Carbon is the universal building block for life as we know it. Its ability to form complex, stable molecules with itself and other elements, particularly hydrogen, oxygen, and nitrogen is unique. Rings are also formed by -O- bridges between carbon atoms lanation.
Answer:
Option C, The cell membrane allows water to enter and leave the cell.
Explanation:
Options for the question are –
A. The cell membrane is an impermeable barrier that prevents water from entering the cell.
B. The cell membrane allows solutes to enter the cell, which causes the cell to shrink.
C. The cell membrane allows water to enter and leave the cell.
D. The cell membrane removes solutes from the environment.
Solution -
The cell membrane is semi permeable to water and some other substances. Whenever there is a difference in concentration or volume on the two sides of the membrane, either the solute or the solvent starts moving till equilibrium is reached. In few cases, the flow continues uninterrupted thereby increasing the cell size to its maximum extent and hence bursting it.
Hence, option C is correct
<h2>
Answer:</h2><h2>Sclerenchyma</h2><h2 /><h2>AND </h2><h2 /><h2>Collenchyma</h2>
Explanation:
<h3>The tissue which provides support and mechanical strength to a plant or a growing organ in a plant is known as a mechanical tissue. </h3><h3>Both the ground tissues- collenchyma (living) and sclerenchyma (dead) provide maximum mechanical strength to a plant.</h3><h3>Collenchyma mainly provides mechanical strength to the growing plant parts.</h3><h3>The cell wall of collenchyma is made up of- pectin, hemicellulose, protein and cellulose. </h3><h3>These thickening materials get deposited at the corners or at the tangential walls of collenchyma cells.</h3><h3>It is a living cell which retains protoplasm even at maturity.</h3><h3>Due to the presence of hydrated pectin in the walls of collenchyma cells, they also provide elasticity to the cell.</h3><h3>Sclerenchyma is the tissue which makes the plant hard and stiff. Sclerenchyma is the supporting tissue in plants.</h3><h3>So, the correct answer is 'Sclerenchyma and Collenchyma'.</h3>
Answer :Erwin Chargaff a Biochemist
Explanation:
He formulated the base paring of double helix of DNA. He reasoned that since the percentage of four DNA bases are of this proportions in human;
Adenine=30.9% and Thymine =29.4%;
Guanine=19.9% and Cytosine =19.8%
Then, the amount of adenine will always be equal to thymine,
And the amount of Guanine equals to cytosine based on this percentages of distribution.
(Adenine and Guanine are large, molecule of Purines, while thymine and Cytosine are Pyrimidine)
He concluded (although scientist believed, he did not explicitly stated this) that this should be the base paring patterns in DNA molecule. This is the first Chargaff Rule.
His second rule is that the DNA composition, in the relative amount of the four bases Adenine, Thymine, Cytosine and Guanine varies in proportion from one organisms to another. And this is the basis of molecular diversity.
