Test 2 study guide Flashcards
1
Q
Characterize the features common to viruses
A
- small
- infectious
- non-living
- consists of protein and nucleic acid
2
Q
Describe the structures of viruses and the function of each of the parts
A
- composed of nucleic acid, proteins, and sometimes, a membranous envelope
- capsid: protective protein coat made of capsomeres around the nucleic acid
- other proteins besides the capsid; like glycoproteins or viral enzymes
3
Q
Describe bacteriophages strutures and their functions
A
- are viruses that infect bacteria
* bacteriopages have a complex capsid consisting of an icosahedral head and a tail apparatus
4
Q
Compare and contrast the two types of bacteriophage reproductive cycles
A
- lytic cycle: phage reproduces killing the host cells; lytic bacteriophages attach to the cell wall of a bacterial cell (attachment/absorption); inject viral DNA into the cell (penetration); phage takes over the cell’s metabolic machinery, degrades the cell’s DNA, and makes copies of its own genome and proteins. (replication); virus components assemble into new phage particles (assembly); the viruses lyse, or burst open the cell, resulting in death to the bacterial host (release)
- lysogenic cycle: phage reproduces without killing the host; phage attaches to the cell wall of a bacterial cell (attachment); virus genome enters the cell (penetration); phage circularized DNA will become inserted into a host cell chromosome and referred to a prophage (integration); DNA essentially “hidden” in the host cell’s DNA; prophage is replicated along with the bacterial host chromosome during cell (replication); A switch from lysogenic to a lytic cycle can be triggered; usually occurs as a result of an environmental factor, such as radiation or certain chemicals; the prophage is released from the host chromosome and returns to an active replication cycle that will lyse the host cell
5
Q
Understand how viruses infect a host and what determines their ability to infect a host
A
- They have to fit the proteins (specific)
* “host range”
6
Q
Contrast viroids and prions and the host range for each. Which targets plants? Animals?
A
- viroids: a plant pathogen consisting of molecule of naked, circular RNA
- prions: infectious agent consisting of a misfolded protein of a normal cellular protein; slow-acting, virtually indestructible infectious proteins that cause brain diseases in mammals by slowly converting correctly folded versions of the protein to more prions
7
Q
Understand retrovirues and their reproductive cycle
A
- retroviruses us reverse transcriptase to copy their RNA genome into DNA
- reverse transcriptase: an enzyme encoded by retroviruses that uses RNA as a template for DNA synthesis
- replicative cycle: the viral DNA that is integrated into the host genome is called a provirus; the host’s RNA polymerase transcribes the proviral DNA into RNA molecules; the RNA molecules function both as mRNA for synthesis of viral proteins and as genomes for new virus particles released from the cell
8
Q
Understand how humans prevent and treat viruses
A
- good hygiene: avoid contact with contaminated food, water, fecal material or body fluids; wash hands frequently
- vaccines: stimulate natural defenses in the body; contain a component of or a weakened or killed virus particles; developed for many once common illnesses such as smallpox, polio, mumps, chicken pox; not available for all viruses
- anti-viral drugs (but not antibiotics): available for some viruses; inhibit some virus development and/or relieve symptoms.
9
Q
Describe how new viruses emerge
A
- through mutation and evolution
- by spreading from one species to a new host species
- by spreading from an isolated location to more widespread locations
10
Q
Characterize the features common to prokaryotes
A
- single-celled
- most have distinctive cell walls
- lack membrane-bound organelles
- both anaerobic and aerobic
- genetic material is single circular bacterial chromosome and sometimes plasmids
- cell division is mostly asexual reproduction via binary fission also budding
11
Q
Compare and contrast features of prokaryotes and eukaryotes
A
- similar - they are both living; have DNA; plasma membrane; cytoplasm, and ribosomes
- prokaryotes - nucleoid region; very small; not very complex; only single-celled;
- eukaryotes - nucleus and other membrane bound organelles; large cells; complex; most multicelled but also some single-celled;linear chromosmes
12
Q
Describe three types of shapes that are used to classify bacteria
A
- bacilli (singular - bacillus): rod-shaped; usually solitary but in some forms the rods are arranged in chains
- cocci (singular - coccus): shperical shaped; occur singly, in pairs, in chains of many cells, and in clusters resembling bunches of grapes
- spiral (singular - spirillum): spirilla - comma shaped and loose coild; spirochetes - corkscrew shaped
13
Q
Explain how and where bacteria are able to carry out the functions of chlorophasts and mitochondira, which they lack
A
- the plasma membrane
- infoldings of plasma membrane functions in cellular respiration in some aerobic prokaryotes
- photosynthetic prokaryotes called cyanobacteria have thlakoid membranes much like those in choloroplast
14
Q
Describe the structures and their functions of a typical bacteria cell
A
- DNA loose in the cytoplasm, located in the nucleoid region. may also have small rings of DNA called plasmids
- ribosomes in the cytoplasm
- plasma membrane
- cell wall
- outer surface coating called a glycocalyx (capsule or slime layer)
- some have appendages (pili, fimbriae, endospore, flagella)
15
Q
Compare and contrast the cell walls of Archaea and Eubacteria
A
- gives them shape; protects them; prevents lyse
- eubacteria has peptidoglycan cell wall
- archaeabacteria cell wall is not made of peptidoglycan
