4.1 Communicable Diseases (up to secondary defence) Flashcards
What is a pathogen?
A microorganism that causes disease
What are hyphae and mycelium?
Hyphae are clusters of cells in a fungus that grow in a branch-like design; mycelium are large groups of hyphae
Where do bacteria live in plants?
Vascular tissue
Where does fungus most often live in plants?
Vascular tissue
What are the four types of pathogen that we need to know?
Bacteria, viruses, fungi and protoctista
What diseases are caused by bacteria?
TB, bacterial meningitis, ring rot (potatoes and tomatoes)
What diseases are causes by viruses?
HIV/AIDS, influenza (animals), tobacco mosaic virus (plants)
What diseases are caused by fungi?
Black sigatoka (bananas), athletes foot, ringworm (cattle)
What diseases are caused by protoctista?
Malaria, potato/tomato late blight
What is direct transmission?
Passing a pathogen from host to new host, with no intermediary.
What is indirect transmission?
passing a pathogen from a host to a new host via a vector
What is transmission?
Passing a pathogen from an infected to uninfected individual
What is a vector?
An organism that carries a pathogen from one host to another.
What social factors affect transmission?
- Overcrowding
- Poor ventilation
- Poor health
- Poor diet
- Homelessness
- Being around people who have migrated from an area where a disease is more common.
What diseases are transmitted through direct physical contact?
HIV, bacterial meningitis, ringworm, athletes foot
What diseases spread through faecal-oral transmission?
Cholera, food poisoning
Which diseases are spread through droplet infection?
TB, influenza
Which diseases are transmitted by spores?
anthrax, tetanus
Where does plasmodium go after an infected person is bitten?
Their liver, then blood.
How do pathogens infect plants?
- Enter roots through soil (especially if damaged)
- Spores in airbourne transmission
How do plant pathogens spread?
Enter leaves which fall off or go into fruit and seeds so that all new plants will also be infected.
How does indirect transmission occur in plants?
Result of insect attack, transmit to other plants.
What is callose?
a large polysaccharide deposit that blocks old phloem sieve tubes at the end of growing season when not in use
What physical defences do plants have?
- Cellulose cell wall
- Lignin thickening of cell walls
- Waxy cuticles
- Bark
- Stomatal closure
- Callose
- Tylose formation
What are plant’s active defences?
- Additional cellulose
- Callose (often blocks plasmodesmata)
- An increase in chemical production
- Oxidative bursts that produce highly reactive oxygen molecules capable of damaging pathogens
What chemicals do plants use?
Terpenoids, phenols, alkaloids, defensins, hydrolytic enzymes
What is necrosis?
Deliberate cell suicide
What is a canker?
A sunken necrotic lesion
What is inflammation?
swelling and redness of tissue causes by infection.
What is mucous membrane?
specialised epithelial tissue that is covered by mucus
What are primary defences?
Ones that prevent pathogens from entering the body
How is the skin a good primary defence?
Has cells called keratinocytes that migrate outwards out of the epidermis. As they migrate, they dry out and the cytoplasm is replaced by keratin
How is blood clotting an effective primary defence?
Relies on clotting factors which are realised from platelets and the damaged tissue. They activate an enzyme cascade.
How are mucous membrane an effective primary defense?
Goblet cells make mucus. Traps pathogens. Ciliated cells sweep up the trachea, the swallowed to digestive system. Acid in stomach kills.
What are other primary defences?
Coughing, sneezing, tear fluid,ear canal, mucus plug in cervix
Why is inflammation an active primary defences?
mast cells detect pathogens and release histamine. cause vasodilation, more permeable blood. excess tissue fluid is drained into lymphatic system.
Describe neutrophils
Multilobed nucleus
A lot of lysosomes
Dead neutophils=pun
Describe macrophages
Travel in blood as monocytes
Do not fully digest
Antigen moved to special protein complex
How do you look at blood through smears?
Stained Red blood cells pink Monocytes have kidney shaped nucleus Neutophils multilobed Lymphocytes nucleus almost fills as cell
Define antibodies
Specific proteins released by plasma membranes that can attach to pathogenic antigens
Define B memory cells
Cells that remain in the blood for a long time, providing long term immunity
Define clonal expansion
An increase in the number of cells by mitotic cell division
Define interleukins
Signalling molecules that are used to communicate between different white blood cells
Define plasma cells
Derived from B lymphocytes, manufacture antibodies
Define T helper cells
Cells that release signalling molecules to stimulate the immune response
Define T killer cells
Cells that attack and destroy our own body cells that are infected by a pathogen
Define T memory cells
Cells that remain in the blood for a long time, providing long term immunity
Define T regulator cells
Cells that are involved with inhibiting or ending the immune response
Different between T memory and B memory
T= cellular response B= antibody response
How do cells in the blood signal each other?
Cytokines
Examples of communication using cytokines
Macrophages release monokines which attract neutophils or cause B cells to differntiate
T cells and macrophages release interleukins
Interferon which inhibits virus replication
When do autoimmune disease arise?
Antibodies start to attack our own antigens
Examples of autoimmune diseases
Arthritis
Lupus
Vector for malarial parasite
Female Anopheles
Malarial parasite
Plasmodium
Name of cell in which malarial parasite reproduces
Hepatocyte/ liver cell
Erythrocytes
Things missed on B lymphocytes question
Humoral response - carries antigen on surface specific to antigen
Clonal selection - activation of appropriate B cell by antigen presenting cells
Clonal expansion - cell divided by mitosis
Biological reasons no effective vaccines against malaria
Different strains
Different antigens
Due to mutation
More than one stage in the life cycle
Different vaccine for each stage
Hidden in cells
Only exposed for a short time
Describe briefly the sequence of events that result in the destruction of a bacterium
Receptor site Formation of phagosome Lysosomes fuse with phagosome Bacteria broken down Absorbed into cytoplasm
How is an antibody related to its function?
Y shaped Constant region binds to phagocytes Variable region complementary to antigen More than one variable region Allows agglutination Hinge region Light and heavy four polypeptide Disulfide bridges
Ultra structure of neutrophil
Many lysosomes Exoskeleton Ribosomes Mitochondria Golgi Receptors on membrane
Factors that increase chance of TB
No vaccinated Poor diet Homelessness Poor ventilation Overcrowding People visiting where tb is common Contact with people with tb
Role of memory cells
Recognise pathogen
Produce clone
Form plasma and T cells
Responsible for secondary response
Organism that causes TB
Mycobacterium tuberculosis or
Mycobacterium bovis
Organism that causes malaria
Plasmodium falciparum
What does myco mean
Fungus
What does meningitis affect?
meninges (membranes which surround the brain and spinal cord) may become swollen
What does ring rot do?
decay vascular tissue
Life cycle of plasmodium
- plasmodium gametes taken up by female Anopheles mosquito
- develops and goes to salivary glands
- transferred to uninfected person
- goes to liver
- goes to blood and releases gametes
What mnemonic for plant passive defences?
LOST COW BACK
What does LST CW BC
Lignin thickening cell walls Stomatal closure Tylose formation Cell wall Waxy cuticle Bark Callose
What is tylose?
Balloon-like swelling that blocks xylem vessels
Where are terpenoids found and how do they work?
In tyloses
oils with antibacterial and antifungal properties
Where are tannins found?
Bark
What are tannins an example of?
Phenols
How do tannins work?
stop insect attacks
bind to enzymes in insect saliva and digestive system
deactivate them
can be lethal and limits transmittion
What passive defences are fortified in active defence?
Cell walls thickened
Callose (in phloem and blocks plasmodesmata and between cell wall and membrane)
Necrosis
Examples of alkaloids
caffeine
nicotine
morphine
cocaine
What do alkaloids do?
- give plant bitter taste
- some inhibit enzymes
- limits grazing
What are defensins?
Small cysteine rich proteins with antimicrobial properties
What do hydrolytic enzymes do in plants?
- found between cells
- break down bad things
4 steps of tissue repair
- collagen under where needs
- stem cells divide and migrate
- new blood vessels form
- scab released
What cells release histamine?
mast cells
What do histamines do?
- increase leakiness of cells
- white blood cells can enter infected tissue
- increase vasodilation
Describe the events of phagocytosis
- phagocyte recognise bad antigen
- phagocytes membrane = endocytosis = phagosome
- phagosome + lysosome = phagolysosome
- hydrolytic enzymes break down
- resulting products used by phagocyte to build other molecules
Three ways antigens can be presented
- macrophage
- infected cell
- pathogen in body fluid
What kickstarts the specific immune response and where?
antigen presenting cells
lymph nodes
What signalling molecule do macrophages use?
Monokines, which:
- attract neutrophils
- stimulate B cells to relase antibodies
What are interleukins and what do they do?
signalling molecules released by T cells and macrophages to stimulate clonal expansion and B and T cell differentiation
What does interferon do?
inhibits virus replication and stimulates T killer cells
Examples of autoimmune disease
- arthritis
- lupus
How are plasma cell specialised?
- numerous ribosomes
- a lot of RER
- a lot of golgi
- numerous mitochondria
Why is it good that antibodies have a hinge region?
so they are flexible for agglutination
Example of artificial passive immunity
injection of antibodies made by another individual (hepatitis A and B, tetanus)
Where are aspirin and iboprofen derived from?
The bark of a willow tree
Sources of medicines
- accidental discovery
- traditional remedies
- observing wildlife
Examples of how observation of wildlife can help us make medicine
- monkeys and bears rub citrus oil on their coats as insecticides and antiseptics
- birds line nests with medicinal leaves to prevent bites from mites
What are most antibiotics derived from?
bacteria from the genus Streptomyces
Examples of bacterial resistance to antibiotics
Clostridium difficile and MRSA
What methods of pathogen transmission apply to plants?
direct contact
vectors
