Questions and Answers
Which carbohydrates are described as simple and which are complex?
Describe the structure of a monosaccharide and name the three monosaccharides important in nutrition.
A monosaccharide has a ring structure composed of carbon, hydrogen, and oxygen atoms. The three important monosaccharides are glucose, fructose, and galactose.
Name the three disaccharides commonly found in foods and their component monosaccharides.
Sucrose (fructose + glucose), lactose (glucose + galactose), maltose (glucose + glucose).
In what foods are these sugars found?
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What happens in a condensation reaction?
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What happens in a hydrolysis reaction?
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Describe the structure of polysaccharides and name the ones important in nutrition.
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How are starch and glycogen similar and how do they differ?
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How do fibers differ from other polysaccharides?
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Describe carbohydrate digestion and absorption.
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What role does fiber play in the process?
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What are the possible fates of glucose in the body?
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What is the protein-sparing action of carbohydrate?
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How does the body maintain blood glucose concentrations?
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What happens when blood glucose rises too high or falls too low?
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Study Notes
Carbohydrates Overview
- Carbohydrates are categorized as simple (monosaccharides and disaccharides) and complex (polysaccharides).
- Simple carbohydrates include monosaccharides like glucose, fructose, and galactose, and disaccharides like sucrose, lactose, and maltose.
- Complex carbohydrates include glycogen and starch.
Monosaccharides Structure and Importance
- Monosaccharides have a ring structure consisting of carbon, hydrogen, and oxygen.
- Important monosaccharides include glucose, fructose, and galactose.
Disaccharides Composition
- Common disaccharides are sucrose (fructose + glucose), lactose (glucose + galactose), and maltose (glucose + glucose).
- Sucrose is found in many fruits and vegetables, lactose is present in milk, and maltose is located in seeds.
Sugar Sources in Foods
- Glucose is found in nearly all plant foods, while fructose is mainly in fruits and saps.
- Galactose is generally not present in food separately.
Reactions in Carbohydrate Metabolism
- A condensation reaction combines two reactants into one product while removing water.
- A hydrolysis reaction breaks a reactant into two products by adding water.
Polysaccharides Structure and Nutritional Significance
- Polysaccharides consist of many linked monosaccharides.
- Key polysaccharides for nutrition include glycogen, starch, and dietary fibers.
Starch and Glycogen Similarities and Differences
- Both starch and glycogen are glucose polymers.
- Glycogen has highly branched chains of glucose, whereas starch has glucose units linked in straight chains or branching.
Fiber Characteristics
- Fibers are unique polysaccharides as their bonds are not digestible by human enzymes.
Carbohydrate Digestion and Absorption
- Digestion starts with salivary amylase in the mouth followed by pancreatic enzymes in the small intestine.
- Disaccharides are broken down to monosaccharides on the intestinal cell surface.
- Monosaccharides travel via capillaries to the liver, where galactose and fructose can be converted to glucose.
Role of Fiber in Digestion
- Fiber promotes salivation, delays gastric emptying, slows carbohydrate and fat absorption, and attracts water in the large intestine to soften stools.
Fates of Glucose in the Body
- Glucose can be stored as glycogen, utilized for energy, or converted to fat when carbohydrates are available.
Protein-Sparing Action of Carbohydrates
- Carbohydrates provide energy, allowing protein to be available for its specific functions.
Blood Glucose Regulation
- Hormones regulate blood glucose levels in response to fluctuations.
- Elevated blood glucose triggers insulin release from the pancreas for glucose storage, while low blood glucose prompts glucagon release for glucose release into the bloodstream.
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Description
This study guide focuses on carbohydrates, distinguishing between simple and complex types. It covers important monosaccharides in nutrition and their structural characteristics. Perfect for students preparing for exams in nutritional science.