Cell as basic unit of life lesson 2 : lectures 3 and 4 Flashcards
describe the structure of the bacterial cell.
is a type of prokaryotic cell.
1-10 micrometers
has primative nucleus that has no nuclear membrane (nucleiod)
no membrane bound cell organelles . instead they have plasma membrane mesosome
DNA is not associated with histone proteins
if bacterial cells dont have any membrane bound organelles then how do the cell functions get carried out ?
bacterial cells have plasma membrane mesosomes that carry out cell functions
describe the outer covering of the bacteria
o=composed of 3 main coverings -capsule -cell wall -plasma membrane (in that order from superficial to deep)
inside the outer layer of bacteria we can see—-
cytoplasm and its constituents
describe the structure and function of the capsule /
most bacteria have capsules .
it is composed of poly saccharide
the main function is a protective function
bacteria with capsule are more resistant than bacteria without capsule
describe the structure and function of cell wall .
it is composed of lipids , proteins , and poly saccharides (capsule is only made out of poly saccharide)
it gives a firm and rigid shape to the bacteria cell. it is also important for protection
bacteria cannot survive without cell wall.
what bacterial structure is used in gram staining ?
cell wall
what type of stain is used in gram staining ?
crystal violet stain and iodine (which helps staining of violet)
explain the process of gram staining .
bacteria are stained by crystal violet stain and iodine , which helps the staining of violet . it is then left for 2 minutes before ethyl alcohol is added . finally a counter stain (safarnin) is added ). if the bacteria succeeded in retaining violet color of crystal violet stain then it will be gram positive. if it was only stained by the safarnin and has a pinkish color then it is gram negative
how are gram negative and gram positive bacteria different
if the bacteria succeeded in retaining violet color of crystal violet stain then it will be gram positive. if it was only stained by the safarnin and has a pinkish color then it is gram negative .
how are the cell walls of gram positive and gram negative bacteria different?
gram positive bacteria cell walls have an excess of peptidoglycan on the surface . peptidoglycan is responsible for retaining the crystal violet stain . in gram negative peptidoglycan is alot less and is sandwiched between 2 layers lipopolysaccharide
which type of bacteria is more toxic and more resistant to humans ?
gram negative
what is the 3rd layer of the outer covering of bacteria and whats it formed of ?
plasma membrane and it is composed of lipoprotein
describe the cytoplasm in bacteria
it is a dense jelly like structure
what granules does the cytoplasm contain ?
glycogen , proteins , fats , and some polymers of glucose
what type of ribosomes are present in bacterial cytoplasm?
70S ribosomes
what does spedbergs unit of ribosomes mean?
it is the sedimentation rate (weight) and it is not accumulative
bacteria contain more rna than eukaryotic
.
what is the nuclear region ?
area where DNA floats around in cytopalsm (nucleuoid)
what other type of DNA do bacteria have other than linear DNA?
plasmids which are circular DNA and it is responsible for antibiotic resistance .
what is plasmid used for in labs ?
it is taken outside , interested part of DNA that we want to study is inserted into it , and the plasmid is insertedinto animal or human cell and the effects are studied.
what is flagella made of ?
flagellin protein
what is pilli made of ?
pillin protein
what is the main structure of the cell wall?
peptidoglycan
how does penicillin antibiotic work?
by destroying enzyme responsible for peptidoglycan crosslinking ( DD-transpeptidase ) disabling it from crosslinking and forming the cell wall ,causing the bacteria to die.
what enzyme helps with peptidoglycan crosslinking in bacterial cell wall?
DD-transpeptidase / penicellin binding protein
what type of bacteria is penecillin most active against?
gram positive bacteria
why is the cell wall essential to the cells survival ?
because without it the bacteria is vulnerable to outside water and molecular pressure
why is penicillin effective against gram positive but not gram negative bacteria ?
because gram positive has alot of peptidoglycan and breaking all of it down will destroy the cells defence . gram negative bacteria on the other hand dont have as much peptidoglycan and its cell walls are surrounded by a lipopolysaccharide layer that prevents antibiotic entry
