Which of the following statements best summarizes the acid-growth hypothesis in an actively growing shoot?
A) Auxin stimulates proton pumps in the plasma membrane and tonoplast.
B) Auxin-activated proton pumps lower the pH of the cell wall, which breaks bonds and makes the walls more flexible.
C) Auxins and gibberellins together act as a lubricant to help stretch cellulose microfibrils.
D) Auxins activate aquaporins that increase turgor pressure in the cells.
B
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Which of the following is an extension of a lobe of the cytoplasm, and is used by some protists for movement?
a. a pilus b. a cilium c. a pseudopod d. a gullet
The enzyme dicer chops dsRNA molecules into small pieces of
A. mRNA and miRNA. B. siRNA and rRNA. C. miRNA and siRNA. D. mRNA and siRNA.
When does the human embryo implant in the wall of the uterus?
A) within a few hours of fertilization
B) about a day after conception
C) about a week after conception
D) just after gastrulation
CREB1 function as a (A)________, whereas CREB2 function as a (B)________. The consensus sequence for CREB1 and CREB2 is (C)_________.
a. (A) transcriptional activator (B) transcriptional repressor (C) same b. (A) transcriptional repressor (B) transcriptional activator (C) same c. (A) transcriptional activator (B) transcriptional repressor (C) different d. (A) transcriptional repressor (B) transcriptional activator (C) different