that hold specific genes and enhancers in close proximity.

loops

Under a microscope, how would the connective tissue of an animal generally appear?

loosely scattered cells among large amounts of extracellular matrix

MicroRNAs block the expression of a specific gene product by binding to the ___________ and inhibiting ___________.

mRNA; translation

The fruit fly, Drosophila melanogaster (D. melanogaster) is an excellent model for studying fundamentals of development because

many of the genes involved in the development of the fruit fly are also found in humans.

Strong and specific associations between macromolecules or between an enzyme and its substrate are due to

many weak noncovalent bonds

A binding site on the surface of a protein interacts specifically with another protein through

many weak noncovalent interactions

The proton flow through the transmembrane H+ carrier of ATP synthase results in

mechanical rotation that is converted into the chemical-bond energy of ATP.

A protein helix that has amino acid side chains oriented to produce a hydrophobic stripe will readily insert into a membrane.

False

Which of the following is NOT an intracellular signaling protein activated by an RTK?

G-protein

Which of the following organelles is surrounded by a single membrane?

Golgi apparatus

The organelle shown in the figure is the ___________ and one of its main functions is to ___________.

Golgi apparatus; package and modify proteins for secretion

Which of the following chemical groups could confer nonpolar/hydrophobic characteristics on the region of a molecule in which it is found?

methyl group (−CH3)

Which nucleic acid often base pairs with itself to fold into complex three-dimensional shapes in the cell?

RNA

The splicing of introns out of an mRNA molecule is catalyzed by

RNA molecules that base pair with the splice sites to promote intron removal.

How does the binding of a signal molecule activate an RTK for downstream signaling?

The RTK forms a dimer and cross-phosphorylates itself.

In a sperm cell, where are the mitochondria located?

The mitochondria form elongated tubes that wrap around the flagellar core.

Shown below is the mechanism believed to be used for pumping protons by cytochrome c oxidase across the inner mitochondrial membrane. One of the steps shown is unidirectional because it is driven by the energy of electron transport. Why must this step be performed only in one direction?

The protons could be also captured from the intermembrane space and released back into the matrix.

A single-pass transmembrane protein destined for one of the organelles in the endomembrane system would be marked by what type of signal sequence?

a cleaved N-terminal ER signal sequence and an internal stop-transfer sequence

Which of the following is UNLIKELY to be hydrophilic?

a molecule with primarily nonpolar covalent bonds

Transplanting the nucleus of an epithelial cell into an egg cell lacking genetic information leads to the formation of

a normally developing embryo

Which cAMP-mediated signaling pathway would take on the order of minutes to hours for a response to develop (as opposed to seconds)?

a response where cAMP leads to the activation of a transcriptional regulator

What is an epithelium?

a sheet of cells joined tightly together

Which molecule is primarily responsible for providing tensile strength in the connective tissues of animals?

collagen

Many transcriptional regulators function together to decide the expression level of a particular gene. This describes the concept of

combinatorial control.

Long polymers are made from single subunits in cells using a ___________ reaction, which ___________ water.

condensation; releases

Disulfide bonds stabilize protein shape outside the cell by

covalent bonds between cysteines.

What is a function common to all epithelia?

creation of a barrier

Which cell component is indicated in the figure below by the line labeled "1"?

cytosol

Which of these macromolecules is NOT commonly found in the plasma membrane?

nucleic acids

Fully folded proteins can be transported into which of the following organelles?

nucleus

Which of the following organelles is NOT a part of the endomembrane system?

nucleus

An oncogene is different from a tumor suppressor gene in that

oncogenes have mutations causing increased activity of the protein.

Which of the following cell types is responsible for removing matrix for renewal in bone tissue?

osteoclasts

Which of the following correctly matches a G-protein-activated enzyme with the second messenger molecule it produces?

phospholipase C à diacylglycerol

What is the name used for a molecule in which two carbons of glycerol are attached to fatty acid chains, and the third carbon is attached to a phosphate group?

phospholipid

What kind of lipid molecule is represented in this figure?

phospholipid

Which of the following is a mobile electron carrier in the electron-transport chain?

ubiquinone

The following image shows two triacylglycerol molecules with different fatty acid chains. If these fatty acids were in a phospholipid molecule, which of the two would form the most fluid membrane?

unsaturated

The information in an mRNA molecule is converted into protein sequence using

three consecutive bases, with no overlap between triplets.

The pH of the mitochondrial matrix is ___________, which is ___________ than that of the intermembrane space.

7.9; higher

The process of gene expression always involves which process(es) described in the central dogma?

transcription

Which of the following is the main point of control for regulating gene expression levels?

transcription

Cancer cells often lack normal DNA damage response and cell-cycle control mechanisms. Why does this make them more susceptible to DNA-damaging chemotherapies?

Cancer cells might ignore the normal mechanisms that halt the cell cycle in response to damage, and subsequent division with damage leads to death.

Glycolysis alone captures approximately what percentage of the free energy available in a molecule of glucose?

10%

The number of ATP molecules that could be synthesized from the energy released by the transfer of two electrons from NADH to molecular oxygen is

2.5

Shown is the structure of a mitochondrion with different compartments labeled. Which of the numbers represents the most permeable membrane of the mitochondrion?

3

Approximately what percentage of the volume of a typical eukaryotic cell is comprised of cytosol?

50%

Export of RNA from the nucleus requires the RNA to have which characteristic(s)?

5′ cap and poly-A tail

Which of the following describes negative feedback regulation?

A component late in the pathway inhibits an enzyme early in the pathway.

What is the difference between a malignant tumor and a metastasis?

A metastasis is a tumor in different distant tissue

Which of the following accurately describes a step in GTP-driven nuclear transport?

Binding of Ran-GTP to the receptor releases the cargo protein

Protein concentration can be regulated by all of the steps listed EXCEPT

DNA replication

A reporter gene is an experimentally engineered regulatory DNA sequence from a gene of interest that has been fused to a gene that encodes a protein that is easily observed experimentally. Why is this approach useful?

It provides information into where and when a gene is expressed.

Shown below is a gene with the direction of transcription noted. How does the RNA polymerase know which strand to use as a template for the RNA, and which strand would it choose in this case?

It would use the bottom strand because the promoter sets the direction and the polymerase moves from 3′ to 5′ along the template strand.

________ are the most abundant molecules in the animal cell membrane, whereas ________ make up 50% of the membrane by mass.

Lipids, proteins

The citric acid cycle produces which activated carriers that transfer high-energy electrons to the electron-transport chain?

NADH and FADH2

Which of the following has the lowest electron affinity?

NADH dehydrogenase complex

Cytochrome c oxidase catalyzes the reaction that reduces molecular oxygen (two oxygen atoms) to two water molecules. The electrons are added sequentially, and during the process cytochrome c oxidase must bind the oxygen tightly in the active site. Why?

Superoxide radicals are formed as an intermediate, and are dangerous to the cell.

How do the high-energy electrons of activated carriers contribute to forming the high-energy phosphate bonds of ATP?

They are used by the electron-transport chain to make a proton gradient.

Which of the following depicts the correct order of steps involved in nitric oxide (NO) signaling to trigger smooth muscle relaxation?

acetylcholine receptor activation à activation of NO synthetase à NO diffusion into neighboring cells à activation of guanylyl cyclase à cGMP production

A molecule with a lot of polar covalent bonds is likely to

be highly soluble in water

Steroid hormones trigger transcription of target genes by

binding to nuclear receptors that act as transcription factors for specific genes.

What would the final destination be for a protein bearing both an ER sorting signal and a nuclear localization signal?

endoplasmic reticulum

Which type of cell-surface receptor(s), when activated, catalyze(s) a reaction inside the cell?

enzyme-coupled receptors

Which type of movement is the least common for lipids in a bilayer?

flip-flop

Which of the following microscopy techniques allows the observation of living cells (i.e., NOT fixed cells)?

fluorescence microscopy

What performs the function of bacterial sigma factor in eukaryotes?

general transcription factors

Hemopoietic stem cells in the bone marrow produce all of the following specialized cells EXCEPT

heart muscle cell

Individuals with inherited diseases causing mitochondrial dysfunction typically experience which of the following symptoms?

heart problems

The cytochrome complexes contain heme prosthetic groups, which have a higher redox potential than the iron-sulfur centers found in other electron-transport chain complexes like NADH dehydrogenase. Where in the electron-transport chain would the cytochrome complexes thus be located relative to iron-sulfur center complexes?

later in the chain

The main function of the nucleus is to

house the DNA in a separate cell compartment

Which of the following occurs by bringing nonpolar surfaces together to exclude water?

hydrophobic forces

Phospholipids assemble into in a membrane using

hydrophobic forces.

Proteins encoded by nuclear genes and destined for the mitochondrial matrix are

in possession of a signal sequence for targeting to the mitochondria.

The figure below shows the attachment of a cell to a collagen molecule in the extracellular matrix. What is the identity of the molecule labeled B?

integrin

Protons are pumped across the mitochondrial inner membrane to accumulate in the

intermembrane space.

Nuclear pores restrict larger molecules from traversing the membrane due to their

interwoven meshwork of protein fibrils.

Which of these tissues has the fastest turnover rate?

intestinal epithelium

Which of the following would produce the fastest response to G-protein activation?

ion channel activation

When activated, a G-protein has a structure that

is bound to GTP

The defining property that differentiates prokaryotic cells from eukaryotic cells is their

lack of a nucleus

The figure below depicts which of the following mechanisms that cells use to maintain their identity through cell divisions?

positive feedback

Mutations in which of the following elements would abrogate RNA polymerase's ability to activate gene expression?

promoter

What is the name of the complex that degrades proteins that have reached the end of their lifespan, are damaged, or are misfolded?

proteasome

Long noncoding RNA (lncRNA) can function as a(n)

protein scaffold

How is pyruvate imported into the mitochondrial matrix for use in the citric acid cycle?

proton gradient-driven symport

Which of the following levels of protein structure involves the interaction of more than one polypeptide chain into a three-dimensional structure?

quaternary

Which of the following is NOT a way that cells restrict the lateral movement of membrane proteins?

reducing the temperature of the membrane

Two atoms held together solely by ionic bonds are referred to as a(n)

salt.

Which of the following microscopy techniques would allow the most detailed image showing the 3-D structure of a flagellum?

scanning electron microscopy

A phospholipid is inserted into the cytosolic side of the ER membrane. Which of the following could randomly reposition this phospholipid to the other (lumen) side of the ER membrane?

scramblase

All living cells

share the same basic chemistry.

The low redox potential of NADH means that it has a

tendency to give up electrons.

In eukaryotes, multiple genes can be expressed simultaneously by

the binding of a specific transcriptional regulator to several genes.

If a phospholipid is located in the outer layer of the bilayer in a vesicle, where will it end up when the vesicle fuses with the plasma membrane?

the cytosolic face of the bilayer