The RNA world proposal suggests that the first information molecules were
a. transfer RNA.
b. ribosomes.
c. messenger RNA.
d. ribozymes.
e. unpaired strands of DNA.
D
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Which of the following statements is false?
A. Circulation requires a pump to generate pressure to drive flow, whereas ventilation does not. B. Ventilation maximizes the concentration of oxygen in the air on the outside of the respiratory surface. C. The same amount of oxygen enters the blood through diffusion as is transported by circulation. D. Oxygen and carbon dioxide both move across the respiratory surface by diffusion. E. Larger, more complex animals rely on bulk flow and diffusion to deliver oxygen to their cells, whereas some simpler animals rely on diffusion alone.
Which form of calcium is found in bones?
a. calcium citrate b. calcium carbonate c. calcium lactate d. calcium bicarbonate e. calcium phosphate
Position of bone ends after fracture
What will be an ideal response?
Indicate by writing "yes" or "no" whether amplification of a signal could occur at the particular steps described below. Explain your answers
A. An extracellular signaling molecule binds and activates a GPCR. B. The activated GPCRs cause G? to separate from G? and G?. C. Adenylyl cyclase produces cyclic AMP. D. cAMP activates protein kinase A. E. Protein kinase A phosphorylates target proteins.