Determine whether each phrase describes starch, glycogen, or cellulose.
Starch
plant polysaccharide
that is easily
digested by humans
made up of two glucose
polysaccharides:
amylose and amylopectin
Glycogen
major storage form
in animals
Cellulose
structural support
for plant
The Correct Answer And Explanation is:
Here’s how each phrase correctly corresponds to starch, glycogen, or cellulose:
Starch:
- Plant polysaccharide
- That is easily digested by humans
- Made up of two glucose polysaccharides: amylose and amylopectin
Glycogen:
- Major storage form in animals
Cellulose:
- Structural support for plants
Explanation (300+ words):
Starch, glycogen, and cellulose are all polysaccharides, meaning they are complex carbohydrates composed of long chains of glucose units. However, they differ in structure, biological function, and how they are metabolized by humans.
Starch:
Starch is a plant-based polysaccharide that serves as an energy storage molecule in plants. It is made up of two types of glucose polymers: amylose (a linear chain) and amylopectin (a branched chain). Because of this structure, starch is easily digested by humans using enzymes like amylase. Foods like potatoes, rice, and bread are rich sources of starch and serve as major energy providers in the human diet.
Glycogen:
Glycogen is the major storage form of glucose in animals, particularly in the liver and muscle tissues. It is highly branched, which allows for rapid release of glucose when energy is needed quickly. Glycogen is structurally similar to amylopectin but even more extensively branched, enhancing its efficiency as an energy reserve. When blood sugar drops, glycogen is broken down into glucose and released into the bloodstream to maintain energy levels.
Cellulose:
Cellulose is a structural polysaccharide found in the cell walls of plants. It provides rigidity and strength to plant structures. Unlike starch and glycogen, cellulose consists of β-glucose linkages, which form straight, rigid chains that hydrogen-bond with each other. Humans lack the enzyme cellulase, so cellulose cannot be digested. However, it plays an important role in the human diet as dietary fiber, aiding in digestion and bowel movement regularity.
Summary Table:
| Polysaccharide | Source | Function | Digestibility by Humans |
|---|---|---|---|
| Starch | Plants | Energy storage | Yes |
| Glycogen | Animals | Energy storage | Yes |
| Cellulose | Plants | Structural support (cell walls) | No (dietary fiber onl |