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Questions and Answers
What type of glycosidic bond is present at the branching point of amylopectin?
What is the predominant form of dietary carbohydrate for humans?
Which enzyme initiates the digestion of starch in the mouth?
During starch digestion, which products are released by the action of α Amylase?
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What color does starch produce when reacted with iodine?
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Which statement accurately describes the solubility of starch in water?
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Where is starch primarily found in plants?
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What is the approximate percentage of amylopectin in starch?
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What structural property differentiates amylose from amylopectin?
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Which type of sugar has a higher sweetness level than sucrose?
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What is the repeating unit found in glucosan?
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What distinguishes dietary oligosaccharides from other carbohydrate types?
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What physical property is the basis for the iodine test used to identify polysaccharides?
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Which of the following is a common characteristic of homopolysaccharides?
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What components make up starch?
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Which enzyme cleaves the glycosidic bond of sucrose to produce invert sugar?
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Which of the following disaccharides is formed by β (1-4) glycosidic bonds?
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What type of glycosidic bond is present in cellobiose?
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Which of the following enzymes is responsible for digesting lactose?
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Why is sucrose classified as a non-reducing disaccharide?
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What is the main source of maltose in the human gastrointestinal tract?
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What therapeutic benefits does lactulose provide?
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Which of the following disaccharides is NOT a reducing sugar?
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Which glycosidic bond type is found in isomaltose?
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Which of the following statements about cellobiose is correct?
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What is the primary source of sucrAl?
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What occurs as a consequence of lactase deficiency in the gastrointestinal tract?
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What is one of the end products of sucrose hydrolysis?
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Which of the following bacteria can ferment lactose to produce lactic acid?
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How is lactulose primarily prepared?
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Which disaccharide consists of two α D Glucose units linked by an α (1-4) glycosidic bond?
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What makes invert sugar reducing?
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Study Notes
Starch and Its Structure
- Starch consists of two main components: amylose and amylopectin.
- Amylopectin accounts for 80-85% of starch with a branched structure.
- Branching in amylopectin occurs every 25-30 glucose units via α(1-6) glycosidic bonds.
- Amylose features α(1-4) glycosidic bonds, forming a linear chain.
Properties of Starch
- Starch is a white, odorless, and tasteless powder.
- Insoluble in cold water; forms a gel or paste when heated.
- Non-reducing carbohydrate; yields a negative Benedict's test.
- Reacts with iodine to produce a blue color.
Occurrence of Starch
- Found in plants: seeds, tubers, roots, and raw fruits.
- Dietary sources include grains (rice, wheat, jawar, bajra), potatoes, beetroot, sago (tapioca), vermicelli, and raw mangoes.
Biomedical Importance of Starch
- Acts as a storage form of glucose, serving as an energy reservoir in plants.
- Primary dietary carbohydrate for humans, providing high calorific value.
Digestion of Starch
- Begins in the mouth with salivary α-amylase.
- Continues in the intestine with pancreatic α-amylase, breaking down α(1-4) glycosidic bonds.
- Results in the production of maltose and isomaltose, further split into glucose by maltase and isomaltase.
Invert Sugar
- Formed during the hydrolysis of sucrose; sweeter than sucrose due to free fructose.
- Used as a sweetening agent and in honey adulteration.
- Invert sugar is laevorotatory, possessing a high optical rotation.
Importance of Sucrose
- Sucrose has significant dietary and calorific value.
- Cleaved by the enzyme sucrase or invertase into glucose and fructose, creating invert sugar.
Oligosaccharides
- Composed of 3-10 monosaccharide units linked by glycosidic bonds.
- Can be branched or unbranched; are not digested by humans, thus have no calorific value.
- Serve as components of glycoproteins.
Polysaccharides Characteristics
- Composed of more than ten monosaccharide units linked by glycosidic bonds.
- General formula represented as (C6H10O5)n.
- Characteristic iodine test gives a distinct color indicating presence.
Homopolysaccharides
- Type consisting of more than ten identical monosaccharide units.
- Examples include glucosan (polymer of glucose) and fructosan (polymer of fructose).
Examples of Homopolysaccharides:
- Glucosan examples: starch, glycogen, cellulose, dextrin, and dextran.
- Fructosan example: inulin, important in various plant foods.
Disaccharides Types
- Reducing disaccharides: lactose, maltose, isomaltose, lactulose, cellobiose.
- Non-reducing disaccharides: sucrose, trehalose.
Lactose
- Milk sugar connected via β(1-4) glycosidic bond; found in milk and dairy products.
- Lactase enzyme breaks down lactose into galactose and glucose.
Maltose
- Reducing disaccharide known as malt sugar; consists of two glucose units linked by α(1-4) bonds.
- Formed during starch digestion in the human gastrointestinal tract.
Isomaltose
- Reducing disaccharide deriving from starch digestion; consists of two glucose units with α(1-6) glycosidic bonds.
Cellobiose
- Obtained from cellulose digestion, linking β D-glucose by β(1-4) bonds.
- Lacks biomedical importance in humans due to the absence of cellulase.
Lactulose
- A reducing disaccharide composed of β D-galactose and β D-fructose (β(1-4) bond).
- Used therapeutically as a laxative and for chronic constipation relief.
Sucrose
- Non-reducing disaccharide (cane sugar) formed from α D-glucose and β D-fructose linked by α(1-β2) bond.
- Dextrorotatory, with no free anomeric carbon atoms, hence classified as non-reducing.
Inversion Process
- Sucrose hydrolysis results in invert sugar composed of free glucose and fructose.
- The inversion leads to the creation of a reducing and laevorotatory sugar mixture.
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Description
This quiz covers key concepts related to amylose and amylopectin, two important polysaccharides in biochemistry. Questions will explore their structures, functions, and differences, particularly focusing on amylopectin's branching structure. Test your understanding of carbohydrate biochemistry with this informative quiz!
