Question

Bacteria that produce vitamin \(\mathrm{B}_{12}\) and beneficial short-chain fatty acids (SCFAs) live in the ________. a. stomach b. small intestine c. large intestine d. esophagus

Short answer

The bacteria live in the large intestine (c).

Step-by-step solution

Identify the Location of Beneficial Bacteria

The task is to identify where vitamin B12 and SCFAs-producing bacteria are most likely found. These beneficial bacteria primarily reside where fermentation of nutrients and absorption of vitamins occur, which requires regions with a high concentration of microbiota.

Eliminate Unlikely Options

Consider the four options: stomach, small intestine, large intestine, and esophagus. The stomach and esophagus are not primary sites for bacterial colonization due to unfavorable conditions like high acidity.

Analyze the Functionality of the Intestines

The small intestine absorbs most nutrients and is not the primary site for these bacteria due to faster transit and lower bacterial density. The large intestine, however, is designed for fermentation and is densely populated with bacteria.

Confirm the Answer Choice

Given that the large intestine is the main site for fermentation and has a dense bacterial population, it is the most appropriate environment for supporting bacteria that produce vitamin B12 and SCFAs.

Key concepts

Bacteria

Bacteria play a crucial role in our digestive system, particularly in the large intestine. Unlike the stomach and small intestine, the large intestine is a hub for bacterial activity. Thousands of different types of bacteria coexist here, each contributing to the complex process of digestion. These bacteria break down substances that are not digested in the small intestine, further aiding in nutrient absorption.

Bacteria in the large intestine specialize in fermenting carbohydrates and proteins. They convert these substances into energy-yielding compounds, which our body can use. Some bacteria in this region are also responsible for producing valuable compounds that the human body cannot synthesize by itself. This symbiotic relationship showcases the essential roles that bacteria play in maintaining optimal digestive health.

Vitamin B12

Vitamin B12 is a crucial nutrient produced by certain bacteria in the large intestine. This vitamin is vital for forming red blood cells and maintaining healthy nerve cells. It also plays a significant role in DNA synthesis and energy production within the body.

Our diet provides a major source of vitamin B12, found in animal products like meat, eggs, and dairy. However, our digestive system also relies on the bacterial synthesis of vitamin B12 in the large intestine. Here, bacteria take up residence and work to produce this essential nutrient, which is then absorbed into the bloodstream.

• Red blood cell production
• Nerve cell maintenance
• DNA synthesis

The presence of vitamin B12-producing bacteria exemplifies how the microbiota supports essential bodily functions.

Short-chain Fatty Acids

Short-chain fatty acids (SCFAs) are metabolites produced by the fermentation process in the large intestine. Beneficial bacteria break down complex carbohydrates and fibers into SCFAs, which the body can easily absorb.

• Primary types of SCFAs include acetate, propionate, and butyrate.
• SCFAs serve as an energy source for colon cells and play a role in maintaining the health of the colon.
• They help regulate inflammation and are involved in signaling pathways that influence fat metabolism.

SCFAs have far-reaching effects on overall health. They influence immune system functioning, protect against colon cancer, and assist in cholesterol metabolism. This reflects how important these fatty acids are in maintaining a balanced and healthy digestive system.

Microbiota

The term "microbiota" refers to the diverse community of microorganisms residing in the human body. In the large intestine alone, the microbiota is composed of trillions of bacteria, viruses, fungi, and other microorganisms. They work together to support various functions essential for health and well-being.

In the context of digestion, the microbiota helps break down food particles, assists in the synthesis of nutrients like vitamin B12, and produces short-chain fatty acids. Additionally, the microbiota acts as a protective barrier, preventing harmful pathogens from colonizing the gut.

• Prevention of pathogen colonization
• Synthesis of essential nutrients
• Breaking down of indigestible substances

The balance and diversity of the microbiota are vital. If disrupted, it can lead to digestive problems, infections, and other health issues. Maintaining a healthy microbiota is key, often supported by a diet high in fiber and fermented foods.