2.5 b) + c) Parasitic Life Cycles + Transmission and Virulence Flashcards
Some parasites only require ___ host to complete their ___ ___.
one, life cycle
Many parasites require more than one ___ to complete their ___ ___.
host, life cycle
What is meant by the term…
Intermediate host?
Definitive host?
an intermediate host is a host which helps some parasites complete their life cycles
A definitive host is a host in or on which a parasite reaches sexual maturity
A vector plays an ___ role in the ___ of a parasite, and may also be a ___.
active, transmission, host
The two parasite life cycles to study are:
___, which cause malaria, and
___, which cause schistosomiasis.
plasmodium (plural - plasmodia)
schistosome(s)
The life cycle of a plasmodium has 6 steps. Give a brief summary of each:
1.
2.
3.
4.
5.
6.
- an infected mosquito bites a human
- the plasmodia enter the blood
- the plasmodia reproduce asexually in red blood cells and liver
- the red blood cells burst, releasing gametocytes
- another mosquito bites the human, the gametocytes enter the mosquito, mature into gametes, and then sexual reproduction occurs
- the mosquito can then infect another human
Schistosomes cause ____.
Plasmodia cause ___.
schistosomiasis.
malaria
What are the 4 steps to the life cycle of schistosomes?
1.
2.
3.
4.
- Schistosomes reproduce sexually in the human intestine
- the fertilised eggs pass out via faeces, into water, where they develop into larvae
- the larvae infect water snails, where asexual reproduction occurs, producing another type of motile larvae
- these larvae escape the snail and penetrate the skin of a human, entering the bloodstream and starting the process again.
What are viruses?
viruses are parasites that can only replicate inside a host cell
Viruses are ___ that can only replicate inside a ___ cell
parasites,host
Viruses contain ___ ___ (in the form of __ or __), packaged inside a ___ coat.
genetic material, (RNA, DNA), protein
Some viruses are surrounded by a ___ ___, derived from ___ ___ materials.
phospholipid membrane, host cell
The outer surface of a virus contains ___ that a host cell ___ or ___ ___ be able to detect as ___.
antigens, may or may not, foreign
What are the 4 steps to the viral life cycle?
- 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.
What do RNA retroviruses do? (2)
they use reverse transcriptase to form double stranded DNA from RNA, and then insert the DNA into the genome of the host cell.
The host cell then expresses the viral genes to form new viral particles