Answer:
Letter B.
Explanation:
Aquaporins, also known as "water channels," are the main transport of water through the membranes of plant, animal, and bacterial cells. These channels allow the water to travel into and within cells and, at the same time, exclude the passage of ions and solutes.
What makes letter B the correct answer, is the form of transport and shape of the channel that allow water according to the osmotic gradient. In this model, letter A shows simple diffusion, while C and D seem to illustrate gated channels.
As the experts says, solar eclipse do not happen always like lunar
eclipses do that is visible for a long periods of time and are observable. Unlike
solar eclipse, it happens hundreds and thousands of years to see it. Few people
can only see solar eclipse, and those only those people
who are in the small region where the Moon's umbra strike's Earth can witness
one.
Answer:
Blood clothing is an example of positive feedback.
This type of feedback mechanism is useful to the body because it multiplies the factor that intervenes in clotting accelerating the process.
If a toxin affects the molecules that signal for platelets the feedback will not be effective enough to produce clotting and the body will keep bleeding.
Explanation:
Blood clotting is an example of positive feedback due to the fact that when the vascular endothelium is damaged platelets will go to this area and activate themselves once they are in contact with the collagen fibers of the damaged structure. When the platelets are activated they will release the contents that is stored in their granules. One of the contents is a Gq-linked protein receptor cascade, that will increase the concentration of calcium in the platelets. Calcium activates protein kinase C, which, in turn, activates phospholipase A2 (PLA2). PLA2 will modifies an integrin membrane increasing its affinity to bind fibrinogen. The activated platelets change their shape , and the fibrinogen cross-links with the integrin membrane aiding in the aggregation of adjacent platelets. After this the coagulation cascade takes place. there are two pathways the extrinsic and the extrinsic one.
The extrinsic pathway will be activated due to tissular factor released by the platelets and the intrinsic pathway will be activated due to endothelial collagen. The final product of both pathways is factor x.
Factor x will transform prothrombin into thrombin will activate the conversion of fibrinogen into fibrin. Thrombin will form a net of fibrin that will the clot.
A cascade reaction is useful because every component of the cascade are related making a quick reaction once that one of then is activated and can activate other or more factors.
If a toxin affects the molecules that signals for platelets, platelets will not go to the damaged area and in consequence there will not be thrombin and fibrin to form the clot together with platelets.
Answer:
MNP stands for the most probable number which is used for finding out the concentration of viable bacteria in a sample. It is commonly used to check the quality of water and its safety. Usually, the presence of fecal coliform bacteria is checked in this test.
Principle of MNP: The sample which is to be tested is diluted serially and then inoculated into a broth medium containing lactose. If coliforms are present in the tube than it will consume lactose and release acid and gas.
Color change represents acid production and gas trapped in the Durham tube represents the gas production by bacteria. Then the number of tubes at each dilution that showed positive results are compared with standards to determine the most probable number of the bacteria.
