Answer:
Constitutive activation is the alteration of a protein or signaling pathway such that it is functional or engaged even in the absence of an upstream activating event. For example, RasD is constitutively active because it cannot bind GAP and therefore remains in the GTP-bound, active state even when cells are not stimulated by growth factor to activate a receptor tyrosine kinase.
Constitutively active Ras is cancer promoting because cells will proliferate in the absence of growth factors, and thus normal regulatory mechanisms for cell proliferation are bypassed.
(a) A mutation that resulted in Smad3 binding Smad4, entering the nucleus, and activating transcription independent of phosphorylation by the TGFβ receptor would render Smad3 constitutively active.
(b) A mutation that made MAPK active as a kinase and able to enter the nucleus without being phosphorylated by MEK would render MAPK constitutively active.
(c) A mutation that prevented NF-KB from binding to IK-B or that allowed NF-KB to enter the nucleus and regulate transcription even when bound to IK-B would render NF-KB constitutively active.
All living cells and many of the tiny organelles internal
to cells are bounded by thin membranes. These membranes are composed
primarily of phospholipids and proteins and are typically described as
phospholipid bi-layers.
<span>Hope I helped. :) </span>
There aren't enough oxygen molecules in the air are higher altitudes
The chamber is the left atrium.
The lungs help exchange the deoxygenated blood which are full of wast materials into oxygenated and blood full of nutrients. These oxygenated blood are then transported through the pulmonary vein, the only vein in the body which transports oxygenated blood. These blood are then transported back into the heart, which is the left atrium specifically.
Those blood is then pushed down to the left ventricle, and then pumped to the whole body (except lungs), in order to keep the body functioning by providing oxygen and nutrients for cellular respiration.
Meanwhile, the deoxygenated blood are received by the right atrium, and is then transported back to the lungs for exchange again, through the right ventricle and pulmonary artery.
