1 In a conventional light microscope which of the following

1. In a conventional light microscope, which of the following paths does light take after leaving the light source and before reaching the observer’s eye?

A. condenser lens -> specimen-> objective lens -> ocular lens

B. specimen -> condenser lens -> objective lens -> ocular lens

C. condenser lens -> specimen-> ocular lens -> objective lens

D. condenser lens -> objective lens -> specimen -> ocular lens

E. objective lens -> condenser lens -> specimen -> ocular lens

2. Siderophores are iron-binding agents that transport iron into cells. Although there are structural differences among different siderophores they generally all share the property of: A. binding extracellular ferrous iron (in its +2 oxidation state) and releasing it in the cytoplasm of the cell as ferric iron (in its +3 oxidation state).

B. binding extracellular ferric iron (in its +2 oxidation state) and releasing it in the cytoplasm of the cell as ferrous iron (in its +3 oxidation state).

C. binding extracellular ferric iron (in its +3 oxidation state) and releasing it in the cytoplasm of the cell as ferrous iron (in its +2 oxidation state).

D. binding extracellular ferrous iron (in its +3 oxidation state) and releasing it in the cytoplasm of the cell as ferric iron (in its +2 oxidation state)

3.  In bacterial chemotaxis, which feature of the bacterial flagella determines whether the bacterium is in a run or tumble?

A. the shape of the flagella.

B. whether the flagella rotate of move in a whip-like fashion.

C. the speed of rotation of the flagella.

D. the direction of rotation of the flagella.

E. all of the above.

Solution

Answer :

Question number 1 : The correct answer is A (condenser lens -> specimen-> objective lens -> ocular lens)

Supplementary information : Objective and ocular lenses are two series of lenses which functions together to resolve the image. Ocular lens magnifies the image formed by the objective lens. The magnification of ocular lens is 10X.

And the total magnification of a microscope can be calculated by using the formula

Total magnification = Objective magnification X ocular magnification