Allergy in humans is a result of release of the following chemicals from the mast cells:
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- Histamine and Serotonin
- Adrenaline and Acetylcholine
- Dopamine and Nor-adrenalin
- Endorphins and GABA
The Correct Option is A
Solution and Explanation
Top Questions on human health and disease
- Samples of blood and urine of a sportsperson are collected before any sports event for drug tests.
(a) Why there is a need to conduct such tests?
(b) Name the drugs the authorities usually look for.
(c) Write the generic names of two plants from which these drugs are obtained.
- CBSE CLASS XII - 2025
- Biology
- human health and disease
Immunity in our body is of two types: (i) Innate immunity and (ii) acquired immunity. Innate immunity is a non-specific defence mechanism, whereas acquired immunity is pathogen-specific; it is called specific immunity too. Acquired immunity is characterised by memory. Antibodies are specific to antigens and there are different types of antibodies produced in our body: they are IgA, IgE, IgG and IgM. It shows primary response when it encounters the pathogen for the first time and secondary response during the subsequent encounters with the same Antigen/Pathogen.
(a) Name the two types of specialised cells which carry out the primary and secondary immune response.
(b) Why is the antibody-mediated immunity also called as humoral immune response?
Attempt either sub-part (c) or (d):
(c) The organ transplants are often rejected if taken from suitable compatible persons.
(i) Mention the characteristic of our immune system that is responsible for the graft rejection.
(ii) Name the type of immune response and the cell involved in it.
OR
(d) How is active immunity different from passive immunity?- CBSE CLASS XII - 2025
- Biology
- human health and disease
Student to attempt either option (A) or (B).
(A) Describe any two situations where a medical doctor would recommend injection of pre-formed antibodies (antitoxins) into the body of a patient.
OR
(B) The symptoms of malaria do not appear immediately after the entry of sporozoites into the human body when bitten by female Anopheles mosquito. Explain why it happens.- CBSE CLASS XII - 2025
- Biology
- human health and disease
- Assertion (A): Streptococcus pneumoniae and Haemophilus influenzae are responsible for causing infectious disease in human beings.
Reason (R): A healthy person acquires the infection by inhaling the aerosols released by an infected person.- CBSE CLASS XII - 2025
- Biology
- human health and disease
- The decrease in the T-Lymphocytes count in human blood will finally result in
- CBSE CLASS XII - 2025
- Biology
- human health and disease
Questions Asked in CBSE CLASS XII exam
(a) Calculate the standard Gibbs energy (\(\Delta G^\circ\)) of the following reaction at 25°C:
\(\text{Au(s) + Ca\(^{2+}\)(1M) $\rightarrow$ Au\(^{3+}\)(1M) + Ca(s)} \)
\(\text{E\(^\circ_{\text{Au}^{3+}/\text{Au}} = +1.5 V, E\)\(^\circ_{\text{Ca}^{2+}/\text{Ca}} = -2.87 V\)}\)
\(\text{1 F} = 96500 C mol^{-1}\)- CBSE CLASS XII - 2025
- Electrochemistry
Define the following:
(i) Cell potential
(ii) Fuel Cell- CBSE CLASS XII - 2025
- Electrochemistry
Calculate the emf of the following cell at 25°C:
\[ \text{Zn(s)} | \text{Zn}^{2+}(0.1M) || \text{Cd}^{2+}(0.01M) | \text{Cd(s)} \] Given: \[ E^\circ_{\text{Cd}^{2+}/\text{Cd}} = -0.40 \, V, \, E^\circ_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \, V \] \[ [\log 10 = 1] \]- CBSE CLASS XII - 2025
- Electrochemistry
Write chemical equations of the following reactions:
(i) Phenol is treated with conc. HNO\(_3\)
(ii) Propene is treated with B\(_2\)H\(_6\) followed by oxidation by H\(_2\)O\(_2\)/OH\(^-\)
(iii) Sodium t-butoxide is treated with CH\(_3\)Cl- CBSE CLASS XII - 2025
- Alcohols, Phenols And Ethers
Give a simple chemical test to distinguish between butan-1-ol and butan-2-ol.
- CBSE CLASS XII - 2025
- Alcohols, Phenols And Ethers