Organisms and evolution - 5 Flashcards
what is a microbe?
parasite with only one host species and are transmitted by direct contact
what are the three main components of a virus?
nucleic acid, protein coat, antigen
what are antigens?
proteins coded for by viral genes
what are the 5 stages of virus replication?
- attachment
- penetration
- synthesis of new components
- assembly
- release
(APSAR)
what happens once the virus DNA has been replicated?
virus genes are transcribed to RNA which is translated to make viral protein coats
what is an RNA retrovirus?
use enzyme reverse transcriptase to form DNA copy of virus genome
what are the body’s first-line defences?
physical barriers and chemical secretions
what occurs in an inflammatory response?
- histamine released from infected cells
- blood vessels dilate to increase blood flow
- permeability of blood vessels increases
- swelling stimulates phagocytes
what are non-specific defences?
- first line defences
- second line defences, eg inflammation, phagocytes, natural killer cells
what are phagocytes?
white blood cells that engulf and digest foreign objects
what are natural killer cells?
detect abnormal cell-surface proteins and cause apoptosis
what are the third line of defence?
specific cellular response
what is the specific cellular response triggered by?
triggered by antigens on surface of parasite
what is they type of white blood cell involved in specific cellular defences?
lymphocytes
what do each lymphocyte present on the surface of cell?
one type of antigen-receptor protein
what do lymphocytes carry out?
carry out immune surveillance, checking for specific antigens
what are lymphocytes part of?
part of a clone
when are B lymphocytes selected?
selected when antigen-receptor protein binds to specific antigen
what is activated if phagocytes present the correct antigen fragments?
T lymphocytes
what is the role of helper T lymphocytes?
target immune response cells and stimulate to rapidly divide
what produces the antibodies which bind to antigens on parasite?
B lymphocytes
what does a B lymphocyte do to a parasite?
neutralises parasite to make it easier for phagocytes to engulf
what do cytotoxic T lymphocytes do?
destroy infected cells by inducing apoptosis
why is immunological memory important?
quicker and larger response if specific antigen is detected again. Ensures long-term survival of larger population
what is epidemiology?
study of the outbreak and spread of infectious disease
what is herd immunity?
results if high proportion of population are immune to disease
what is the herd immunity threshold?
the density of resistant hosts required in a population to prevent an epidemic
what does the herd immunity threshold depend on?
- the disease
- effectiveness of vaccine
- contact parameters for the population
what are some difficulties of developing a vaccine?
- some parasites hard to culture in lab
- parasite may use rapid antigen change
if there are similarities between host and parasite metabolism, what difficulties can this cause?
if drug kills parasite it could have other negative effects on host
what can be done to help control parasites?
- civil engineering projects to improve sanitation
- coordinated vector controlled strategy, eg mosquito nets
in what type of places is is difficult to control parasites?
overcrowded and tropical climates
what are three benefits of controlling parasites?
- reduce child mortality
- general health improves
- improvements in child development and intelligence
