Podcast
Questions and Answers
How does the glycosidic bond arrangement contribute to the differing digestibility of cellulose versus starch in humans?
How does the glycosidic bond arrangement contribute to the differing digestibility of cellulose versus starch in humans?
Cellulose has β-1,4 glycosidic bonds, which humans lack the enzyme to break down, whereas starch has α-1,4 or α-1,6 glycosidic bonds that human enzymes can hydrolyze.
Distinguish between the structural organization of amylose and amylopectin within starch, and how does this influence their properties?
Distinguish between the structural organization of amylose and amylopectin within starch, and how does this influence their properties?
Amylose is a linear polysaccharide composed of α-1,4-glycosidic bonds, while amylopectin is branched with both α-1,4- and α-1,6-glycosidic bonds. This branching in amylopectin affects its solubility and enzymatic breakdown compared to amylose.
What role do the enzymes α-amylase and α-1,6-glucosidase play in the breakdown of glycogen, and why is this important for energy regulation?
What role do the enzymes α-amylase and α-1,6-glucosidase play in the breakdown of glycogen, and why is this important for energy regulation?
α-amylase breaks down the α-1,4-glycosidic bonds in the linear chains, while α-1,6-glucosidase hydrolyzes the α-1,6-glycosidic bonds at the branch points. This is important for rapidly mobilizing glucose from glycogen stores for energy.
Compare and contrast the structural features of amylopectin and glycogen.
Compare and contrast the structural features of amylopectin and glycogen.
Describe the composition and industrial application of inulin, noting why it cannot be digested in the human GIT.
Describe the composition and industrial application of inulin, noting why it cannot be digested in the human GIT.
How does the structural arrangement of monosaccharides in heteropolysaccharides like hyaluronic acid dictate their biological functions, compared to homopolysaccharides?
How does the structural arrangement of monosaccharides in heteropolysaccharides like hyaluronic acid dictate their biological functions, compared to homopolysaccharides?
What is the significance of glycosidic bonds in polysaccharides?
What is the significance of glycosidic bonds in polysaccharides?
How would you classify dermatan sulfate and keratan sulfate? What is their function?
How would you classify dermatan sulfate and keratan sulfate? What is their function?
Explain why herbivores, such as cattle, can digest cellulose while humans cannot, relating this to specific enzymatic capabilities.
Explain why herbivores, such as cattle, can digest cellulose while humans cannot, relating this to specific enzymatic capabilities.
Outline the key differences between homopolysaccharides and heteropolysaccharides, providing specific examples of each and their respective functions?
Outline the key differences between homopolysaccharides and heteropolysaccharides, providing specific examples of each and their respective functions?
Describe how the branching pattern in glycogen contributes to its role as a rapid source of glucose in animal cells.
Describe how the branching pattern in glycogen contributes to its role as a rapid source of glucose in animal cells.
If you were analyzing a sample of starch and found that it stained blue with iodine, what polysaccharide would you expect to be most abundant, and why?
If you were analyzing a sample of starch and found that it stained blue with iodine, what polysaccharide would you expect to be most abundant, and why?
What is the primary structural difference between amylose and cellulose that leads to their distinct physical properties and digestibility?
What is the primary structural difference between amylose and cellulose that leads to their distinct physical properties and digestibility?
Explain how the structure of inulin prevents its digestion in the human gastrointestinal tract, and describe one of its practical applications.
Explain how the structure of inulin prevents its digestion in the human gastrointestinal tract, and describe one of its practical applications.
Describe the role of cellulose in plants, and explain why it is an essential component of a healthy diet for humans despite being indigestible.
Describe the role of cellulose in plants, and explain why it is an essential component of a healthy diet for humans despite being indigestible.
How does the difference in branching between amylopectin and glycogen affect the rate at which glucose can be released from these polysaccharides?
How does the difference in branching between amylopectin and glycogen affect the rate at which glucose can be released from these polysaccharides?
Explain why the arrangement of glycosidic bonds is crucial for the different functions of starch and cellulose.
Explain why the arrangement of glycosidic bonds is crucial for the different functions of starch and cellulose.
What are the two types of classifications for polysaccharides?
What are the two types of classifications for polysaccharides?
Describe the role of intestinal bacteria in ruminants in the context of cellulose digestion, and why is this process not observed in humans?
Describe the role of intestinal bacteria in ruminants in the context of cellulose digestion, and why is this process not observed in humans?
How are the different glycosidic linkages within amylopectin and glycogen relevant to their biological functions related to energy metabolism?
How are the different glycosidic linkages within amylopectin and glycogen relevant to their biological functions related to energy metabolism?
Flashcards
Polysaccharides (Glycans)
Polysaccharides (Glycans)
Polysaccharides containing more than 10 monosaccharides linked together via glycosidic bonds.
Homopolysaccharides
Homopolysaccharides
Polysaccharides formed from only one kind of monosaccharide.
Heteropolysaccharides
Heteropolysaccharides
Polysaccharides formed from different kinds of monosaccharides.
Branched Polysaccharides
Branched Polysaccharides
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Unbranched/Linear Polysaccharides
Unbranched/Linear Polysaccharides
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Polysaccharide - Starch
Polysaccharide - Starch
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Starch - Amylose
Starch - Amylose
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Starch - Amylopectin
Starch - Amylopectin
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Glycogen
Glycogen
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Inulin
Inulin
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Cellulose
Cellulose
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Study Notes
- Polysaccharides, also known as glycans, contain more than 10 monosaccharides linked by glycosidic bonds
Homopolysaccharides
- Formed by the same kind of monosaccharides
- Examples include starch, glycogen, and cellulose
- Each is formed by hundreds of glucose molecules linked by glycosidic bonds
Heteropolysaccharides
- Polysaccharide molecules are formed by different kinds of monosaccharides
- Hyaluronic acid, formed by thousands of alternating units of N-acetyl glucosamine and glucuronic acid serves as an example
- Other examples include chondroitin sulfate, heparin, keratan sulfate, and dermatan sulfate
Polysaccharide Classification by Structure
- Polysaccharides can be classified based on the type of linkages of the monosaccharides
Branched Polysaccharides
- Starch and glycogen serve as examples of branched polysaccharides
Unbranched/Linear Polysaccharides
- Examples include amylose and cellulose
Starch
- A product of photosynthesis and storage polysaccharide in higher plants
- Composed of D-glucose units
- Has a high molecular weight
- Not a single molecule, but a grain formed by amylose and amylopectin
- A good source of glucose in diet
Amylose
- A linear homopolysaccharide
- Made up of D-glucose units linked by α 1,4- glycosidic bonds
- Insoluble in water
- Gives a blue color with iodine
- Forms the outer layer of the starch granule
- Composes about 30% of the granule
- Hydrolysis by α-amylase yields maltose and glucose
Amylopectin
- A branched homopolysaccharide
- D-glucose units are linked by α-1,4-glycosidic bonds at the linear chains
- α-1,6-glycosidic bonds exist at the branches
- Insoluble in water
- Gives a red-violet color with iodine
- Forms the inner layer of the starch granule
- Makes up about 70% of the granule
- Linear chains are hydrolyzed by α-amylase, similarly to amylose
- α-1,6-bonds are hydrolyzed by α-1,6-glucosidase
- Amylopectin shows a branch at each 24-30 units of glucose
Glycogen
- A storage polysaccharide in animal tissues, found mainly in the liver and skeletal muscle
- A branched homopolysaccharide composed of D-glucose units linked by α-1,4-glycosidic bonds at the linear chains
- α-1,6-glycosidic bonds are present at the branches
- Similar to amylopectin, but more highly branched
- Hydrolyzed by α-amylase and α-1,6-glucosidase for maltose and glucose
- Glycogen shows a branch at each 8-10 units of glucose
Inulin
- Polymers composed mainly of fructose units, typically containing a terminal glucose
- Linked by β(2,1) glycosidic bonds
- Not digested by enzymes in the human GIT due to the β(2,1) linkages
- Standard inulin is slightly sweet
- Soluble in water
- Used to determine glomerular filtration rate for kidney function
Cellulose
- A linear homopolysaccharide of D-glucose units found in the cell wall of plants for structural function
- Constitutes the strength and framework of plants
- Glucose units are linked by β-1,4- glycosidic bonds
- Bonds are resistant to acid hydrolysis and glucosidases in the GIT, thus making it indigestible in humans and other higher animals
- Hydrolyzed by the intestinal bacteria in cattle and other ruminants with the enzyme cellulase (β-glucosidase)
- Termites and snails secrete similar cellulase enzymes
- Important source of “bulk” in the diet
- Partial hydrolysis with strong mineral acids yields cellobiose
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