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 salmonella
they can be triggered by the use of antibiotics to kill the salmonella

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.

Question 5

Anti-malarial drugs can be used to protect people from malaria.
These drugs are not always effective because Plasmodium develop resistance.
Explain how drug-resi

Answer 5

{random / chance} mutations (1)
 produce {proteins / enzymes} that make the drug
ineffective (1)
 therefore resistant organisms pass on allele (1)
 drug is the selection pressure