Lect16 Disease NVC Bio105 Sp16 - napavalley.edu

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Diseases

Biol 105 Chapter 13a

Copyright © 2009 Pearson Education, Inc.

Disease

I.  Bacteria II.  Viruses (including HIV)


Pathogens

§  Pathogens are disease-causing organisms


Domain Bacteria Characteristics

1.  Domain Bacteria are prokaryotic.

2.  Lack a membrane-bound nucleus, lack membrane bound organelles.

3.  Have ribosomes, but different than eukaryotic ribosomes.

4.  Generally have a single chromosome.

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Domain Bacteria Characteristics

5.  Cell wall present in many species.

6.  Reproduce by binary fission.

7.  Great metabolic diversity.


Bacteria Shapes

1.  Coccus – spherical

2.  Bacillus – rod

3.  Spirilla – spiral shaped


Pathogens

Figure 13a.1a Copyright © 2009 Pearson Education, Inc.

Pathogens

Figure 13a.1b

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Pathogens

Figure 13a.1c Copyright © 2009 Pearson Education, Inc.

Some Bacteria can Cause Disease

§  Diseases caused by bacteria are caused by:

§  Toxins or enzymes released by the bacteria. (tetanus, botulism).

§  By the response of the host.


Pathogenic Bacteria

§  Some Escherichia coli cause health problems – vomiting and diarrhea, may cause kidney failure.

§  Clostridium botulinum bacteria produce the toxin that causes botulism, interferes with nerve function.

§  Borrelia burgdorferi (spirilia) – bacteria that uses deer ticks to move from host to host, causes Lyme disease.


Beneficial Bacteria

§  Examples of Beneficial Bacteria:

§  Lactobacillus. §  Nitrogen fixing bacteria. §  Normal flora in body.

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Antibiotics

§  Chemicals that inhibit the growth of microorganisms.

§  They work by disrupting the processes that are common to bacteria but not to human cells.


Antibiotic Resistance §  Bacteria populations can rapidly mutate,

antibiotic resistance can result.

§  The few bacteria that mutate and are resistant to antibiotics will repopulate the area with antibiotic resistant bacteria.

§  The overuse and misuse of antibiotics are largely to blame for increasing antibiotic resistance.

§  When bacteria become resistant to antibiotics, the drugs are no longer effective.


Viruses

§  Viruses are responsible for many illnesses including colds.

§  Antibiotics do not kill viruses.


Virus Characteristics

1.  Have genetic material (DNA or RNA). 2.  Many have a protein coat = capsid. 3.  Some have a fatty membrane = envelope with

glycoproteins. 4.  Very small. 5.  Viruses may remain inactive or latent in the

host for many years. 6.  Not cellular. 7.  Not living organisms.

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Typical Virus

Figure 13a.3a

Glycoprotein

Envelope

Capsid

Viral DNA

(a) Copyright © 2009 Pearson Education, Inc.

Virus Replication Steps

1.  Attach to a host cell. 2.  Penetrate host cell by endocytosis. 3.  Production of genetic material and

proteins (Transcription and Translation).

4.  Assemble new viral particles. 5.  Release by budding or by rupturing

host cell.


Viral Replication

Figure 13a.3b

Step 1: Attachment The virus attaches to a specific receptor on the host cell. This is responsible for host specificity.

Step 2: Penetration All or part of the virus enters the host cell. With animal cells, the entire virus enters the cell.

Step 3: Production of viral genetic information and proteins The virus directs structures in the host cell to make parts of new viruses.

Step 4: Assembly of new viruses Newly synthesized viral genetic information and proteins are used to form new viruses.

Step 5: Release New viruses leave the cell. Some viruses leave by a process called budding (or shedding), as shown here.

Plasma membrane of host cell (b)


Human Immunodeficiency (HIV)

§  HIV is the virus responsible for Acquired Immune Deficiency Syndrome (AIDS)

§  The HIV virus contains: §  mRNA §  Enzymes including: reverse

transcriptase, integrase, and protease

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HIV is a Retrovirus

§  HIV has mRNA.

§  It uses reverse transcriptase to turn mRNA into DNA.


HIV and AIDS

Figure 17a.7

The tip of HIV’s protein spike fits into receptors on the host cell, allowing HIV to enter the cell.

HIV’s protein spikes are embedded in the envelope of HIV. The envelope

comes from the cell membrane of the previous host cell.

HIV’s genetic information is in the form of RNA.

Reverse transcriptase is the enzyme that rewrites HIV’s RNA as DNA.

Core proteins

Viral proteins surrounding

the core


HIV Virus Replication Steps

1.  Glycoproteins on HIV envelope bind to CD4 receptors (and CCR5) on a host cell = Helper T cell.

2.  Penetrate host cell by endocytosis.

3.  Uses the enzyme reverse transcriptase to turn its mRNA into DNA.



4.  Uses the enzyme integrase to integrate the viral DNA into the host DNA.

5.  Transcribes viral DNA to make mRNA.

6.  Translates viral mRNA to make viral proteins.

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7.  Uses the enzyme protease to assemble new viral particles.

8.  Release by budding.


HIV Replication

Figure 17a.8


HIV

§  HIV attacks the Helper T cells.

§  Not only does the HIV attack the Helper T cells but they hijack them so they are produce more HIV viruses.


HIV

§  Why can’t we fight HIV like we do other viruses? §  It multiplies in the immune system and attacks

the immune system, making fighting it more difficult.

§  It mutates rapidly so it is hard fight.

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§  For a period of time the viral DNA may not be transcribed, or will be transcribed at a low rate.

§  Then the T cell will begin to transcribe the viral DNA at a high rate.

HIV


HIV Treatments

§  There is no cure. These treatments can slow the spread of the virus in the body but not completely get rid of it.

§  There are drugs that work to slow the progress of HIV in the body.


HIV Treatments

§  HIV drugs:

1.  Fusion inhibitors 2.  Reverse transcriptase inhibitors 3.  Protease inhibitors 4.  Integrase inhibitors 5.  HIV entry inhibitors


Important Concepts

§  Read Chapter 14 for next lecture

§  What are the characteristics of bacteria?

§  What are the shapes of bacteria (latin names)?

§  How do bacteria cause disease?

§  What are examples of pathogenic bacteria?

§  What are examples of beneficial bacteria?

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Important Concepts

§  Be able to discuss antibiotic resistance, including the causes and effects.

§  How would you design an antibiotic, what target would you use?

§  What are characteristics of viruses?

§  What are the steps of viral replication, be able to discuss in detail HIV viral replication?


Important Concepts

§  What enzymes and genetic material do HIV particles have and what is their function?

§  How would you design HIV drugs – what targets would you attach, what are the classes of HIV drugs currently available?

§  How is HIV spread?


Definitions

§  Pathogen, binary fission, antibiotics, capsid, envelope, glycoproteins, latent, integrase, reverse transcriptase and protease, retrovirus

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