Cell Compartmentalization

5 Key excerpts on "Cell Compartmentalization"

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  eBook - ePub

  Microcompartmentation

  • D.P. Jones(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  V. Overview: Physiological Significance of Functional Compartmentation of Metabolism

  Subcellular compartmentation attributable to the various cellular organelles, mitochondria, golgi, etc., has been generally accepted for some time. Compartmentation of the cytosol itself, with less distinct structures and boundaries, is still a controversial hypothesis.12 We have summarized evidence from our laboratories and others which clearly demonstrates that in a variety of tissues, a functional compartmentation of metabolism can be observed in a number of circumstances. By this we mean that a number of pathways for the transformation of metabolic energy via the synthesis of ATP, which have been traditionally viewed as being nonlocalized in the cytosol, appear to be coordinated with the energy requirements of specific endergonic processes, which are known to be localized within the cell. The clearest example is the association of glycolysis with Na-pump activity and glycogenolysis with actin-myosin interactions in some vascular smooth muscles. The independence of these pathways and the lack of mixing of their intermediary metabolites argues for some form of cytosolic compartmentation. The major questions, of course, are how is this apparent compartmentation achieved and what, if any, are the advantages of this organization to the cell.

  There are two aspects that have circumscribed our thinking in terms of potential structural bases underlying functional compartmentation. First, is that the observed compartmentation is never absolute. In the absence of glucose, for example, normal ionic gradients can be maintained by the Na-pump in VSM. Similarly, the labeled and unlabeled metabolites of glycolysis and glycogenolysis appear to freely mix within the cell under anaerobic conditions. These observations suggest that the observed compartmentation is not the result of any permanent barrier structures. This would be consistent with dynamic structural elements, as suggested for the assembly-disassembly associated with actin polymerization.34

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  eBook - PDF

  Principles of Anatomy and Physiology for Nursing and Healthcare Students in Australia, 1st Edition

  • Ian Peate, Suzanne Evans, Amy Byrne, Will Deasy, Michele Dowlman, Pauline Gillan, Siva Purushothuman, Dan Wadsworth(Authors)
  • 2021(Publication Date)
  • Wiley

    (Publisher)

  CHAPTER 2 Cells, cellular compartments, transport systems, fluid movement between compartments TEST YOUR PRIOR KNOWLEDGE • Where do cells come from? • What, approximately, is the average size of a human cell? • What are the various forms human cells can take? • How are human cells taken and examined for diagnostic purposes? • An understanding of cell biology is particularly vital for finding a cure for which group of diseases? LEARNING OBJECTIVES After reading this chapter you will be able to: 2.1 describe the functions of the major cell organelles 2.2 describe how the structure of the plasma membrane determines its permeability 2.3 list the various ways in which substances move into and out of cells 2.4 list the major differences in ionic composition between intracellular and extracellular compartments 2.5 predict the movements of water by osmosis, based on the circumstances, and explain the reason for its importance to living organisms. Introduction Cells are the basic structural and functional units that make up all living organisms. Some organisms, such as bacteria and protozoans, are unicellular, consisting of a single cell, but many are multicellular, made up of billions of cells sometimes, as in the case of humans. Multicellular animals possess a range of cells that are specialised to perform various special functions (figure 2.1) — these are some great examples of the relationship between anatomy and physiology (i.e. structure and function) that was introduced in the chapter on basic scientific principles of physiology. FIGURE 2.1 Examples of some cells of the human body Sperm cell Smooth muscle cell Nerve cell Epithelial cell Red blood cell Source: Tortora and Derrickson (2009). Reproduced with permission of John Wiley & Sons. 2.1 Inside the cell LEARNING OBJECTIVE 2.1 Describe the functions of the major cell organelles.

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  eBook - ePub

  Berne and Levy Physiology E-Book

  Berne and Levy Physiology E-Book

  • Bruce M. Koeppen, Bruce A. Stanton, Julianne M Hall, Agnieszka Swiatecka-Urban(Authors)
  • 2023(Publication Date)
  • Elsevier

    (Publisher)

  With a few exceptions (e.g., mature human red blood cells and cells within the lens of the eye), all cells within the human body contain a nucleus. The cell is therefore effectively divided into two compartments: the nucleus and the cytoplasm. The cytoplasm is an aqueous solution containing numerous organic molecules, ions, cytoskeletal elements, and a number of organelles. Many of the organelles are ­membrane-enclosed compartments that carry out specific cellular function. An idealized eukaryotic cell is depicted in Fig. 1.1, and the primary functions of some components and compartments of the cell are summarized in Table 1.1. Readers who desire a more in-depth presentation of this material are encouraged to consult one of the many textbooks on cell and molecular biology that are currently available. Fig. 1.1 Schematic drawing of a eukaryotic cell. The top portion of the cell is omitted to illustrate the nucleus and various intracellular organelles

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  eBook - ePub

  The Cell

  • Britannica Educational Publishing, Kara Rogers(Authors)
  • 2010(Publication Date)
  • Britannica Educational Publishing

    (Publisher)

  CHAPTER 3Cellular Organelles

  A cell with its many different DNA, RNA, and protein molecules is quite different from a test tube containing the same components. When a cell is dissolved in a test tube, thousands of different types of molecules randomly mix together. In the living cell, however, these components are kept in specific places, reflecting the high degree of organization essential for the growth and division of the cell. Maintaining this internal organization requires a continuous input of energy, because spontaneous chemical reactions always create disorganization. Thus, much of the energy released by ATP hydrolysis fuels processes that organize macromolecules inside the cell.

  THE RELATIVE VOLUMES OCCUPIEDBY SOME CELLULAR COMPARTMENTSIN A TYPICAL LIVER CELL

  When a eukaryotic cell is examined at high magnification in an electron microscope, it becomes apparent that specific membrane-bound organelles divide the interior into a variety of subcompartments. Although not detectable in the electron microscope, it is clear from biochemical assays that each organelle contains a different set of macromolecules. This biochemical segregation reflects the functional specialization of each compartment. Thus, the mitochondria, which produce most of the cell’s ATP, contain all of the enzymes needed to carry out the tricarboxylic acid cycle and oxidative phosphorylation. Similarly, the degradative enzymes needed for the intracellular digestion of unwanted macromolecules are confined to the lysosomes.

  It is clear from this functional segregation that the many different proteins specified by the genes in the cell nucleus must be transported to the compartment where they will be used. Not surprisingly, the cell contains an extensive membrane-bound system devoted to maintaining just this intracellular order. The system serves as a post office, guaranteeing the proper routing of newly synthesized macromolecules to their proper destinations.

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  Tortora's Principles of Anatomy and Physiology

  • Gerard J. Tortora, Bryan H. Derrickson(Authors)
  • 2017(Publication Date)
  • Wiley

    (Publisher)

  55 CHAPTER 3 In the previous chapter you learned about the atoms and molecules that compose the alphabet of the language of the human body. These are combined into about 200 different types of words called cells. All cells arise from existing cells in which one cell divides into two identical cells. Different types of cells fulfill unique roles that support homeostasis and contribute to the many functional capabilities of the human organism. As you study the various parts of a cell and their relationships to one another, you will learn that cell structure and function are intimately related. In this chapter, you will learn that cells carry out a dazzling array of chemical reactions to create and maintain life processes—in part, by isolating specific types of chemical reactions within specialized cellular structures. Although isolated, the chemical reactions are coordinated to maintain life in a cell, tissue, organ, system, and organism. Q Did you ever wonder why cancer is so difficult to treat? 3.1 Parts of a Cell OBJECTIVE • Name and describe the three main parts of a cell. The average adult human body consists of more than 100 trillion cells. Cells are the basic, living, structural, and functional units of the body. The scientific study of cells is called cell biology or cytology. Figure 3.1 provides an overview of the typical structures found in body cells. Most cells have many of the structures shown in this diagram. For ease of study, we divide the cell into three main parts: plasma membrane, cytoplasm, and nucleus. 1. The plasma membrane forms the cell’s flexible outer surface, sep- arating the cell’s internal environment (everything inside the cell) from the external environment (everything outside the cell). It is a selective barrier that regulates the flow of materials into and out of a cell. This selectivity helps establish and maintain the appropriate environment for normal cellular activities.

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