Question

A. Define intracellular digestion, extracellular digestion, and complete digestion. B. List at least one organism that has each type of digestion. C. List one way the systems are all similar. D. List one way they are all different from each other

Answer 1

A.INTRACELLULAR DIGESTION:Intracellular digestion, or cellular digestion, is the process in which large molecules, from outside or from a cell’s own metabolism, are broken down into smaller molecules within the cell. Products and wastes of intracellular digestion are either used by the cell or excreted.Intracellular digestion is classified into two types: heterophagic intracellular digestion and autophagic intracellular digestion.

• The organelles responsible for intracellular digestion are lysosomes. Lysosomes are vesicles that contain digestive enzymes capable of breaking down large molecules into smaller ones. These vesicles fuse with others carrying the material to be digested and, as a result, digestion takes place.
• Heterophagic intracellular :digestion is the breaking down into smaller substances of external substances brought into the cell via pinocytosis or phagocytosis. Phagosomes or pinosomes fuse with lysosomes to make digestive vacuoles. Within the digestive vacuoles, the molecules to be digested are hydrolyzed. The products of digestion either cross the membrane and reach the cytoplasm or remain inside the vacuoles. Vacuoles containing residues from digestion are called residual bodies. Via exocytosis, they fuse with the plasma membrane and release their “waste” externally.

• Autophagic intracellular :digestion is the internal cellular digestion of waste and residual materials. In general, it is carried out by lysosomes.

  Autophagic intracellular digestion is intensified in situations of starvation because under such conditions, the cell tries to obtain the nutrients necessary to stay alive from its own material components.

Extracellular digestion: is the process in which food is broken down into useful molecules that can be internalized by the cell. It is carried out in the extracellular space; that is, outside the cell. In extracellular digestion, cells secret substances that break down large molecules into smaller ones in the external environment. Later, the cell benefits from these products of digestion.

complete digestive :system is a digestive system that has different start and end points. Organs in the digestive system break down food into usable parts for the body and help us get energy. The other type of digestive system is an incomplete digestive system, which has the same opening for food and exit for waste.

B. Intracellular digestion example:Most organisms that use intracellular digestion belong to Kingdom Protista, such as amoeba and paramecium. Amoeba uses pseudopodia to capture food for nutrition in a process called phagocytosis. Paramecium uses cilia in the oral groove to bring food into the mouth pore which goes to the gullet.

• Extracellular digestion example:Fungi and other decomposers utilize nutrients derived from breaking down the substrate they grow on. Another example of extracellular digestion being used is in the hydra, or sea anemone. A large cavity, called the gastrovascular cavity, fills the center of the animal, with one opening for both food and waste.
• Complete digestion examples:complete digestive systems can get the most nutrients out of their food and keep eating, larger, more complex animals evolved. All mammals, like dogs, cats, and humans; reptiles, amphibians, fish, birds, and even insects have complete digestive systems.

C. In extracellular, intracellular or in complete digestion the mechanism of digestion is different but the end result of all the digestion process is absorbs nutrients to the body.

D. Intracellular degistion: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

• extracellular digestion: digestion occurs outside the body( gut).
• complete digestion:Digestion begins in the mouth, when we chew and swallow, and is completed in the small intestine.