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Questions and Answers
Which of the following describes why sucrose is not a reducing sugar?
What happens to sucrose when it undergoes hydrolysis?
Which monosaccharide is 50% sweeter than glucose?
What is a common consequence of overconsumption of sucrose?
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What defines a disaccharide?
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Which disaccharide is commonly known as table sugar?
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What is invert sugar sweeter than sucrose mainly due to?
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Which of the following is NOT a reducing sugar?
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Which term describes a monosaccharide with three carbon atoms?
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What classification applies to a monosaccharide with the carbonyl group located at the end of the molecule?
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How are the two stereoisomers of a chiral molecule differentiated?
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Which of the following statements regarding ring structures of monosaccharides is true?
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What term describes the gradual change in optical rotation at the anomeric carbon of a sugar?
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What suffix is typically added to the name of a carbohydrate?
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Which type of monosaccharide has seven carbon atoms?
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Which structure is typically predominant in hexoses?
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What is one of the main functions of oligosaccharides found on blood cells?
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Which of the following is a highly glycosylated protein found in saliva?
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Which type of polysaccharide produces only one kind of monosaccharide upon hydrolysis?
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What are the components of starch?
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What effect does starch consumption have on body weight?
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Which of the following does NOT describe the properties of mucins?
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Which enzyme is responsible for hydrolyzing amylose to maltose and glucose?
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Which of the following oligosaccharides types can determine blood types A, B, O, and AB?
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What is the primary source of energy for newborn mammals provided by their mother's milk?
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Which of the following statements about lactose is correct?
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What is a significant consequence of consuming excessive sucrose in one's diet?
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How is maltose primarily broken down in the body?
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What proportion of adults worldwide are affected by lactose intolerance?
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Which type of sugar is maltose classified as?
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What characteristic makes lactose a reducing sugar?
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Which of the following is true regarding oligosaccharides?
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What is the main storage form of carbohydrates in animals?
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Which of the following statements about cellulose is true?
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What role does glycogen play in the liver?
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What type of glycosidic linkage is found in cellulose?
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What is one of the biological functions of glycogen in muscles?
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Which type of polysaccharide is characterized by producing more than one kind of monosaccharide upon hydrolysis?
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What is the composition of chondroitin and its significance?
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What is the characteristic of heparin?
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Study Notes
Carbohydrate Classification
- Carbohydrates are classified based on the number of carbon atoms present, the position of the carbonyl group, and the chirality of the molecule.
- The number of carbon atoms determines the name, with suffixes like "triose" for three carbons, "tetrose" for four carbons, and so on.
Carbonyl Group Placement
- The location of the carbonyl group (–C=O) classifies carbohydrates as aldehydes or ketones.
- If the –C=O group is at the end of the molecule, it's an aldehyde and the monosaccharide is an aldose.
- If the –C=O group is within the molecule's structure, it's a ketone and the monosaccharide is a ketose.
Chirality
- Chirality refers to a molecule that cannot be superimposed on its mirror image.
- The prefix D- or L- indicates the stereoisomer of the monosaccharide.
Monosaccharide Structures
- Monosaccharides exist in two structural forms: linear and ring.
- Linear structures are represented by Fischer projections, while ring structures use Haworth projections.
- Hexoses (six-carbon sugars) commonly exist as ring structures.
- A six-membered ring is called a pyranose (e.g., glucose and galactose).
- A five-membered ring is called a furanose (e.g., fructose).
Mutarotation
- Mutarotation is the gradual change in rotation at the anomeric carbon.
- It occurs due to the interconversion between α and β anomers.
Common Monosaccharides
- Glucose, fructose, and galactose are important monosaccharides with distinctive properties.
- Glucose is found in fruits, is an aldose sugar, is sweet and crystalline, and is the end product of polysaccharide digestion.
- Fructose is found in cane sugar, is a ketose sugar, is 50% sweeter than glucose, and is crystalline. It is converted to fat stores less efficiently than glucose.
- Galactose is found in milk, is an aldose sugar, is sweet and crystalline.
Disaccharides
- Disaccharides consist of two sugars linked by an O-glycosidic bond (ether link –O–).
- They are formed by the condensation of two monosaccharide molecules.
- Common disaccharides include sucrose, lactose, and maltose.
Sucrose
- Sucrose is also known as table sugar and is obtained from sugar cane or beets.
- It is the sweetest disaccharide and is made up of glucose and fructose.
- Sucrose is not a reducing sugar because both carbonyl groups are involved in the glycosidic bond formation.
- Hydrolysis of sucrose by acid or invertase yields glucose and fructose, referred to as "inversion of the sugar."
- Invert sugar is sweeter than sucrose due to the presence of fructose.
Biological Importance of Sucrose
- Sucrose provides quick energy, leading to a rapid rise in blood glucose.
- Excessive sucrose consumption contributes to tooth decay due to bacteria converting sugars into acids that erode tooth enamel.
- High sucrose intake can displace essential nutrients from the diet, potentially increasing the risk of chronic diseases.
Lactose
- Lactose is known as milk sugar and is found in the milk of mammals.
- Human milk contains a higher percentage of lactose than animal milk, making it sweeter.
- It is composed of glucose and galactose.
- Lactose is a reducing sugar due to the free carbonyl group on C#1 of the glucose ring.
- It is non-fermentable, meaning it cannot be broken down by yeast cells to produce ethanol.
- Hydrolysis of lactose using lactase produces glucose and galactose.
Biological Importance of Lactose
- Cells use lactose building blocks for chemical energy.
- Lactose is the primary energy source for newborn mammals from their mother's milk.
- Lactose intolerance results from a deficiency in lactase enzyme, leading to inability to digest lactose.
- More than ¾ of the world's adult population is lactose intolerant.
Maltose
- Maltose is referred to as malt sugar and is not commonly found in nature.
- It is the simplest disaccharide and is composed of two glucose molecules.
- Maltose is a reducing sugar due to the free carbonyl group on C#1 of the glucose ring.
- It is fermentable, meaning yeast cells can break it down to produce ethanol.
- Hydrolysis of maltose using dilute acid or the enzymes maltase and diastase produces glucose molecules.
Oligosaccharides
- Oligosaccharides contain 3 to 10 monosaccharide molecules.
- They are found linked to proteins and lipids, forming glycoproteins and glycolipids.
- They function as receptors on cell membrane surfaces.
- Oligosaccharides on blood cells determine blood groups A, B, O, and AB.
Glycoproteins
- Mucins are glycoproteins found in saliva and other mucosal barriers.
- Their glycosylation makes them resistant to breakdown by enzymes and able to hold water, contributing to their gel-like properties.
- Mucins are involved in lubrication, tissue coating, protection against microbes, and formation of protective barriers in the oral cavity.
- They are overexpressed in lung diseases like asthma, bronchitis, COPD, and cystic fibrosis.
Polysaccharides
- Polysaccharides are complex sugars with high molecular weights.
- They can be straight chain or branched.
- They are classified into homopolysaccharides and heteropolysaccharides.
Homopolysaccharides
- Homopolysaccharides consist of only one type of monosaccharide.
- Examples include starch, glycogen, and cellulose.
Starch
- Starch is a major food storage in plants.
- It comprises two components:
- Amylose (straight chain)
- Amylopectin (branched)
- Hydrolysis of amylose by α-amylase (digestive tract) produces maltose and glucose.
- β-amylase (plants) produces maltose.
- Amylopectin is hydrolyzed by α-amylase and α-1,6-glucosidase to yield maltose and glucose.
Biological Importance of Starch
- Starch contributes to weight management, especially when combined with exercise.
- It is crucial for proper gut function.
- It serves as a fuel source for the brain and active muscles.
Glycogen
- Glycogen is the storage form of carbohydrate in animals.
- It is structurally similar to amylopectin but has more branching.
- It is soluble in water.
- Hydrolysis using α-1,6-glucanmaltohydrolase produces maltose, while acid hydrolysis yields glucose.
- It is a non-reducing sugar.
Biological Importance of Glycogen
- The liver stores glycogen for rapid conversion to energy.
- Muscles also store glycogen for intense physical activity.
- The uterus stores glycogen during pregnancy to nourish the embryo.
- High glycogen levels improve endurance, while depletion is associated with fatigue.
Cellulose
- Cellulose is the most abundant extracellular polysaccharide.
- It is structurally similar to amylose but with β-1,4-glycosidic linkages.
- It is insoluble in water.
- It absorbs water.
- Hydrolysis produces glucose molecules.
- Cellulase is present in some insects, allowing them to digest cellulose.
Biological Importance of Cellulose
- In humans, cellulose is a major component of dietary fiber, essential for proper digestion.
- It passes through the digestive system unchanged, acting as bulk or roughage to aid intestinal movement.
- Only ruminant animals (e.g., cows, horses) can process cellulose using specialized bacteria in their digestive tracts.
Heteropolysaccharides
- Heteropolysaccharides consist of more than one type of monosaccharide.
- Examples include chondroitin and heparin.
Chondroitin
- Chondroitin is found in cartilage and the cell coat.
- It is a major component of the extracellular matrix, maintaining tissue integrity.
- Loss of chondroitin sulfate from cartilage contributes to osteoarthritis.
- Chondroitin sulfate is commonly used as a dietary supplement for osteoarthritis.
Heparin
- Heparin is an anticoagulant found in the liver and lung arterial wall.
- It helps prevent blood clotting.
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Description
This quiz covers the classification of carbohydrates based on carbon atoms, carbonyl group placement, and chirality. You will explore monosaccharide structures and their representations. Test your understanding of these essential biochemical concepts!
