PCB3134 EXAM 3 (PRACTICE)
What is required for MT assembly and closure?
Where are MT sub units added/removed
The plus end of the microtubule is where subunits are added and removed
During muscle contraction, the length of which region of the sarcomere stays unchanged?
During muscle contraction the length of which reigon of sarcomeres shorten?
H zone and I Band
What is the A band?
the length of the sarcomere that remains unchanged during muscle contraction
- the diameter of ~8nm
- polymerization as a force-generating mechanism
Elongation of the microtubule occurs by addition of G-actin subunits to the + end
True or False
False (tubulin makes up microtubules, G-actin makes up microfilaments)
Steps of Ciliary and Flagella Locomotion
2) Power stroke
Which of the following structures encircle each of the cell near its apical surface to hold the cells together?
Rank the following from smallest to largest in terms of DNA packaging: heterochromatin, nucleosome, looped domains, chromatin fiber
- chromatin fiber
- looped domains
How are actin filaments formed?
Using ATP, actin polymerizes to form actin filaments ("F-actin").
Which protein blocks the myosin binding site on actin thin filaments in a resting sacromere?
Actin filaments are composed of 4 linear strands?
True or False
False (its only 2 intertwined strands)
T/F: DNA replication of linear chromosomes happens at multiple sites?
True (replication bubbles)
If concentration of ATP-bound G-actin is HIGH then _____
microfilaments will assemble until the G-actin is limiting
which region of the sacromere contains only actin thin filaments or MF?
Contraction pulls the Z lines _____
closer together and causes it to shrink
Myofibrils in a muscle cell are made up of a repeating linear array of contractile units called ___
During muscle contraction
- Thick and thin filaments remain constant length but SLIDE with respect to each other
- I band shortens
- Z-lines pulled together
- myosin heads to the + end
Rise in Ca2+ causes
tropomyosin slides out of the way and contraction occurs
Decrease in Ca2+ causes
tropomyosin to bind and block Myosin binding causing relaxation
Phosphorylation of ____ is required for chromosome condensation.
During skeletal muscle contraction as the sacromeres shorten, the following changes can be observed
The H zone and I band are both shorten but the A band remains constant
Cell fusion experiments showed that fusion of a cell in S phase with one in G1 phase leads to the nucleus that was in G1 phase to begin S phase. The best interpretation is that
the cytoplasm of the S phase cell contains a diffusible signal that causes the G1 nucleus to enter S phase
How are integral membrane proteins thought to enter the lipid bilayer?
Translocation occurs in a translocon of the RER that allows transmembrane segments to partition themselves into the lipid bilayer
Adherens junctions encircle each of the cells near is apical surface to hold cells together. 30nm is the distance and they connect the ____ environment to the ___, to provide potential pathway for "outside-in" signaling.
- multiple subunits with different functions
- clathrin-coated vesicles formed in PM in endocytosis
- microsubunits bind to the cytoplasmic tail of specific PM receptors
which protein is not made on the membrane bound ribosomes of the RER?
soluble cytosolic proteins
Which of the following sentences describes characteristics shared by ALL myosins?
A. They are motor proteins that bind to GTP
B. They are motor proteins that are active in muscle cells
C. They are motor proteins that carry vesicles during intraflagellar transport
D. They are motor proteins that bind to and exert force on MFs
D. They are motor proteins that bind to and exert force on MFs
What do all motor proteins have in common?
They convert chemical energy into motion
To what residue of a polypeptide are N-linked oligosaccharide chains attached as that polypeptide enters the RER lumen through the translocon?
The plus end has a ______ Cc than the minus end
How does UGGT recongnize incompletely folded or misfoleded proteins that have been recently synthesized?
such proteins display exposed hydrophobic residues that are absent from properly folded proteins
Genome size generally _________ with an organism's complexity
As temperature ____, hydrogen bonds _____, causing DNA strands to _____
- separate (This is denaturing DNA)
What does the conformation-sensing enzyme UGGT do if it binds to a misfolded or imcompletely folded glycoprotein?
it adds a single glucose back to one of the mannose residues at the exposed end of the recently trimmed oligosaccharide
Which is the best mechanistic explanation for why there are no Okazaki fragments in PCR?
There are no replication forks in a PCR reaction
Plasmodesmata are most similar in function to which structure in animal cells?
What is the role of fibronectins in the ECM of animals?
To serve as a bridge connecting cells to the rest of the extracellular matrix
How does calcium regulate muscle contraction?
It causes a conformational change in tropomyosin
The assembly of GTP-hydrolysis requires ___ molecule to be bound to ____ subunit.
What evolves as a response to nutrient deprivation, protection against intracellular threats, and functions in the prevention of certain cancers/slowing aging process?
What is the basal body?
an organelle that forms the base of a flagellum or cilium
Chargaff's Rule states
the base composition of DNA in the cells of all tissues of an
organism is identical
[A]=[T], [G]=[C], [A]+[T] does not equal [G]+[C]
Cisternae are a series of tubes and flattened membraneous areas in the ____. Each layer is connected by ____.
- Helicoidal ramps
The plant centralvacuole often occupies as much as 90% of the volume of a plant cell. Which of the following is NOT a function of the central vacuole?
regulate turnover of cell's organelles
Release of a clathrin-coated vesicle from the plasma membrane during endocytosis requires a GTP-binding protein named _____________.
Clathrin-Coated Vesicles move specific extracellular macromolecules into cell interior during a _____-____ endocytosis.
Mediate trafficking from Golgi back to ER
COP I-coated vesicles
found in between the ER and Golgi Complexes
COP II-coated vesicles
Desmosome is a cell-cell interaction structure of 2 cells, with a distance of ____
What is the breakdown of material brought into the cell from the extracellular environment?
Dyneins are ___ ends that are responsible for moving along IMF. Kinesins are ____ ends that are directed at the MT motor proteins.
Encode for rRNA
A single, symmetrical curve of renaturation represents ____.
a simple genome
A 3+/- steps with high repeating fragments, moderate repeats is referred as the
range from 12-100 base pairs and found in clusters (<3,000 repeats)
1-5bp, clusters of 10-40 basepairs
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.
Short sequences 5 few to 100, that form large clusters (millions of base pairs)
Intermediate Filament (IMF) has a diameter of __ to __nm and is composed of "rope" fibers. The assemble and disassembly are controlled by phosphorylation and dephosphorylation of subunits.
10 to 12
What happens when the bound Pi molecule is released from the active site on the myosin head?
It triggers a large conformation change and causes the actin filament tp shift towards the center of the sarcomere
Kinesins have a fan-shaped tail that binds cargo. True or False
Lysosomes are only found in ___ cells. They are the end product of ____ and contain a large number of acid hydrolases.
- animal cells
Microfilaments are ___nm in diameter. When actin monomer binds ATP, it becomes ATPase. Then the ATP with the actin monomer is hydrolyzed to ADP.
The donor in Glycoslylation in RER is always a ______ sugar: CMP-Salic acid, GDP-mannose, or UDP-N-acetylgulcosamine.
Kinesins move along the _____ of microtubules at a velocity proportional to the [ATP].
According to the DNA double helix model, the distance from the phosphorus atom of the backbone to the center of the axis is ____.
According to what we have learned, which of the following structures can be found in plants?
None of the above (only plasmodesmata)
the temperature at which the shift in absorbance is half completed
The melting temperature (Tm)
During muscle contraction, the calcium concentration in myofibrils increases. Calcium interacts with ____________ to initiate the contraction.
Plasmodesmata are cell-cell interaction structures found in plants. Plasmodesmata contain a dense central structure called desmotubule, which is derived from ___.
Creates a transient break in both strands of a DNA duplex. is required to unlink DNA before duplicated chromosomes can be separated during mitosis.
Type II topoisomerase
The structure of DNA molecule can be changed by different enzymes. An enzyme that creates a transient break in both strands of a DNA duplex and then allows another DNA fragment to pass through to form a relax supercoil is called a ____.
type II topoisomerase
DNA renaturation is the basis for many DNA analysis methods. which of the following is not a factor influencing the rate of DNA denaturation?
the presence of enzymes
DNA renaturation is the basis for many DNA analysis methods. Which of the following techniques is NOT based on DNA renaturation?
DNA gel electrophoresis
During muscle contraction, the length of which region of the sarcomere stays unchanged?
N-linked oligosaccharides are synthesized in ____________.
the rough ER and then finished in the Golgi complex
In the ER, during the modification of the core oligosaccharide on glycoproteins, 2 of the 3 terminal glucose residues are removed. The remaining glucose binds to an ER chaperone protein called calnexin to help the glycoprotein to fold properly. The remaining glucose is then removed by ___ to release the glycoprotein from the chaperone.
Where are misfolded secretory proteins eventually destroyed?
in the cytosol
Protein coat contains soluble proteins that assemble on the _______ surface of the donor membrane at sites where budding takes place.
In response to the accumulation of misfolded proteins, genes encoding what kinds of proteins are not induced during the unfolded protein response (UPR).
ER-based secretory proteins
Localize to a particular site on a particular chromosome, contain the greatest amount of genetic information, code for all proteins other than histones are called ____________.
The ability for DNA to separate its two strands into its two component strands is called __________.
A complex eukaryotic genome generally has 3 broad classes of DNA sequences. Which class of DNA sequences contains the greatest amount of genetic information?
nonrepeated DNA sequences
How are membranes thought to be made?
- Membranes arise from pre-existing membranes
- Membranes arise as newly made proteins and lipids are inserted into ER membranes
In muscle cells, how is the arrangement relative to one another of thin and thick filaments as seen in a cross-sectional electron micrograph described?
thin filaments in a hexagonal array around thick filament
In the endocytic pathway, endocytotic vesicles fuse with each other to form ___, in which the pH is lowered to around 6.0 by ____.
- early endosomes
- H+-ATPases in the membrane
Plasmodesmata are plant cytoplasmic channels that pass through the cell wall of adjacent cells. The plasmodesmatal pore is capable of dilation, allowing molecules up to ___kDa to pass between cells.
Proteins destined for peroxisomes possess a peroxisomal targeting signal (PTS). The PTS will be recognized by the PTS receptor in ___.
Proteins maintained in the membrane of the ER contain a short amino acid sequence at the C-terminus as a retrieval signal, which is ____.
Lysosomes are found in animals but not in plants. Which of the following descriptions is not correct for lysosomes?
Lysosomes have simiar size with a diameter about 100nm
Lysosomes are found in animals but not in plants. Which of the following descriptions is NOT correct for lysosomes?
Lysosomes have double membranes
Proteasomes are hollow, cylindrical, protein-degrading machines found in both the cytosol and the nucleus of cells. A protein that is to be degraded by a proteasome is labeled by ___.
a polyubiquitin chain
At the trans-Golgi network, the formation of clathrin-coated vesicles is initiated by a small GTP-binding protein named ___.
In animal cells, centrosome is a microtubule-organizing centeer. Each centrosome contains ____________ centrioles and each centriole contains _________ evenly spaced fibrils.
The eukaryotic cilia and flagella have a complex structure. The core of a cillium/flagellum is called the ____, which contains ___ and ____.
- 9 peripheral doublet MTs
- 2 single central MTs
The endomembrane system functions as a coordinated unit, which includes which of the following organelles?
- Golgi complex
The enzyme that catalyzes the excision of a transposon from a donor DNA site and subsequent insertion at a target DNA site is called____. This enzyme is encoded by ____.
- Transposon DNA
Which of the following structures is not involved in cell-cell adhesion?
The pectins and hemicellulose found in plant cell walls are synthesized in ____.
the Golgi complex
There are a large number of integral proteins that are involved in cell-cell adhesion. Which of the following integral proteins do not require Ca2+ when the mediate cell-cell interactions?
immunoglobulin superfamily proteins
There are some "footprints" that can be used to identify sites in the genome, which used to be occupied by transposable elements. These "footprints" are ___.
direct repeats of recipient DNA
The wall of a MT is composed of globular proteins arranged in longitudinal rows, termed protofilaments. MTs consist of ___ protofilaments aligned by side in a circular pattern within the wall.
In nonmuscle motility and contractility, actin filaments work together with myosin motors. Which of the following processes does not involve actin-myosin movement?
receptor-mediated endocytosis (uses receptors)
What happens immediately after ATP binds to a myosin head during muscle contraction?
ATP binding induces the detachment of the myosin head from the actin filament
Golgi complexes contain flattened disklike membranous cisternae with dilated rims and associated vesicles and tubules. Typically, in each Golgi complex, fewer than ___ cisternae are arranged in an orderly stack.
Muscle contraction uses energy from hydrolysis of ATP. After ATP binds to myosin head, it is hydrolyzed to ADP and Pi. What happens after the bound Pi is released?
Release of the bound pi induces a large conformational change in the myosin head. no
In the cytoplasmm, vesicles travel along microtubules and microfiliments to different directions. _______________ moves from ER to Golgi along ____________.
What part of molecular motor dynein is responsible for traveling along microfilaments?
none of the others (it only travels along microtubules on the negative side, always to the golgi complex)
Gene duplication often occurs during meiosis. What process is generally thought to produce gene duplication?
unequal crossing over
When a cilium or flagellum emerges from a basal body, ___ moves building materials to the assembly site at the tip of the growing axoneme.
After an unequal chromosome crossover, a small portion of the chromosome is duplicated. Which of the following is the fate of the duplicated gene.
- lost through deletion
- inactivated by unfavorable mutation
- the extra copy acquires a new function
- both copies of the gene undergo mutations and each acquires a more specific function
After a transposon moves from a donor DNA site to a new site using the "cut and paste" mechanism, it leaves a "footprint"at the donor site. The "footprint" is ____________.
direct repeat in recipient DNA
When proteins are synthesized on ER-membrane-bound ribosomes, the signal peptide emerging from the ribosome binds to the signal recognition particle (SRP) complex. The SRP complex contains____.
proteins and small RNAs
Kinesins are ____________ motor protein.
plus end-directed microtubular
Which of the following molecular motors is known to mostly travel along MTs to the plus end of the MTs?
Which of the following is a general description of a type II myosin motor?
- a pair of globular heads each with a catalytic site,
- a pair of necks and a single long,
- alpha-helical coiled-coil tail
In the current version of the Golgi complex cisternal maturation model, a role of ________ is appreciated.
Which of the following proteins are NOT synthesized on "free" ribosomes?
proteins secreted from the cell
Which of the following proteins are NOT made of ribosomes attached to the cytosolic surface of the ER?
proteins to be incorporated into peroxisomes
Which of the following is a correct description of the transmembrane sequence which blocks further translocation of the peptide through the channel in the ER membrane during synthesis?
at least 15 continuous hydrophobic or uncharged amino acids
Cellulose is a major component of the plant cell. cellulose is synthesized by cellulose synthase in _________.
The plasma membrane