intracellular digestion

(noun)

Intracellular digestion is a form of digestion which takes place within the cytoplasm of the organism. Intracellular digestion takes place in animals without a digestive tract, in which food items are brought into the cell for digestion.

Related Terms

Examples of intracellular digestion in the following topics:

  • Invertebrate Digestive Systems

    • Invertebrates can be classified as those that use intracellular digestion and those with extracellular digestion.
    • The simplest example of digestion intracellular digestion, which takes place in a gastrovascular cavity with only one opening.
    • The food particles are engulfed by the cells lining the gastrovascular cavity and the molecular are broken down within the cytoplasm of the cells (intracellular).
    • Because the food has been broken down exterior to the cells, this type of digestion is called extracellular digestion.
    • Their food is broken down in their digestive tract (extracellular digestion), rather than inside their individual cells (intracellular digestion).

  • Extracellular Immune Avoidance

    • Bacteria usually overcome physical barriers by secreting enzymes that digest the barrier in the manner of a type II secretion system.
    • Some pathogens avoid the immune system by hiding within the cells of the host, a process referred to as intracellular pathogenesis.

  • The Deltaproteobacteria

    • A pathogenic intracellular Deltaproteobacteria has recently been identified.
    • Individuals benefit from aggregation as it allows accumulation of extracellular enzymes which are used to digest food.

  • Proteolytic Degradation

    • However, proteolytic degradation can also occur utilizing various mechanisms, including intramolecular digestion and non-enzymatic methods.
    • The mechanisms of proteolytic degradation are necessary for obtaining amino acids via degradation of digested proteins, preventing accumulation or abnormal concentrations of proteins, and by regulating cellular processes by removing proteins no longer needed.
    • The intracellular process that utilizes lysosomes involves autophagy.

  • Common Bacterial Traits

    • In addition, they grow in organic matter and the live bodies of plants and animals, providing outstanding examples of mutualism in the digestive tracts of humans, termites, and cockroaches.
    • Bacteria do not tend to have membrane-bound organelles in their cytoplasm and thus contain few large intracellular structures.
    • Small size is extremely important because it allows for a large surface area-to-volume ratio which allows for rapid uptake and intracellular distribution of nutrients and excretion of wastes.

  • Natural Killer Cells

    • T cells are lymphocytes that mature in the thymus gland and identify intracellular infections, especially from viruses, by the altered expression of major histocompatibility class (MHC) I molecules on the surface of infected cells.
    • A granzyme, a protease that digests cellular proteins, induces the target cell to undergo programmed cell death, or apoptosis.
    • Phagocytic cells then digest the cell debris left behind.

  • Ecological Associations Among Microorganisms

    • These include organisms such as Myxococcus xanthus, which forms swarms of cells that kill and digest any bacteria they encounter.
    • Other bacterial predators either attach to their prey in order to digest them and absorb nutrients, such as Vampirococcus, or invade another cell and multiply inside the cytosol, such as Daptobacter.
    • Other organisms invariably cause disease in humans, such as the Rickettsia, which are obligate intracellular parasites able to grow and reproduce only within the cells of other organisms.
    • Chlamydia, another phylum of obligate intracellular parasites, contains species that can cause pneumonia, or urinary tract infection and may be involved in coronary heart disease.

  • Cell-Mediated Immunity

    • First, an antigen-presenting cell (APC, such as a dendritic cell or a macrophage) detects, engulfs (via phagocytosis in the case of macrophages or by entry of the pathogen of its own accord in the case of dendritic cells), and digests pathogens into hundreds or thousands of antigen fragments.
    • TC cells attempt to identify and destroy infected cells by triggering apoptosis (programmed cell death) before the pathogen can replicate and escape, thereby halting the progression of intracellular infections.
    • MHC I complexes display a current readout of intracellular proteins inside a cell and will present pathogen antigens if the pathogen is present in the cell.
    • An antigen-presenting cell (APC), such as a macrophage, engulfs a foreign antigen, partially digests it in a lysosome, and then embeds it in an MHC class II molecule for presentation at the cell surface.

  • Chemical Buffer Systems

    • Outside the acceptable range of pH, proteins are denatured and digested, enzymes lose their ability to function, and death may occur.
    • Extracellular buffers include bicarbonate and ammonia, whereas proteins and phosphate act as intracellular buffers.

  • The lac Operon: An Inducer Operon

    • The lac operon encodes the genes necessary to acquire and process the lactose from the local environment, which includes the structural genes lacZ, lacY, and lacA. lacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose. lacY encodes β-galactoside permease (LacY), a membrane-bound transport protein that pumps lactose into the cell. lacA encodes β-galactoside transacetylase (LacA), an enzyme that transfers an acetyl group from acetyl-CoA to β-galactosides.
    • The cell can use lactose as an energy source by producing the enzyme b-galactosidase to digest that lactose into glucose and galactose.