But it was not until 1928 that penicillin, the first true antibiotic, was discovered by Alexander Fleming, Professor of Bacteriology at St. Mary's Hospital in London.
Of its valence electrons or the no. Of valences in its Valence shell .In case of noble gases, their outermost shell is absolutely crammed so no emptiness is available in the outer maximum shell. Thus the oxidation kingdom is 0(zero)for Noble gases. Because, they've complete electrons in their out maximum shell.
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Answer: During mitosis a eukaryotic cell undergoes a carefully coordinated nuclear division that results in the formation of two genetically identical daughter cells.
Explanation:
The correct answer is A. Lac repressor.
Lac repressor prevents lac gene which are found in the DNA of Escherichia Coli from being expressed for many times.
Lac repressor is termed as DNA which binds proteins. It allows the expression of genes from coding which are made for proteins to be involved in metabolism of lactose which is in bacteria.
When there is no lactose which is available in the cell, then the genes are being repressed. Lactose are being converted to allolactose if they are available.
14. Surface Area , and Volume Area limits the size of cells.
15 .A cell is a metabolic compartment where a multitude of chemical reactions occur. The number of reactions increase as the volume of metabolic volume within a cell increases. (The larger the volume the larger the number of reactions)
All raw materials necessary for metabolism can enter the cell only through its cell membrane.
The greater the surface area the larger the amount of raw materials that can enter at only one time.
Each unit of volume requires a specific amount of surface area to supply its metabolism with raw materials. The amount of surface area available to each unit of volume varies with the size of a cell.
As a cell grows its SA/V decreases.
At some point in its growth its SA/V becomes so small that its surface area is too small to supply its raw materials to its volume. At this point the cell cannot get larger.
16. Cells only divide when they receive specific signals from proteins called mitogens,the presence of mitogens can limit cell division. Mitogens are needed for cell division in healthy cells and are released depending on what cells the body needs.
