Structure of Prokaryotes Flashcards
cell wall
peptidoglycan, pollysaccharide+amino acids
or
murein
whihc part is analogous to lysosome
The space between cell wall and cell membrane is known as periplasmic space. This
space, is analogous (functionally same) to lysosome because in this space the
digestion of complex substance is done.
nucleus
In Prokaryotic cell, the nucleus is primitive. The nucleus of prokaryotes is also known
as incipient nucleus, genophore, nucleoid or fibrillar nucleus. Nuclear membrane is
absent around nucleus. It also lacks nucleolus.
chromosome
Prokaryotes also lack the true chromosome. Instead of it, a false chromosome is
present, which is made up of ds circular naked DNA and polyamines. This false
chromosome coils and forms the chromosomal region, which is known as nucleoid.
peritrichous meaning
surrounded with flagella
explain the 3 parts of flgaella
(i) basal body
It is the basal part of flagellum and rod shaped in structure.
It lies with in the cell wall and cell membrane
This proteinaceous rod shaped structure is surrounded by two pairs of
rings
(ii) hook
It connects the basal body to filament
It is the middle part of flagellum
(iii)
Longest portion and extends from the cell surface to the outside.
It is cylindrical hollow structure made up of protein monomers.
Each monomer is made up of Flagellin protein. Monomers are arranged
in spiral manner. Flagellin is a contractile protein.
what are types of pili
Longer pili are also known as ‘F’ pili or ‘sex’ pili. Longer pili occur in only donor
(F+ or male) bacteria and help in conjugation. These are absent in recipient
bacteria or female.
(c) The shorter pili take part in attachment to rocks in streams and to the host
tissue. These are also known as ‘infective’ pili or Fimbriae.
structure of pili
Every pilus is cylindrical hollow structure and composed of protein monomers.
Each monomer is made up of ‘pilin’ protein. Pilin is non-contractile protein.
Pili do not play role in motility.
structure and func of glycocalyx
made of polysacchardes and polypeptides
Glycocalyx protects the bacteria from W.B.C. and also helps in colony
formation.
types of plasmid
F-plasmid (fertility factor) – On the basis of presence or absence of ‘F’
plasmid, there are two types of bacteria.
(a) F – Cells, carrying ‘F’ plasmid, act as donor and are called F+ or male.
(b) F – Cells, lacking ‘F’ plasmid, act as recipient and are called F- or female.
When ‘F” plasmid is attached with main DNA, it is designated as Episome and
this type of cell is known as Hfr cell. (Hfr – Highly frequent recombinant) cell
R-factor - Resistance to certain antibiotics.
Ti plasmid- tumor inducing plasmid
what is photosynetheic structure
In bacterial cytoplasm many photosynthetic pigments are present.
In purple bacteria (sulphur & non-sulphur) : Bacteriochlorophyll a & b, bacteriopurpurin
In green sulphur bacteria : Bacteriochlorophyll a, Bacterioviridin
photoautotrophic bactera
These bacteria use light energy for food synthesis.
In bacterial photosynthesis H-donor is not water, so they do not release
oxygen during photosynthesis hence this is called Non-oxygenic
photosynthesis.
– Purple sulphur bacteria – e.g. Chromatium,gives s2 gas
– Green sulphur bacteria – e.g. Chlorobium, Thiothrix, gives s2
– Purple non sulphur bacteria – e.g. Rhodospirillum, Rhodopseudomonas,no s2
explain chemoautotrophic
Chemical energy is obtained by oxidation of chemical compounds
(Inorganic or organic)
e.g. - Nitrifying bacteria – They oxidise nitrogenous compounds and obtain
energy.
nitrogen –rhizobium—nh3—-nitrosomonas/nitrococcus—-no2—-nitrobacter—-no3
respiration
On the basis of respiration bacteria are of two types
Aerobic bacteria :-They use oxygen in respiration.
e.g. Azotobacter, Acetobacter aceti (it causes souring of wine), Clostridium tetani
Anaerobic bacteria :- They do not use oxygen in respiration.
e.g. Clostridium botulinum, Fermentation bacteria (Lactobacillus) except
Acetobacter aceti. Lactobacillus causes souring of milk.
who differentiate bacteria on the basis of staining
HC Gram differentiates into gram +ve and gram -ve bacteria
gram+ve bacteria retian crystal violet stain while gram -ve bacteria loose the crystal violet and take up saffranin when aceton/alcohol is added.
explain asexual repro in bacteria
(i) Binary Fission
during favourable conditions
through amitosis
cell divides into two cells due to
formation of a septum (partition) in the centre of the cell.
(ii) spore
Endospore formation occurs under unfavourable conditions.
It is a highly resistant structure. It is resistant to high temperature, radiations,
antibiotics and chemicals.
Endospore is highly resistant structure due to presence of Calcium-dipicolinate in
its thick wall.
Only one endospore is formed in a bacterial cell.
Endospore formation usually seen in** bacillus** type of bacteria
explain sexual repro in bacteria
Transformation –
Transfer of genetic material from one bacterium to another
bacterium through surrounding is called transformation.
Transformation in bacteria was discovered by Griffith.
Transduction : When the gene transfer process between two different
bacteria is carried out by virus (bacteriophage) called transduction.
Conjugation – Gene transfer by physical contact between two bacterial
cells.
Conjugation between F and F
First of all donor cell is attached to recipient cell with the help of
sex pili. Sex pili help in formation of conjugation tube.
The ‘F’ factor now replicates and the replica moves to F– through
conjugation tube.
Both the cells are then separated. Due to transfer of ‘F’ factor F–
cell now becomes F+ cell.
Important economic uses of bacteria
(i) Ammonification
They conert proteins in dead/decaying organisms to ammonia.
(ii) Nitrificayion
convert ammonia is nitrates and nitrites
(iii) coverting ammonia into amino acids and other nitrogenous cpds
this may be done symbiotically or asymbiotically
(iv) curdling of milk my lactobacillus
(v) genetic engineering ( e.coli/agrobacterium tumefaciens)
Nitrogen fixation:
These bacteria convert the atmospheric nitrogen into ammonia and then into
nitrogenous compounds like amino acids, nitrate or ammonium salts.
Symbiotically – Some bacteria live symbiotically and exhibit nitrogen fixation.
Rhizobium – found in the root nodules of legumes
Azorhizobium – found in the stem nodules of Sesbania plant
Azospirillum – found on root surface of cereals (eg. Wheat, Rice, Maize)
i.e., superficial symbiosis.
Frankia (Filamentous bacteria or actinomycetes) - It is found In root
nodules of non leguminous plant Casuarina and Alnus plants.
Asymbiotically – Some free living bacteria are present in soil and perform
nitrogen fixation.
e.g. Clostridium, Azotobacter, Azospirillum, Beijernickia, Rhodospirillum
bacterial diseases
a. Pathogenic bacteria causing damage to human
Disease
Bacteria
Cholera
Typhoid
Tetanus
Tuberculosis
– Vibrio cholerae
Salmonella typhi
–
–
Clostridium tetani
– Mycobacterium tuberculosis
b. Pathogenic bacteria causing damage to crops :-
Disease
Bacteria
Citrus canker
Crown gall disease
–
–
Bacterial leaf blight of rice –
Xanthomonas citri
Agrobacterium tumefaciens
Xanthomonas oryzae
describe bga
Cyanobacteria were the first organism that produced O2 on our earth.
(v) Cyanobacteria are photosynthetic prokaryotes.
(vi) Cyanobacteria have following pigments :-
Chlorophyll ‘a’ - green
Carotenoids – yellow
C - Phycocyanin - blue
C - Phycoerythrin – red
Note : B.G.A. are not always of blue-green colour. e.g. Trichodesmium is red
coloured.
The red colour of red sea is due to this alga.
they havw cyanophycean granules containing energy reserve like glycogen. have gas vcuoles
during rain it becomes slippery due to bga
different forms of bga
(i) unicellular- spirulina
(ii) colonies-anabena
(iii) filamentous
Some B.G.A. are filamentous. There are many cells arranged in
a row to form a filamentous body.
Note : The filament of B.G.A. is known as trichome.
e.g. Oscillatoria, Nostoc
mucilagenous sheath
m/o mucopolysaccharides ( pectic acid)
universal photosynthetic pigments
cholorophyll a, beta-carotene
what are hetrocysts
Special type of cells are found for nitrogen fixation in Nostoc and Anabaena known as
Heterocyst. Heterocyst is a thick walled, non green cell.
Heterocyst does not perform photosynthesis like other vegetative cells.
