Lecture 7.pt 2 Flashcards
Features of prokatyocies
- genetic material does not have a nuclear memebrnae
- they are ribosome machines -> as a gene is transcribed -> poly transcription??
- motility is a common characteristic of cells but not all cells
Whats a big differnt in eukarotic cells?
Not in the number of genes, but rather difference in the post translational modifications in higher eukaryotes. Rough ER, golgi are importatn in secretion
Whats the genome size difference like in
variable. planst are greater than most anials. while fungal genomes are only around 10X larger than bacterial genomes. Most mitochondrial and chloropast genomes are 10X smaller than the average bacterial genome. Viral genomes are similar in size as plasmid genomes
THis variability is due to speciesi specific exhcanges of genetic material
Whats the genome of eukaryotic cells like?
- Ds DNA orgamized into chromosnesm (usually more than 1 per nuclear genome)
- nuclear genome are usually linear strucures, contain 50% DNA 50% proteins.
with histones to wrap DNA
nonhistones: enzymes that add or rekove post translatial modification.
DNA, histones, non-histones tgt are reffered to as chromatin
Mitchondrial and chlropast genome type?
What do they encode for?
Most organellar proteins?
Do they have the ability to divide independently of nucleus
- DS circular DNA, some ssDNa, much less DNA than in the respective genome
encode ribosomal RNA, tRNA,
Most organellar proteins are nuclear encoded and are imported into the organelles.
both mitochondira and chlropasts have the ability to divide outisd eof cytoplasm indpeently of nucleus (binary fission) but canmot exist outsid of cell
Bacterial genome
- dsDNA
- contained in a nucleoid
- genome is orgnaized a s single ciruclar supercoiled molecule
- there is only one chromosone/nucleoid
- a typical eubacterial or cyanobacteiral nucleodi has less DNA than the amoint of DNA found in a haploid eukarotoci nnuclear but more than in mitochonidra an chodromast
- aerchabacteiral genoms are smaller than most eubaterial genomses
histones in eubacteria and cyanobacteira/ vs acherbacteira
-eubacteria and cyanobacteria have around 10-120% protein continuosly associated with DNA (approx. 75% are basic and therefore histone lke but the protien DNA interactin does not form nucleosomes)
- some arhcaerbacteria (thermophibilic) have euaryotic type histones and the chormatina dn nucleosome structure
eubacterial thermohiles and other aerhcabacteiral thermoacidophiles lakc histones but have higher level of choromosonal proteins relative to the mesophilic bacteria
suggest the association of proteins with DNA ->adaptiatin to life at higher tmeperaters
Whats monocistonric
usually one polypeptide is encoded by a single eukaryuotic mRA. Unique of eukaryotes
Protein coding genes in eukaryotic nucleus
- Most genes in the eukrayotic nucleous have in introns.
- Genes in lower eukaryotes have fewer introns than genes in higher eukaryotes.
- inrtrons aer rare in mitchondiral and chlropast genes: self splicing and have ribozyme activity
- introns of eukaryotes are not self splicing but need additional snRNA, poly A tail, 5’ cap
- the primary transcript transcribed from DNA sequence of a eukaryotic usually contains introns.
- nucleotides of the mRNA is colinear with the aa seuqnece
- monocistonic
In prokaryotes (eu and archae), mt and chorlopast,
translationcan begin before transcription finichies
numerous ribosomes concurrently translate the mRNA transcripts into polypeptides.
Protein coding region in protkayotes, mt and chloropasts
- Introns are rare and self splicing
- the primary transcript transcribed from the DNA sequence is a transtable mRNA which is translated without further processing.
Trascription takes place in the cytoplasm.
in most cases, ribosomes bind to the 5’ end of the mRNA and translation occurs before transcription has terminated.
Most genes, the nucleotide sequenece of the DNA is colinear with the primary transcript and the amino acid sseuqnce
polycistronic (more than 1 poly peptide/ mRNA)
Purpose of operon
Genes can be put together -> controlled by1. transcription factor like the lac operon -> respond quicl
How are ribsomes made?
rRNA (ribosomal RNA) is transcribed in the nucleolus (a dense region inside the nucleus).
Ribosomal proteins are made in the cytoplasm (by existing ribosomes) and then imported back into the nucleus, specifically into the nucleolus.
In the nucleolus, rRNA and ribosomal proteins assemble into the small and large ribosomal subunits:
Whats the composition of eubacteria/cyanobacteria monosme subunits
- monosome 70s (3 types of RNA) ,
30S (contains 1 RNA type) and
50S (2 RNA types)
Ribosomes in eu and cyanobacteira
- 97% of the riboseoms are free in teh cytomasme: syntehsize cytopkasmic proteins
, remainger are bound to inner face of plasma memberneae: synstheies of extracytolasmic (secreted proteins) tsargeted to the plasma membrane, preiplasmic, cell envelope, celllw wall or to outsid eof the prokaryotic cells
Comparison of ribosomes between pro and eu
small subunit: similar
but there is a difference in the large subunit, an extra rRNA
-> good when making drugs can target one not the other
Comparison of gene organization between pro and eu
pro: in an operon: rapid resposne
eu: need to translate indiciually
if drug targets bacteria, can u be affected
Yes, with ribsomes in the mitochondria
What is the monomer of eukaryotes
80s
What is the monomer of prokaryotes and archaebacteria
70S
Is ribosome function of the 5 major target sites of antibiotics?
yes.
What are the 5 major antibiotic sites with examples
- Inhibiton of cell wall synthesis (penicillin, ampicillin, vancomycin, cephalosporin)
- Disruption of cell membrane function ex. polymycin
- Inhibiton of protein synthesis (tetracycline TET, streptomycin (STR), chlorampenicol (CAM), erythromycin (ERY)
- Inhition of metabolic pathways by functioning as an antimetabolite ex. sulfanilamide
- inhibtion of nucleic acid synthesis (rifamycin - RNA)
Which antibiotics are 70S ribosomes sensitive to?
TETs, ERYs, STRs, CAMs
Are 70s ribsomes inhibited by antibiotics that inhibit eukaryotic ribosomes such as cyclohiximide
no
What are some facts about archebacterial ribosomes
70s like eubacterial ribosomes
exhibit a different pattern of sensititivy to antibiotics than eubacteria and cyanobacteria
resisstant to ERY, STR, CAM
WHERE ARE eukaryotic ribsomes found
- free in the cytoplasm,
2, bound to the ER
within mitochondira
within chloropasts
some characteristis of cytoplasmic ribosomes or ER bound
80S monomor,
consists of 4 types of rRNA
small subunit: contains 18S rna
large subunit contains 2 + 5.8S rRNA (compared to only 2 in the prokaryotes)
Antibiotic sensititiveis of eukaryotic cytoplasmic
resistant to: tetracycliine, erythromycin, streptomycin , chlrophenicol
Eukaryotic mitochondira and chloropast ribsomes
70S monosome,3 RNAs
Antibiotic sensistiies: sensitive to TET, ERY, STR, CAM, CHX
Whats the effect of antibiotics on viruses
no effect. but if host protein is affected -> there is an effect. but do not use for viral infections.
RNA polymerase of eubacteira and cynaobacteira
1 major RNA polymerase used to make all major RNAs in the cell, 2nd primase involved in DNA synthesis.
Composed of 5 different subunits.
Rpase is inhibited by? it
riframycin
is iis RPAse in eubacteira and cyanobacteria inhibited by alpha amanitin
no
RNA poluymerase in archaebacteria
More than 1 major type of RPase per cell
more subunits than bacteria, simialr to eukartotes
is RPase in archaebacteria resistant to Rif? alpha amanitin
Yes. not sensitive to alpha amnitin
How many types of of RNA polymerase are there in eukaryotes for animals. fungi. plants
animals, fungi: 4
plants: 5 (3 major types + the 2 organicells)
as well as primase
Are there RPase in mitochondria and chloropasts
yes. and they are similar to eubacteria and cyanobacteria
resistance of RPase in mitochondria and chloropast to rif and alpha aminitin
sensitive to Rif.
resistnat to amanitin
Where are the RNA polymerases found
3 are in the nuclueus,
1 in mitochodria, 1 in chloropasts.
What are the different types of RNA polykease
type 1: transcirbes rRNA excetpt 5S
type 2: transcribes mRNA
type 3: transcibed tRNA and 5S rRNA
What are the 2 pathways for gram psotive cell secertionsystem
- Sec pathway.
unfolded protein with signal moleucle moves through the compelx and can come and stay in the periplasm or go out side
as it goes in its fold. once its in, the signal peptide can be removed
Examples: flagella, type 4 secretion system
- Twin Arginine pathway:
start: folded protein -> goes through
example of recombinatn protein secreiton
