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Questions and Answers
What is the primary structural component of cell walls that accounts for over half of the carbon in the biosphere?
What is the primary structural component of cell walls that accounts for over half of the carbon in the biosphere?
Which type of glycosidic bond links the glucose residues in cellulose?
Which type of glycosidic bond links the glucose residues in cellulose?
How does the structural arrangement of cellulose fibers contribute to their strength?
How does the structural arrangement of cellulose fibers contribute to their strength?
Which biomolecule is second most abundant after cellulose and serves as a structural component in the exoskeletons of invertebrates?
Which biomolecule is second most abundant after cellulose and serves as a structural component in the exoskeletons of invertebrates?
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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 statement accurately describes the arrangement of glucose units in cellulose?
Which statement accurately describes the arrangement of glucose units in cellulose?
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What complicates the conversion of cellulose to biofuels?
What complicates the conversion of cellulose to biofuels?
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What type of glycosidic bond links the N-acetyl-d-glucosamine residues in chitin?
What type of glycosidic bond links the N-acetyl-d-glucosamine residues in chitin?
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How do cellulose and chitin compare in their structural properties according to X-ray analysis?
How do cellulose and chitin compare in their structural properties according to X-ray analysis?
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What is the role of cellulases in the digestive tract of herbivores and termites?
What is the role of cellulases in the digestive tract of herbivores and termites?
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What type of glycosidic bond is present in lactose?
What type of glycosidic bond is present in lactose?
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Which of the following statements accurately describes cellulose?
Which of the following statements accurately describes cellulose?
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What is a characteristic of aspartame as a sweetener?
What is a characteristic of aspartame as a sweetener?
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Which feature distinguishes sucrose from reducing sugars?
Which feature distinguishes sucrose from reducing sugars?
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Which polysaccharide is primarily found in the exoskeletons of arthropods?
Which polysaccharide is primarily found in the exoskeletons of arthropods?
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What is the main health risk associated with saccharin?
What is the main health risk associated with saccharin?
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Which type of polysaccharide consists of only one type of monosaccharide?
Which type of polysaccharide consists of only one type of monosaccharide?
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What is one property of cellulose that contributes to its function in plants?
What is one property of cellulose that contributes to its function in plants?
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Which of the following describes a characteristic of artificial sweeteners like aspartame?
Which of the following describes a characteristic of artificial sweeteners like aspartame?
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How are exo-glycosidases and endoglycosidases related to polysaccharides?
How are exo-glycosidases and endoglycosidases related to polysaccharides?
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What type of glycosidic bond primarily links glucose residues in amylopectin?
What type of glycosidic bond primarily links glucose residues in amylopectin?
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Which enzyme initiates starch digestion in the mouth?
Which enzyme initiates starch digestion in the mouth?
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In what form does glycogen primarily exist within animal cells?
In what form does glycogen primarily exist within animal cells?
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What is the average branching point interval for amylopectin's α(1→6) linkages?
What is the average branching point interval for amylopectin's α(1→6) linkages?
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What structural feature of glycogen allows for rapid mobilization of glucose?
What structural feature of glycogen allows for rapid mobilization of glucose?
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How does the structure of cellulose differ from that of amylose?
How does the structure of cellulose differ from that of amylose?
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Which enzyme is responsible for cleaving α(1→4) bonds in glycogen degradation?
Which enzyme is responsible for cleaving α(1→4) bonds in glycogen degradation?
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Which statement correctly describes the reducing ends of starch?
Which statement correctly describes the reducing ends of starch?
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What role does α-glucosidase play in starch digestion?
What role does α-glucosidase play in starch digestion?
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What distinguishes glycogen's branching from amylopectin's?
What distinguishes glycogen's branching from amylopectin's?
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Study Notes
Cellulose
- Primary structural component of plant cell walls.
- Accounts for over half of the carbon in the biosphere.
- Linear polymer of up to 15,000 D-glucose residues linked by β(1→4) glycosidic bonds.
- Fibers consist of ~40 parallel, extended glycan chains.
- Tightly packed, fully extended conformation due to β(1→4) linkages and interchain hydrogen bonds.
- Exceptional strength and water insolubility despite hydrophilicity.
- Linked with other polysaccharides and lignin, hindering biofuel conversion.
- Hydrolyzed by cellulases in herbivores and termites.
Chitin
- Structural component of invertebrate exoskeletons and fungal cell walls.
- Second most abundant biomolecule after cellulose.
- Homopolymer of β(1→4) linked N-acetyl-d-glucosamine residues.
- Differs from cellulose by an acetamido group replacing each C2-OH group.
- Similar structure to cellulose based on X-ray analysis.
Starch
- Plant's principal energy reserve.
- Mixture of α-amylose and amylopectin.
- Deposited in chloroplasts as insoluble granules.
α-Amylose
- Linear polymer of several thousand glucose residues linked by α(1→4) bonds.
- Irregularly aggregating helical coiled (left-handed helix) conformation due to α-glycosidic bonds.
Amylopectin
- Primarily α(1→4) linked glucose residues with α(1→6) branch points every 24-30 residues.
- Contains up to 106 glucose residues.
- Large molecules.
Starch Digestion
- Reducing sugar with one reducing end.
- Digestion begins in the mouth with salivary amylase.
- Pancreatic amylase degrades starch to oligosaccharides in the small intestine.
- α-glucosidase and debranching enzyme further hydrolyze to monosaccharides for absorption.
Glycogen
- Animal storage polysaccharide.
- Most prevalent in skeletal muscle and liver as cytoplasmic granules.
- Structure resembles amylopectin but is more branched (every 8-14 glucose residues).
- Degraded by glycogen phosphorylase (cleaves α(1→4) bonds).
- Highly branched structure allows rapid glucose mobilization.
- α(1→6) branches cleaved by glycogen debranching enzyme.
Polysaccharides (Glycans)
- Monosaccharides linked by glycosidic bonds.
- Homopolysaccharides: one type of monosaccharide.
- Heteropolysaccharides: more than one type of monosaccharide.
- Form branched and linear polymers.
- Hydrolyzed by exo- and endoglycosidases.
Lactose
- Reducing disaccharide found naturally only in milk.
- Composed of galactose and glucose (O-β-D-galactopyranosyl-(1→4)-D-glucopyranose).
- Free anomeric carbon on glucose.
Sucrose
- Most abundant disaccharide.
- Major carbohydrate transport form in plants.
- Composed of glucose and fructose (O-α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside).
- Non-reducing sugar due to participation of both anomeric carbons in glycosidic bond.
Artificial Sweeteners
- Added to foods and beverages for sweetness without calories.
- Examples: saccharin, aspartame, acesulfame.
- Varying levels of sweetness relative to sucrose.
- Potential health concerns and limitations (e.g., saccharin, aspartame).
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Description
This quiz covers the structural and functional aspects of cellulose, chitin, and starch. Explore the primary components of plant walls, invertebrate exoskeletons, and the energy reserves of plants. Test your knowledge on their compositions and significance in the biosphere.
