myoglobin and by displacing the oxygen
haemoglobin dissociation curve to the
left.
- (a) Assertion and reason both are
correct and reason is the correct
explanation of assertion. HIV is a
retrovirus that attacks helper T-cells.
These helper T-cells stimulate antibody
production by B-cells. Thus, a loss of
natural defence against pathogens is
observed.
- (c) Toxoids are inactivated toxins
and used as vaccines against many
diseases, e.g. tetanus toxoid, diphtheria
toxoid. These toxoids are directed at the
toxins produced by a pathogen.
23.(d) Both assertion and reason are
false. Sarcomas are located in
connective and muscular tissues
derived from mesoderm. About 80% of
all tumours are carcinomas.
- (c) Lysozyme is present in tissue
fluids and in almost all secretions
except cerebrospinal fluid, sweat and
urine. It attacks bacteria and dissolves
their cell wall. It is found in saliva and
tears also.
- (e) Interferons are cytokines which
act as chemical messengers of immune
cells. They provide protection against
viral infections.
- (e) Effector B-cells or plasma
B-cells are produced by the
differentiation of some activated
B-cells. These plasma cells live for only
a few days, but secrete enormous
amounts of antibody during this period.
- (c) Alcohol is a depressant to the
brain. It affects cerebrum. As a result
person loses judgement, self control and
willpower. It is followed by the adverse
affect on cerebellum due to which
co-ordination of muscles is lost.
- (a) Haptens are unable to induce
antibody production by themselves.
However, when they combine with some
larger molecules (usually proteins)
which serve as carriers, they can induce
formation of antibodies.
- (b) Antigens carry epitopes. Each
Y-shaped antibody can get attached to a
specific epitope on an antigen. This
combination is very much like the lock
and key analogy. Thus, assertion and
reason both are correct, but reason is
not the correct explanation of assertion.
- (e) IgA is the second most abundant
class of antibodies. It is mainly found in
sweat, tears, saliva, mucus, colostrum,
etc. IgA has a polypeptide called as
J (joining)-chain.- (e) ‘A’ is the flower of Datura. Seeds of
Datura are misused for their hallucino-
genic properties. These drugs change
one’s behaviour, thoughts, feelings and
perceptions without any actual sensory
stimulus. They produce a dream like state. - (e) The non-communicable diseases
remain confined to the persons who
suffer from them. These are not
transmitted from the infected persons to
other persons. Diabetes mellitus is
non-communicable disease. This is the
most common endocrine disorder of the
pancreas. The insulin-dependent diabetes
mellitus is caused by a failure of the
β-cells to produce adequate amounts of
insulin due to an autoimmune response. - (a) The part ‘B’ is known as Fc region,
i.e. fragment crystallisable. It is named so,
because it crystallises in cold storage. - (b) In India, filariasis is usually
caused by Wuchereria bancrofti and
Wuchereria malayi. It is transmitted from
one individual to the others by female
Culex mosquitoes. The worms live in the
lymphatic system. - (e) Lymph nodes and spleen are
secondary lymphoid organs. In primary
lymphoid organs T-lymphocytes and
B-lymphocytes mature and acquire their
antigen specific receptors. In secondary
lymphoid organs they undergo
proliferation and differentiation. - (a) Detection and diagnosis of cancer
depend upon histological features of
malignant structure. MRI is used in the
detection of cancer as pathological and
physiological changes in the living tissues
can be determined with its help. - (c) Barbiturates are derivatives of
barbituric acid. They are synthetic drugs
which are general depressants for all
excitable cells, but CNS (Central Neural
System) is most sensitive to these drugs.
These are taken to reduce anxiety and
induce sleep. - (a) ‘A’ is bone marrow and ‘B’ is
thymus, where maturation of respectively
B-lymphocytes and T-lymphocytes occurs.
Therefore, they are known as primary
lymphoid organs. - (c) IgM is about 5-10% of all
antibodies in the blood. It is the largest Ig
which is secreted first by the plasma cells.
It is also the earliest immunoglobulin to
be synthesised by the foetus. It cannot
cross placental barrier. - (d) Both assertion and reason are
false. TH 1 cells mostly activate cells
related to cellular immunity, viz; CD-8,
macrophages. TH 2 cells produce cytokines
and are associated with allergic reactions
or with response to certain parasite
infections. - (c) Arteriosclerosis is related to the
hardening and loss of elasticity of the
arteries. It causes hypertension. - (e) Malignant Tertian malaria is
caused by Plasmodium falciparum. Its
incubation period is about 12 days.
Recurrence of fever is after every
48 hours, i.e. every third day. - (b) Monocytes circulate in the
bloodstream for about 8 hours. In this
duration they enlarge and then migrate
into the tissues. In these tissues they
differentiate into specific macrophages.
Macrophages of liver cells are known as
Kupffer cells. - (a) Stimulants are drugs that
stimulate the nervous system. It makes a
person more wakeful, alert and active.
Caffeine is a CNS (Central Neural System)
stimulant. - (c) Hay fever is caused due to the
pollen of grasses, plants, etc. It is
characterised by the inflammation of the
membrane lining the nose. The symptoms
are sneezing , running or blocked nose and
watering eyes due to histamine release. - (e) Vaginal secretions form the first
line of defence. They are physiological
barriers. It is slightly acidic and
discourages microbial growth. It flushes
microbes out of vagina. - (b) Typhoid or enteric fever is caused
by Salmonella typhi. This pathogen is
found in the stool and urine. Therefore,
this is carried by water and contaminated
food. - (b) Primed cells or memory T-cells are
formed by T-lymphocytes as a result of
exposure to antigen and remain in the
lymphatic tissue. They can recognise
original invading antigens even years
after the first encounter. - (b) MALT (Mucosal Associated
Lymphoid Tissues) are aggregations of
lymphoid tissues, which are seen in
relation to the mucosa of the major tracts.
They constitute about 50% of the
lymphoid tissue in human body. They do
not serve as filters of lymph. - (b) Opioids are termed as analgesic,
i.e. pain killer. It relieves pain by acting on
the CNS (Central Neural System).