Review test questions
Classification Test In examining a cell in an electron
microscope, you observe that the cell has a nucleus and a cell membrane but no cell wall. You conclude that the cell probably comes from a(n) sea-weed plant fungus animal
Birds and snakes share a common ancestor from over 250 million years ago, but now they show many physical differences. These differences are most directly the result of coevolution between species. molecular clocks ticking at different rates. the long-term accumulation of mutations. differences in the alleles of the ancestor.
Which scientific advancement enabled the discovery of differences between prokaryotes and eukaryotes? Light microscope Electron microscope Computers DNA analysis
Based on the given characteristics, this organism would be classified in which kingdom? Bacteria Fungi Plantae Protists
Chapters 18 & 31 Viruses, Bacteria &
Immunity
What is a virus? Virus – a very
small, nonliving particle that can cause disease
What are some diseases that are caused by viruses?
Influenza RubellaCommon cold MumpsChicken pox MeaslesHerpes Small poxAIDS Viral hepatitisShingles RabiesGastroenteritis Cold soresMononucleosis Ebola
Many viruses affect humans!Next slide: Beware if you are squeamish
SmallpoxChicken pox
Measles
Girl infected with smallpox in Bangladesh, 1973
WHO certified eradication of Smallpox in 1979
How are viruses spread? Air Direct physical contact Body fluids Vector - a carrier of an infectious agent
Examples: insect, rodent, monkey…
Viruses are found in the air, soil, and water!
Viruses can attack animals, plants, and bacteria!
BacteriophageAnimal Virus
Plant Virus
Bacteriophage
Influenza
Tobacco mosaic virus
Are viruses alive?
They DO have an orderly structure with genetic material.
They DO produce offspring, but not on their own!
They DO respond to the environment.
3 Criteria of Life They DO NOT respire They DO NOT grow They DO NOT move
In fact, all viruses can do is reproduce, and they can’t even do that alone!
Host cell – a living cell that a virus uses to reproduce.
Anatomy of a Virus Outer coat of protein Inner core of nucleic acid
Contains the viruses’ genetic material Can be RNA or DNA
This simplicity allows it to be very efficient at reproducing.
Viral reproduction
Lytic Cycle
1. Virus attaches to host cell and injects its genetic material
2. Host cell DNA is destroyed
3. New viruses are formed
4. Host cell bursts (lyses), releasing the viruses and killing the host cell
Lysogenic Cycle
1. The virus DNA (RNA) becomes part of the host cell’s DNA
2. The host cells reproduce normally with the virus DNA hidden in each new daughter cell.
3. Host cell is not killed until lytic cycle is entered
Viral reproduction
How can viral diseases be cured?
Many cannot be “cured” because they are constantly evolving.
The body gets rid of viruses through the immune system.
Many can be treated with antiviral drugs to keep symptoms under control.
What is a vaccine?
Vaccine - substance that contains parts of dead or weakened microbes. Vaccines cause your body to make antibodies
that will recognize and destroy the virus if it enters the body in the future.
Vaccines can prevent illness from happening.
Personal Health Issues The vaccine cannot cause the disease but
may produce a non-specific response at the site of the shot.
Swelling or redness at the site of the injection.
Some individuals may still get the disease after vaccination. Average flu vaccine effectiveness is 60%
Public Health Issues Vaccines can protect the people who
receive them and those around them. Creates “herd immunity”. Smallpox eradicated due to mandatory
vaccination. Used to have 13,000-20,000 cases each year in the US.
Type B meningitis, polio, diphtheria and measles are now rare.
Public Health Issues People underestimate the dangers of not
vaccinating against disease. A small trend away from vaccinations puts
people at risk. A resurgence of some diseases is occurring
because vaccinations rate are too low to provide the herd immunity.
How can viruses be helpful? Viruses may help cure
other diseases through gene therapy.
Other Types of Viruses Prions - composed of proteins, but no nucleic
acids. Act on other proteins causing them to fold improperly.
Example: Mad cow disease, Creutzfeldt-Jakob disease
Plant Viruses - Do not undergo lytic or lysogenic cycle
Example: Tobacco mosaic virus
Bacteria
The smallest and simplest living things
Intro to Bacteria
Bacteria: Two Kingdoms
1. Archaea (Archaebacteria): Found in three extreme habitats
Methanogens - Oxygen free environments Halophiles - Very salty environments Thermophiles - Extremely hot, acidic
waters
Yellowstone National Park – hot springs
2. Bacteria (Eubacteria): Found in many environments and live a variety of lifestyles.
EverywhereCyanobacteriaAnimal intestines
Salmonella
Soil Pseudomonas
Means of acquiring food
Heterotrophs – feed on other organisms
Saprobes – feed on dead things, important decomposers
Autotrophs – make their own foodPhotosynthesis or Chemosynthesis
Identifying Bacteria
Three most common cell shapes:
Cocci – Spheres
Bacilli – Rods
Spirilla – Spirals
Identifying BacteriaArrangement: Diplo – Pairs
Staphylo – Grape-like clusters
Strepto – Long chains
Identifying Bacteria
So what would a “Streptospirilla” look like?
Long chains of spirals
Diversity of Metabolism
Obligate Aerobes - bacteria that require oxygen for cellular respiration.
Example: Mycobacterium tuberculosis
Diversity of Metabolism
Obligate Anaerobes - bacteria that cannot use oxygen and are killed by it.
Example: Tetanus, botulism
Deep wounds are hard to clean and provide ideal conditions for growth of anaerobes.
Clostridium botulinum: Causes food poisoning
Botox injections comes from C. botulinum
Adaptations for Survival
Endospores - hard outer covering, resistant to drying out, boiling, and many chemicals.
Bacteria form endospores when environmental conditions are unfavorable.
During this time, no growth or reproduction takes place.
Have been found to germinate after thousands of years.
Endospore
Bacterial Reproduction:
Binary Fission asexual reproduction Cell grows larger, copies its chromosome
and then the cell divides in half. Daughter cells are genetically identical to
each other and to the parent cell.
Bacterial Reproduction:
Conjugation Sexual reproduction One bacterium transfers all or part of its
chromosome to another cell through a pilus (bridge like structure) that connects the two cells.
Beneficial bacteria
1.Decomposers2.Nitrogen fixers3.Help digestive processes
Rhizobium in root nodules
Harmful bacteria
Human pathogens: Diptheria Typhoid Tetanus Leprosy TB Plague Strept. Throat
Plague
Tuberculosis – lung tissue
Ways to fight or prevent problem bacteria
Sterilization – medical equipment Pasteurization – milk Vaccinations – DPT Antibiotics – Penicillin
Discovered by Alexander Fleming in 1929, while observing mold growing in a petri dish
Penicillin
Antibiotics A variety of drugs that kill bacteria usually
by destroying the cell wall or by preventing them from reproducing. Antibiotics do not help with viral infections like the flu or cold viruses.
Personal Health Issues Some people are allergic to certain
antibiotic types like penicillin. Antibiotics kill good bacteria in your body as
well as the bad. This may allow fungal infections to take hold.
Doctors recommend eating yogurt after you finish all your antibiotics.
Public Health Issues Overuse and improper use of antibiotics
has resulted in many strains of antibiotic resistant bacteria.
Patients must take the full course of antibiotics even if they start feeling better.
80% of antibiotics used in the US are given to livestock.
Immune SystemChapter 31
Germ Theory BC 7000 – Spirits: drilling of holes in peoples
heads to release evil sprits that cause disease. BC 460-1800s – Humors: fluids called humors
thought to cause disease (blood letting). AD 1330-1352 – Herbal: attempt to use incense
to cure the Black Death. 1857 – Germ Theory – Louis Pasteur
hypothesized that disease is caused by small “animals” (microbes)
George Washington – Blood letting
Pathogens A pathogen is a disease causing micro-
organism. Bacteria – E. coli Viruses – cold, flu Fungi – athlete’s foot Protists - malaria Parasites – parasitic worms
First Lines of Defense The first line of defense are barriers to keep
pathogens out of the body.
1. Physical Barriers – skin, natural bacteria
2. Mechanical barriers – cilia, mucus, tears
3. Chemical barriers – pH of urine, gastric juices, vaginal tract.
Second Line of Defense The non-specific responses that the body
uses for all pathogens. Response is quick.
1. Phagocyte
2. Fever
3. Swelling
Phagocyte
Third Line of Defense Specific response for specific pathogens.
1. B Cells (white blood cell)
2. T Cells (white blood cell)
3. Phagocytes (white blood cell)
4. Antibodies (proteins)
Antibody
Allergies An allergy is an oversensitivity to a normally
harmless antigen.
Lifestyle Choices and Health Some lifestyle choices can prevent chronic
diseases and keep your immune system working at its best.
Regular exercise Healthy diet No smoking Sufficient sleep