bacteria in the digestive system

bacteria in the digestive system

Your large intestine is not just made up of cells. It is also an ecosystem, home to trillions of bacteria known as the "gut flora" ( Figure 1.1). But dont worry, most of these bacteria are helpful. Friendly bacteria live mostly in the large intestine and part of the small intestine. The acidic environment of the stomach does not allow bacterial growth. Gut bacteria have several roles in the body. For example, intestinal bacteria: Produce vitamin B12 and vitamin K. Control the growth of harmful bacteria. Break down poisons in the large intestine. Break down some substances in food that cannot be digested, such as fiber and some starches and sugars. Bacteria produce enzymes that digest carbohydrates in plant cell walls. Most of the nutritional value of plant material would be wasted without these bacteria. These help us digest plant foods like spinach. Your intestines are home to trillions of bacteria. A wide range of friendly bacteria live in the gut. Bacteria begin to populate the human digestive system right after birth. Gut bacteria include Lactobacillus, the bacteria commonly used in probiotic foods such as yogurt, and E. coli bacteria. About a third of all bacteria in the gut are members of the Bacteroides species. Bacteroides are key in helping us digest plant food. It is estimated that 100 trillion bacteria live in the gut. This is more than the human cells that make up you. It has also been estimated that there are more bacteria in your mouth than people on the planet. There are over 7 billion people on the planet. The bacteria in your digestive system are from anywhere between 300 and 1000 species. As these bacteria are helpful, your body does not attack them. They actually appear to the bodys immune system as cells of the digestive system, not foreign invaders. The bacteria actually cover themselves with sugar molecules removed from the actual cells of the digestive system. This disguises the bacteria and protects them from the immune system. As the bacteria that live in the human gut are beneficial to us, and as the bacteria enjoy a safe environment to live, the relationship that we have with these tiny organisms is described as mutualism, a type of symbiotic relationship. Lastly, keep in mind the small size of bacteria. Together, all the bacteria in your gut may weight just about 2 pounds.


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there are more bacterial cells in your body than human cells.

-->  a. true

b. false

there could be as many as 1,000 species of bacteria in your digestive system.

-->  a. true

b. false

which bacteria help us digest plant food?

a) lactobacillus

-->  b) bacteroides

c) e. coli

d) probiotic bacteria

bacteria live in all areas of the gastrointestinal tract except the

a) large intestine.

b) small intestine.

-->  c) stomach.

d) mouth.

why are gut bacteria not attacked by the host immune system?

a) because the bacteria appear as digestive system cells.

b) because the bacteria are covered sugars produced by the digestive system cells.

c) because the immune system does not see these cells as foreign.

-->  d) all of the above

what is a role of digestive system bacteria?

-->  a) break down fibers and some starches.

b) break down poisons in the stomach.

c) control the growth of helpful bacteria.

d) all of the above are roles of digestive system bacteria.

there are some plant foods that we cannot digest on our own. how do bacteria help us digest these foods?

a) bacteria produce enzymes that digest proteins in plant cells.

b) bacteria produce enzymes that digest lipids in plant cell walls.

-->  c) bacteria produce enzymes that digest carbohydrates in plant cell walls.

d) bacteria produce enzymes that digest carbohydrates in plant cell membranes.

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