Biochem 7.2 Untitled Quiz
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Questions and Answers

What is the term used for the chemical linkage between two monosaccharides?

  • Peptide bond
  • Glycosidic bond (correct)
  • Fructose bond
  • Ether bond

What is released during the formation of a glycosidic bond?

  • Glucose
  • Water (correct)
  • Oxygen
  • Carbon dioxide

What term describes carbohydrates formed from several monosaccharides linked together?

  • Saccharides
  • Peptides
  • Glycans (correct)
  • Nucleotides

Which of the following may NOT form a glycosidic bond with monosaccharides?

<p>Fatty acids (A)</p> Signup and view all the answers

What happens to monosaccharides upon glycosidic bond formation?

<p>They become monosaccharide residues (C)</p> Signup and view all the answers

Which best describes the term 'oligosaccharides'?

<p>A few sugars (D)</p> Signup and view all the answers

What type of reaction occurs when a glycosidic bond forms?

<p>Condensation (A)</p> Signup and view all the answers

Which of the following statements about glycosidic bonds is correct?

<p>They may link carbohydrates to proteins or lipids. (A)</p> Signup and view all the answers

What is the primary function of polysaccharides in cells?

<p>For energy storage and structure (D)</p> Signup and view all the answers

Which type of glycosidic bond is found in the simplest form of starch, amylose?

<p>α-1,4-glycosidic bonds (B)</p> Signup and view all the answers

How does the structure of amylopectin differ from amylose?

<p>Amylopectin includes both linear chains and branch points. (A)</p> Signup and view all the answers

What role does storing carbohydrates in the form of polysaccharides play regarding cellular osmolarity?

<p>It decreases the total cellular osmolarity. (C)</p> Signup and view all the answers

What is the average frequency of branch points in amylopectin?

<p>Every 25 glucose units (D)</p> Signup and view all the answers

Which polysaccharide is recognized as the primary form of glucose storage in animals?

<p>Glycogen (D)</p> Signup and view all the answers

Which of the following is NOT true regarding amylose?

<p>It can have multiple branch points. (B)</p> Signup and view all the answers

What type of molecules can polysaccharides be assembled from?

<p>Monosaccharides (C)</p> Signup and view all the answers

What is the primary structural difference between glycogen and amylopectin?

<p>Glycogen has more branched structures. (C)</p> Signup and view all the answers

What is the molecular formula for a disaccharide formed from two monosaccharides?

<p>Cn(H2O)n-1 (B)</p> Signup and view all the answers

Which of the following describes the effect of glycosidic bonds on monosaccharide units?

<p>They lock monosaccharides in cyclic form. (C)</p> Signup and view all the answers

How does the branching of glycogen affect its function?

<p>It allows for rapid mobilization of glucose units. (B)</p> Signup and view all the answers

How does the molecular formula change as carbohydrates form larger structures?

<p>The formula decreases in hydrogen and oxygen counts. (D)</p> Signup and view all the answers

Why can't animals digest cellulose?

<p>They lack the enzymes to hydrolyze ẞ-1,4-glycosidic bonds. (B)</p> Signup and view all the answers

What defines an a-1,4-glycosidic bond?

<p>Linkage between carbon 1 and carbon 4 with a α configuration. (A)</p> Signup and view all the answers

What type of bond links the glucose units in cellulose?

<p>Beta-1,4-glycosidic bonds. (C)</p> Signup and view all the answers

Which property of cellulose allows for its structural role in plant cell walls?

<p>Its linear chains of glucose linked by β-1,4-glycosidic bonds. (C)</p> Signup and view all the answers

What happens to a monosaccharide's anomeric configuration after it participates in a glycosidic bond?

<p>It becomes fixed and cannot open to linearize. (A)</p> Signup and view all the answers

What is the role of glycogenin in glycogen structure?

<p>Providing an anchor for glycogen chains. (C)</p> Signup and view all the answers

In the context of carbohydrate structure, what does the term 'branches' refer to?

<p>Multiple glycosidic bonds to other monosaccharides. (A)</p> Signup and view all the answers

How do animals that consume cellulose primarily digest it?

<p>With the help of symbiotic microflora. (B)</p> Signup and view all the answers

Which configuration is associated with a ẞ-2,6-glycosidic bond?

<p>Çarbon 2 of a cyclic ketose linked to carbon 6. (C)</p> Signup and view all the answers

Which statement accurately reflects the characteristics of complex carbohydrates?

<p>They can include multiple branches from a single monosaccharide. (A)</p> Signup and view all the answers

What type of end does glycogen lack, which is present in amylopectin?

<p>A free reducing end. (D)</p> Signup and view all the answers

What is required for a carbohydrate to form a glycosidic bond?

<p>An anomeric carbon must be free (D)</p> Signup and view all the answers

What distinguishes reducing sugars from nonreducing sugars?

<p>Reducing sugars have free anomeric carbons (D)</p> Signup and view all the answers

During the Tollens test, which group is primarily responsible for reducing silver ions?

<p>Aldehyde group (C)</p> Signup and view all the answers

What happens to the aldehyde group of an aldose during oxidation?

<p>It is converted to a carboxylic acid (C)</p> Signup and view all the answers

Which statement is true regarding trehalose?

<p>Both anomeric carbons are involved in glycosidic bonds (B)</p> Signup and view all the answers

What defines the reducing end of a complex carbohydrate?

<p>It terminates with an anomeric carbon (D)</p> Signup and view all the answers

Which sugar can act as a reducing sugar despite having a ketone group?

<p>Fructose (C)</p> Signup and view all the answers

How is the configuration of a glycosidic bond in trehalose specified?

<p>By combining both anomeric carbon configurations (B)</p> Signup and view all the answers

What structural difference exists between maltose and cellobiose?

<p>They differ in the orientation of the glycosidic linkage. (D)</p> Signup and view all the answers

What type of glycosidic bond is present in sucrose?

<p>a-1,β-2-glycosidic bond (A)</p> Signup and view all the answers

Which monosaccharide is in the pyranose form in sucrose?

<p>Glucose (A)</p> Signup and view all the answers

What is the main reason animals cannot digest cellobiose?

<p>The orientation of its glycosidic bond is different. (D)</p> Signup and view all the answers

Why do humans experience lactose intolerance?

<p>They do not produce enough lactase enzyme. (D)</p> Signup and view all the answers

What is the relationship between lactose and cellobiose?

<p>They have different glycosidic bond orientations. (C)</p> Signup and view all the answers

What happens to the anomeric carbons when forming sucrose?

<p>They flip along their vertical axes to align. (D)</p> Signup and view all the answers

Which enzyme is responsible for digesting lactose in humans?

<p>Lactase (C)</p> Signup and view all the answers

Flashcards

Glycosidic Bond

A chemical bond formed between the anomeric carbon of a carbohydrate and a nucleophilic atom of another molecule, such as another carbohydrate, protein, lipid, or nitrogenous base.

Anomeric Carbon

The carbon atom in a monosaccharide that is involved in the formation of a glycosidic bond. It is typically the carbonyl carbon in the ring structure.

Disaccharide

Two monosaccharides linked together by a glycosidic bond.

Trisaccharide

Three monosaccharides linked together by glycosidic bonds.

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Polysaccharide

A carbohydrate composed of a large number of monosaccharide units linked by glycosidic bonds.

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Glycan Chain

A common name for polysaccharides, emphasizing their chain-like structure.

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Hydrolysis of Glycosidic Bonds

The process of breaking down a glycosidic bond using water.

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Condensation Reaction (Glycosidic Bond Formation)

The process of forming a glycosidic bond by removing water.

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Glycosidic Bond Formation and Formula Change

The general formula for carbohydrates changes when glycosidic bonds form. Disaccharides have the formula Cn(H2O)n-1, trisaccharides have Cn(H2O)n-2, and so on.

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Glycosidic Bond Connection

A glycosidic bond connects the anomeric carbon of a monosaccharide to another molecule, like another sugar.

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Cyclic Form Lock

The anomeric carbon involved in a glycosidic bond is locked into a cyclic form, preventing the sugar from linearizing.

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Glycan Branching

Branching is common in complex carbohydrates. A single monosaccharide can be linked to multiple other sugars at different points.

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Glycosidic Linkage Nomenclature

Glycosidic linkages are named based on the carbons involved and the anomeric configuration of the sugar.

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a-1,4-Glycosidic Bond

An a-1,4-glycosidic bond links the anomeric carbon (carbon 1) of an aldose in the alpha configuration to carbon 4 of another sugar.

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ẞ-2,6-Glycosidic Bond

A ẞ-2,6-glycosidic bond links the beta-anomeric carbon (carbon 2) of a ketose to carbon 6 of another sugar.

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The Importance of Glycosidic Linkages

Understanding glycosidic linkages is essential for characterizing complex carbohydrates. Each linkage determines the shape and properties of the carbohydrate structure.

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Maltose

A disaccharide formed by two glucose units linked by an α-1,4-glycosidic bond. It is a product of starch digestion and can be further broken down into individual glucose units.

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Cellobiose

A disaccharide similar to maltose, but with a β-1,4-glycosidic bond between its glucose units. Animals lack the enzymes to digest cellobiose.

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Sucrose

A disaccharide composed of glucose and fructose linked by an α-1,β-2-glycosidic bond. It is a nonreducing sugar and is commonly known as table sugar.

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Lactose

A disaccharide composed of galactose and glucose linked by a β-1,4-glycosidic bond. It is the sugar found in milk and can be digested by most humans using the lactase enzyme.

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Lactase

The enzyme responsible for breaking down lactose into glucose and galactose.

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Lactose Intolerance

A condition where individuals lack the enzyme lactase and cannot properly digest lactose, leading to digestive discomfort.

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Enzyme Specificity

The study of how enzymes interact with specific molecules, highlighting the importance of molecular structure and shape in enzyme activity.

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Reducing Sugar

A carbohydrate that can donate electrons to silver ions (Ag+) in the Tollens test, reducing them to silver metal. This is because they have a free anomeric carbon (not involved in a glycosidic bond).

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Nonreducing Sugar

A carbohydrate that cannot act as a reducing agent because all anomeric carbons are involved in glycosidic bonds. They lack a free anomeric carbon.

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Reducing End

The end of a complex carbohydrate that terminates with a free anomeric carbon, making it capable of reducing silver ions.

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Nonreducing End

The end of a complex carbohydrate that does not have a free anomeric carbon, making it incapable of reducing silver ions.

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Tautomerization

The process of converting a ketose into an aldose under specific reaction conditions, like the Tollens test.

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Tollens Test

A test used to identify reducing sugars by their ability to reduce silver ions to silver metal.

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Amylose

A polysaccharide composed entirely of glucose units linked by α-1,4 glycosidic bonds. It is a major component of starch and is a readily available source of energy for humans.

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Amylopectin

A polysaccharide made of glucose units linked by α-1,4 glycosidic bonds, but also branching with α-1,6 glycosidic bonds, found in plants.

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Glycogen

A polysaccharide, primarily found in animals, consisting of glucose units linked together by α-1,4 glycosidic bonds with branches created by α-1,6 glycosidic bonds. It's the primary energy storage molecule in animals.

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α-1,4 Glycosidic bond

A glycosidic bond where the linkage occurs between the anomeric carbon of one monosaccharide and the hydroxyl group on carbon 4 of another monosaccharide.

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α-1,6 Glycosidic bond

A glycosidic bond where the linkage occurs between the anomeric carbon of one monosaccharide and the hydroxyl group on carbon 6 of another monosaccharide. This bond creates branches in polysaccharides.

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Glycogen: What is it?

A highly branched polymer of glucose units, primarily found in animals. It's similar to amylopectin but with more frequent branching (every 10-15 glucose units), making it more compact.

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Glycogen: Key Feature

Glycogen chains are linked to a protein called glycogenin via a glycosidic bond to a tyrosine residue. This means that glycogen does not have a free reducing end, unlike amylopectin, which has a free reducing end.

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Glycogen: Branching Advantage

The frequent branching in glycogen provides multiple non-reducing ends, which increases the efficiency of adding or removing glucose units.

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Cellulose: What is it?

A linear chain of glucose units linked by β-1,4-glycosidic bonds, making it a major component of plant cell walls. Animals lack enzymes to break down these bonds, making it indigestible.

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Cellulose: Haworth Projection

The alternating glucose units in a cellulose chain are flipped in their Haworth projections to facilitate a horizontal depiction of the linear structure.

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Cellulose Digestion

Animals that rely on diets high in cellulose, like ruminants, have a symbiotic relationship with bacteria that possess enzymes to break down the β-1,4-glycosidic bonds in cellulose, allowing them to digest it.

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Humans and Cellulose

The β-1,4-glycosidic bonds in cellulose make it indigestible for humans. This is because humans lack the enzyme cellulase, which breaks down these bonds.

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Cellulose vs. Amylose

The orientation of the glycosidic bonds in cellulose is different from that in amylose, which is similar to maltose, thus making cellulose indigestible by animals.

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Study Notes

Introduction to Complex Carbohydrates

  • Monosaccharides combine to form more complex carbohydrates via glycosidic bonds.
  • Disaccharides, trisaccharides, and polysaccharides are formed.
  • Glycans are another name for polysaccharides, often chains with multiple branch points.
  • Carbohydrates can form glycosidic bonds with proteins, lipids, and nitrogenous bases.
  • This modification can change the molecules.

Glycosidic Bonds

  • A glycosidic bond is a chemical linkage between a carbohydrate's anomeric carbon and another molecule's nucleophilic atom.
  • The other molecule can be another carbohydrate, a protein, a lipid, or a nucleoside.
  • Glycosidic bond formation is a condensation reaction, releasing water.
  • The reaction can be reversed by hydrolysis.
  • Monosaccharides become monosaccharide residues (units) after glycosidic bond formation.

Changes in Molecular Formulas

  • Disaccharides have the formula Cn(H2O)n-1.
  • Trisaccharides have the formula Cn(H2O)n-2.
  • Each additional monosaccharide in a chain reduces the water component.

Concept Check 7.7

  • The molecular formula for a tetrasaccharide formed from one glucose (C6H12O6), one ribose (C5H10O5), one erythrose (C4H8O4), and one fructose (C6H12O6) molecule is C18H32O16.

Glycosidic Bond Formation

  • The acetal or ketal is formed when a hemiacetal (or hemiketal) carbon from one monosaccharide condensates with a hydroxyl on another.
  • The resultant molecule is locked in a cyclic form.

Reducing and Nonreducing Sugars

  • Free anomeric carbons are reducing sugars as they can reduce silver ions.
  • Nonreducing sugars have all anomeric carbons involved in glycosidic bonds.
  • Reducing sugars are those with a free anomeric carbon that can be involved in a redox reaction.
  • Nonreducing sugars cannot react.

Glycosidic Bonds Between Carbohydrates and Noncarbohydrates

  • Glycoproteins and glycolipids are important examples of these types of bonds.
  • Glucose units can link with other molecules, forming glycoproteins and glycolipids.
  • Viruses or pathogens often use glycoproteins as a first step during infection.

Disaccharides Summary

  • Maltose is a disaccharide formed from two glucose units linked by an α-1,4-glycosidic bond. Animals can digest it.
  • Cellobiose is similar to maltose, but with a β-1,4-glycosidic bond. Animals cannot digest it.
  • Sucrose has a glucose and a fructose unit linked by an α-1,β-2 glycosidic bond.

Polysaccharides Summary

  • Starch is entirely glucose, and composed of amylose (linear) and amylopectin (branched).
  • Glycogen is the primary energy storage in animals and is even more branched than amylopectin.
  • Cellulose is also a glucose polymer, but its β-1,4-glycosidic linkages cannot be broken down by most enzymes thus, is indigestible to most animals.

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