Final Exam Flashcards
Which of the following is a tenet of the Cell Theory?
All organisms are composed of 1+cells. The cell is the structural unit of life. Cells can only arise by the division from a preexisting cell.
Which of the following description of embryonic stem cells is wrong?
They can differentiate into only two or several mature cell types in the body
The process by which a relatively unspecialized call becomes highly specialized is called
differentiation
An artificially prepared spherical vesicle composed of a lipid bilayer is referred to as a
liposome
Which property of the plasma membrane enables H2O to pass through it freely but glucose
cannot?
Providing a selectively permeable barrier
What are the determinants of diffusion rate for a non electrolyte during simple diffusion procedure?
Polarity and Size
An important mechanism of transportation by transporter proteins is through
conformational change
Lipid composition differs among different types of cellular membranes. This difference can
be due to
types of lipids, nature of the head groups, and particular species of fatty acyl
chains
Which of the following ECM components provide resistance to compression forces for cells?
Proteoglycan
What substance joins proteoglycans together into gigantic complexes called proteoglycan
aggregate? These complexes can occupy very large volumes.
Hyaluronic acid
For some cell types, there is a protective cover outside of the plasma membrane formed by
carbohydrate chains of glycoproteins and glycolipids projecting out of the plasma
membrane, what is the name for this protective cover?
Glycocalyx
All of the following proteins are components for extracellular matrix, except for
selectin.
Which of the following descriptions about collagen is NOT correct?
Type IV collagen is
fibrillar.
What directly or indirectly determines the transition temperature?
Ability of lipids to pack
together, saturation of fatty acids, double bonds of fatty acids, and the length of fatty acids
What word below characterizes that amino acids that are found in an alpha-helical segment
that spans a membrane?
Predominantly hydrophobic
What property of membranes allows interactions to take place within the membrane,
including the assembly of membrane protein clusters at particular sites and the formation of
specialized structures?
Membrane fluidity
In what way can a given solute get through a membrane?
Bilayer, Aqueous channel, Pore
What advantage do the cristae confer on the mitochondria?
They greatly increase the surface area for aerobic respiration machinery
How do mitochondria generate and store the energy used to produce most of the ATP made
during aerobic respiration?
By generating an ionic (electrochemical) gradient
A channel that opens in response to charge gradient is called a
voltage-gated channel
The NaCl concentration inside an animal cell is about 0.7%. When you put this cell into a
beaker with 5% NaCl solution, what will happen to the cell?
Shrink
In the sodium-glucose cotransporter, ____ moving down its gradient drives the transport of ____ against its gradient.
Na+ ions, glucose
The tightest attachment between a cell and its extracellular matrix is seen at the site where an epithelial cell is attached to the underlying basement membrane. The specialized adhesive structure found at such a site is called a
hemidesmosome
Focal Adhesions___
act as a sensory structure, collect info about physical & chemical properties
of the extracellular environment, and transmit info to the cell interior that lead to changes in
cell adhesion
You disaggregate cells from two different developing organs and mix them together. Initially,
they form a mixed clump. What happens next?
The cells sort themselves out so that each cell
adhered only to cells of the same type.
While most IgSF members are involved in various aspects of immune function, some of
them mediate____ cell-cell adhesion
calcium-independent
What determines the strength of adhesion between apposing cells held together by
cadherins?
The number of cadherins in a cluster connecting the cells
From the apical surface to the basal surface of an epithelial cell, what is the order of cell
junctions in the junctional complex?
tight junction, adherent junctions, desmosomes, gap
junctions
What kind of molecule does not pass through a gap junctions?
Ribosomes
What accounts for the differences in function between the types of ER?
The protein content
of the ER
Which of the following is NOT a function associated with the smooth endoplasmic reticulum
in at least some cells?
Synthesis of integral proteins
What is the arrangement of organelles in a secretory cell from the basal end to the apical end,
an arrangement that reflects the flow of secretory products from synthesis to discharge?
Nucleus and RER- Golgi complex- Secretory vesicles
What are the two sires within a cell at which protein synthesis is generally thought to occur?
Cytosolic surface of RER and free ribosomes
Biobel, Sabatini and Dobberstein proposed that the site of protein synthesis is determined by
information contained in the N-terminal portion of the protein, the first part to emerge from
the ribosome. What did they call their proposal?
the Signal Hypothesis
What effect does the binding of the SRP to the growing polypeptide chain and the ribosome
have on protein synthesis?
Protein synthesis ceases temporarily.
Why is the ER so well suited and ideally constructed for its role as a port of entry for
secretory proteins?
It has a large surface area allowing the attachment of many ribosomes.
The ER cistern lumen favors folding and assembly of proteins
How are integral membrane proteins thought to enter the lipid bilayer?
The aqueous
translocon channel seems to have a gate that continuously opens and closes, giving each
nascent polypeptide segment a chance to partition itself into the lipid bilayer hydrophobic
core.
How and where is the symmetry of the phospholipid bilayer initially established?
Initially
established in the ER during lipid and protein synthesis
To what residue of a polypeptide are N-linked oligosaccharides chain attached as that
polypeptide enters the RER lumen through the translocon?
Asparagine
How do protein coats select the cargo molecule to be carried by the vesicles they help to
form?
The protein coat have a specific affinity for the cytosolic tails of integral membrane
proteins that reside in the donor membrane.
The coat of vesicles that transport materials around the cell interior is
composed of 2 distinct
protein layers, possesses an outer cage or scaffolding that forms the framework for the coat,
possesses adaptors that are able to select specific cargo molecules, and possesses an inner
layer of adaptors that serves primarily to bind the vesicle’s cargo
Which of the following enzymes are typically found in lysosomes?
Hydrolytic enzymes
acid hydrolases
What is thought to shield lysosomal membranes against attack by their enclosed enzymes?
carbohydrate chains attached to integral membrane proteins
What process is responsible for organelles turnover in the cell and carries out the regulated
destruction of the cell’s own organelles for the purpose of recycling the components of which
they are made?
Autophagy
The two separate (basic) categories of uptake of extracellular materials into cytoplasmic
vesicles are _____and _____.
Phagocytosis, Endocytosis
What types of molecules below can a cell internalize by receptor-mediated endocytosis?
All of the above: hormones and growth factors, enzymes, blood-borne proteins carrying nutrient
Which of the following organelles does not belong to the endomembrane system?
Mitochondria
What would happen to the movement of vesicles toward their eventual target if a
microtubule inhibitor, which can prevent assembly of the microtubule, were added to cells?
Vesicle movement would slow or stop
The microtubule wall is composed of globular proteins arranged in longitudinal rows called
protofilaments.
Initiation site for microtubule nucleation is
pericentriolar materials (PCM)
Which type of cytoskeletal element is described as tough, replace fibers composed of a
variety of related proteins like keratin?
intermediate filaments
Which of the following is a function performed by the cytoskeleton?
provides structural
support, positions various organelles, provides network of tracks, serves as a forcegenerating
apparatus
- What is the direct source of energy that powers molecular motors?
Hydrolysis of ATP
How does the current model for the nucleation of microtubules account for the polarity of
microtubules?
Only the alpha-tubulin of a heterodimer can bind to the ring of gamma
subunits
Which MTOC gives rise to cilia and flagella?
basal bodies
To which end of microtubules are tubular subunits primarily added in vitro?
the plus end
With which of the following structures are intermediate filaments associated?
All of the
above: the nuclear envelope, hemidesmosomes, desmosomes, neurofilaments of neuron
axons
Which of the following description of assembly of microfilament in vitro are correct?
All of
the above: ATP-bound actin monomer is the building block of microfilaments, nucleations of
microfilament in vitro requires performed microfilament as a seed, assembly of
microfilaments have polarity, the length of microfilament and free ATP-actin remain constant
The building blocks of a nucleotide are a
pentose sugar, a phosphate group and a nitrogenous
base
The backbone of a DNA molecule is made up of
alternating phosphate and sugar groups
_____ refers to the fact that the sequence of one DNA strand specifies the
sequence of the other strand in the double helix
Complementarity
The information encoded in DNA resides in the
DNA base sequence
What kind of DNA is the DNA that codes for histones?
moderately repetitive DNA
The bonds that hold individual nucleotide to make DNA and RNA are known as
3’—5’ phosphodiester linkages
The genome is essentially equivalent to all of the genetic information that is present in a _____ set of chromosomes
haploid
The genetic rearrangement that Barbara McClintock discovered was called transposition and
the mobile genetic elements she discovered were called
transposable elements
_____ is an enzyme that catalyzes transposon excision from a donor DNA site and its subsequent insertion at a target DNA site.
Transposase
DNA sequences in bacteria that on rare occasions moved from one place in the genome to
another are called
transposons.
When temperature increases gradually, one double stranded DNA molecule can be separated
from each other and become two single stranded DNA molecules, and when temperature
!7
gradually decreases, the two single stranded DNA molecules can come back together to form
one double stranded DNA molecule. This phenomenon is referred to as
Denaturation and renaturation/reannealing
You isolate DNA from a particular organism and analyze it. The amount of adenine was 6 μmoles and the A+T/G+C ratio is 4. How much guanine should be in the sample?
1.5 μmoles
A single gene can encode a number of related proteins as a result of a process called
alternative splicing.
Single stranded DNA molecules are capable of reassociating with correct base pairing when
temperature decreases gradually. This property is referred to as DNA
reannealing
The site on DNA to which RNA polymerases bind with help of transcription factor before
initiating transcription is called the
promoter
What enzyme is responsible for synthesizing mRNAs in the Eukaryota organianism?
RNA polymerase II
Which of the following is NOT a normal property of eukaryotic mRNAs?
They reside in the nucleus
The 3’ end of most eukaryotic mRNAs contain ____, while the 5’ end contains the _____
Poly A tail, methylated guanosine cap
In eukaryotic cells, RNA polymerase II is composed of several subunits, which play different
functions. ____ subunit helps to unwind the DNA double helix to generate the transcription bubble
TFIIH
Which enzyme is responsible for the activation of amino acids?
aminoacyl-tRNA synthetase
The amino acid bound to the A site tRNA linked to carboxyl carbon of the amino acid bound
to the P site through
Peptidyl bond
What is the significance of the variability of the third nucleotide in a codon?
The same tRNA
can recognize more than one codon
The macromolecular complex that associates with each intron and splice it is called a
spliceosome
Without help of the sigma factor, the core enzyme can carry out all of the following
functions except
recognize the promoter region
Which of the phenomena below is responsible for the ability of one gene to code for more
than one polypeptide?
Alternative splicing
A tRNA has an anticodon with the sequence 5’-CAU-3’. What would be the sequence of the
complementary codon? Do not consider the wobble hypothesis
3’-AUG-5’
Based on the interchangeability of the nucleotide at the third position, Francis Crick
proposed that the same tRNA may be able to recognize more than one tRNA. What was his
proposal called?
The wobble hypothesis
Which of the following is not required for protein synthesis?
general transcription factors
What enzyme is responsible for covalently linking amino acids to the 3’-end of the conjugate
tRNA?
aminoacyl-tRNA synthetase
The initiator tRNA enters the 60s ribosomal unit at the ___ during euaryotic proteins synthesis
P site
A mature mRNA is composed of all of the following segments except for
introns
The specific site on the bacterial chromosome at which replication begins is called the
origin
Replication moves outward from the origin in ____ directions and is said to be ____
both, bidirectional
Which of the following DNA molecules could go for successful DNA synthesis?
Partially double stranded DNA
All DNA polymerases lay nucleosides in a _____ direction and move along the template
in a _____ direction
5’——3’ ,3’——5’
During replication, DNA is constructed in small segments called _____ that are rapidly linked to longer pieces of DNA synthesized earlier.
Okazaki fragments
What is the advantage of transcription-coupled repair?
It ensures that the genes of the
greatest importance to the cell receive the highest priority on the repair list
What must the mismatch repair system be able to distinguish in order to tell which
nucleotide of a mismatched pair to replace?
Distinguish the newly-made stand from the
parental strand
The DNA strand growing toward the replication fork grows _____ in a 5’——3’
directions as the replication fork advances and is called the ______
continuously, leading strand
Which of the following may be a further advantage of using RNA primers during initiation
of a strand in replication?
Using primers may decrease mistakes; such errors as mismatched
bases are more likely during initiation than elongation, and the use of short, removable RNA
segment avoids inclusion of mismatched bases.
What proteins bind selectively to single-stranded DNA and are responsible for keeping it
extended and preventing it from being rewound?
single-stranded DNA binding (SSB) proteins
What is the function of the 5’——3’ exonuclease activity of DNA polymerase?
Removes the RNA primer laid down by the primes at the 5’ end of the Okazaki fragment.
A double stranded breakage repair pathway that requires the presence of a second
chromosome carrying the same sequence of genes as the damaged chromosome is called
homologous recombination.
What is responsible for joining eukaryotic Okazaki fragments together?
DNA ligase
What happens simultaneously with the removal of RNA primer by the 5’—-3’ exonuclease
activity of DNA polymerase I?
The gap left by the removal of the RNA primer is filled with
deoxyribonucleotides
What is the name of the non catalytic component of the DNA polymerase III holoenzyme
that keeps the polymerase associated with the DNA template?
Beta Clamp
Base excision repair (31254):
Glycolase recognizes. Damaged base is removed. Baseless
phosphate is excised. Gap is filled. The strand is sealed
Nucleotide excision repair (346152):
Lesion recognition. Separation of duplex. Cutting of
damaged strand. Release of damaged DNA. Filling of gap. Sealing of strand.
What protein has recently been shown to play a significant role in chromosome compaction
(condensation?
Condensin
What allows the interaction between the mitotic spindle and the chromosome to occur?
Nuclear envelope breakdown
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells,
Taxol disrupts microtubule formation. Surprisingly, this tops mitosis. Specifically, Taxol must affect
the structure of the mitotic spindle
During which phase of mitosis do the chromatids become chromosomes?
Anaphase
Which of the following does NOT occur during mitosis?
Replication of the DNA
Crossing-over is important for
introducing additional genetic variation into the population.
At metaphase I, the two homologous chromosomes of each bivalent are connected to spindle fibers from the
Opposite spindle poles
After telophase I of meiosis, the chromosomal makeup of each daughter cell is
haploid, and the chromosomes are each composed of two chromatids
Sister chromatids separate from each other during
mitosis and meiosis
Which of the following occurs in meiosis but not in mitosis?
Synapsis of chromosomes
Cyclin-dependent kinase activity stays high though mitosis after rising prior to DNA synthesis. Which of the following results from its elevated activity?
It suppresses the formation of new pre-replication complexes.
Please list 8 basic properties of cells.
1) Cells are alive.
2) Cells are highly complex and organized
3) Cells are able to produce more of themselves
4) Cells acquire and utilize energy
5) Cells Self-Regulate Themselves
6) Cells Evolve
7) Cells are able to respond to stimuli
8) Cells engage in mechanical activities
Please list the different functional compartments of Golgi complex and their functions respectively
Cis Golgi Network (CGN):
- sorting station to determine the destination of proteins
Cis cisternae, Medial cisternae, Trans cisternae:
- modifies newly synthesized proteins from ER
Trans Golgi Network (TGN):
- sorting station for segregating proteins into different types of vesicles for their final destination
Microtubule-Organizing Centers play important roles in the control of microtubule. Please
list what the roles and functions are.
MTOCs- specialized structure for the nucleation (assembly) of microtubules
- initiates de novo (made from nothing) formation of microtubules from alpha and beta tubulins
Please describe what is a promoter and what function a promoter posses.
Promoter: a region of DNA upstream of the transcription start site of a gene.
Functions:
1) Has info that determines which of the two DNA will be used a template
2) Initiates Transcription
Please describe what the functions are for the 5’ cap and 3’ poly(A) tail.
5’ methylguanine cap functions:
- protects 5’ end of mRNA from degradation by enzymes
- aids in export out and the nucleus
- aids in the initiation of translation
3’ poly A tail: protects 3’ end of mRNA from degradation by enzymes
Please list the mutations that can occur in the DNA molecule, and briefly explain what happens for each mutation.
A single nucleotide mutation
- Synonymous: DNA mutation makes the same Amino Acid
- Nonsynonymous: DNA mutation makes different AA (causes substitution)
- Nonsense: DNA mutation causes a premature stop codon
Insertion or Deletion:
- One or more nucleotide has been included/erased from sequence
- frameshift DNA mutation: alters the normal reading frame of mRNA
List enzymes required for DNA replication and their functions.
Helicase: unwinds DNA double helix
Topoisomerase: release tension from supercoiled DNA by nicking it
DNA Primase: initiates DNA synthesis
DNA Polymerase III: synthesizes new DNA from template
Ligase: binds Okazaki Fragments together
List the major components of the cytoskeleton, their individual composition, and major function.
microtubules: resist compression - composed of tubulin subunits - come out of and attach to the centrosome
intermediate filaments (IF): made of true fibrous protein subunits- an important part of maintaining cell shape - anchors organelles in place so they don’t float off somewhere
microfilaments: resist tension - help maintain cell shape - made of actin - achieve both cellular and organism movement
