Problem 1 - Campbell Biology

Question

Which of the following categories includes all others in the list? (A) disaccharide (C) starch (B) polysaccharide (D) carbohydrate

Step-by-Step Solution

Answer

(D) carbohydrate

Step 1: Understand the definitions

First, understand the definitions of each term: A carbohydrate is a broad category that includes sugars and starches. A disaccharide is a type of carbohydrate made up of two monosaccharides. Starch is a type of polysaccharide that is a carbohydrate. A polysaccharide is a complex carbohydrate made up of many monosaccharides.

Step 2: Identify the General to Specific Hierarchy

Determine which term is the broadest category encompassing the others. Carbohydrates are the broadest category, as they include both disaccharides and polysaccharides, and starch is a type of polysaccharide.

Step 3: Choose the Correct Option

Since carbohydrates include all disaccharides, polysaccharides, and starches, the correct answer is (D) carbohydrate.

Key Concepts

Disaccharides

Disaccharides are simple carbohydrates composed of two monosaccharide molecules linked together. Common examples include sucrose (table sugar), lactose (milk sugar), and maltose (malt sugar).
Disaccharides are important because they provide energy quickly. When consumed, enzymes in our digestive system break them down into monosaccharides, such as glucose and fructose, which can be absorbed into the bloodstream.
The process of breaking down a disaccharide into its two monosaccharide components is called hydrolysis. For example, sucrose is split into glucose and fructose when consumed.

Key points about disaccharides:
• They are composed of two linked monosaccharides.
• They provide quick energy via digestion.
• Common examples include sucrose, lactose, and maltose.

Polysaccharides

Polysaccharides are complex carbohydrates made up of many monosaccharides linked together. They can contain hundreds or even thousands of monosaccharide units. Examples include cellulose, glycogen, and starch.
Polysaccharides have several important functions in living organisms. They can serve as storage forms of energy, such as glycogen in animals and starch in plants. Additionally, they provide structural support, like cellulose in plant cell walls.
The complexity of polysaccharides means that they take longer to digest compared to disaccharides and monosaccharides. This slow digestion results in a more gradual release of energy.

Key points about polysaccharides:
• They consist of many monosaccharide units.
• They act as energy storage and structural support.
• Examples include cellulose, glycogen, and starch.

Starches

Starches are a specific type of polysaccharide found in plants. They serve as one of the primary storage forms of energy in many plants, including potatoes, rice, and wheat.
Starches are long chains of glucose molecules linked together. When we consume starchy foods, our digestive system breaks down the starch into glucose, which our body then uses for energy.
There are two main types of starch molecules: amylose and amylopectin. Amylose has a linear structure, whereas amylopectin has a branched structure. Foods high in amylopectin tend to be more quickly digested than those high in amylose.

Key points about starches:
• They are a type of polysaccharide.
• They serve as energy storage in plants.
• Commonly found in foods like potatoes, rice, and wheat.