Protection against invaders Flashcards by luv hi

what is pathogen ?

Pathogen:
•	Disease-causing microorganism
•	Pathogens include:
	Bacteria
	Viruses
	Fungi
	Animal parasites

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what is vectors?

Vectors:
• Some diseases are contagious – passed on by direct contact with the people suffering from the disease or by contact with something touched by the person
• Some may spread via vectors
 Agents such as insects (eg. mosquitoes or fleas)
 Capable of transferring the pathogen from one person to another but are themselves, NOT affected by the disease

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Describe bacteria

All bacteria are classified as prokaryotes (Do not have a nucleus/ organelles with internal membranes)
Most bacteria are non-pathogenic (harmless) to human
Bacteria play vital roles in the environment – cycling of elements, decomposition of organic materials, etc

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Benefits of bacteria

Genetically modified bacteria are used to produce insulin to treat diabetes
Normal microbial flora
Population of microorganisms that inhabit the skin and mucous membranes in human
They are harmless to the host (human)

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What is peptidoglycan?

Most bacterial cell wall is made of peptidoglycan

Peptidoglycan is a network of carbohydrate cross-linked with polypeptides

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Difference of gram positive and gram negative bacteria

Gram-positive bacteria:
simpler walls with a relatively large amount of peptidoglycan
Gram-negative bacteria:
less peptidoglycan and have outer membrane that contains lipopolysaccharides

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Which gram bacteria is more dangerous ?

Gram-negative bacteria are more dangerous as disease organisms, because their outer membrane is often hidden by a capsule or slime layer which hides the antigens of the cell and so acts as “camouflage”. Harder to kill, quick to develop resistance.

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What is the function of capsule in bacteria?

The cell wall of some bacteria are covered with capsule or slime layer (if it is very thin and diffuse)
Capsule is made of complex carbohydrate
Role: for protection

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What is the function of flagellum in bacteria?

Present on the outer surface

Role: for movement

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Structure of virus ?

Extremely small
Non-cellular (Non-living)
Infectious agents

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Virus consist of ?

Nucleic acid 
May be DNA or RNA
Capsid
Made of repeating units of capsomere
Membrane envelope
For certain viruses
Contain viral proteins

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Can virus stay alive without host?

Viruses are obligate intracellular parasites

Can only reproduce inside host’s cell

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What does virus do ?

Some viruses cause diseases in human.
Diseases caused by virus range from serious (eg. AIDS) to annoying (eg. colds)
Viruses are used to insert new genes into other organisms in genetic engineering

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explain transmission by contact

By contact
•Direct contact involves touching an infected individual
•Indirect contact involves touching an object that has been touched by an infected person
e.g: Skin infections, STD

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explain transmission by body fluids

Transfer by body fluids

•Body fluids from an infected person comes into contact with the mucous membranes or the bloodstream of an uninfected person
HIV, Hepatitis B & C

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explain transmission by Airborne transmission

Airborne transmission
•When moisture in inhaled droplets evaporate leaving dried particles of viruses and some bacteria.
•These particles can then be inhaled and remain viable for greater distances compared to droplet transmission
Measles, chicken pox

explain transmission by Ingestion

Ingestion
•Consumption of contaminated water or food
Dysentery, Salmonella food poisoning

explain transmission by droplets

By droplets
•Tiny droplets of moisture containing pathogens emitted during talking, breathing and sneezing and are breathed in or ingested with food if particles settle on cutlery or food
•Covid-19
•Ebola 
•Influenza

explain transmission by vectors

By vectors
•Transfer of pathogens by other animals
•
•Some vectors transfer the pathogen directly; some spread the pathogen to food or water
•Malaria and dengue fever are spread by mosquitoes
•
•Trypanosomiasis (African sleeping sickness) is spread by the tsetse fly
•
•Lyme disease is spread by ticks
•
•Bubonic plague is spread by fleas from rats and mice

NON-SPECIFIC RESPONSE

Non-specific defenses – they do not target specific pathogens & are our first line of defense
Non-specific immunity can be divided into 3 types:
External defenses
Protective reflexes
Internal non-specific defenses

External defenses

Skin
Mucous membranes
Hairs
Cilia

Acids
Lysozyme in tears
Cerumen (earwax)
Flushing action

PROTECTIVE REFLEXES

Reflex is the body’s automatic response to certain stimuli
A reflex protects the body by providing a rapid, involuntary response without any conscious thought 
occurs similarly each time
e.g:
Sneezing
Coughing
Vomiting
Diarrhoea

explain inflammatory response

The response to tissue injury (infection, burns, irritating chemicals)
Involves redness, heat, swelling, & pain in the affected area
Roles:
prevent the damage from spreading
remove damaged tissue and cell debris
begin tissue-repair mechanisms

what is a phagocyte?

Phagocytes are cells that are able to engulf and digest microorganisms and cell debris
Several white blood cells (leucocytes) are capable of carrying phagocytosis

Phagocytosis process

Process:  Phagocyte migrate to site of infection and approaches and captures bacterium  Phagocyte engulf / extend pseudopodia to surround the bacterium  Bacteria becomes enclosed in vesicle, forming phagosome  Phagosome fuses with lysosome to form phagolysosome  Hydrolytic enzyme ( lysozyme and protease) in the lysosome digest the bacteria  Waste and debris are discarded by exocytosis

what is fever?

* Fever, or pyrexia, is an elevation in body temperature caused by a cytokine-induced upward displacement of the set point of the hypothalamic thermoregulatory center. * It also may result from physiological stresses, such as strenuous exercise or ovulation, or from heat exhaustion or heat stroke

how do fever occur ?

– Pyrogens are substances that cause fever. – There are two types: o Exogenous pyrogens are usually microbes or their products. o Exogenous pyrogens induces the release of endogenous pyrogens, such as interleukin-1 by leukocytes and macrophages

benefits of fever

1. Inhibit the growth of some bacteria and viruses 2. Increase the rate of reactions (metabolic rate) faster tissue repair 3. Increases heart rate/blood flow  Enables lymphocytes to reach sites of infection faster

inflammation response By Histamine:

* Histamine trigger vasodilation of arterioles which ↑ blood flow (causing heat & redness) * Histamine↑ permeability of capillaries, causing fluid to leak into tissue spaces (causing swelling) * abnormal conditions in the tissue creates sensation of (pain)

inflammation response By Heparin:

* type of anticoagulant. * prevents clotting in the immediate area of the injury. Allow blood to site * a clot will form around the damaged area to slow the spread of the pathogen

inflammation response to form pus

• When dead phagocytes mixed by with cellular debris and tissue fluid form a yellow fluid > pus

inflammation response By phagocyte:

Phagocytes such as macrophages are attracted by the chemicals released from the mast cells. They engulf and digest micro-organisms and cell debris at the site of the damage.

Explain why someone with an infected toe may develop a lump in the groin.

* Bacteria and cell debris from the infected toe enter the lymph system. * There are large numbers of lymph nodes in the groin and those nodes filter and destroy bacteria and other debris in the lymph coming from the toe. * Micro-organisms are attacked by macrophages and there is an increased production of lymphocytes to assist with the destruction. * The increased activity causes the groin lymph nodes to become swollen and painful.

Define non-specific response

work against all pathogen | includes external defense, protective reflexes and internal nonspecific defense

Define specific response

target particular pathogen | Confronts pathogen that is able to get past all the non-specific barriers