Structure of Prokaryotes

Question 1

cell wall

Answer 1

peptidoglycan, pollysaccharide+amino acids
or
murein

Question 2

whihc part is analogous to lysosome

Answer 2

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.

Question 3

nucleus

Answer 3

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.

Question 4

chromosome

Answer 4

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.

Question 5

peritrichous meaning

Answer 5

surrounded with flagella

Question 6

explain the 3 parts of flgaella

Answer 6

(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.

Question 7

what are types of pili

Answer 7

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.

Question 8

structure of pili

Answer 8

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.

Question 9

structure and func of glycocalyx

Answer 9

made of polysacchardes and polypeptides
Glycocalyx protects the bacteria from W.B.C. and also helps in colony
formation.

Question 10

types of plasmid

Answer 10

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

Question 11

what is photosynetheic structure

Answer 11

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

Question 12

photoautotrophic bactera

Answer 12

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

Question 13

explain chemoautotrophic

Answer 13

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

Question 14

respiration

Answer 14

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.

Question 15

who differentiate bacteria on the basis of staining

Answer 15

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.

Question 16

explain asexual repro in bacteria

Answer 16

(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

Question 17

explain sexual repro in bacteria

Answer 17

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.

Question 18

Important economic uses of bacteria

Answer 18

(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

Question 19

bacterial diseases

Answer 19

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

Question 20

describe bga

Answer 20

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

Question 21

different forms of bga

Answer 21

(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

Question 22

mucilagenous sheath

Answer 22

m/o mucopolysaccharides ( pectic acid)

Question 23

universal photosynthetic pigments

Answer 23

cholorophyll a, beta-carotene

Question 24

what are hetrocysts

Answer 24

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.

Question 25

reproduction if bga

Answer 25

(i) binary fission ins spirulina
(ii) fragmentation in nostoc
(iii) spore formation
in unfavourable conditions
akinete formation in nostoc

Question 26

describe archaebacteria

Answer 26

(i) they are primitive first organisms to be on earth
(ii)mostly anerobic
(iii) thermococcus, methanococcus, methanobacterium, contain proteins homologous to eukarytoic core histones
(iv) cell wall= polysaccharide and complex polypeptide
(v) their cell membrane has one layer of branched chain lipids while cell membrqane of eubacteria have onyl straight chain lipids. This gives them high resistance

Question 27

where are methanogens found

Answer 27

These bacteria convert CO2 of swampy areas (marshy) into methane
(CH4).
e.g. Methanococcus, Methanomicrobium
 These bacteria convert the organic substance (cellulose) present in cow
dung into methane by fermentation.
 An archaebacterium is found in the rumen or gut of cattles as a symbiont
where it digests the cellulose by fermentation and convert it into
methane.

Question 28

mycoplasma

Answer 28

(i) joker of plant kingdom- because bfr they were placed in plant kingdom and removed after discovery of cell wall absence

(ii) joker of microbiology- exhibit pleomorphism( ability to exist in many life forms)

(iii)osmotrophic mode of nutrition( aborbs food by osmosis)

(iv) resistant to antibiotics like penicillin which act on cell wall while they are sensitive to antibiotics acting on metabolic activities

(v)repro thru binary fission

(vi) can survive w/o oxygen

vii) saprophytic/parasitics

Question 29

which bga helps in reclamation of soil

Answer 29

reclamation- improving soil quality
-> nostoc

Question 30

(i) free living aerobic bacteria capable of fixing nitrogen

(ii) free living anaerobic bactera

Answer 30

(i) azotobacter

(ii) clostridium botulinum

Question 31

which one fizes carbon dioxide in carbohydrates

Answer 31

rhodospirillum

Question 32

what is the cell wall of pathogenic bacteria

Answer 32

both gram +ve or -ve

Question 33

anabaena symbiosis

Answer 33

it is present on the leaves of azolla and in the corlloid roots of cycas

Question 34

why are there many holes in swiss cheese

Answer 34

the large holes in swiss
cheese are due to production of a large amount of CO2 by a bacterium named
Propionibacterium sharmanii.

Question 35

how is spreptokinase made? what it is used for

Answer 35

Streptokinase produced by the bacterium Sterptococcus and modified by genetic
engineering is used as a clot buster for removing clots from the blood vessels of patients.

Question 36

What kind of antibiotics are mycoplasma resistant to

Answer 36

Antibiotics such as beta-lactams-penicillin,
methicillin, cephalosporin-and non-beta-lactams such as vancomycin, attack the peptidoglycan cell wall to quell bacterial infections.

Antibiotics like chloramphenicol and tetracycline still affect mycoplasma

Mycoplasma has trilateral cell membrane
.it is a facultative parasite

Question 37

The cells of the bacterium Streptococcus remain arranged in the form of

Answer 37

chain