Biology
Recognising the role of bacteria
We are learning how to: • Describe the role of bacteria in our digestive system. • Explain how the natural flora of bacteria can be disturbed. • Analyse data about the effects of antibiotics on gut bacteria.
Scientists think that humans have over 500 different types of bacteria living in their digestive system. Most of the time, these bacteria do not harm us, indeed some help us to take the nutrients from the food that we eat during digestion. How bacteria help with digestion
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It is normal to have bacteria in your digestive system; the huge number and range found throughout your gut make up your gut flora. Many of these bacteria help with digestion. Bacteria are found throughout the gut, but the number and type vary in different parts and is highest in the large intestine. The helpful bacteria have several roles in digestion:
FIGURE 1.2.12a: Bacteria can be clearly seen in this magnified view of the inner surface of a healthy large intestine.
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They release energy from some foods such as sugars by fermentation.
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They make some enzymes that we need.
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They help to protect us from disease-causing bacteria.
Fermentation allows us to gain more energy from foods that have not been digested in the small intestine. The process also produces gases such as nitrogen, carbon dioxide and methane. The gas is passed out as ‘wind’. 1. State where in the digestive system most bacteria are found. 2. Describe three ways in which some bacteria can help in digestion. 3. Suggest why few bacteria are found in the stomach.
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Did you know . . . ? The digestive system is sterile at birth, but bacteria start to colonise the gut within a few hours of birth. By the time we are adults we should have up to 2 kg of bacteria in our gut.
KS3 Science Book 1: Eating, Drinking and Breathing
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09/12/2013 15:22