Tutor profile: Hadeel A.
What is the difference between saturated and unsaturated fats?
When looking at the structure of saturated fats, you can see all carbon atoms are " saturated" or covered in hydrogen bonds. this makes it easy for the molecules to stack on top of one another, and so these saturated fats will be solid at room temperature. Unsaturated fats, or fats not covered in hydrogen bonds will have at least one double bond formed between carbons. This double bond will give the molecule a bent structure, making it harder for the molecules to stack on top of one another. This is the case with olive oil, which is liquid at room temperature. Unsaturated fats are seen as healthier because they will not solidify in the body and clog arteries.
What is the difference between Ionic and Covalent bonds? What about polar and non-polar covalent bonds?
IONIC BONDS involve the TRANSFER of electrons between a metal and nonmetal. The nonmetal has a high electronegativity, or a higher tendency to attract electrons, and thus will take the electrons that the metal is willing to donate. Electronegativity increases upward and to the right, thus metals tend to have lower electronegativity than nonmetals. COVALENT BONDS involve the SHARING of electrons between two nonmetals. Because the two nonmetals will have similar electronegativity, they will share the electrons. If the electronegativity difference is large, one atom will pull on the electrons more than the other, and this will result in polarity or a polar covalent bond. If the pull is equal, this will result in a non-polar covalent bond.
What is a gram stain? What is the difference between a gram positive bacteria and a gram negative bacteria?
GRAM STAINING, or the process of staining the cell wall of bacterial cells, is a method of determining whether a cell is Gram positive or Gram negative. GRAM POSITIVE bacteria will have a thick peptidoglycan layer within their cell wall, while GRAM NEGATIVE have a thin peptidoglycan layer. If a cell has a thick peptidoglycan layer, it will retain the initial purple stain. If the cell has a thin peptidoglycan layer, the purple dye will not hold, and will wash off in the following step in which the cells are rinsed with water. In order to then visualize the unstained gram negative cells, a pink counterstain is used. It is important to counterstain, or the now rinsed gram negative bacteria would not be visible.
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