Biology (Miller and Levine) Chapter 20

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virus
a non-living particle made up of proteins, nucleic acids, and sometimes lipids.
Viral Structure
capsid - protein coat on outside of virus
membrane envelope - not all viruses have this
genes - may have RNA or DNA - number of genes varies
Most viruses enter the body by...
"tricking" a normal cell to let them in
bacteriophages
viruses that infect bacteria
- also known as "bacteria killers"
Viral Infections
Viruses use their genetic information to take over the host cell and make multiple copies of the virus
- some viruses replicate immediately
- other viruses persist in an inactive state
Lytic Infection
- virus enters bacterial cell
- forces cell to make copies of virus
- causes cell to burst
(i.e. t4 bacteriophage)
Lysogenic Infection
- host cell not immediately taken over
- viral DNA inserted into host DNA and copied as host reproduces
- the embedded viral DNA is called prophage
- a virus eventually leaves the lysogenic cycle and enter the lytic cycle.
prophage
embedded viral DNA
prokaryotes
unicellular organisms that lack a nucleus
- vary in size, shape, movement, and energy use
-- bacilli - rod-shaped
-- cocci - spheres
-- spirilla - spiral
Domain Bacteria
not all bacteria have all the layers or methods of movement, but all have a cell wall made of peptidoglycan.
Domain Archaea
- cell walls lack peptidoglycan
- membranes have different lipids
- DNA more closely related to Eukarya
- may live in extremely harsh environments
heterotroph
feeds on other organisms
photoheterotroph
feeds on other organisms but also uses light energy
photoautotroph
uses light energy to convert CO2 to Sugars
chemoautotroph
uses energy released by chemical reactions involving ammonia or hydrogen sulfide
- usually found in deep, dark environments without light
An endospore
forms when conditions for growth become unfavorable
- a thick wall encloses DNA and cytoplasm, protecting the prokaryote until the environmental conditions change
conjugation
the exchange of genetic material between prokaryotes
- plasmids (independent DNA) are transferred
decomposers
continue the nutrient cycles
producers
- carry out photosynthesis
- make oxygen
- base of aquatic food webs
nitrogen fixers
convert atmospheric nitrogen into forms plants can use
- produce foods like yogurt
- make drugs and chemicals
pathogeon
organism that causes disease
bacteria
cause disease by destroying cells (causes TB) and by releasing chemicals (causes diptheria and botulism) that upset homeostatis
controlling bacteria
- physical removal by washing
- disinfectants
- food storage - low temperatures
- food processing - raising temperature kills bacteria
- sterilization by heat - above 100 degrees celcius
Bacteria prevention and treatment
- prevent bacterial diseases by vaccination
- treat bacterial diseases with antibiotics
Viral Diseases
- viruses attack and destroy cells in the body
- some viruses attack cellular processes
- viral diseases can be prevented by vaccination
- antibiotics do not treat viruses
Emerging Diseases
disease that appears in a population for the first time OR when a well-known disease suddenly becomes harder to control
- the short time between successive generations of pathogens allows them to evolve quickly
- changes in lifestyle, like commerce and travel, make emerging diseases more of a threat
- are threatening to humans because we have no resistance to them and treatment methods have yet to be developed
"Super bugs"
antibiotic-resistant forms of bacterial diseases
- the use of antibiotics has acted as a type of natural selection
New viruses
emerge when a virus move from an animal to a human
Prions
clumps of tiny proteins that are improperly folded
- damage nervous system tissue