+

Chapter 7: Infection and disease 1EL: To explore what a disease is and what causes them

+Study design – key knowledge detecting ‘self’ and ‘non-self’ molecules: antigens and membrane

receptors

– pathogens: non-cellular agents, cellular agents; controls;

physical and chemical barriers to infection in plants and animals;

immune response

– structure and overall function of the lymphatic system

– non-specific: inflammatory response; phagocytosis; blood clotting

– specific immune response: T-cell lymphocytes and cell-mediated response; B-cell lymphocytes and humoral response, antigens and antibodies; memory cells;

disorders of the immune response: autoimmunity; hypersensitivity, allergens and allergic responses;

acquired immunity: natural, artificial including vaccines and antibody serums.

Chapter 7: Pre-testQuestion Start of unit End of unit

What is a disease?

What is a pathogen

What is a cellular agent?

What is a non-cellular agent?

+Disease

Any condition that interferes with how an organism or any part of it functions

Can be acquired through: Genetic causes – inherited from parents Pathogens and parasites

+Pathogens

disease causing organism or agent (frequently but NOT always a MO)

Non-cellular pathogens Prion virus

Cellular pathogens bacteria fungi protozoa exo- and endo-parasites

+

+Nature of Disease Intensity of pathogenic effect: VIRULENCE

Due to special characteristics of the pathogenic organism, such as ability to produce toxins

Individuals level of susceptibility to pathogen: RESISTANCE Varies with age, state of health, immunity

Some pathogens are able to survive outside the host, others are not

Time between infection and symptoms: INCUBATION PERIOD Depends on pathogen achieving sufficient numbers, reaching target

tissue, toxin accumulation etc

+Nature of Disease: TransmissionInfective agents can be transmitted from

one host to another by:

Direct contact Droplets in air breathed or sneezed by host Sexual contact (e.g. STIs) Contaminated food or water A carrying vector (e.g. rats carrying fleas) An injecting vector (e.g. mosquitoes carrying

malaria parasites) Injection with infected needles and syringes

+Non cellular pathogens: Viruses A virus is a non-cellular agent composed of a protein

coat (capsid) and nucleic acid (RNA OR DNA) Rely on living cells to function and replicate:

Not able to respire OBLIGATE intracellular parasites Often integrated into host chromosomes and replicated during

cell division Highly specific to host cell or organism it infects

(e.g. adenovirus specific to lung cells -> common cold)

All organisms on Earth are susceptible to virus infection (e.g. bacteriophages)

http://www.youtube.com/watch?v=Rpj0emEGShQ

Chicken pox

+Shingles

+

Rubella

or

German measles

+Mumps

+Cold sore

+Warts

+Verruca

+Polio

+Small pox – a killer

+Non cellular pathogens: PrionsProteinaceaous infectious particles: NO

GENOMEDeviant versions of a normal cell surface

protein that are transmissableDisease caused by accumulation of abnormal

protease-resistant proteinDiseases include BSE

(or mad cow), CJD, Kuru

+Cellular pathogens: BacteriaProkaryotic organisms lacking

organellesContain circular DNA moleculeCan be classified according to

metabolic characteristics and/or shapeRound Rod-shaped Spiral

+Cellular pathogens: BacteriaCell wall contains PEPTIDOGLYCAN

and is chemically and morphologically complex

Can have flagellum, capsules or spores

Reproduce rapidly by binary fission in favourable conditions

http://www.youtube.com/watch?v=gEwzDydciWc&NR=1

+Eye infection

+Leprosy

+Tetanus

+Plant blight

+NOB Activity 7.1 & 7.2

One group will set up activity 7.1 pg 58-59 (procedure 1-5)

One group will set up activity 7.2 part A pg 61-62 (procedure 1-8)

One group will set up activity 7.2 part B pg 63 (procedure 1-6)

We will make observations next lesson

+Homework – Chapter 7

Quick check qu 1-25Biochallenge 1Chapter Review qu 2

+Reflection

What did you learn about infection and disease today?

What was the most disgusting disease today?

+

Chapter 7: Infection and disease 2EL: To examine our bacteria investigations

+Activity 7.1 & 7.2

Everyone will complete:Activity 7.1 pg 59, procedure 6-8, qu 1-

7Activity 7.2 part A pg 63, procedure 9,

qu 1-8Activity 7.2 part B pg 63, procedure 7,

qu 10-15

+Homework – chapter 7

Quick check qu 26-30Biochallenge qu 2Chapter review qu 4, 5, 6, 8

+Reflection

Were you surprised by the results of any of the experiments and why?

+

Chapter 7: Infection and disease 3EL: To further explore the causes of disease

+Expected learning

To further explore the causes of disease

+Cellular pathogens: FungiEukaryotic heterotrophs

break down organic matter by secreting enzymes and other chemicals

These chemicals are the main cause of the diseasePrimarily terrestrial, but need

moistureReproduce using sporesCell wall made of chitinFilamentous moulds and

unicellular yeasts

+Athletes foot

+Oral Thrush

+Frogs – chytrid fungus

+Cellular pathogens: ProtistsUnicellular eukaryotic organismsVery diverseUsually motile (i.e. flagella, cilia)HeterotrophicReproduce sexually and asexuallyMay have specialist life cycle

involving different hosts

+Protist Life Cycle

http://www.youtube.com/watch?v=Q_nCHDry0s8

+Endoparasites: wormsFlat and round worms may be parasitic,

but aren’t necessarily pathogenicPathogenic worms include tapeworms,

roundworms

+Endoparasites: worms

+Ectoparasites: arthropodsGenerally parasitic, but aren’t

necessarily pathogenicPathogenic arthropods include head lice

and body lice

+Nelson Activity 5.2

Complete activity 5.2 and hand in

+Reflection

Why do you think parasites have evolved such a complex life cycle?