Problem 52 - Chemistry Matter and Change

Question

Carbohydrates Classify the following carbohydrates as monosaccharides, disaccharides, or polysaccharides. $$\begin{array}{llll}{\text { a. starch }} & {\text { d. ribose }} & {\text { g. fructose }} \\ {\text { b. gucose }} & {\text { e. clululose }} & {\text { h. lactose }} \\ {\text { c. sucrose }} & {\text { f. glycosen }}\end{array}$$

Step-by-Step Solution

Answer

Monosaccharides: ribose, fructose, glucose. Disaccharides: sucrose, lactose. Polysaccharides: starch, cellulose, glycogen.

Step 1: Identify Monosaccharides

Monosaccharides are the simplest form of carbohydrates and cannot be hydrolyzed into simpler sugars. Examples include glucose, fructose, and ribose. In the given list, identify the monosaccharides: d. ribose, g. fructose, and b. glucose.

Step 2: Identify Disaccharides

Disaccharides are carbohydrates composed of two monosaccharide units. Examples include sucrose and lactose. In the given list, identify the disaccharides: c. sucrose and h. lactose.

Step 3: Identify Polysaccharides

Polysaccharides are complex carbohydrates composed of long chains of monosaccharide units. Examples include starch, cellulose, and glycogen. In the given list, identify the polysaccharides: a. starch, e. cellulose, and f. glycogen.

Key Concepts

Monosaccharides

Monosaccharides are the building blocks of carbohydrates, often referred to as simple sugars. They have the most basic structure and cannot be broken down into simpler forms of sugar through hydrolysis. This makes them a fundamental unit in carbohydrate chemistry. Monosaccharides typically consist of carbon, hydrogen, and oxygen atoms, following the general formula \( C_nH_{2n}O_n \), where \( n \) usually ranges from 3 to 7.
Some common examples of monosaccharides are glucose, fructose, and ribose. Each of these has unique properties and roles in the body:

• Glucose: Known as blood sugar, it's vital for cellular energy production.
• Fructose: A sugar found in many fruits; it's sweeter than glucose.
• Ribose: Essential for the formation of RNA and plays a critical role in metabolism.

Naturally, monosaccharides are processed by the body quickly due to their simple structure, providing immediate energy. They are found in foods like fruits, honey, and some vegetables.

Disaccharides

Disaccharides are carbohydrates formed by the chemical bonding of two monosaccharide molecules, resulting in a structure that can be hydrolyzed into the simpler sugars. The glycosidic bond is what links these two monosaccharides together. Disaccharides serve as an important dietary source of energy.
Common examples include sucrose and lactose:

• Sucrose: Known as table sugar, it is composed of one glucose and one fructose molecule. It's commonly found in sugarcane and sugar beets.
• Lactose: Found in milk and dairy products, it consists of glucose and galactose. Lactose intolerance occurs when the body lacks the enzyme lactase, needed to break down lactose into its monosaccharides.

Disaccharides need to be broken down into their monosaccharide components before they can be utilized by the body. This process ensures that the energy stored in their bonds is released slowly, providing a more sustained energy source compared to monosaccharides.

Polysaccharides

Polysaccharides are large and complex carbohydrates formed from long chains of monosaccharide units linked together. They serve several essential roles in biological processes, including energy storage and providing structural support.
These macromolecules are classified based on their structure and the specific monosaccharides they contain. Some key examples of polysaccharides include:

• Starch: Used by plants to store energy; it consists of glucose units. It's found in high amounts in foods like potatoes and grains.
• Cellulose: A major component of plant cell walls, providing rigidity and strength. Though humans can't digest cellulose due to the absence of necessary enzymes, it is important for dietary fiber.
• Glycogen: The primary storage form of glucose in animals, particularly in liver and muscle tissues. It can be rapidly mobilized to glucose when energy is needed.

Unlike monosaccharides and disaccharides, polysaccharides don't taste sweet and require enzymatic breakdown to be used as an energy source. This breakdown process occurs over a longer period, making polysaccharides excellent for energy storage.