Infectious DiseasesInfectious Diseases

What causes them, andWhat causes them, and

How do we stay How do we stay healthy?healthy?

Standard Standard 10: 10:

• 10A10A -- Students know the role of -- Students know the role of the skin in providing nonspecific the skin in providing nonspecific defenses against infectiondefenses against infection

• 10B10B -- Students know the role of -- Students know the role of antibodies in the body’s antibodies in the body’s response to infectionresponse to infection

• 10C10C -- Students know how -- Students know how vaccination protects an vaccination protects an individual from infectious individual from infectious diseasesdiseases

Organisms have a variety of mechanisms to combat disease.

• 10D -- 10D -- Know the important Know the important differences between bacteria and differences between bacteria and viruses (i.e.: their requirement for viruses (i.e.: their requirement for growth and replication, the body’s growth and replication, the body’s primary defenses against bacterial primary defenses against bacterial and viral infections, and effective and viral infections, and effective treatments of these infections)treatments of these infections)

• 10E --10E -- Know why an individual with a Know why an individual with a compromised immune system (ex: a compromised immune system (ex: a person with AIDS) may be unable to person with AIDS) may be unable to fight off and survive infections by fight off and survive infections by microorganisms that are usually microorganisms that are usually benignbenign

• 10F -- 10F -- Students know the Students know the roles of phagocytes, B-roles of phagocytes, B-lymphocytes, and T-lymphocytes, and T-lymphocytes in the immune lymphocytes in the immune systemsystem

What is a Virus?What is a Virus?• Nonliving particles that have a Nonliving particles that have a

nucleic acid core and a protein-nucleic acid core and a protein-containing capsid. containing capsid.

• Cause disease by disrupting the body’s Cause disease by disrupting the body’s homeostasis (balance).homeostasis (balance).

• Don’t exhibit all life criteria:Don’t exhibit all life criteria:

Don’t carry out respirationDon’t carry out respiration

No growth or developmentNo growth or development

(all they can do is replicate)(all they can do is replicate)• Host CellHost Cell – where a virus replicates – where a virus replicates• Cannot be killed by antibiotics (medicines)Cannot be killed by antibiotics (medicines)

Viral Structure:Viral Structure:

T4 Virus – E. ColiT4 Virus – E. Coli

HERPESHERPES HIVHIV

Influenza – The common Influenza – The common ColdCold

Viral Replication – Lytic Viral Replication – Lytic CycleCycle

1.1. Attachment – Attachment – attaches to host cellattaches to host cell

2.2. Entry – Entry – injects nucleic acid into host injects nucleic acid into host cellcell

3.3. Replication – Replication – host uses it energy to host uses it energy to replicate viral nucleic acidreplicate viral nucleic acid

4.4. Assembly – Assembly – New viruses made (in New viruses made (in 30 minutes, 200 new viruses)30 minutes, 200 new viruses)

5.5. Lysis and Release – Lysis and Release – Host cell breaks Host cell breaks open, and virus particles are open, and virus particles are releasedreleased

What is Bacteria?What is Bacteria?• Small cell with all the structures Small cell with all the structures

necessary to carry out its life necessary to carry out its life functions.functions.

• 2 types of Bacteria:2 types of Bacteria:1.1. Archaebacteria – inhabit extreme Archaebacteria – inhabit extreme

environmentsenvironments2.2. Eubacteria – live almost Eubacteria – live almost

everywhere else. (heterotrophs, everywhere else. (heterotrophs, photosynthetic autotrophs, and photosynthetic autotrophs, and Chemosynthetic autotrophs)Chemosynthetic autotrophs)

Structure of BacteriaStructure of Bacteria• Prokaryotic Cells (typically)Prokaryotic Cells (typically)• Contain:Contain:

ChromosomesChromosomes – Single DNA molecule – Single DNA molecule (no nucleus)(no nucleus)

Cell WallCell Wall – shape and support – shape and supportPlasma MembranePlasma Membrane – regulates entry – regulates entry

and exitand exitPilusPilus – help stick to a surface and – help stick to a surface and

bridge for DNA exchangebridge for DNA exchangeFlagellumFlagellum – Whip-like tail for – Whip-like tail for

locomotionlocomotionRibosomesRibosomes – helps in protein – helps in protein

formationformation

Bacterial ReproductionBacterial Reproduction• AsexualAsexual

Binary FissionBinary Fission – –

1.1. Chromosome replicates, attaches to Chromosome replicates, attaches to plasma membraneplasma membrane

2.2. Cell grows and splitsCell grows and splits• Sexual ReproductionSexual Reproduction

ConjugationConjugation – –

Transfers all or part of chromosomes Transfers all or part of chromosomes to another bacteria through its pilusto another bacteria through its pilus

How do bacteria make How do bacteria make you sick?you sick?

• Produce disease in one of 2 ways:Produce disease in one of 2 ways:

1.1. Damage cells and tissuesDamage cells and tissues of of the infected organism the infected organism directlydirectly,, by by breaking downbreaking down the cells the cells for for foodfood..

2.2. Release toxinsRelease toxins (poisons) that (poisons) that travel throughout the body travel throughout the body interfering with homeostasisinterfering with homeostasis of the host.of the host.

Defense Against Defense Against Infectious DiseasesInfectious Diseases

How do we stay How do we stay healthy?healthy?

What is an Infectious What is an Infectious Disease?Disease?

• Disease =Disease = a change that a change that disrupts the homeostasisdisrupts the homeostasis in in the bodythe body

• Pathogens =Pathogens = disease causing disease causing agentsagents (what makes you sick) (what makes you sick)

Our Bodies Defense Our Bodies Defense Mechanisms:Mechanisms:

• SkinSkin – the first line of defense – the first line of defense• Phagocytes, B-lymphocytes, Phagocytes, B-lymphocytes,

and T-lymphocytes –and T-lymphocytes – the 2 the 2ndnd line line of defenseof defense

• Antibiotics and VaccinesAntibiotics and Vaccines – – outside sources of helpoutside sources of help

What is the role of What is the role of Phagocytes?Phagocytes?

• PhagocytesPhagocytes – White blood cells – White blood cells that surround and destroy that surround and destroy

pathogens.pathogens.• MacrophagesMacrophages – –

Located in body’s tissuesLocated in body’s tissues

Giant Scavengers – engulf pathogens Giant Scavengers – engulf pathogens and damaged cellsand damaged cells

What if phagocytes don’t What if phagocytes don’t help?help?

• Acquired ImmunityAcquired Immunity – defense – defense against a specific pathogen by against a specific pathogen by building up resistancebuilding up resistance

• Lymphatic System – the body’s Lymphatic System – the body’s system that is in charge of keeping system that is in charge of keeping it healthyit healthy

• Uses T-lymphocytes (T-cells) and Uses T-lymphocytes (T-cells) and B-lymphocytes (B-cells)B-lymphocytes (B-cells)

What are T and B cells all What are T and B cells all about?about?

Produced in bone marrowProduced in bone marrow• Helper T-cellHelper T-cell – – activates B-cellsactivates B-cells• Cytotoxic T-cellCytotoxic T-cell – “killer T-cells” – “killer T-cells”

produce clones to enter infection site, produce clones to enter infection site, release enzymes into pathogens which release enzymes into pathogens which causes them to causes them to lyselyse (explode) and die. (explode) and die.

• B-cellsB-cells – turn into antibodies once – turn into antibodies once activated by T-cellsactivated by T-cells

• Memory B-cellsMemory B-cells – remain in blood – remain in blood stream armed and ready for a 2stream armed and ready for a 2ndnd attackattack

What are antibodies?What are antibodies?• AntibodiesAntibodies – proteins produced to – proteins produced to

react with and disable antigensreact with and disable antigens• AntigensAntigens – Foreign substances that – Foreign substances that

stimulate an immune response stimulate an immune response in the bodyin the body

AntigensAntigens are displayed on pathogen are displayed on pathogen like an address (like an address (mark pathogensmark pathogens)), , Antibodies attach to antigensAntibodies attach to antigens to to

help the body fight the intruder.help the body fight the intruder.

What about What about Antibiotics?Antibiotics?

• Substance produced by a Substance produced by a microorganism that microorganism that kills or inhibits kills or inhibits the growth of other the growth of other microorganismsmicroorganisms

• Use to fight and kill bacteria Use to fight and kill bacteria • Does NOT work with virusesDoes NOT work with viruses

Why do you think that is?Why do you think that is?

How can Vaccinations How can Vaccinations help?help?

• Vaccine =Vaccine = substance with substance with weakened, dead, or incomplete weakened, dead, or incomplete portions of pathogenportions of pathogen (typically a (typically a viral pathogen)viral pathogen)

• Produces an Produces an immune responseimmune response• Creates antibodiesCreates antibodies in the body (T in the body (T

and B cells)and B cells)

What are RetrovirusesWhat are Retroviruses• Contain RNA instead of DNAContain RNA instead of DNA• When cell is infected, it produces When cell is infected, it produces

DNA copy of RNA to insert into DNA copy of RNA to insert into the Host Cell’s DNAthe Host Cell’s DNA

• Lays dormant for long time Lays dormant for long time (hidden from bodies defenses)(hidden from bodies defenses)

• HIV is a retrovirusHIV is a retrovirus• Harder to stop because can Harder to stop because can

undergo more mutations.undergo more mutations.

What is HIV and AIDS all What is HIV and AIDS all about?about?

• Caused by Caused by HIV (Human HIV (Human Immunodeficiency Virus)Immunodeficiency Virus)

• Compromises your immune systemCompromises your immune system• Kills white blood cells (Helpers T-Kills white blood cells (Helpers T-

Cells) and can lead to Cells) and can lead to AIDS AIDS (Acquired Immune Deficiency (Acquired Immune Deficiency Syndrome)Syndrome)

• HIV contains 2 copies of RNA that HIV contains 2 copies of RNA that penetrate a cell and hide for penetrate a cell and hide for months. In the infected cell, RNA is months. In the infected cell, RNA is used to synthesize viral DNA.used to synthesize viral DNA.