What types of infectious agents are there?

Bacteria (prokaryotes) 1-5 micrometers, contain RNA and DNA, can synthesise and metabolise protein, generally free livingMajority are harmless, but a certain small list can cause infectious diseasesOne of diseases with highest disease burden (impact of a disease as measured by e.g. financial cost, mortality, morbidity) is TB (Mycobacterium tuberculosis)Other diseases: bacterial pneumonia, food poisoning, tetanus, typhoid fever, diphtheria, syphilis, leprosy, chlamydia (intracellular) Virus 20-300 nanometers, contain proteins and either RNA or DNA, obligate parasites (cannot reproduce autonomously)Much more likely to be pathogenicSmallpox, influenza, mumps, measles, chickenpox, ebola and rubella Fungi Eukaryotic microbes that normally consume dead organisms (saprophytes); can cause diseases in animals, but mostly affect plants; spore size 1-40 micrometresAspergillosis and candidiasis Parasites Either protozoa (unicellular eukaryotes with a flexible cell membrane) or parasitic worms (helminths, multicellular eukaryotes)Key one is malaria, causes 900,000 deaths/annum, caused by Plasmodium spp.Other diseases include Leishmaniasis, trypanosomiasis, schistosomiasis, Chagas disease Prions Simplest infectious agents, single protein molecule that can catalyse a conformational change in an endogenous protein (PrP) ad infinitumDisease is produced by structural and functional changes that resultScrapie, BSE (mad cow disease) and Creutzfeldt-Jakob disease

AT
Answered by Adam T. Biology tutor

2594 Views

See similar Biology A Level tutors

Related Biology A Level answers

All answers ▸

What might happen to the rate of glucose production as the temperature of a solution of sucrose and (human) sucrase was raised from 33°C to 43°C and why?


What are the different types of epistasis?


What are the stages of cell division?


Explain the process of ultrafiltration in the kidney.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning