Which of the following statements about the sodium-potassium pump is true?
a. It transports hydrogen ions out of the cell.
b. It transports 3 sodium ions out of the cell in exchange for 2 potassium ions.
c. It transports 2 sodium ions out of the cell in exchange for 2 potassium ions.
d. It transports 2 sodium ions out of the cell in exchange for 3 potassium ions.
e. It transports water directly out of the cell.
B
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Considering the catabolite repression mechanism, which observation would make you suspect it is NOT occurring?
A) CRP bound to promoter sites B) elevated levels of transcripts for maltose and sucrose catabolism C) relatively low intracellular cyclic AMP levels D) RNA polymerase bound to biosynthetic promoter sequences
The atmosphere and seas of the early Earth lacked oxygen. What kind of organisms could NOT have lived under those conditions?
A. obligate aerobes B. obligate anaerobes C. facultative anaerobes D. chemoautotrophs E. cyanobacteria
Liverworts, hornworts, and mosses are ____
a. seedless vascular plants b. seed plants c. nonvascular plants d. charophytes e. gymnosperms
Jill broke her cheekbone in an ice skating accident. Which bone did she break?
A. frontal bone B. mandible C. zygomatic bone D. temporal bone E. maxilla