Unit 4 Study Guide Cell bio
Indicate which of the three major classes of cytoskeletal elements each statement below refers to. A. monomer that binds ATP B. includes keratin and neurofilaments C. important for formation of the contractile ring during cytokinesis D. supports and strengthens the nuclear envelope E. their stability involves a GTP cap F. used in the eukaryotic flagellum G. a component of the mitotic spindle H. can be connected through desmosomes I. directly involved in muscle contraction J. abundant in filopodia
A. actin B. intermediate filaments C. actin D. intermediate filaments E. microtubules F. microtubules G. microtubules H. intermediate filaments I. actin J. actin
Indicate whether each of the following statements refers to a ciliary microtubule, a microtubule of the mitotic spindle, both types of microtubule, or neither type of microtubule. A. The basal body is the organizing center. B. The monomer is sequestered by profilin. C. It is arranged in a "9 + 2" array. D. It is nucleated at the centrosome. E. It uses dynein motors. F. It is involved in sperm motility. G. It is involved in moving fluid over the surface of cells.
A. ciliary microtubules B. neither C. ciliary microtubules D. microtubules of the mitotic spindle E. both F. neither (this involves flagellar microtubules) G. ciliary microtubules
Which of the following statements about the cytoskeleton is true?
Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end.
Which of the following statements is false?
Actin filaments are usually excluded from the cell cortex.
Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments?
Actin filaments would grow longer.
Which of the following statements about transport into mitochondria and chloroplasts is false?
After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane.
Which of the following statements is true?
CorrectC. Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation.
Which of the following statements about the cytoskeleton is false?
Covalent bonds between protein monomers hold together cytoskeletal filaments.
Consider the mechanism by which actin and tubulin polymerize. Which of the items below does not describe something similar about the polymerization mechanisms of actin and microtubules?
Depolymerization initiates at the plus ends of filaments.
Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels?
ER Golgi plasma membrane
Which of the statements below about intermediate filaments is false?
Each filament is about 10 mm in diameter.
Which of the following statements is true?
Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.
Dynamic stability refers to the coexistence of assembly and disassembly at the ends of a microtubule
False
Intermediate filaments are approximately 25nm in diameter
False
The nucleation sites on centrosomes from which microtubules extend, are made up of
Gamma-tubulin
Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following statements is false?
Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family.
Which of the following statements about the function of the centrosome is false?
Microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome.
You discover a protein, MtA, and find that it binds to the plus ends of microtubules in cells. The hypothesis that best explains this localization is ________________.
MtA binds to GTP-bound tubulin on microtubules.
Which of the following statements about phagocytic cells in animals is false?
Phagocytic cells are important in the gut to take up large particles of food.
Which of the following statements about the protein quality control system in the ER is false?
Proteins that are misfolded are degraded in the ER lumen.
The process whereby one type of signal is converted to another is called:
Signal transduction
Which of the following statements about a protein in the lumen of the ER is false?
Some of the proteins in the lumen of the ER can end up in the plasma membrane.
Which of the following statements about G-protein-coupled receptors (GPCRs) is false?
The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains.
Which of the following statements about actin is false?
The dynamic instability of actin filaments is important for cell movement.
Which of the following statements about secretion is true?
The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior.
Which of the following statements regarding dynamic instability is false?
The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end.
Which of the following statements is true?
The nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA.
Which of the following statements is true?
The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling.
The following happens when a G-protein-coupled receptor activates a G protein.
The α subunit exchanges its bound GDP for GTP.
Actin filaments are also referred to as microfilaments
True
Rank the following cytoskeletal filaments from smallest to largest in diameter (1 = smallest in diameter, 4 = largest) ______ intermediate filaments ______ microtubules ______ actin filament ______ myofibril
__2___ intermediate filaments (10 nm diameter) __3___ microtubules (25 nm) __1___ actin filament (5-9 nm) __4___ myofibril (1-2 mm)
The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation?
a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor
The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization?
a mutation that prevents RGFR from binding to RGF
Which of the following statements about the structure of microtubules is false?
a-Tubulin and b-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments.
Order the following types of cell signaling from 1 to 4, with 1 representing the type of signaling in which the signal molecule travels the least distance and 4 the type of signaling in which the signal molecule travels the largest distance (note: order the followng letters (a-d) with the order numbers 1 through 4 for each answer box). a. ______ paracrine signaling b. ______ contact-dependent signaling c. ______ neuronal signaling d. ______ endocrine signaling
a. 3 b. 1 c. 2 d. 4
You are interested in cell-size regulation and discover that signaling through a GPCR called ERC1 is important in controlling cell size in embryonic rat cells. The G protein downstream of ERC1 activates adenylyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cells, while cells that express a mutant, constitutively activated version of PKA are 15% larger than normal cells. Given these results, which of the following treatments to embryonic rat cells should lead to smaller cells?
addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive
Which of the situations below will enhance microtubule shrinkage?
addition of a drug that inhibits GTP exchange on free tubulin dimers
The hydrolysis of GTP to GDP carried out by tubulin molecules ________________.
allows the behavior of microtubules called dynamic instability.
Which of the two is likely to occur more rapidly in response to an extracellular signal.
changes in cell secretion
Which of the two is likely to occur more rapidly in response to an extracellular signal.
changes in membrane potential
Which of the two is likely to occur more rapidly in response to an extracellular signal.
changes in protein phosphorylation
Vesicles from the ER enter the Golgi at the ______.
cis Golgi network.
During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in ______________ signaling.
contact-dependent
For both actin and microtubule polymerization, nucleotide hydrolysis is important for ______.
decreasing the binding strength between subunits on filaments.
Signal sequences that direct proteins to the correct compartment are _________.
encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination.
Keratin filaments are a type of intermediate filament found in
epithelial cells
Intermediate filaments help protect animal cells from mechanical stress because ____________.
filaments in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells.
When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________.
hormone.
In which cellular location would you expect to find ribosomes translating mRNAs that encode ribosomal proteins?
in the cytosol
All members of the steroid hormone receptor family __________________.
interact with signal molecules that diffuse through the plasma membrane.
Match the type of intermediate filament with its appropriate location. lamins _________ A. nerve cells neurofilaments _________ B. epithelia vimentins _________ C. nucleus keratins _________ D. connective tissue
lamins ____C____ neurofilaments ____A____ vimentins ____D____ keratins ____B____
Which of the following statements is correct? Kinesins and dyneins ____________________.
often move in opposite directions to each other.
Which of the following structures shorten during muscle contraction?
sarcomeres
Which of the following items is not important for flagellar movement?
sarcoplasmic reticulum
The microtubules in a cell form a structural framework that can have all the following functions except which one?
strengthening the plasma membrane
Proteins that are fully translated in the cytosol and lack a sorting signal will end up in ____.
the cytosol.
