Communicable diseases, biodiversity and evolution past paper qs

Question 1

Plasmodium is described as a parasite.
Define the term parasite

Answer 1

lives , in / on , host ;
gains nutrition / feeds , from (host) ;
at the expense of / harms (host) ;

Question 2

Explain why the human body’s primary defences do not prevent the entry of Plasmodium
into the body

Answer 2

mosquito / vector / Anopheles , feeds on blood ;
breaks skin / skin cannot act as barrier / mosquito pierces
skin / mosquito bites skin

Question 3

Suggest two reasons why governments in parts of the world other than tropical areas,
are also becoming increasingly concerned about malaria

Answer 3

-resistance of , parasite to drugs / mosquito to
insecticides ;
-idea of increased movement of (infected) people

Question 4

neutralisation

Answer 4

cover / block , binding site / antigen / receptor site (on
pathogen) ;
bind to toxins ;
prevent , binding / entry , to (host) cell ;

Question 5

agglutination

Answer 5

clump / bind together , (many) pathogens ;
(clump) too large to , enter (host) cell / cross
membranes ;
increase likelihood of being consumed by (named)
phagocyte / more can be consumed by phagocyte at
once

Question 6

Why are phagocytes described as a secondary defence against pathogens?

Answer 6

(involved) after , pathogen / AW , has entered the
body ;

Question 7

Why is the response involving phagocytes regarded as non-specific?

Answer 7

(phagocytes) able to, digest / break down / engulf /
target / deal with, a range of / many
different , pathogens

Question 8

Explain how phagocytes, are able to pass from the
blood into the tissue fluid

Answer 8

lobed / narrow , nucleus ;
(cells) can change shape ;
can squeeze / move / fit / AW , between cells
/ through pores , in (walls of) capillaries ;
histamine makes , capillary walls /
endothelium , leaky

Question 9

Describe the process by which a pathogen is destroyed after it has become attached to
the surface of a phagocyte (7)

Answer 9

-pathogen engulfed by cytoplasm of phagocyte=phagocytosis
-initiates formation og phagosomes and phagolysosomes which fuse w pathogen
-enzymes in lysosome eg protease digest pathogen + is broken down into amino acids + sugar
-absorbed by cytoplasm/ removed by exocytosis

Question 10

Name the infective agent that causes TB + how is it spread

Answer 10

Mycobacterium /M. tuberculosis / M. bovis
droplets (containing pathogen) ;
(released by) coughing / sneezing ;
inhaled by (uninfected) , individual

Question 11

State two features of the malarial parasite that indicate that it is not a prokaryote

Answer 11

-membrane bound organelles
-nucleus
-linear chromosomes ;
DNA, associated with / AW, histones / protein ;
80S / 22nm / large, ribosomes ;
large cells / AW ;
no cell wall

Question 12

Describe how the mosquito transmits the malarial parasite to a human

Answer 12

-plasmodium in the saliva of mosquito
-pierces barrier (skin), which transmits pathogen from saliva to blood
-mosquito is a vector