Module 4 - Immunity Flashcards
Define the term ‘pathogen’ and give one example of each of the four main types of pathogen ?
(4 marks)
A pathogen is a microorganism that causes disease.
- Bacteria causes tuberculosis
- Virus causes HIV and influenza
- Protists causes malaria
- Fungus causes athlete’s foot
Give examples of diseases caused by pathogens in plants?
- Bacteria causes ring rot
- Virus causes TMV
- Protists causes late blight
- Fungus causes black sigatoka
Describe how pathogens can cause disease in their hosts in humans?
(4 marks)
Pathogens cause diseases by infecting the host cells or tissues by breaking down the cell membranes and releasing toxins. Pathogens can enter the body by skin, respiratory system and digestive system. Once pathogens are inside the body, they reproduce rapidly (binary fission for bacteria, virus replicating and bursting the cell), causing damages to the host cells. The immune system’s response to the infection is inflammation that can lead to symptoms like fever and tissue damage, which can contribute to the disease.
Suggest how climate change could affect the spread of communicable diseases in plants and animals?
(4 marks)
- In plants, higher temp and increased humidity can increase the growth and production of plant pathogens like bacteria and fungi. Climate change can make plants stress, making them more susceptible to disease by reducing the ability to defend themselves.
- In animals, warmer temp can allow disease carrying vectors like mosquitoes and extreme weather events like flooding can disrupt the ecosystem and increase in contact between animals and disease carrying vectors.
Explain how protoctists cause disease and give an example?
(3 marks)
Protists cause diseases by entering into the host cell, producing toxins and disrupting the cellular functions. They can be transmitted through vectors. An example is Plasmodium which causes malaria and is transmitted by mosquitoes.
Name two animal diseases caused by bacteria and describe how they are transmitted?
(4 marks)
- Tuberculosis is transmitted by airborne droplets by infected animals.
- Brucellosis is transmitted by infected animals by direct contact with them or their products like milk or meat.
Describe how fungi cause disease in plants and give one named example?
(3 marks)
Fungi infect plant tissues by digesting the cells externally using enzymes, causing the plants to decay. They often produce spores that can spread easily. An example is black sigatoka in bananas.
Describe one structural feature of a virus and explain how this allows it to be pathogenic?
(2 marks)
Viruses have a protein coat called capsid, that protects them their genetic information and helps them to bind to host cells, allowing them to inject their DNA or RNA
State one similarity and one difference between bacterial and fungal pathogens?
(2 marks)
- Similarity: Both can reproduce and spread through spores.
- Difference: Bacteria are prokaryotic, while fungi are eukaryotic.
Describe how bacteria cause disease in the human body?
(4 marks)
Bacteria can cause disease in the human body in two mechanisms: either by directly damaging the cells or producing toxins. Bacteria can directly damage cells by invading and multiplying, disrupting the normal cellular function, or potentially evening killing. Bacteria can break down tissue barriers using enzymes, allowing them to spread within the host. Bacteria can produce toxins like exotoxins, which can damage the host cell, when bacteria break down cell membranes or disrupt protein synthesis. Endotoxins is released by Gram-negative bacteria and can cause inflammation.
Compare and contrast the roles of endotoxins and exotoxins in bacterial diseases?
(4 marks)
- Exotoxins can proteins, secreted by bacteria causing direct tissue damage or cellular function by interfering with protein synthesis or nerve function. They can have specific targets (eg. cells or tissues), triggering inflammatory response.
- Endotoxins are part of the outer membrane of Gram-negative bacteria and are released when bacteria die or divide. They trigger inflammatory responses that can lead to fever, septic shock or even organ damage.
Discuss the differences between bacterial and viral pathogens in terms of their structure and replication?
(6 marks)
- Bacterial structure: Bacteria are prokaryotic cells with a cell wall, cell membrane, cytoplasm, and circular DNA. Some have additional structures like capsules and flagella.
- Viral structure: Viruses are acellular and consist of a protein coat (capsid) that protects their genetic material (DNA or RNA). They lack a cell membrane and organelles.
- Replication in bacteria: Bacteria reproduce through binary fission, where the cell divides into two identical daughter cells.
- Replication in viruses: Viruses replicate by hijacking host cell machinery. The viral genetic material is injected into a host cell, and the host cell is forced to replicate the viral genome and assemble new virus particles.
