Answer:
Enzymes are one kind of protein which functioning as catalyst that speed up reactions by lowering activation energy.Enzyme accelerate a reaction without altering its chemical equilibrium.
Explanation:
Energy which is required for start a biochemical reaction is called activation energy.Activation Energy helps to jump and start a thermodynamically favorable reactions.
Enzymes can many way to its activation energy.
1. The enzyme may hold the substrates in such a way as to distort the substrate bonds closer to their form in the transition state. This reduces the amount of energy needed to complete the transition.
2.Enzyme create a charge distributor which opposite of transition state his lowers the energy of the transition state and decreases the activation energy.
3.The enzyme may reduce the reaction entropy by bringing substrates together in the correct orientation to react.
4. The enzyme may provide a completely different chemical pathway for the reaction. It may form new bonds in the ES complex that would be difficult to form without the enzyme.
The answer is; cell surface receptors that are recognized as antigens by the recipient's immune system.
Therefore the organ is attacked as a foreign substance . This is why organ transplants are given by the closest family member to reduce the antigen variability that causes transplant rejection. Tissue typing is done to ensure that the organ or tissue is as similar as possible to the tissues of the recipient.
ITS D I THINK PRETTY SURE BUT DO TAKE MY WORD FOR IT.
Answer:
You did not write the concept, so i will try to answer in a general way.
Why sometimes we really need to model concepts?
Well, sometimes the things are really complicated, or we just do not have the knowledge or tools to fully understand them.
Here is where the models came to be handy, we can somewhat "simplify" the things, and explain them with models.
For example, the movement of a particle as the wind pushes it can be really complex, so this can only be explained with a model.
Now, once we have a model (supported by theory and experiments) we can start to investigating furthermore in the given subject.
So for example, we could model how a given therapy acts on a given disease, and with that model, we could extrapolate the effects of the therapy in a similar disease (for example, testing how radiotherapy acts on a given tumor in some organ, can give information on how the same therapy can act on other types of tumors)
Concluding, models simplify some concepts, which allow us to understand them and work better with them
