What are the tiny closeable gaps within the cell wall that allow gases to diffuse?
a. Stroma
b. Cristae
c. Stomata
d. Gap junctions
e. Nuclear pores
c
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Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?
A) Enzymatic activity was proportional to the amount of calcium added to a cell-free extract. B) Receptor studies indicated that epinephrine was a ligand. C) Glycogen breakdown was observed only when epinephrine was administered to intact cells. D) Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined. E) Epinephrine was known to have different effects on different types of cells.
The condition occurring when an organism has a 2n
+ 1 chromosome composition is known as a. monosomy. b. deletion. c. diploid. d. aneuploidy. e. both deletion and aneuploidy.
Auxins are secreted by
a. most tissues undergoing ripening. b. apical meristems of shoots, coleoptiles, and roots. c. vascular tissues of stems and leaves. d. root caps. e. root cells in response to water stress.
Two principal organelles in eukaryotes that were apparently derived from different types of bacteria are the
A. plasma membrane and nuclear membrane. B. rough ER and smooth ER. C. mitochondria and chloroplasts. D. microfilaments and microtubules.