5b: Parasitic Life Cycles

Question 1

how does plasmodium cause malaria

Answer 1

 An infected mosquito, acting as a vector, bites a human.
 Plasmodium enters the human bloodstream.
 Asexual reproduction occurs in the liver and then in the red blood cells.
 When the red blood cells burst gametocytes are released into the
bloodstream.
 Another mosquito bites an infected human and the gametocytes enter the
mosquito, maturing into male and female gametes, allowing sexual
reproduction to now occur.
 The mosquito can then infect another human host.

Question 2

How do schistosomes cause schistosomiasis

Answer 2

 Schistosomes reproduce sexually in the human intestine.
 The fertilised eggs pass out via faeces into water where they develop into
larvae.
 The larvae then infect water snails, where asexual reproduction occurs.
 This produces another type of motile larvae, which escape the snail and
penetrate the skin of a human, entering the bloodstream.

Question 3

Viruses are parasites that can only replicate…

Answer 3

inside a host cell

Question 4

Viruses contain genetic material in the form of DNA or RNA, packaged in _______

Answer 4

a protective protein coat

Question 5

Some viruses are surrounded by ___________ derived from host cell materials

Answer 5

a phospholipid membrane

Question 6

The outer surface of a virus contains …

Answer 6

antigens that a host cell may or may not be able to detect as foreign

Question 7

Viral life cycle stages

Answer 7

• infection of host cell with genetic material,
• host cell enzymes replicate viral genome,
• transcription of viral genes and translation of viral proteins,
• assembly and release of new viral particles

Question 8

RNA retroviruses use the enzyme _________ to form DNA, which is then inserted into the genome of the host cell

Answer 8

reverse transcriptase

Question 9

Viral genes can then be expressed to…

Answer 9

form new viral particles