Ecologist has proposed following explanation to lead biodiversity at tropic.

a.Higher productivity in the tropics allows for more species

b)  Environments are more stable and predictable in the tropics, with fairly constant temperatures and rainfall levels year-round

c) Predators and pathogens limit competition in the tropics, which allows more species to coexist

d) High evolutionary speed at tropic than temperate

#Question id: 1156

#Unit 4. Cell Communication and Cell Signaling

Which of the following mechanisms cannot terminate an intracellular signaling pathway once the concentration of an external signal decreases?

#Question id: 1157

#Unit 4. Cell Communication and Cell Signaling

When the regulatory domain of PKA is bound to cAMP:

#Question id: 1158

#Unit 4. Cell Communication and Cell Signaling

Muscarinic acetylcholine receptors are GPCRs that slow the rate of heart muscle contraction upon ligand binding/activation. Activation of this receptor leads to opening of potassium channels triggered by decreases in cAMP levels. The muscarinic acetylcholine receptor likely couples to:

#Question id: 1159

#Unit 4. Cell Communication and Cell Signaling

Cholera toxin can make you sick through overactivation of a Gs pathway even if your body stops making the ligand associated with activation of the pathway. Knowing this, which of the following CANNOT be true about cholera toxin?

#Question id: 1160

#Unit 4. Cell Communication and Cell Signaling

Signal amplification is an important part of GPCR-mediated signaling. Which of the following steps do NOT directly amplify the signal?

#Question id: 1161

#Unit 4. Cell Communication and Cell Signaling

A mutation renders a Gαq subunit constitutively active (also known as dominant active). Which of the following effects might you observe in a cell with this mutation?