Q2. Identify each of the following statements as True (T) or False (F) with brie
ID: 63770 • Letter: Q
Question
Q2. Identify each of the following statements as True (T) or False (F) with brief justification of your answer.
a) The minus end of the microtubules and microfilaments is named so because subunits are lost and never added there
b) The energy required for tubulin and actin polymerization is provided by hydrolysis of a nucleotide triphosphate
c) Microtubules, microfilaments and intermediate filaments all exist in a typical eukaryotic cell in dynamic equilibrium with a pool of subunit proteins
d) Latrunculin A treatment would block intracellular movements of Listeria
e) An algal cell contains neither tubulin nor actin f) All of the protein subunits of intermediate filaments are encoded by genes in the same gene family
g) All microtubules within animal cells have their minus ends anchored at the centrosome
h) As long as actin monomers continue to be added to the plus end of the microfilament, the MF would continue to elongate
Explanation / Answer
a. The statement is False. The minus end is named because the protofilaments bundle parallel to each other and microtubules can undergo treadmilling, with the addition of tubulin heterodimers at the plus end and dissociation of tubulin heterodimers at the minus end. Heterodimers can add or dissociate at either end of a microtubule, but there is greater tendency for subunits to add at the plus end, where b-tubulin is exposed.
b. The statement is False - it is the minus end because the alpha tubulin is exposed and has a negative charge. Also, the loss and addition both occur, just that the rate of loss is greater then the rate of addition.
c. The statement is True. All the components exist in equilibrium because there would be always a constant polyemerisation and depolymerisation of individual subunits in the cells.
d. The statement is True. Listeria requires polymerization of actin to move through cells. Latrunculin A sequesters actin monomers, making them unavailable to Listeria.
e. The statement is False. Algae are eukaryotes and possess the same kinds of components as other eukaryotic cells.
f. The statement is True. They ar encoded by genes in the same gene family.
g. The statement is False. In ciliated or flagellated, cells the minus end of MT's can also be embedded in basal bodies.
h. The statement is True. It depends on the monomer concentration is above the overall critical concentration.
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