Questions and Answers
What is the main site for carbohydrate digestion and absorption in the body?
The small intestine.
What enzyme breaks down starch molecules into maltose in the mouth?
Salivary amylase.
What happens to starch digestion when food enters the stomach?
Starch digestion stops.
What is the final product of starch digestion?
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What is the role of the enzyme sucrase in carbohydrate digestion?
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What is the primary component of oat carbohydrates?
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What happens to lactose and sucrose molecules in the small intestine?
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What is the fate of glucose molecules absorbed into the intestinal bloodstream?
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What is the function of the enzyme lactase in the breakdown of lactose from milk?
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What are the three types of monosaccharides absorbed by intestinal cells?
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What are fructans and galactooligosaccharides examples of?
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What is the function of postbiotics secreted by certain lactobacilli?
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What is the primary difference between soluble and insoluble fiber?
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How much energy does a gram of fiber contribute to the human diet?
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What are the two hormones produced by the pancreas that play key roles in regulating blood glucose levels?
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What happens to the glucose absorbed from food in the intestinal tract?
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What is the normal range of blood glucose level within 2 hours after eating?
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What is the normal range of blood glucose levels after sleeping overnight or not eating for several hours (fasting)?
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What is the function of insulin in regulating blood glucose levels?
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What is the function of insulin in the body?
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What is the benefit of adding oligosaccharides and probiotics to food products?
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What is the process called when the liver stores glucose as glycogen?
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What is the function of glucagon in the body?
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What is the byproduct of glucose metabolism in cells?
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What is the primary fuel for the body's cells?
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What happens to excess glucose in the liver when glycogen storage is at maximum capacity?
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What is the condition called when ketone bodies accumulate in the blood?
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What is the severe condition that can occur in people with poorly controlled type 1 diabetes?
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What is the minimum daily intake of carbohydrates recommended to prevent ketosis?
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Why does the body need glucose to fuel vital activities during starvation?
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What is the consequence of using muscle proteins as a source of energy during starvation?
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What happens to amino acids in skeletal muscles during starvation?
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What is the normal source of energy for human cells?
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What is the result of the body's altered energy metabolism during starvation?
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Study Notes
Carbohydrate Digestion and Absorption
- Cooked oatmeal, milk, and brown sugar contain carbohydrates in the form of starch, fiber, lactose, and sucrose.
- Salivary amylase breaks down starch into maltose in the mouth, but digestion stops in the stomach due to acidic environment.
- In the small intestine, pancreatic amylase breaks down remaining starch into maltose, which is then converted into glucose molecules by the enzyme maltase.
- Glucose molecules are absorbed into the intestinal bloodstream and transported to the liver via the hepatic portal vein.
Sucrose and Lactose Digestion
- Sucrose molecules are broken down into glucose and fructose molecules by the enzyme sucrase in the small intestine.
- Lactose molecules are broken down into glucose and galactose molecules by the enzyme lactase.
- Galactose, fructose, and glucose are absorbed by intestinal cells and transported to the liver.
Fructans and Galactooligosaccharides
- Fructans and galactooligosaccharides are forms of carbohydrate that are poorly digested by humans but can be metabolized by beneficial gut microbes (probiotics).
- Fructans and galactooligosaccharides support the growth of probiotics, promoting health benefits such as increased calcium absorption, reduced constipation, and protection against infections.
Fiber
- Fiber in oats is not digested by the small intestine and enters the large intestine, where it is fermented by "friendly" bacteria.
- Soluble fiber is broken down by bacteria, producing energy for cells, while insoluble fiber contributes to softer and easier-to-eliminate bowel movements.
Maintaining Blood Glucose Levels
- Insulin and glucagon are hormones produced by the pancreas that regulate blood glucose levels.
- Insulin lowers blood glucose levels by allowing glucose to enter cells, stimulating glycogen synthesis, and promoting fat and protein synthesis.
- Glucagon raises blood glucose levels by promoting glycogen breakdown, stimulating glucose production from amino acids, and stimulating lipolysis.
Glucose for Energy
- Cells metabolize glucose to release energy, producing carbon dioxide and water as byproducts.
- Glucose is a primary fuel for the body's cells, especially red blood cells, brain cells, and nervous system cells.
- When glucose is abundant, the liver stores excess glucose as glycogen or converts it into fat, which is stored in adipose cells.
Carbohydrate Requirements
- The Recommended Dietary Allowance (RDA) for carbohydrate is 130 g/day, which is sufficient to prevent ketosis.
- Under normal conditions, human cells obtain a small proportion of their energy needs by converting certain amino acids into glucose.
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Description
Understand how carbohydrates such as starch, fiber, lactose, and sucrose are broken down and absorbed in the digestive system. Learn about the role of salivary amylase, pancreatic amylase, and maltase in carbohydrate digestion.
