In the human body, the 'Blood-Brain Barrier' (BBB) is highly selective. Which of the following substances can easily cross the BBB? MCQ with Answer and Explanation

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In the human body, the 'Blood-Brain Barrier' (BBB) is highly selective. Which of the following substances can easily cross the BBB?

A. Large proteins and peptides

B. Glucose, oxygen, and carbon dioxide

C. Bacteria and viruses

D. Most water-soluble drugs

Answer: Option B

Solution (By JKSSB Mock Tests)

The Blood-Brain Barrier (BBB) is formed by tight junctions between endothelial cells in brain capillaries, making it highly selective. It allows the free diffusion of small, lipid-soluble molecules and essential gases. Therefore, oxygen, carbon dioxide, and lipid-soluble substances (like alcohol, nicotine, and some anesthetics) easily cross. Glucose, a water-soluble molecule essential for brain energy, crosses via specific carrier-mediated transport (GLUT1 transporters). Large proteins, peptides, most water-soluble drugs, and pathogens like bacteria and viruses are generally blocked from entering the brain parenchyma.

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Question #1

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In the human body, the 'Medulla oblongata' is a vital part of the brainstem that controls involuntary functions such as:

A. Balance and coordination

B. Heartbeat, breathing, and blood pressure

C. Memory and learning

D. Vision and hearing

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Correct Answer: Option B

Explanation:
The medulla oblongata is the lowest part of the brainstem, connecting the pons to the spinal cord. It contains vital autonomic centers that control essential, involuntary life-sustaining functions. These include the cardiovascular center (regulating heart rate and blood vessel diameter), the respiratory center (regulating the rate and depth of breathing), and reflex centers for vomiting, coughing, sneezing, and swallowing. Damage to the medulla is often fatal due to the cessation of these vital functions.

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Question #2

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The technique of producing many identical copies of a plant from a single tissue is:

A. Selective breeding

B. Hybridization

C. Cross-pollination

D. Tissue culture (micropropagation)

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Correct Answer: Option D

Explanation:
Tissue culture (micropropagation) involves growing plant cells/tissues on a sterile nutrient medium to regenerate whole plants, producing clones. Hybridization is crossing varieties, cross-pollination is natural or artificial pollination, selective breeding chooses parents.

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Question #3

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Consider the following statements about enzymes:
1. They are biological catalysts.
2. They are consumed in the reaction.
3. They lower the activation energy of reactions.
Which of the above is/are correct?

A. 1, 2, and 3

B. 1 and 2 only

C. 2 and 3 only

D. 1 and 3 only

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Correct Answer: Option D

Explanation:
Enzymes speed up reactions by lowering activation energy and are not consumed; they remain unchanged after the reaction. Thus, statement 2 is false. 1 and 3 are correct.

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