Problem 52 - Chemistry Matter and Change

Question

Carbohydrates Classify the following carbohydrates as monosaccharides, disaccharides, or polysaccharides. \(\begin{array}{lll}{\text { a. starch }} & {\text { d. ribose }} & {\text { g. fructose }} \\ {\text { b. glucose }} & {\text { e. cellulose }} & {\text { h. lactose }} \\ {\text { c. sucrose }} & {\text { f. glycogen }}\end{array}\)

Step-by-Step Solution

Answer

The given carbohydrates can be classified as follows: - Monosaccharides: ribose (d), glucose (b), fructose (g) - Disaccharides: sucrose (c), lactose (h) - Polysaccharides: starch (a), cellulose (e), glycogen (f)

Step 1: Identify Monosaccharides

Monosaccharides are simple sugars that cannot be broken down into smaller sugar molecules. Given the list of carbohydrates, we can identify the following as monosaccharides: ribose (d), glucose (b), and fructose (g).

Step 2: Identify Disaccharides

Disaccharides are composed of two monosaccharide units linked together. Given the list of carbohydrates, we can identify the following as disaccharides: sucrose (c), and lactose (h).

Step 3: Identify Polysaccharides

Polysaccharides are composed of multiple monosaccharide units that are linked together. Given the list of carbohydrates, we can identify the following as polysaccharides: starch (a), cellulose (e), and glycogen (f).

Step 4: Summarize the classification

Now that we have identified each carbohydrate as either a monosaccharide, disaccharide, or polysaccharide, let's summarize the classification of each one: - Monosaccharides: ribose (d), glucose (b), fructose (g) - Disaccharides: sucrose (c), lactose (h) - Polysaccharides: starch (a), cellulose (e), glycogen (f)

Key Concepts

Monosaccharides

Monosaccharides are the simplest form of carbohydrates and are often referred to as simple sugars. These molecules are the building blocks for more complex carbohydrates. Their general formula is typically \\( C_nH_{2n}O_n \), with common examples being glucose, ribose, and fructose.

Monosaccharides have several key characteristics:

• Single Unit: They consist of a single sugar molecule, which is why they cannot be broken down into simpler sugars.
• Water Soluble: Due to their simple structure, they easily dissolve in water, which makes them accessible for biological processes.
• Energy Providers: They are rapidly metabolized, providing a quick source of energy for the body.

Examples from the exercise include ribose, glucose, and fructose. Glucose is vital for energy, whereas ribose is essential in the structure of RNA. Fructose is found naturally in fruits and is used as a sweetener.

Disaccharides

Disaccharides consist of two monosaccharide molecules joined together by a glycosidic bond. This link is typically formed during a dehydration reaction where a molecule of water is removed. Their general formula is often \\( C_{12}H_{22}O_{11} \).

Notable properties of disaccharides include:

• Intermediate Complexity: Comprising two sugar units, they are more complex than monosaccharides but simpler than polysaccharides.
• Sweet Taste: Like monosaccharides, they often taste sweet, notably sucrose, which is common table sugar.
• Digestive Breakdown: Disaccharides need to be broken down into their monosaccharide components before they can be metabolized for energy.

In our exercise, sucrose and lactose are examples of disaccharides. Sucrose is a combination of glucose and fructose, while lactose, found in milk, comprises glucose and galactose. Many people are familiar with lactose intolerance, a condition where the enzyme to break down lactose is deficient.

Polysaccharides

Polysaccharides are complex carbohydrates made from long chains of monosaccharide units. Unlike the simple structures of monosaccharides and disaccharides, polysaccharides can range from hundreds to thousands of sugar units.

Here are some significant features of polysaccharides:

• Complex Structure: They form complex three-dimensional structures, which can be either branched or unbranched.
• Insoluble in Water: Due to their large size, polysaccharides are generally insoluble in water.
• Energy Storage and Support: They serve as important energy reserves and structural components in cells. For example, starch and glycogen are key energy storage polysaccharides, while cellulose offers structural support in plant cell walls.

In the exercise, starch, cellulose, and glycogen are given as examples. Starch is a primary energy source in plants, glycogen serves a similar role in animals, and cellulose gives strength to plant structures. These carbohydrates play crucial roles in both dietary functions and structural dynamics within ecosystems.