Answer: Most of the hormones released by endocrine system are regulated by negative feedback mechanism.
- Negative feedback mechanism functions to reduce the intensity of original stimulus in order to maintain homeostasis.
Explanation:
When blood calcium levels are decreased, parathyroid gland releases parathyroid hormone (PTH).
PTH acts on bone and stimulate bone resorption by promoting osteoclastic activity. It stimulates reabsorption of calcium in kidneys. PTH promotes calcitriol synthesis that acts on small intestine to increase calcium absorption.
Action of PTH increases blood calcium levels.
When blood calcium levels are increased, thyroid gland releases hormone calcitonin.
Calcitonin opposes PTH and acts to deposit calcium in the bone.
Calcitonin acts on osteoblasts and promote increase in bone mass.
Action of calcitonin decreases blood calcium levels.
Answer:
a) there are three transition states
b) there are two intermediates; carbocation and protonated alcohol
c) The first step in the forward direction
Explanation:
The acid-catalysed hydration of alkenes proceeds via a carbocation mechanism.
Three transition states can be identified in this mechanism for the acid-catalyzed hydration of alkenes.
The three transition states are derived from the three steps in the reaction sequence:
1) Protonation of the alkene by hydronium ion
2) Addition of water to the carbocation
3) loss of a proton to yield the alcohol
The first step involves the breaking of a pi bond, hence it is a slow step hence it has the smallest rate constant. The other two steps are fast steps.
Answer:
The density of the swimmer is 0.0342 lbm/in3.
This value makes sense as the density of the body is very similar to the water.
Explanation:
If the swimmers is floating, the weight of the swimmer must be equal to the upward buoyant force.
We can express the weight force as the product of density and volume of the swimmer.
Then
It makes sense as the density of the body is very similar to the water.