What are the infoldings of mitochondria called?

Appeared in: CIP Ranchi 2023

Explanation

Cristae are the specific anatomical term for the folds of the inner mitochondrial membrane.
The primary function of these folds is to significantly increase the surface area available for the processes of cellular respiration.
This increased surface area accommodates more proteins of the electron transport chain and ATP synthase, thereby maximizing the cell's capacity for ATP production.

Option A: Granules are small particles within a cell's cytoplasm, often used for storage (e.g., glycogen granules) or secretion. They are not structural folds of a membrane.
Option B: The spindle (or mitotic spindle) is a cytoskeletal structure that forms during cell division to segregate chromosomes. It is unrelated to the internal anatomy of a mitochondrion.
Option D: Thylakoids are membrane-bound compartments found inside chloroplasts, which are present in plant cells and some protists. They are the site of photosynthesis, not cellular respiration.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Structure of the Mitochondrion as background academic context rather than a clinical decision trigger.
Mitochondria are vital for cellular energy production, and their function is especially critical in high-energy-demand tissues like the heart, brain, and muscles.
Defects in the structure of cristae can impair the efficiency of the electron transport chain, leading to reduced ATP production. This is a hallmark of many mitochondrial diseases, which can cause a wide range of severe symptoms, including muscle weakness (myopathy), neurological problems, and heart failure.
What if? If a genetic mutation prevented the proper formation of cristae, the cell's energy output would be severely compromised. This would lead to cellular stress and dysfunction, particularly in tissues with high metabolic rates, resulting in a mitochondrial disease phenotype.

How to Approach the Question

This is a factual recall question from basic cell biology.
First, identify the key terms in the question: 'infoldings' and 'mitochondria'.
Access your knowledge about the structure of cellular organelles. Recall that the mitochondrion is unique for having two membranes.
Remember that the inner membrane is not smooth but is highly folded to increase its surface area.
Associate the specific term 'cristae' with these inner folds.
Briefly consider the other options to confirm their irrelevance: 'granules' are storage particles, 'spindle' is for cell division, and 'thylakoids' belong to chloroplasts.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 1 p. 44-46

E6 Anatomy Grays 43e Vol 1 Part 1 p. 37-39

Practise the full CIP Ranchi 2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.