Which of the following statements about secretion is true?
(a) The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior.
(b) Vesicles for regulated exocytosis will not bud off the trans Golgi network until the appropriate signal has been received bythe cell.
(c) The signal sequences of proteins destined for constitutive exocytosis ensure their packaging into the correct vesicles.
(d) Proteins destined for constitutive exocytosis aggregate as a result of the acidic pH of the trans Golgi network.
Choice (a) is correct. Vesicles for regulated exocytosis bud from the trans Golgi network and accumulate at the plasma membrane until the appropriate signal has been received [choice (b)]. There are no signal sequences for proteins destined for exocytosis [choice (c)]. Those proteins that are to be secreted by regulated exocytosis aggregate in the trans Golgi network as a result of the acidic pH and high Ca2+ concentrations [choice (d)]; those proteins that do not aggregate are packed into transport vesicles for constitutive exocytosis.
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When DNA is replicated, ____
a. parental histones are degraded and entirely replaced by new histones b. DNA is permanently freed from histone binding
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____________________ rights are violated because the programs are mandatory. Fill in the blank(s) with the appropriate word(s).
Which of these white blood cells are phagocytic?
A. neutrophils B. macrophages C. lymphocytes D. both neutrophils and macrophages E. both lymphocytes and macrophages
Imagine you start a population of 1 million bacteria from a single bacterial cell. Now imagine that a population this large is started from a male and female housefly. How would these two populations differ?
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