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Questions and Answers
What distinguishes a sugar alcohol from regular sugars?
What distinguishes a sugar alcohol from regular sugars?
Which of the following statements is true about reducing sugars?
Which of the following statements is true about reducing sugars?
How can sucrose be hydrolyzed into glucose and fructose?
How can sucrose be hydrolyzed into glucose and fructose?
Which of the following sugars are classified as non-reducing sugars?
Which of the following sugars are classified as non-reducing sugars?
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What characterizes an oligosaccharide?
What characterizes an oligosaccharide?
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What occurs during the hydrolysis of a disaccharide?
What occurs during the hydrolysis of a disaccharide?
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Which reaction forms a disaccharide from two monosaccharides?
Which reaction forms a disaccharide from two monosaccharides?
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Reducing sugars can be oxidized by which of the following?
Reducing sugars can be oxidized by which of the following?
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Which polysaccharide is primarily a storage form of carbohydrates in animal tissues?
Which polysaccharide is primarily a storage form of carbohydrates in animal tissues?
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What type of linkage primarily connects glucose units in amylopectin?
What type of linkage primarily connects glucose units in amylopectin?
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What is the main structural difference between homopolysaccharides and heteropolysaccharides?
What is the main structural difference between homopolysaccharides and heteropolysaccharides?
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What is a primary characteristic of dextrins compared to starch?
What is a primary characteristic of dextrins compared to starch?
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Which of the following is a non-reducing sugar?
Which of the following is a non-reducing sugar?
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What type of carbohydrate is raffinose?
What type of carbohydrate is raffinose?
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Which of the following carbohydrates has a structure similar to glycogen?
Which of the following carbohydrates has a structure similar to glycogen?
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What is the primary function of starch in plants?
What is the primary function of starch in plants?
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Which of the following sugars is classified as a ketose?
Which of the following sugars is classified as a ketose?
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What is the general formula for monosaccharides commonly found in food?
What is the general formula for monosaccharides commonly found in food?
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Which type of carbohydrate consists of many sugar units combined?
Which type of carbohydrate consists of many sugar units combined?
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What type of bond is formed between two monosaccharides to create a disaccharide?
What type of bond is formed between two monosaccharides to create a disaccharide?
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Which of the following statements about α and β sugars is true?
Which of the following statements about α and β sugars is true?
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Which of the following sugars cannot be digested by the body's enzymes due to its β linkage?
Which of the following sugars cannot be digested by the body's enzymes due to its β linkage?
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What distinguishes D-Glucose from L-Glucose?
What distinguishes D-Glucose from L-Glucose?
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What is the maximum number of sugar rings in an oligosaccharide?
What is the maximum number of sugar rings in an oligosaccharide?
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Which characteristic is true for reducing sugars?
Which characteristic is true for reducing sugars?
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In which order are the carbon atoms classified in carbohydrates?
In which order are the carbon atoms classified in carbohydrates?
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Study Notes
Food Chemistry - Carbohydrates
- Carbohydrates are compounds containing carbon, hydrogen, and oxygen.
- General formula: Cn(H₂O)n = CnH₂nOn (e.g., if n=6, C₆H₁₂O₆ (Glucose))
- Common carbohydrates have 6 carbon atoms, like glucose, mannose, and galactose.
- Carbohydrates are a major source of energy for humans.
Topic Outline
- Introduction: General structure, functional roles in foods, sources, general reaction
- Classification: Simple carbohydrates, complex carbohydrates
Simple Carbohydrates
-
Sugars: Monosaccharides (single sugars) contain 3-8 carbon atoms.
- Most common have 5 or 6 carbon atoms (e.g., Glucose, Fructose).
- General formula: C₆H₁₂O₆.
- Glucose is an aldose sugar - it has an aldehyde group. D- form is more common.
- Two isomers: D-Glucose and L-Glucose.
- The straight chain form exists in equilibrium with ring confirmations (alpha and beta). These forms are fixed when reacting to form other molecules.
- Alpha and beta forms determine many chemical properties including digestibility.
- D-Fructose is an important ketose sugar.
Simple Carbohydrates: Disaccharides
- Glycosidic bond – formed when the carbonyl group of one monosaccharide reacts with the hydroxyl group of another, with the elimination.
- Examples:
- Maltose (2 glucose units with a-1, 4-glycosidic bond)
- Cellobiose (2glucose units with β-1, 4-glycosidic bond)
- Sucrose (Glucose + Fructose in a-1,2 -glycosidic bonds)
Simple Carbohydrates: Other
-
Sugar Alcohols: Carbonyl group reduced to hydroxyl group
- Examples: Xylitol, Mannitol, Sorbitol
- Sweet in nature but not as sweet as sucrose.
- Products containing sugar alcohols are often labeled "sugar-free".
- Reducing Sugars: Sugars that can be oxidized by mild oxidizing agents (e.g., Benedict's reagent or Fehling's solution).
- Non-reducing Sugars: Sugars that cannot be oxidized by these reagents. Sucrose is an example.
Simple Carbohydrates: Nomenclature
- Glycose: Generic name for sugars.
- Number of sugar units:
- Monosaccharides (1)
- Disaccharides (2)
- Oligosaccharides (3-10)
- Polysaccharides (>10)
- Number of carbon atoms: triose, tetrose, pentose, hexose
- Aldose vs. ketose: glucose (dextrose) vs. fructose (levulose)
Complex Carbohydrates
- Oligosaccharides: Composed of 3-10 monosaccharides, and are joined by the elimination of a water molecule.
- Examples: raffinose (Galactose-Glucose-Fructose)
- Formed during transition of complex carbohydrates (starch) into simpler di- and monosaccharides.
-
Polysaccharides: Large molecules formed by linking many monosaccharides with the elimination of a water molecule at each linkage point.
- Examples: dextrans, starch, glycogen, cellulose.
- Non-glycosidic carbohydrates (e.g., pectic substances, gums)
- Examples: dextrans, starch, glycogen, cellulose.
Starch
- Stored in plant cells.
- Intestine enzymes hydrolyze plant starch to glucose.
- Examples of complex carbohydrates (storage carbohydrates): potato, corn, cassava, wheat, and legumes.
- Starch has two fractions: amylose and amylopectin
Glycogen
- Storage form of carbohydrate in animal tissues.
- Similar to amylopectin in structure (long, branched chains of glucose molecules).
- More extensively branched than starch, so it is more compact.
- Released as glucose for energy.
Cellulose
- Key structural component of plant cell walls.
- Linear configuration.
- 1,4-β-glucosidic linkage.
- Insoluble, indigestible.
- Dietary fiber; maintains intestinal mobility.
- Used in the production of low-calorie food products.
Inulin
- Polymer of fructose.
- Built as a linear chain of fructose units by β-1,2- bonds.
- Has one terminal glucose molecule.
- Non-digestible.
- Sugar and fat substitute.
- Nutritional source for probiotic bacteria.
Pectic Substances
- Group of complex carbohydrates found in fruits.
- Polymer of galacturonic acid.
- Methylated to form methyl esters.
- Gel formation (MW and esterification).
- Low-ester pectin forms gel at low pH, with sugar and/or Ca++. High-ester requires high sugar.
- Stabilizer
Gums
- Found in seeds, plant exudates, and seaweeds.
- Galactose is the dominant monomer.
- Mannose, arabinose, xylose, and rhamnose are other monomers found.
- Emulsifier, binder, foam stabilizer.
- Flavor fixative.
- Retards sugar crystallization, fat separation, and ice formation in ice cream.
Sources of Carbohydrates
- Many foods including fruits and vegetables.
- Commercial source of sucrose: sugarcane and sugar beet.
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Description
Explore the essential aspects of carbohydrates in food chemistry, including their structure, classification, and functional roles. This quiz covers simple and complex carbohydrates, highlighting common types such as glucose and their importance as energy sources. Understand how these compounds react and their significance in nutrition.
