Problem 67 - Chemistry The Central Science

Question

Indicate whether each statement is true or false: (a) Disaccharides are a type of carbohydrate. (b) Sucrose is a monosaccharide. (c) All carbohydrates have the formula \(\mathrm{C}_{n} \mathrm{H}_{2 m} \mathrm{O}_{m} .\)

Step-by-Step Solution

Answer

In conclusion: - Statement A: Disaccharides are a type of carbohydrate. (True) - Statement B: Sucrose is a monosaccharide. (False) - Statement C: All carbohydrates have the formula \(\mathrm{C}_{n} \mathrm{H}_{2 m} \mathrm{O}_{m}\). (False)

Step 1: (Statement A: Disaccharides are a type of carbohydrate.)

Disaccharides are indeed a type of carbohydrate. Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen, and are a major source of energy. Disaccharides are formed when two monosaccharides (simple sugars) join together, which also classifies them as carbohydrates. Therefore, Statement A is true.

Step 2: (Statement B: Sucrose is a monosaccharide.)

Sucrose is a sugar, specifically a disaccharide, formed by the combination of glucose (a monosaccharide) and fructose (another monosaccharide). Since sucrose is made up of two monosaccharides and is not a single simple sugar, it is not itself a monosaccharide. Therefore, Statement B is false.

Step 3: (Statement C: All carbohydrates have the formula \(\mathrm{C}_{n} \mathrm{H}_{2 m} \mathrm{O}_{m}\).)

The general formula for a carbohydrate is \(\mathrm{C}_{n} (\mathrm{H}_{2} \mathrm{O})_{m}\). In this formula, "n" and "m" represent the number of carbon atoms and the number of water molecules, respectively. However, not all carbohydrates follow this formula in a strict sense, and there are exceptions such as deoxy sugars and amino sugars. So, while most carbohydrates fall under this formula, it's not true for all of them. Therefore, Statement C is false. In conclusion: - Statement A: Disaccharides are a type of carbohydrate. (True) - Statement B: Sucrose is a monosaccharide. (False) - Statement C: All carbohydrates have the formula \(\mathrm{C}_{n} \mathrm{H}_{2 m} \mathrm{O}_{m}\). (False)

Key Concepts

Disaccharides

Disaccharides are a fascinating and significant group within the carbohydrate family, bridging the simplicity of monosaccharides and the complexity of polysaccharides. Imagine them as a team of two monosaccharides holding hands through a bond known as a glycosidic linkage. When we digest disaccharides, our bodies break them down into monosaccharides that can be absorbed and utilized for energy. Common examples of disaccharides include sucrose, lactose, and maltose.

Understanding the structure of disaccharides is key—they are made by a condensation reaction where each monosaccharide contributes a hydroxyl (OH) group, resulting in a molecule of water being released as they bond. This process is reversible; by adding water, we can split them back into monosaccharides, a reaction called hydrolysis. In real-world scenarios, enzymes in our body facilitate this reaction during digestion.

Monosaccharide

A monosaccharide is the simplest form of carbohydrates and includes glucose, fructose, and galactose—think of them as the individual building blocks. They are essentially single sugar molecules that cannot be broken down into simpler sugars, which is why they are considered the simplest form of carbohydrates.

Monosaccharides play vital roles beyond just energy sources; they contribute to the structure and function of cell walls and communicate cellular signals. Their chemical formula is generally \( C_{6}H_{12}O_{6} \), though it can vary depending on the number of carbon atoms present. The arrangement of atoms and spatial configuration in these molecules defines their properties and how they interact with other biological molecules. In addition, the type of monosaccharide can affect the properties of disaccharides and polysaccharides when they join through glycosidic linkages.

Molecular Formula of Carbohydrates

The molecular formula for carbohydrates, often \( C_{n}(H_{2}O)_{m} \), is a roadmap showing the proportion of carbon to water molecules. Typically, 'n' equals 'm', giving us the empirical formula \( C_{n}H_{2n}O_{n} \) which suggests a balanced ratio of carbon to water, reflecting the name 'carbohydrate' or 'hydrates of carbon'.

It's important to note that while this general formula provides an overview, the actual structure of carbohydrates is much more complex and varied. Carbohydrates include a variety of structures from the simple monosaccharides to complex polysaccharides like starch, cellulose, and glycogen. Although carbohydrates generally follow this pattern, structural variations and other elements like nitrogen can be introduced, giving rise to an even wider variety of compounds. In reality, the diverse world of carbohydrates showcases a vast array of structures and functions, all crucial to life as we know it.