This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Extracellular Matrix and Cell Interactions – Gap Junctions and Plasmodesmata”.
1. Who discovered plasmodesmata?
c) J Rhodin
d) Van Beneden
Explanation: Plasmodesmata serves as a connective system between two plant cells and in some algal cells. These were first discovered by Strasburger in 1901. The discovery was aided by electron microscopic studies.
2. Gap junctions are otherwise known as plasmodesmata.
Explanation: Plasmodesmata and gap junctions are similar in function but they have difference in their structures. Gap junctions helps substance pass through the cell membranes while the plasmodesmata forms a connection between the two cells.
3. How many plasmodesmata are present in a plant cell?
Explanation: The plant cells have around 1000 plasmodesmata, which connects them with the neighboring cells. These plasmodesmata serves as a channel, which helps the transfer of materials from one cell to another.
4. Gap junctions are absent in __________
a) Sperm cells
b) Reproductive cells
c) Cardiac cells
d) Brain cells
Explanation: Gap junctions are absent in all the cell that are motile. Gap junctions are also absent in erythrocytes. These motile cells do not have a necessity for the passage of molecules or ions.
5. What is the gap junction in nerves called?
a) Chemical synapse
b) Electrical synapse
c) Post synapse
d) Pre synapse
Explanation: The nerves and the neurons have the gap junctions, which helps them in the transmission of electrical signals from one nerve cell to another called electrical synapse. These coexist with chemical synapse.
6. What is the diameter of a gap junction?
a) 2.2 – 3 nm
b) 3 – 3.2 nm
c) 1.2 – 2 nm
d) 0.2 – 2 nm
Explanation: The gap junctions have a wide diameter of about 1.2 – 2 nm. These gap junctions are capable of allowing molecules that are slightly larger than the normal sized ones.
7. What is the chemical formula for rotigaptide?
Explanation: Rotigaptide has a chemical formula of C28H39N7O9 which is shortly known as ZP-123. This is a drug which is now used to treat atrial fibrillation. This drug has shown to increase the conductance of gap junctions in cardiac muscle cells.
8. Which cell organelle covers the plasmodesmata of the cells?
c) Rough endoplasmic Reticulum
d) Smooth endoplasmic reticulum
Explanation: The plasmodesmata in exclusively present in plant cells. These are covered by the smooth endoplasmic reticulum of both the cells. This helps in the transport of materials across the cells.
9. Which genetic disorder is associated with dysfunction of gap junction?
a) Vohwinkel’s syndrome
b) Down’s syndrome
c) Zellweger Syndrome
d) Bubble Boy Syndrome
Explanation: Vohwinkel’s syndrome is a skin disease caused by a disorder in the gap junction. It is characterized by thick calluses in the palms of hands and foot. This disease is seen in the infant stages or early childhood.
10. Which of the following disease associated with the nervous system is caused by disorder in gap junctions?
a) Parkinson’s disease
b) Brain ischemia
Explanation: Brain ischemia, otherwise known cerebral ischemia where the blood flow to the brain is constricted. The gap junctions are unable to provide oxygen thus the brain undergoes hypoxia. This situation is permanent if it is untreated for prolonged time.
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