This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Extracellular Matrix and Cell Interactions – Tight Junctions”.
1. Which of the following contains tight junctions?
Explanation: Tight junctions are present only in vertebrates, otherwise known as chordates. The invertebrates contain a junction called septate junction.
2. Which of the following is defined by the tight junctions?
a) Efficiency of drugs
b) Diffusion of drugs
c) Breakdown of drugs
d) Absorption of drugs
Explanation: The tight junctions take care of the permeability of the molecules through the cells. Thus the tight junction is responsible for the diffusion of the drugs through the cells.
3. Which of the following protein is present in large amount in tight junctions?
Explanation: The tight junctions contain the protein claudin in large amount followed by occluding and other proteins. The tight junctions are useful in the transport of materials.
4. The endocytosis happens in the apical surface and the exocytosis happens in the basolateral surface.
Explanation: The apical surface which is exposed to the lumen helps in the transport of materials inside the cell. The basolateral surface which is at the sides of the helps in the transport of materials outside the cell.
5. Leaky epithelium is present in bile ducts.
Explanation: Epithelium can either be tight or leaky. Leaky epithelium contains small gaps in between which allows water and solutes to pass. Bile ducts do not have a leaky epithelium however tubules of the nephron in the kidneys have leaky junctions.
6. Which of the following is the first observed tight junction proteins?
a) Zonula occludens – 1
b) Zonula occludens – β
c) Zonula occludens – A
d) Zonula occludens – α
Explanation: Zonula occludens – 1 was the first tight junction protein discovered in the year 1986, which is abbreviated as ZO-1. This has a molecular weight of 220kDa.
7. What is the radius of the tight junctions?
a) 3 Å
b) 4 Å
c) 5 Å
d) 6 Å
Explanation: The radius of the tight junction depends on the permeability of the materials which has to pass through it. The claudin based pores have a radius of 4 Å. This may vary with different types of proteins.
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