Topic 6

Question 1

exotoxins

Answer 1

Exotoxins are released by gram negative and gram positive bacteria, they are released while the bacteria cell are living

Question 2

endotoxins

Answer 2

Endotoxins are released by gram negative bacteria they are found in the outer lipopolysaccharide cell wall and are released after the bacteria cell die.
eg samonella

Question 3

streak plating

Answer 3

Steps for Streak Plating
Sterilize the loop – Heat a metal inoculating loop in a Bunsen burner flame until red-hot, then let it cool.
Obtain the bacterial sample – Dip the loop into the bacterial culture (broth or colony).
Streak the first section – Lightly drag the loop across one quadrant of the agar plate in a zigzag pattern.
Flame the loop – Sterilize it again to prevent cross-contamination.
Streak the second section – Drag the loop from the first section into a new quadrant to spread and dilute the bacteria.
Repeat for two more sections – Sterilizing the loop between each streak to dilute the bacteria further.
Incubate the plate – Place it upside down in an incubator (usually at 25-37°C) for 24-48 hours.
Observe colonies – Distinct, isolated colonies should appear in the later streaks.

Question 4

how does phagocytosis occur?

Answer 4

The pathogen is engulfed into a phagosome.
The phagosome fuses with a lysosome, forming a phagolysosome, where enzymes break down the pathogen.