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

Question

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

A. Most water-soluble drugs

B. Bacteria and viruses

C. Glucose, oxygen, and carbon dioxide

D. Large proteins and peptides

Answer: Option C

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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The type of fruit that develops from a single flower with multiple carpels fused together is:

A. Multiple fruit

B. Aggregate fruit

C. Simple fruit

D. Accessory fruit

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Correct Answer: Option C

Explanation:
A simple fruit develops from a single ovary of a single flower, which may be a single carpel or fused carpels (e.g., tomato, peach). Aggregate fruits develop from separate carpels of one flower (e.g., strawberry). Multiple fruits from many flowers (e.g., pineapple).

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Question #2

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The structure that produces cerebrospinal fluid in the brain is the:

A. Choroid plexus

B. Pineal gland

C. Corpus callosum

D. Meninges

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Correct Answer: Option A

Explanation:
The choroid plexus, located in the ventricles of the brain, is a network of capillaries and ependymal cells that secretes cerebrospinal fluid (CSF). CSF cushions the brain, removes waste, and maintains chemical environment. Meninges are protective coverings, corpus callosum connects hemispheres, pineal secretes melatonin.

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Question #3

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The pressure that develops in roots due to active absorption of minerals and water is:

A. Root pressure

B. Wall pressure

C. Transpiration pull

D. Turgor pressure

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Correct Answer: Option A

Explanation:
Root pressure is the positive hydrostatic pressure developing in the xylem of roots due to active transport of ions into the vascular cylinder, drawing water osmotically. It can cause guttation in some plants. Transpiration pull is the main driving force for water ascent. Turgor pressure is the pressure of cell contents against the cell wall.

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