Question

1. what is the primary purpose of gram staining?

a) to observe cell motility
b) to determine the chemical composition of bacterial dna
c) to differentiate between gram - positive and gram - negative bacteria
d) to identify bacterial spores

1. which of the following is the correct order of reagents used in gram staining?

a) safranin → crystal violet → alcohol → iodine
b) crystal violet → iodine → alcohol → safranin
c) alcohol → iodine → crystal violet → safranin
d) iodine → alcohol → safranin → crystal violet

1. when preparing a bacterial smear, overheating during heat - fixing can:

a) destroy the bacterial cell wall and morphology
b) make the smear too thick
c) enhance staining effectiveness
d) prevent the smear from adhering to the slide

1. what is the primary purpose of aseptic technique?

a) to create a sterile environment in the lab
b) to avoid contamination of samples and the lab environment
c) to sterilize laboratory equipment
d) to ensure bacteria grow faster

Explanation:

Question 1

Gram staining is a technique in microbiology (part of Biology, a Natural Science subfield) used to classify bacteria into Gram - positive and Gram - negative based on cell wall differences. Option a is wrong as cell motility is observed via other methods like hanging drop. Option b is wrong as Gram staining doesn't analyze DNA composition. Option d is wrong as spore identification uses other staining methods. So the correct option is c.

The correct Gram staining reagent order is: first apply Crystal Violet (primary stain), then Iodine (mordant), followed by Alcohol (decolorizer), and finally Safranin (counter - stain). Option a has the wrong order. Option c has incorrect reagent order. Option d also has the wrong sequence. So the correct option is b.

During heat - fixing of a bacterial smear, overheating can damage the bacterial cell wall and alter the cell's morphology. Option b is wrong as smear thickness is related to the amount of bacteria applied, not overheating. Option c is wrong as overheating doesn't enhance staining. Option d is wrong as heat - fixing is to make the smear adhere, and overheating doesn't prevent adhesion. So the correct option is a.

Answer:

c) To differentiate between Gram - positive and Gram - negative bacteria

Question 2