C3.2 Defense Against Diseases Flashcards
1
Q
What are pathogens?
A
Disease-causing organisms, and can be directly or indirectly passed from one infected organism to another (eg. virus, bacteria, fungi, prokaryotes, and protozoa)
2
Q
What are the causes of a disease?
A
- Genetics
- Environmental
- Infection with a pathogen
3
Q
What are the features of bacteria?
A
- Prokaryotes lacking a real nucleus and instead have a nucleoid
- Divide by binary fission (asexual reproduction)
- Cell walls composed of peptidoglycan
- Can exist as infectious or non-infectious
4
Q
What are the features of viruses?
A
- Not an organism because they lack a nucleus but have DNA or RNA
- Needs to attach to a host cell to reproduce
- Cannot be killed by antibiotics
5
Q
What are features of fungi?
A
- Eukaryotes with a nucleus and have chitin cell walls
- Reproduce by producing spores
- Causes athletes’ foot, skin rashes, vaginal candidiasis allergic reactions (mold spores), ringworm
6
Q
What are features of protozoan parasites?
A
- Unicellular eukaryotes, making treatment difficult
- Often parasitic or symbiotic organisms
- Can cause malaria, leishmaniosis, giardia, trypanosoma, sleeping sickness, lyme’s disease
7
Q
What are features of Helminthic parasites?
A
- Multicellular and eukaryotic
- Parasitic diseases
- Can cause Elephantiasis, Schistosomiasis, Toxocariasis, Pinworm, Roundworm or tapeworm infections
8
Q
Characteristics of innate immune system
A
- Responds to broad categories of pathogens
- Timeline: 0 - 12 hours
1st line of defence:
- skin and secretions
- mucous membrane with cilia in respiratory tract (produced by goblet cells)
- saliva, stomach acid
2nd line of defense:
- phagocytes
9
Q
Characteristics of adaptive immunity
A
- Responds in a specific way to particular pathogens. This system builds up a memory of pathogens it has encountered, offering more effective protection against common infectious diseases.
– Timeline: 1 - 7 days
– 3rd line of defense:
- T-Lymphocytes
- B-Lymphocytes
- Antibodies
- Memory B-Lymphocytes
10
Q
What is an example of first line of defense (skin)?
A
- The outermost layer is a tough layer of dead cells containing large amounts of keratin, acting as a physical barrier to the entry of pathogens
- Natural microorganism on the skin live in competition for nutrients with harmful pathogens.
- Sebaceous glands associated with hair follicles
secrete sebum, which maintains skin moisture and lowers pH. A low pH inhibits growth of bacteria and fungi.
11
Q
What is an example of first line of defense (mucous membrane)?
A
- A thinner and softer type of skin. Can be found in areas such as the vagina, the foreskin & head of penis, and airways leading to the lungs
- The skin in these areas secrete mucus, a sticky solution of glycoproteins
- traps pathogens or harmful particles which will then be swallowed or expelled
- contains anti-bacterial enzymes called lysozymes which destroy pathogens.
12
Q
Outline the process of blood clotting
A
- When there is a cut in the skin, platelets aggregate at the site to form a temporary plug and release clotting factors to control bleeding.
- The enzyme thrombin is produced which converts soluble fibrinogen dissolved in blood plasma into insoluble fibrin
- This forms a mesh of fibres over the damaged area to help trap blood cells.
- Platelets aggregate at the area of damage to form a temporary plug and form a solid clot.
13
Q
What is the second line of defense (phagocytes)?
A
- A type of white blood cell that squeezes out through pores in the walls of capillaries and moves to sites of infection, engulfing pathogens through endocytosis and digests them using lysosome enzymes.
- Dendritic cells and macrophages activate an inflammatory response, secreting proteins called cytokines that trigger an influx of defensive cells from the blood.– Macrophages are a type of phagocyte that ingests pathogens and displays antigens from it on its surface to other cells
- All phagocytes are non-specific, responding to all pathogens
14
Q
What is the third line of defense (lymphocytes)?
A
- Circulates in the blood and is contained in lymph nodes
- Produces antibodies which are large proteins that help destroy pathogens by binding to an complementary antigen
- makes pathogen more recognizable to phagocytes for easy engulfing
- prevents viruses from docking to host cells, so they cannot enter the cells
- Each lymphocyte produces only one type of antibody, hence when a pathogen infects the body for the first time, the lymphocytes that can produce the appropriate antibodies work together to produce antibodies in large quantities to control the pathogen and clear the infection.
15
Q
Explain the production of antibodies
A
- When macrophages ingests pathogens, antigens of the pathogen are displayed on the plasma membrane of the macrophage.
- Helper T-lymphocyte cells specific to the antigen of the macrophage will bind to its antigen, becoming activated.
- B-lymphocyte cells specific to the antigen is activated by the helper T-lymphocyte cells upon binding to it.
- The B-lymphocyte cells divide repeatedly, grow in size and develop an extensive endoplasmic reticulum with many ribosomes attached to it, along with a large Golgi apparatus. This allows a rapid production of antibody-secreting plasma cells.
- Antibodies produced by the clone of plasma cells are specific to antigens on the pathogen and help to destroy it
