6.3 Defense againstinfectious diseases

Courtesy to i-Biology

Bacteria• Prokaryotes (no real nucleus)• Divide by binary fission

Can cause:• Food poisoning (e.g. Salmonella)• Ear and eye infections• Cholera, diarrhea http://en.wikipedia.org/wiki/File:Ericson_Type

_II_Conjunctivitis.JPG

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The 1918 flu epidemic killed between 50 and 130 millionpeople. http://en.wikipedia.org/wiki/1918_flu_pandemic

Viruses• Acellular (non-living?)• Need a ‘host’ cell to carry out functions of life, including reproduction• Can have DNA or RNA• Mutate, evolve and recombine quickly

Cause:• Flu, HIV/AIDS, smallpox, measles, common cold, herpes, ebola

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Fungi• Eukaryotes, reproduce with spores

Cause: • Athlete’s foot, mould, ringworm• Allergic reactions and respiratory

problemsImage from: http://en.wikipedia.org/wiki/Athlete's_foot

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Antibiotics• Antibiotics take are advantage of the difference

between prokaryotic and eukaryotic cells• Antibiotics designed to disrupt structures or

metabolic pathways

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What happens when pathogens get in?

• Phagocytic leucocyte – Phagosytosis = eating cell– Leucocyte = white blood cell

1. Chemotaxis (movement in response to chemicals) attracts the phagocytes to the area of invasion as response to: proteins produced by the pathogen, phospholipids released by damaged cells

2. The phagocyte attaches to the pathogen’s cell surface proteins and engulfs it.

3. A phagosome (vesicle that contains pathogen) forms. Lysosomes deposit the enzymes into the phagosome.

4. The digestive enzymes break down the pathogen and the waste products are expelled from the cell by exocytosis.

Antibody production

• Antibody = protein we produce in response to a specific type of pathogen

• Antigen = cell marker (protein)

Immune attack! 1. A specific antigen is identified

(e.g. a particular cold virus)

2. A specific B lymphocyte is identified that can produce an antibody that will bind to the antigen

3. Clonal Selection: B lymphocyte clones themselves and begins massive antibody production.

4. Some of the cloned lymphocytes remain in the bloodstream. Memory cells.

HIV/AIDS

TODAY1. In your blog: Describe the process of an immune attack

Immune attack! 1. A specific antigen is identified

(e.g. a particular cold virus)

2. A specific B lymphocyte is identified that can produce an antibody that will bind to the antigen

3. Clonal Selection: B lymphocyte clones themselves and begins massive antibody production.

4. Some of the cloned lymphocytes remain in the bloodstream. Memory cells.

HIV/AIDS• HIV (Human

Immunodeficiency Virus) AIDS (Acquired Immune Deficiency Syndrome)

• Transmission of HIV– Bodily fluids during sex– Reusing unsterile syringe

needles for legal/illegal drug infections

– Blood transfusions

HIV/AIDS• HIV recognizes certain

proteins in cell membrane of helper T cells

• Helper T cells: cells that communicate which cells need to undergo cloning process and begin antibody production weakened immune system

HIV/AIDS• Viral load: measure of how much virus is within a host• HIV has a latency period, so AIDS can develop years after

HIV develops

• HIV 2001 http://www.biology.arizona.edu/immunology/activities/aids2001/main.html

The Immune System @ Nobel Prize

• Readings: ‘Overview’ & ‘In more detail’

• Play the immune responses game: http://www.nobelprize.org/educational/medicine/immuneresponses/