<span>Ribonucleic acid (RNA) occurs
primarily as single strands, often giving rise to single polynucleotide
structures. RNA is a polymeric molecule
that is responsible for the regulation, coding, decoding and expression of
genes. Each nucleotide has a ribose sugar attached to the carbon, a base that
is composed of purines and pyrimidines, a negatively charge phosphate groups
and a hydroxyl group which causes helix to mostly adopt the A-form geometry.</span>
Bromothymol blue is an indicator dye that turns yellow in presence of an acid. It remains blue if the pH of the given solution is greater than 7.6 and yellow when the pH is less than 6. The yellow coloration is due to the formation of carbonic acid in the from the carbon dioxide present in the solution.
When aquatic plants are added to two test tubes containing bromothymol blue, stoppered and kept in dark for two days, no color change is observed. It is because the carbon dioxide present is utilized in the process of photosynthesis by plants. If the experiment is conducted in presence if the light, the color of bromothymol blue would be yellow due to the presence of carbon dioxide.
It's caused by blood pooling in the legs, so there's insufficient return to the heart and brain. Normally, moving one's legs helps to pump blood back to the heart through muscle contraction. Locking the knees makes standing still easier, but reduces use of the leg muscles. In some people, this pooling may lead to hypoperfusion of the brain and fainting, which is essentially the body's way of putting the brain and the legs and the heart at the same level.
