TNPSC Free Notes Biology

இந்தக் கட்டுரையில், TNPSC குரூப் 1, குரூப் 2, குரூப் 2A, குரூப் 4 மாநிலப் போட்டித் தேர்வுகளான TNUSRB, TRB, TET, TNEB போன்றவற்றுக்கான முறைகள் இலவசக் குறிப்புகளைப் பெறுவீர்கள்.தேர்வுக்கு தயாராவோர் இங்குள்ள பாடக்குறிப்புகளை படித்து பயன்பெற வாழ்த்துகிறோம்.

Human Disease

Immunology:
• A study of the immune system is known as Immunology.
• The Latin term “Immunis”, meaning “exempt” or “freedom”, gave rise to the
English word immunity.
• It refers to all the mechanisms used by the body for protection from
environmental agents that are foreign to the body.
• These agents may be microorganisms or their products, certain food items,
chemicals, drugs and pollen grains.
• Immunity is of two types:

▪ Innate immunity and
▪ Acquired immunity.
A. Innate Immunity (Non-specific):
• Innate immunity comprises all those natural defense mechanisms with which an
organism is protected from infection.
• This is the first line of defence in most animals.
• Innate immunity consists of the following four types of barriers. They are,
Anatomical Barriers:
• These barriers block the entry of organisms into the body.
• The skin and the mucous membrane lining the respiratory and intestinal as well
as the reproductive passages constitute the barriers.
Physiological Barriers:
• Factors like body temperature, pH and various body secretions, prevent the
growth of pathogenic micro-organisms.
• For example, fever response inhibits growth of many pathogens.
• Acidity of the stomach contents due to HCl secretion kills ingested micro-
organisms.
• Lysozyme present in secretions, such as tears and saliva, digest bacterial cell
walls.
• Certain cells, like WBC, when infected with a virus, respond by releasing
antiviral proteins, called interferons
Phagocytic Barriers:
• Phagocytosis is an important mechanism of innate immunity.
• It is performed by leucocytes. In response to pathogenic infections, the total count
of leucocytes will increase sharply.
• Humans contain wandering phagocytes that circulate throughout the body.
• The most important phagocytes are the macrophages and the neutrophils
Inflammatory Barriers:

• Usually, an infection or tissue injury results in redness and swelling, along with
pain and production of heat that may result in fever. The above phenomenon is
known as inflammatory response.
• This response occurs due to release of chemical alarm signals, notably histamine,
serotonin and prostaglandins, by the damaged mast cells.
NK cells (T- Lymphocytes):
• Besides the phagocytes, natural killer cells (NK cells) (T Lymphocytes) kill
virus-infected cells and some tumour cells of the body by creating perforin-lined
pores in the plasma membrane of the target cells.
• These pores allow entry of water into the target cell, which then swells and
bursts.
B. Acquired Immunity (Specific immunity)
• Acquired immunity, also known as adaptive or specific immunity, is capable of
recognizing and selectively eliminating specific micro organisms.
• Acquired immunity is found only in verterbrates.
Viruses
• The word virus is derived from Latin meaning ‘Poison’.
• Viruses are sub-microscopic, obligate intracellular parasites.
• They have nucleic acid core surrounded by protein coat.
• Viruses in their native state contain only a single type of nucleic acid which may
be either DNA or RNA.
• The study of viruses is called Virology.
• An American Scientist obtained virus in crystallized form from infected tobacco
juice in the year 1935.
• He was jointly awarded “Nobel Prize” with Dr. J.H. Northrop for Chemistry in
1946.
Milestones in Virology
• 1796 Edward Jenner used vaccination for small pox
• 1886 Adolf Mayer demonstrated the infectious nature of Tobacco mosaic virus
using sap of mosaic leaves

• 1892 Dimitry Ivanowsky proved that viruses are smaller than bacteria
• 1898 M.W. Beijierink defined the infectious agent in tobacco leaves as
῾Contagium vivum fluidum’
• 1915 F.W.Twort identified Viral infection in Bacteria
• 1917 d’Herelle coined the term ‘Bacteriophage’
• 1984 Luc Montagnier and Robert Gallo discovered HIV (Human Immuno
Deficiency Virus)
Size and Shape
• Viruses are ultramicroscopic particles.
• They are smaller than bacteria and their diameter range from 20 to 300 nm. (1nm
= 10-9 metres).
• Bacteriophage measures about 10-100 nm in size. • The size of TMV is 300×20
nm.
• Generally viruses are of three types based on shape and symmetry
1. Cuboid symmetry – Example: Adenovirus, Herpes virus.
2. Helical symmetry – Example: Influenza virus, TMV.
3. Complex or Atypical – Example: Bacteriophage, Vaccinia virus.
Characteristic Features of Viruses
Living Characters
• Presence of nucleic acid and protein.
• Capable of mutation
• Ability to multiply within living cells.
• Able to infect and cause diseases in living beings.
• Show irritability.
• Host –specific
Non-living Characters
• Can be crystallized.
• Absence of metabolism.
• Inactive outside the host.
• Do not show functional autonomy.
• Energy producing enzyme system is absent.

Five types of virus
1. Zoophage – Animal virus
2. Phytophage- Plant Virus
3. Phycophage – Algal Virus
4. Mycophage – Fungal Virus
5. Bacteriophage – Bacterial
Virus Viral Diseases in Human
AIDS (Acquired Immune deficiency Syndrome)
• AIDS is a severe viral disease and caused by Human Immunodeficiency Virus
(HIV).
• It is a condition in which immune system fails and suppress the body’s disease
fighting mechanism.
• They attack the lymphocytes and the affected individual is prone to infectious
diseases.
• Dr. Suniti Solomon, pioneered HIV research and treatment in India.
• She set up the first voluntary testing and counselling centre and an AIDS
Research group in Chennai during 80’s.
• Her team was the first to document evidence of HIV infection in India in 1985
(First Indian AIDS patient in Chennai).
Transmission of HIV
1. HIV is transmitted generally by Sexual contact with infected person
2. Use of contaminated needles or syringes especially in case of intravenous drug
abusers
3. By transfusion of contaminated / infected blood or blood products
4. From infected mother to her child through placenta
Treatment of AIDS
Diagnosis:
The presence of HIV virus can be confirmed by Western Blot analysis or Enzyme
Linked Immunosorbent Assay (ELISA)

SARS (severe acute respiratory syndrome)
A contagious fatal respiratory illness caused by a coronavirus.
Hepatitis – B or Serum Hepatitis
• It occurs due to infection of hepatitis-B virus (HBV).
• The virus damages the liver cells causing acute inflammation and cirrhosis of
liver.
• It is transferred from infected mother to their babies or by sexual contact.
• It is also transmitted by contact with infected person’s secretions such as saliva,
sweat, tears, breast milk and blood.
• Symptoms observed are fever, loss of appetite, nausea, vomiting, yellowness of
eyes and skin, light coloured stools, itching of skin, headache and joint pain.
Prevention and Control
• The hepatitis B vaccine offers excellent protection against HBV.
• The vaccine is safe and highly effective.
Swine Flu
• Swine Flu first originated from pigs.
• It is caused by virus that affects pigs and has started infecting humans.
• The virus spreads through air.
• It affects the respiratory system.
• Influeuza virus H1N1 has been identified as the cause of this disease. It is
transmitted from person to person by inhalation or ingestion of droplets containing
virus from people sneezing or coughing.
• Fever, cough, nasal secretion,fatigue, headache, sore throat, rashes in the body,
body ache or pain, chills, nausea, vomiting and diarrhoea, and shortness of breath
are the symptoms associated with the disease.
Measles
• Rubeala virus
• It affects the respiratory tract
Symptoms

Eruption of small red spots, or rashes inn skin, cough, sneezing, redness of eye,
pneumonia, bronchitis are the symptoms.
Mumps
• Myxovirus parotidis
• Upper respiratory tract is affected.
• Enlargement of parotid gland, movement of jaw becomes difficult.
Chicken pox
• Varicella zoster virus
• Respiratory tract
• Eruptions of the skin, fever and uneasiness.
Plant viral diseases
• Bunchy top of Banana – Bunchy top virus
• Tobacco mosaic disease – Tobacco mosaic virus
• Cucumber mosaic disease – cucumber mosaic virus.

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