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Question 3 : Which of the following combinations correctly describes the influence of certain metabolites on intracellular pH (pHi) regulation?
A. Lactose & pyruvate raise pHi; Amino acids lower it
B. Lactose & pyruvate lower pHi; amino acids balance it
C. Lactose & pyruvate have no effect on pHi; amino acids acidify the cell
D. All metabolites listed increase intracelluar pH
Correct answer: (b) Lactose & pyruvate lower pHi; amino acids balance it.
EXPLANATION
lactose and pyruvate, when metabolized, can lead to the production of lactic acid, which dissociates into lactate and hydrogen ions (H+), thereby lowering intracellular pH.
Amino acids contribute to pH regulation through their buffering capacity, helping to maintain pHi within a narrow range essential for cellular function
Given By Dr Ved Prakash
Question 2 : All the sperms in a man’s semen samples are found to be immotile. An IVF-ICSI is planned. On the day of OPU, the viable sperms were picked-up by hypoosmotic swelling test.
The routine practice is to immobilize the sperms before ICSI. In this case, the sperms are already immotile, do we still need to crush the tail?
A. No, why to bother!
B. Yes, always! No discrimination.
C. Maybe or maybe not, I’m not sure.
Correct answer: (b) Yes, always! No discrimination.
EXPLANATION
The purpose of crushing the tail of a sperm before ICSI is not limited to immobilizing it but also to ensure the plasma membrane is breached. ICSI bypasses the critical natural steps of fertilization, a breach in the plasma membrane of the sperms ensures the release of factors like PLCζ. These sperm factors are necessary for activating the oocytes by triggering the calcium oscillations in the oocyte. Without this activation, sperm fails to fertilize the oocyte.
In some cases, aid like artificial oocyte activation may also be required.
It is important to understand that plasma membrane must be properly disrupted. Experts often suggest a rigorous crushing of the tail (sometimes more than once). Moreover, PVP, along with the sperm, should be injected as little as possible. PVP can mask the sperm and hinders the release of the sperm factors into the ooplasm.
Given By Dr Sanjay Shukla
Question 1 : Which step in trophectoderm biopsy is biologically irreversible for the embryo?
A. Zona breaching
B. Cell aspiration
C. Laser-induced cell separation
D. Blastocoel collapse
Correct answer: C Laser-induced cell separation
EXPLANATION
Laser induced cell separation during trophectoderm biopsy is the only biologically irreversible step because it causes direct photothermal ablation of cellular membranes and intercellular junctions, resulting in permanent loss of viable embryonic cells.
At the cellular level, laser severing disrupts plasma membranes and junctional complexes, irreversibly removing trophectoderm cells from the embryonic architecture with no possibility of reintegration or functional compensation.
At the molecular level, localized laser energy exceeds the thermal tolerance of biological macromolecules, producing lipid bilayer rupture, irreversible protein denaturation, cytoskeletal depolymerization, permanent destruction of junctional proteins (cadherins, claudins, occludins), and uncontrolled ionic flux, collectively triggering immediate cell death and precluding recovery.
In contrast, zona breaching affects only the acellular zona pellucida, blastocoel collapse is a reversible biophysical fluid shift regulated by intact ion transport mechanisms, and cell aspiration remains reversible until membrane ablation occurs.
Therefore, laser-induced membrane severing alone crosses the molecular irreversibility threshold, making it the sole biologically irreversible event in trophectoderm biopsy.
Given by Dr Charu Dutt Joshi
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