Chapter 20 Biology Miller & Levine

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virus
a particle made up of proteins, nucleic acids and sometimes lipids that can replicate only by infecting living cells - smaller and simpler than the smallest cells - developed after living cells - evolving for billions of years
capsid
the protein coat surrounding a virus
bacteriophage
a kind of virus that infects bacteria
How do viruses reproduce?
Infecting living cells
simplest viruses have only
a few genes
complex viruses may have
hundreds of genes
how do viruses infect living cells?
viruses have proteins on the surface that attach to the protein on the host cell - they trick the host cell into into taking the virus or its genetic material
what happens when virus infects host cell?
it uses the cell's genetic information to make copies of itself
lytic infection
when a virus copies itself immediately - it enters a cell, makes copies of itself and causes the cell to burst - thus making more copies of itself when the bacteriophage is released to infect other cells
lysogenic infection
when a virus stays inactive for a period of time within the host cell - it embeds its DNA in to the DNA of the host cell and is replicated along the host cell's DNA - CELL IS NOT DAMAGED BUT DAUGHTER CELLS ARE
retrovirus
an RNA virus that contains RNA as its genetic information - the genetic information of a retrovirus is copied from RNA to DNA rather than DNA to RNA
what percent of viruses have RNA rather than DNA
70%
what happens when a retrovirus infects a cell?
it makes a DNA copy of its RNA and the copy is inserted into the DNA of the host cell. The viral DNA may remain inactive for many cell cycles. Eventually it makes new virus particles and they attack the cells of the host's immune system that normally fights off infection
viruses aren't alive but they have characteristics of living things - 3 things
they can reproduce, they have genetic material, they can evolve
prokaryotes
single-celled organisms that lack a nucleus - their DNA is found in their cytoplam - they are classified as either bacteria or archaea - smaller than eukaryotic cells- 1 - 5 micrometers, some use flagella to move and others put down slime and glide along it and some don't move at all - they also get and release energy differently
bacteria
live almost everywhere - surrounded by cell wall that contains a peptidoglycan. This molecule is made up of sugar and amino acids. Some have a cell membrane outside the cell that protects them. They may also use flagella or pili for movement. Piti also help them attach to surfaces of other bacteria
flegella
part of bacteria that helps it move and helps prokaryotes to move
pili
help bacteria move and also help them attach to the surfaces or other bacteria
archae
look like bacteria - tiny, lack nuclei, have cell walls - but their cell walls don't have peptidoglycan - also cell membranes contain different lipids - the love in harsh environments - mud, animal digestive tracts, salty water, hot springs HOT SPRINGS
bacilli
rod-shaped prokaryotes
spirilla
spiral and cork-shaped prokaryptes
cocci
sphere-shaped prokarotes
how do prokaryotes move?
some use flagella to move and others put down slime and glide along it and some don't move at all
heterotroph
other feeder - type of prokaryotes energy capture
photoheterotroph
light and other feeder - type of prokaryotes energy capture
photoautotroph
light self feeder - type of prokaryotes energy capture
chemoautotroph
chemical self feeder - type of prokaryotes energy capture
binary fission
a type of asexual reproduction in which an organism relicates its DNA and divides in half, producing two identical daughter cells
conjugation
the process in which parmecia and some prokaryotes exchange genetic information - a hollow bridge forms between two bacterial cells and genetic material moves from one cell to the other
endospore
a structure produced by prokaryotes in unfavorable conditions; a thick internal wall that encloses the DNA and a portion of the cytoplasm - can be dormant for months or even years - they help the prokaryotes live in unfavorable conditions
how are prokaryotes so important?
decompose dead organisms and waste - produce the basis of many food chains - nitrogen fixers and some are used in human industry like YOGURT
Louis Pasteur
established Germ Theory of Disease
pathogen
organism that can cause sickness
2 ways bacteria causes diseases
destroys living cells and tissues AND release chemicals that upset normal activities of the host
toxins
chemicals that upset the normal activity of the host
how can you control bacteria
wash hands, wash surfaces, (washing removes but doesn't kill bacteria. disinfectants kill bacteria)
human bacterial disease
lyme (from tick causes fever and fatigue), tetanus (enters through break in skin like stepping on a nail - causes lockjaw, swelling...)
vaccine
a preparation of weakened or killed pathogens used to produce immunity to a disease
antibiotic
drugs to treat bacterial infection - keeps bacteria from growing and reproducing - do not harm host cell
viruses
cause disease by destroying living cells and attack only certain kinds of cells
common viruses
common cold, influenza, AIDS, chicken pox, AIDS...
best way to protect against virus
prevention - wash your hands, use vaccines, only antiviral meds to treat viruses - not antibiotics
emerging disease
disease that appears for the first time or an older one that is harder to control - no resistance to them
superbugs
like bacteria that are resistant to many antibiotics
new viruses
virus that evolves and jumps from one host species to another like bird flu or HIV
prions
formed when a certain type of protein (PrP3) folds incorrectly and as they build up they cause damage to brain cells. spread when animals eat infected animals. Can infect humans too.
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