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5.1: Case Study - The Importance of Cells

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  • Case Study: More Than Just Tired

    We all get tired sometimes, especially if we have been doing a lot of physical activity like these hikers. But for Jasmin, a 34-year-old former high school track star who is now a recreational runner, his tiredness was going far beyond what he thought should be normal for someone who is generally in good physical shape. He was experiencing extreme fatigue after his runs, as well as muscle cramping, spasms, and an unusual sense of heaviness in his legs. At first, he chalked it up to getting older, but his exhaustion and pain worsened to the point where this former athlete could no longer run for more than a few minutes at a time. He also began to experience other unusual symptoms, such as blurry vision and vomiting for no apparent reason.

    tired people lying on the side of road
    Figure \(\PageIndex{1}\): (CC BY 2.0; Dace Kiršpile via

    Concerned, he went to his doctor. His doctor ran many tests and consulted with several specialists. After several months, Jasmin is finally diagnosed with a mitochondrial disease. Jasmin is surprised. He has an 8-year-old niece with a mitochondrial disease, but his niece’s symptoms started when she was very young, and included seizures and learning disabilities. How can Jasmin have the same disease but different symptoms? Why did he not have problems until adulthood while his niece had symptoms at an early age? And what are mitochondria anyway?

    Chapter Overview: Cells

    As you will learn in this chapter, mitochondria are important structures within our cells. This chapter will describe cells, which are the basic unit of structure and function in all living organisms. Specifically, you will learn:

    • How cells were discovered, their common structures, and the principles of cell theory.
    • The importance of size and shape in the functions of cells.
    • The differences between eukaryotic cells (such as those in humans and other animals) and prokaryotic cells (such as bacteria).
    • The structures and functions of parts of cells including mitochondria, the plasma membrane, cytoplasm, cytoskeleton, nucleus, ribosomes, Golgi apparatus, endoplasmic reticulum, vesicles, and vacuoles.
    • How the processes of passive and active transport move substances into and out of cells and help maintain homeostasis.
    • How organisms obtain the energy needed for life, including how the sugar glucose is broken down to produce ATP through the processes of aerobic cellular respiration and anaerobic respiration.

    As you read this chapter, think about the following questions related to Jasmin’s disease:

    1. What are mitochondria? What is their structure, function, and where did they come from during evolution?

    2. Why are fatigue and “exercise intolerance,” such as Jasmin’s extreme exhaustion after running, common symptoms of mitochondrial diseases?

    3. Why do you think Jasmin has symptoms that affect so many different parts of his body including his legs, eyes, and digestive system?