Function of gut flora, which of the following is not the primary function of gut flora? (AIIMS NOV.2011)
|A||Fermentation of mucus|
|B||Synthesis of short chain fatty acids|
|C||Synthesis of vitamin K|
|D||Regeneration of the epithelium|
Research suggests that the relationship between gut flora and humans is not merely commensal (a non-harmful coexistence), but rather a symbiotic relationship.Though people can survive without gut flora, the microorganisms perform a host of useful functions,
a. producing vitamins for the host (such as biotin and vitamin K).
b. Bacteria turn carbohydrates they ferment into short chain fatty acids, or SCFAs
c. These materials can be used by host cells, providing a major source of useful energy and
i. nutrients for humans,as well as helping the body to absorb essential dietary minerals such as
ii. calcium, magnesium and iron.
d. Gases and organic acids, such as lactic acid, are also produced by saccharolytic fermentation.
i. Acetic acid is used by muscle, propionic acid helps the liver produce ATP, and butyric acid
ii. provides energy to gut cells and may prevent cancer.
e. Another, less favorable type of fermentation, proteolytic fermentation, breaks down proteins like
i. enzymes, dead host and bacterial cells, and collagen and elastin found in food.
f. Another important role of helpful gut flora is that they prevent species that would harm the host from colonizing the gut through competitive exclusion, an activity termed the "barrier effect.
g. Gut flora have a continuous and dynamic effect on the host's gut and systemic immune systems. The bacteria are key in promoting the early development of the gut's mucosal immune system both in terms of its physical components and function and continue to play a role later in life in its operation.
h. The bacteria stimulate the lymphoid tissue associated with the gut mucosa to produce antibodies to pathogens.
a. In the digestive system, mucus is used as a lubricant for materials that must pass over membranes,
i. e.g., food passing down the esophagus. A layer of mucus along the inner walls of the stomach is vital to protect the cell linings of that organ from the highly acidic environment within it.
b. Mucus does not digested in the intestinal tract.
c. Mucus is also secreted from glands within the rectum due to stimulation of the mucous membrane within