17- Which of the following is FALSE about bacteria? A. they lack a defined nucle

Question

17- Which of the following is FALSE about bacteria? A. they lack a defined nucleus surrounded by nuclear membrane B. they lack cellular organelles such as mitochondria and chloroplast C. their ribosomes are structurally different than higher cells D. they divide by mitosis E. all the sentences above are true 18-To destroy endospores by heating, they must be exposed for 15-20 minutes to steam under 15 PSI (pounds per square inch) of pressure, which generates a final temperature of 121°C. Such conditions are produced by a. a speed vacuum b. a microwave c. an oven d. an autoclave 19-In negative staining what external bacterial structure can be demonstrated A. Capsule B. Nucleoid C. Flagella D. None of these 20-In sporulation the water content of the endospore is A. Reduce by 1-5% B. Increase by 1-5% C. Increase by 10-30% D. Reduce by 10-30% 21-A microscope has a 10x ocular lens and a 10x objective, what is this microscope's total magnification? ?. 10x B. 100x C. 1x D. 1000x

Explanation / Answer

17) ANSWER IS: D. they divide by mitosis

EXPLANATION:

Bacteria reproduce by binary fission. In binary fission, bacterium which is a single cell will divides into two identical daughter cells.

The cells of bacteria are different from those of plants and animals in many ways such as:
- bacteria lack a nucleus and other membrane-bound organelles such as mitochondria, chloroplast (except ribosomes). Their ribosomes are structurally different than higher cells


18) ANSWER IS: d. an autoclave

EXPLANATION:

To destroy endospores or sterilisation in an autoclave is good when the organisms are either contacted by the steam directly or are contained in a aqueous liquid such as water. Under these conditions, steam at a pressure about 15 psi; attain temperature of 121oC that will kill all organisms and their endospores in about 15 mins.


19) ANSWER IS: A. Capsule

EXPLANATION:

Negative Stains will be useful in studying the morphology of bacterial cells and characterizing some external structures such as capsules, and cell dimensions


20) ANSWER IS: D. Reduce by 10-30%

EXPLANATION:

Water content of endospores can be explained as when the water content is high, then heat resistant the endospore will be less. And water content reduce by 10-30% of the vegetative cell during sporulation


21) ANSWER IS: B. 100x

EXPLANATION:

Microscope's total magnification = Objective magnification X ocular magnification

As in question, 10X objective and 10X ocular, the total magnification = 10 X 10 = 100X , which means the image viewed will appear to be 100 times its actual size.

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