Exploring Carbohydrates and Their Functions

Which of the following best describes the structure of a carbohydrate molecule?

• A chain of amino acids linked by peptide bonds

• A chain of nucleotides linked by phosphodiester bonds

• A chain of monosaccharides linked by glycosidic bonds

• A chain of fatty acids linked by ester bonds

Answer explanation

Carbohydrates are composed of monosaccharides, which are simple sugars. These monosaccharides are linked together by glycosidic bonds to form larger carbohydrate molecules, making this the correct description.

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DOK Level 3: Strategic Thinking

• Sucrose

• Glucose

• Cellulose

• Starch

Answer explanation

The molecular formula C6H12O6 corresponds to glucose, a common monosaccharide. Sucrose is a disaccharide, while cellulose and starch are polysaccharides, making glucose the correct choice.

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DOK Level 3: Strategic Thinking

Which functional group is commonly found in carbohydrates and is responsible for their solubility in water?

• Carboxyl group

• Hydroxyl group

• Amino group

• Phosphate group

Answer explanation

The hydroxyl group (-OH) is a functional group commonly found in carbohydrates. Its presence increases the solubility of carbohydrates in water due to hydrogen bonding, making it essential for their biological functions.

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DOK Level 3: Strategic Thinking

Explain how the structure of cellulose contributes to its function in plant cell walls.

• The branched structure allows for easy storage and quick energy release.

• The linear, unbranched structure forms strong fibers that provide rigidity.

• The helical structure allows for compact storage in plant cells.

• The globular structure makes it soluble in water for easy transport.

Answer explanation

The linear, unbranched structure of cellulose allows it to form strong fibers through hydrogen bonding, providing rigidity and structural support to plant cell walls, which is essential for maintaining plant shape and resisting external pressures.

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DOK Level 3: Strategic Thinking

Which of the following polysaccharides is primarily used for energy storage in animals?

• Cellulose

• Glycogen

• Starch

• Chitin

Answer explanation

Glycogen is the primary polysaccharide used for energy storage in animals, stored mainly in the liver and muscles. In contrast, cellulose is a structural component in plants, starch is used for energy storage in plants, and chitin is found in exoskeletons.

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DOK Level 3: Strategic Thinking

Which of the following is a disaccharide formed from two glucose molecules?

• Lactose

• Sucrose

• Maltose

• Fructose

Answer explanation

Maltose is a disaccharide formed from two glucose molecules. In contrast, lactose is made from glucose and galactose, sucrose from glucose and fructose, and fructose is a monosaccharide.

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DOK Level 3: Strategic Thinking

Describe the role of chitin in the biological systems where it is found.

• It serves as an energy storage molecule in plants.

• It provides structural support in the exoskeletons of arthropods.

• It acts as a transport molecule in the bloodstream.

• It functions as a signaling molecule in cellular communication.

Answer explanation

Chitin is a key structural component in the exoskeletons of arthropods, providing rigidity and protection. It is not involved in energy storage, transport, or signaling, making the second choice the correct answer.

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DOK Level 3: Strategic Thinking

Compare and contrast the structures of starch and cellulose and explain how these differences affect their biological functions.

• Both are branched, but starch is used for energy storage while cellulose is used for structural support.

• Starch is branched and used for energy storage, while cellulose is linear and used for structural support.

• Both are linear, but starch is used for energy storage while cellulose is used for structural support.

• Starch is linear and used for energy storage, while cellulose is branched and used for structural support.

Answer explanation

Starch is branched, allowing for compact energy storage, while cellulose is linear, providing rigidity and structural support in plant cell walls. This structural difference is key to their distinct biological functions.

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DOK Level 3: Strategic Thinking

Explain the significance of glycosidic bonds in the formation of polysaccharides.

• They link amino acids together to form proteins.

• They link nucleotides together to form nucleic acids.

• They link monosaccharides together to form polysaccharides.

• They link fatty acids together to form lipids.

Answer explanation

Glycosidic bonds are crucial as they connect monosaccharides, the building blocks of carbohydrates, to form polysaccharides. This linkage allows for the creation of complex sugars, which serve various functions in biological systems.

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DOK Level 3: Strategic Thinking

Which of the following best explains the function of glycogen in animals?

• Glycogen serves as a structural component in cell walls.

• Glycogen acts as a long-term energy storage molecule.

• Glycogen is involved in the transport of oxygen in the bloodstream.

• Glycogen functions as a signaling molecule in cellular communication.

Answer explanation

Glycogen is a polysaccharide that serves as a primary energy storage molecule in animals, allowing them to store glucose for later use, especially during periods of fasting or intense activity.

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DOK Level 3: Strategic Thinking