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FSc Notes Biology Part 1 Chapter 6 Kingdom Prokaryotae (Monera)

  FSc Notes Biology Part 1 Chapter 6 Kingdom Prokaryotae (Monera)

Q 1. Differentiate between eubacteria and archacobacteria.
Ans. Eubacteria: Eubacteria (Greek of "true bacteria") and a much smaller division. Cell wall is of peptidoglycan or murein. for e.g E.Coli.
Archacobacteria: The archacobacteria (Greek for "ancient bacteria"). Cell wall is of protein, Glycoprotein. polysaccharide. for e.g Methanogenic bacteria.

Q 2. Who was the first scientist who discovered bacteria?
Ans. A dutch scientist "Antone Van Leeuwenhoek" (1673) was the first to report th microbes such as bacteria and protozoa.

Q 3. Leeuwenhoek observed bacteria in which substances?
Ans. He firstly observed small creatures in rainwater, then confirmed these in saliva, vinegar, infusions and other substances.

Q 4. Who formulated the germ theory of disease?
Ans. Robert Koch formulated the "germ theory of disease".

Q 5. Give the postulates of germ theory of disease.
Ans. The postulates of germ theory of disease are:
  1. A specific organism can always be found in association with a given disease.
  2. The organism can be isolated and grown in pure culture in laboratory.
  3. The pure culture will produce the disease when inoculated into susceptible animal.
  4. It is possible to recover the organism in pure culture from experimentally infected animals.

Q 6. What is flagella? What are the important functions performed by flagella?
Ans. Flagella: These are extremely thin, hair like appendages. They come out through cell wall and originate from basal body, structure just beneath the cell membrane in the cytoplasm. They are made up of protein flagellin.
Functions: Primary function of flagella is to help in motility. With the help of flagella, flagellate bacteria can also detect and move in response to chemical signals which is a type of behavior called as chemotaxis.

Q 7. Give classification on the basis of presence of flagella.
Ans. On basis of presence of flagella, pattern pf attachment of flagella and the number of flagella present bacteria are classified into different taxonomic groups:
Atrichous means bacteria are without any flagella.
When single polar flagellum is present then condition is known as monotrichous.
If tuft of flagella is present only at one pole of bacteria then these are lophotrichous flagella.
Amphitrichous is a condition when tuft of flagella at each of two poles is present.
In peritrichous form, flagella surround the whole cell.

Q 8. What is pilli? Describe its functions.
Ans.  Pilli: These are hollow, non-helical, filamentous appendages. Pilli are smaller than flagella and are not involved in motility. True pili are only present in gram-negative bacteria. They are made up of special protein called pilin.
  1. They are primarily involved in a mating process between cells called conjugation process.
  2. Some pili function as a means of attachment of bacteria to various surfaces.
Q 9. Who developed the technique of gram stain?
Ans. Christian Gram developed the technique of gram stain.

Q 10. Define cell envelope.
Ans. Collectively complexes of layer external to the cell protoplasm are called a cell envelope.

Q 11. Differentiate between capsule and slime.
Bacteria produce capsule, which is made up of repeating polysaccharides units, and of protein, or both, capsule is tightly bound to the cell. It has a thicker, gummy nature that gives sticky characters to colonies of encapsulated bacteria.
Some bacteria are covered with loose, soluble shield of macromolecules which is called as slime capsule and slime provides greater pathogenicity to bacteria and protects them against phagocytosis.

Q 12. Describe the function of cell wall.
Ans. It is a rigid structure. It determines the shape of bacterium. Cell wall also protects the cells from osmotic lysis.

Q 13. What is protoplast?
Ans. The plasma membrane and every thing present within it is known as protoplast.

Q 14. Differentiate between Gram-positive ans Gram-negative bacteria.
Ans. Characteristics          Gram-positive                       Gram-negative
         Staining                    It is stained purple                 It is stained pink
         No. of major layers           1                                            2
         Chemical make up    Peptidoglycan Techoic acid    Lipopolysaccharides
                                         Lipotechoic acid                    Lipoproteins peptidoglycan
                                         Lipids (1 - 4%)                      Lipids (11 - 12%)
         Overall thickness      20 - 80 nm                             8 - 11 nm
         Outer membrane       No                                        Yes
         Periplasmic space      Present in some                     Present in all
         Permeability              More permeable                    Less permeable

Q 15. List function that the cell membrane performs in bacteria.
Ans. The functions performed by cell membrane in bacteria are:
  1. Cell membrane performed regulates the transport of proteins, nutrients, sugar and electrons or other metabolites.
  2. The plasma membranes of bacteria also contain enzymes for respiratory metabolism.
Q 16. What are mesosomes? And what are some of their possible functions?
Ans. Mesosomes: The cell membrane, invaginates into the cytoplasm forming structure called as mesosomes. Mesosomes are in the form of vesicles, tubules or lamellae.
Functions: Mesosomes are involved in DNA replication and cell division where as some mesosomes are also involved in export of exocellular enzyme. Respiratory enzyme are also present on the mesosomes.

Q 17. Name a bacterium that has no cell wall?
Ans. Cell wall is only absent in mycoplasma.

Q 18. What is unique about the structure of bacterial ribosomes?
Ans. Ribosomes are composed of RNA and proteins. Some may also be loosely attached to plasma membranes. They are protein factories. There are thousands of ribosomes in each healthy growing cell. They are smaller then eukaryotic ribosomes. They are 70S, small unit of 30S and large of 50S.

Q 19. What are plasmids? What is the role played by the plasmids?
Ans. Many bacteria contains plasmid in addition to chromosomes. These are the circular, double stranded DNA molecules. They are self-replicating and are not essential for bacterial growth and metabolism. They often contain drug resistant, heavy metals, disease and insect resistant genes on them, Plasmids are important vectors, in modern engineering techniques.

Q 20. Name the substances that bacteria store.
Ans. Bacteria store glycogen, sulphur, fat and phosphate.

Q 21. Name the common waste materials of bacteria.
Ans. Common waste materials are alcohol lactic acid and acetic acid.

Q 22. Differentiate between autotrophic and heterotrophic bacteria.
Ans. Autotrophic Bacteria: Some kinds of bacteria are autotrophic i.e., they can synthesize compounds which are necessary for their survival from inorganic substances.
Heterotrophic Bacteria: Most bacteria are heterotrophic i.e., they cannot synthesize their organic compounds from simple inorganic compounds.

Q 23. Differentiate between saprophytic and parasitic bacteria.
Ans.  Saprophytic Bacteria: Saprophytic bacteria get their food from dead organic matter.
Parasitic Bacteria: Parasitic bacteria for their nutrition are fully dependent on their host.

Q 24. Differentiate between photosynthetic and chemo-synthetic bacteria.
Ans.  Photosynthetic Bacteria: Photosynthetic bacteria possess chlorophyll which differs from the chlorophyll of green plants.
 Chemo-synthetic bacteria: Nitrifying bacteria are chemo-synthetic. Chemosynthetic bacteria oxidize inorganic compounds like ammonia, nitrate, nitrite, sulphur on ferrous iron and trap energy thus released for their synthetic reaction.

Q 25. Differentiate between aerobic, anaerobic, facultative and microaerophillic bacteria.
Ans. Aerobic Bacteria: Bacteria, which are able to grow in the presence of oxygen, are called aerobic bacteria. Exp: Pseudomonas is an aerobic bacterium.
Anaerobic Bacteria: Bacteria, which can grow in the absence of oxygen are known as anaerobic bacteria. Exp: Spirochete is an anaerobic bacterium.
Facultative Bacteria: Facultative bacteria grow either in the presence or absence of oxygen. Exp: E.Coli is a facultative anaerobic bacterium.
Microaerophilic Bacteria: Some bacteria require a low concentration of oxygen for growth and are known as microaerophilic. Exp: Campylobacter is a microaerophilic bacteria.

Q 26. What is the type of asexual reproduction in bacteria?
Ans. Bacteria increase in number by an asexual means of reproduction, called binary fission. In binary fission parent cell enlarges, its chromosomes duplicates, and plasma membrane pinches inward at the center of the cell. When nuclear material has been evenly distributed, the cell wall grows inward to separate cell into two.

Q 27. Define generation time.
Ans. The interval of time until the completion of next division is known as generation time.

Q 28. Describe the four distinct phases recognized in bacterial growth curve.
Ans. Four distinct phases are recognized in bacterial growth curve:
Lag Phase:
It is the phase of no growth. Bacteria prepare themselves for division.
Log Phase:
It is the phase of rapid growth. Bacteria divide at exponential rate.
Stationary Phase:
Bacterial death rate is equal to bacterial rate of reproduction and multiplication.
Death/Decline Phase:
Bacteria start dying. Here the death rate is more than reproduction rate.

Q 29. What is the ecological importance of bacteria?
Ans. Bacteria are ecologically very important. They are highly adaptable as a group and are found nearly everywhere. They are able to decompose organic matter and play a significant role in the completion of cycles of nitrogen, phosphorous, sulphur and carbon.

Q 30. How many species of bacteria cause disease in human?
Ans. Approximately 200 species are known to cause disease in humans.

Q 31. What is the sterilization process?
Ans. The process in which we use physical agents to control bacteria/microorganisms is known as sterilization process. Sterilization is deduction of all life forms.

Q 32. How dry and moist heat are effective in killing bacteria?
Ans. Both dry and moist heat are effective. Moist heat cause coagulation of proteins and kills the microbes. Dry heat cause of oxidation of chemical constituents of microbes and kills them.

Q 33. How electromagnetic radiations are effective in killing bacteria?
Ans. Certain electromagnetic radiations below 300 nm are effective in killing of microorganisms. Gamma rays are in general used for sterilization process.

Q 34. How heat sensitive compounds are sterilized?
Ans. Heat sensitive compounds like antibiotics, sears, hormones etc., can be sterilized by means of membrane filters.

Q 35. Differentiate between antiseptic, disinfectants and chemotherapeutic agents?
Ans. Antiseptics: Chemical substances used on living tissues that inhibits the growth of microorganisms are called antiseptics.

Disinfectants: The important chemical agents used for disinfection are oxidizing and reducing agents. For example halogen and phenols, hydrogen peroxide, Potassium permanganate, alcohol and formaldehyde etc. inhibit the growth of vegetative cells and are used on non-living materials.

Chemotherapeutic Agents: Chemotherapeutic agents and antibodies work with natural defense and stop the growth of bacteria and other microbes. These are sulfonamides, tetracycline, penicillin, etc. They destroy or inhibit the growth of microorganisms in living tissues.

Q 36. Differentiate between microbicidal and microbistatic effect.
Ans. Microbicidal Effect: Microbicidal effect is one that kills the microbes immediately.
Microbistatic Effect: Microbistatic effect inhibits the reproductive capacities of the cells and maintains the microbial population at constant.

Q 37. Define antibodies.
Ans. Antibodies, substances that protect the host against infection sue to subsequent exposure to the virulent organism.

Q 38. What is hydrophobia?
Ans. Hydrophobia, or rabies, a disease transmitted to people by bites from rabid dogs, cats and other animals.

Q 39. What are antibodies?
Ans. Antibodies is a Greek word ANTI, against and BIOS, life. Antibodies are the chemotherapeutic chemical substances which are used in treatment of infectious diseases. Antibodies are synthesized and secreted by certain bacteria, antinomycetes and fungi.

Q 40. How misuse of antibodies effect human health?
Ans. Misuse of antibodies such as penicillin can cause allergic reactions. Streptomycin can affect auditory nerve thus causing deafness. Tetracycline and its related compounds cause permanent discoloration of teeth in young children.

Q 41. What are cyanobacteria?
Ans. The cyanobacteria are the largest and most diverse group pf photosynthetic bacteria which was previously known as "blue green algae". Cyanobacteria are true prokaryotes.

Q 42. What is the size of cyanobacteria?
Ans. They range in diameter from about 1 - 10 micro meter.

Q 43. How cyanobacteria exist in nature?
Ans. They may be unicellular, exist as colonies of many shapes, or form filaments consisting of trichomes surrounded by mucilaginous sheath.

Q 44. Describe locomotion in cyanobacteria?
Ans. They lack flagella and often use gas vesicles to move in the water, and many filamentous species have gliding motility.

Q 45. How the photosynthetic system of cyanobacteria resembles that of eukaryote?
Ans. Their photosynthetic system closely resembles that of eukaryotes because they have chlorophyll and photo-system II. They carry out oxygenic photosynthesis i.e. they use water as an electron donor and generate oxygen during photosynthesis.

Q 46. Differentiate between phycobilins and phycobilisomes.
Ans. Phycobilins: Cyanobacteria use phycobilins as necessary pigment.
Phycobilisomes: Photosynthetic pigments and electron transport chain components are located in thylakoid membranes linked with particles called phycobilisomes.

Q 47. What is phycocyanin?
Ans. Phycocyanin is a pigment-protein complex from the light-harvesting phycobiliprotein family. It is an accessory pigment to chlorophyll..

Q 48. How cyanobacteria reproduce?
Ans. Cyanobacteria reproduce by binary fission, fragmentation.
Q 49. What is the reserve food material in cyanobacteria?
Ans. The reserve food material in cyanobacteria is glycogen.
Q 50. What is the hormogonia?
Ans. Hormogonia are motile filaments of cells formed by some cyanobacteria in the order Nostocales and Stigonematales.
Q 51. Differentiate between heterocyst and akinetes.
Ans. Heterocyst: All cells in trichome are mostly similar in structure but at slightly large, round, light yellowish thick walled cells called as heterocyst.
Akinetes: Akinetes are thick walled, enlarged vegetative cells which accumulate food and become resting cells. On arrival of favorable conditions they form normal vegetative cells.

Q 52. What is super blue green algae?
Ans. Super blue green algae are basically expensive pond scum, in which cyanobacterium is a single called organism that produces its own food through photosynthesis. It serves as a "complete whole food" which contains 60% protein with all essential amino acids in perfect balance.
Q 53. What is nucleoid?
Ans. The nuclear material or DNA in bacterial cells occupies  position near to the center of the cell. This material is a single circular and double stranded DNA molecule. It aggregates as an irregular shaped dense area called nucleoid. This chromatin body is actually an extremely long molecule of DNA that is tightly folded so as to fit inside the cell component.

Q 54. How nucleoid is visible in light microscope?
Ans. It is visible in the light microscope after staining with Feulagen stain.

Q 55. What is the size of E.Coli chromosome?
Ans. Escherichia coil closed circle chromosome measures approximately 14,000 micro meter.

Q 56. Give the economic importance of cyanobacteria. 

Ans. Advantages of Cyanobacteria:

Reclamation of Alkaline Soils:
They help in the reclamation of alkaline soils.
Fixation of Nitrogen:
They have heterocysts which are helpful in the fixation of atmospheric nitrogen.
Photosynthetic Activity:
They release oxygen gas in environment due to their photosynthetic activity.
Pollution Indicator:
Oscillation and few other cyanobacteria can be used as pollution indicator.
Symbiotic Associations:
They have symbiotic relationships with protozoa, fungi and nitrogen fixing species from associations with angiosperms. They are photosynthetic partner in most of lichen association.

Disadvantage of Cyanobacteria:

Water Blooms:
Many species form water blooms where they often impart unpleasant smell and due to large amount of suspended organic matter water becomes unfit for consumption.

Q 57. Differentiate between spores and cyst.
Ans. Spores: Spores are metabolically dormant bodies, produced at a large stage of cell growth. They are resistant to change in light, pH,high temperature, dessication. They form vegetative cells.
Cyst: Cyst are thick walled, dormant dessication resistant forms and develop during differentiation of vegetative cells which can germinate. They are not heat resistant.

Q 58. What is the difference between photosynthesis in plants and photosynthesis in bacteria?
Ans. During photosynthesis the autotrophic bacteria utilize hydrogen sulphide instead of water as in plants as a hydrogen source ans liberate sulphur instead of oxygen.
In Bacteria:
CO2  +  2H2S ----------------> (CH2O)n  +  H2O  +  2S
In Plants:
6CO2  +  12H2O  ------------------> C6H12O6  +6O2   +  Energy
Q 59. How cell wall of archeobacteria differ from other bacteria or eubacteria?
Ans. The cell walls of most bacteria have a unique macromolecules called peptidoglycan. It also contains sugar molecules, techoic acid, lipoproteins and lipopolysaccharides which are linked to peptidoglycan. Whereas cell wall of archeobacteria do not contain peptidoglycan. Their cell walls are composed of proteins, glycoproteins and polysaccharides.

Q 60. Write shapes and plane of division of different bacterium?
Ans. Shapes of Bacteria:
  • Bacteria may be Cocci (Spherical or oval in shape), Bacilli (Rod shaped) and Spiral (curved/ spring shaped).
  • Some have characteristic shapes: others are pleomorphic (variable shape)
Type                         Shape                               Division
Coccus                      Spherical                           No
Diplococcus              Two cocci                          Single plane of division
Streptococcus           Cocci in chain                    Single plane of division
Staphylococcus         Irregular arrangement         Random planes
Tetrad                       Group of four                     Two planes of division
Sarcina                      Group of eight                   Three planes of division
Bacillus                      Rod shaped                       No
Diplobacillus              Two bacilli                         Single planes of division
Streplobacillus           Chain of bacilli                   Single planes of division
Spirals                       Spirally coiled                     No
Vibrio                        Comma shaped                  No
Spirillum                     Thick, rigid spiral               No
Spirochete                  Thin, flexible spiral             No
Q 61. Write down the range of different sizes of bacterium?
Ans. Size of Bacteria:
  Type:                                             Size:
Range                                               0.1 - 600 micro meter
Mycoplasma (smallest)                      100 - 200 nano meter
Escherichia coli                                  1.1 - 1.5 micro meter (width), 2.0 - 2.6 micro meter (length)
Spirochete                                         500 micro meter
Staphylococci and Streptococci          0.75 - 1.25 micro meter

Q 62. Name a bacterium that has no cell wall.
Ans. Mycoplasmas

Q 63. A gram stain of discharge from an abscess shows cocci in irregular, grape like clusters. What is the most likely genus of this bacterium?
Ans. Streptococci

Q 64. State the diameter of an average sized coccus shaped bacterium.
Ans. An average sized coccus bacterium has a diameter from 0.5 - 1.0 micro meter.

Q 65. Name several general characteristics that could be used to define the prokaryotes.
Ans. Characteristics of Prokaryotes:
  1. Organisms possessing prokaryotic cells are called prokaryotes e.g., bacteria and cyanobacteria.
  2. They lack many of the membranes bound structures e.g., mitochondria, endoplasmic reticulum, Golgi bodies and chloroplasts etc.
  3. Nuclear membrane is absent, therefore prokaryotic cell has no distinct nucleus.
  4. Prokaryotes have small sized ribosomes i.e., 70S.
  5. Mitosis is missing and cell divides by fission.
  6. The cell wall of prokaryotic cell is composed of polysaccharide chains bounded covalently to shorter chains of amino acids forming peptidoglycan or murein. The entire cell wall is often regarded as a single huge molecule or molecule complex called murein.
Q 66. Do any other microbial groups besides bacteria have prokaryotic cell?
Ans. Yes, Cyanobacteria.
Q 67. In what habitats are bacteria found? Give some general means by which bacteria derive nutrients.
Ans. "Bacteria are ubiquitous" it means that they are found everywhere in air, land, lakes , oceans, oil deposits, still ponds, ditches, running streams, rivers, in food, rubbish and manure heaps, decaying organic matter, plant roots, body surface and cavities, as well in intestinal tracts of man and animals.

General means of nutrition in Bacteria:

Photosynthetic Autotrophs: They utilize sunlight as a source of energy. They have chlorophyll like pigment which is dispersed in the cytoplasm. During photosynthesis they use hydrogen sulphide instead of water as hydrogen source and liberate sulphur instead of oxygen.
CO2  +  2H2S --------------> (CH2O)  +  H2O  +  2S
Chemosynthetic Autotrophs: They obtain energy from oxidation of some inorganic substances like ammonia, nitrogen, sulphur or iron.
Saprophytes: Saprophytic bacteria are those which get their food from dead organic matter.
Parasites: Parasitic bacteria are fully dependent in their host for their nutrition.

Q 68. List five functions that the cell membrane performs in bacteria.
Ans. Functions that cell membrane perform in bacteria:
  1. Give shape to bacteria.
  2. It protects bacteria.
  3. Homeostasis.
  4. Exocytosis.
  5. Endocytosis.
Q 69. What are mesosomes and some of their possible functions?
Ans. Mesosomes: The cell membrane invaginates into the cytoplasm forming a structure called mesosomes. Mesosomes are in the form of vesicles, tubules or lamellae, which may be central or peripheral in position. Central mesosomes are involved in DNA replication and cell division where as peripheral mesosomes are involved in export of exocellular enzyme.

Q 70. What is unique about the structure of bacterial ribosomes?
Ans. They are 70S smaller than eukaryotic ribosomes.

Written By: Asad Hussain