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#Question id: 2255


Following statements are regarding to the Na+/K+ ATPase maintains the intracellular Na+ and K+ concentrations in animal cells. Which of the following statement is incorrect?

#Unit 2. Cellular Organization
  1. In its E1 conformation, the Na+/K+ ATPase has three high-affinity Na+-binding sites and two low-affinity K+-binding sites accessible from the cytosolic surface of the protein. The Km for binding of Na+ to these cytosolic sites is 0.6 mM, a value considerably lower than the intracellular Na+ concentration of ~12 mM; as a result, Na+ ions normally fully occupy these sites.

  2. the affinity of the cytosolic K+-binding sites is low enough that K+ ions, transported inward through the protein, dissociate from E1 and enter the cytosol despite the high intracellular K+ concentration.

  3. During the E1 → E2 transition, the three bound Na+ ions gain access to the exoplasmic face, and simultaneously, the affinity of the three Na+-binding sites drops. The three Na+ ions, now bound to low-affinity Na+ sites, dissociate one at a time and enter the extracellular medium despite the high extracellular Na+ concentration.

  4. Transition to the E2 conformation generates two low-affinity K+ sites accessible from the exoplasmic face. Because the Km for K+ binding to these sites (0.2 mM) is lower than the extracellular K+ concentration (4 mM), these sites will fill with K+ ions as the Na+ ions dissociate.

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#Unit 10. Ecological Principles

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TLS Online TPP Program

#Question id: 12342

#Unit 10. Ecological Principles

Which of the following is a biological attribute that would most likely allow a species to become cosmopolitan in distribution?

TLS Online TPP Program

#Question id: 12343

#Unit 10. Ecological Principles

Hybrids between some related species of plants are sterile because the parent plants had different chromosome numbers. Occasionally the chromosome number of such a hybrid  plant doubles spontaneously. Which of the following best describes the descendants of those plants with the double chromosome number?