Question

An example of a polysaccharide used for energy storage in humans is a. cellulose. b. glycogen. c. cholesterol. d. starch.

Short answer

b. glycogen.

Step-by-step solution

Eliminate the options that are not polysaccharides

Cellulose, glycogen, and starch are polysaccharides, while cholesterol is not. Cholesterol is a lipid molecule. So, we can eliminate option c.

Eliminate the options that are not used for energy storage in humans

Cellulose is a structural polysaccharide found in the cell walls of plants, and humans cannot digest it. So, it does not have a role in energy storage in humans. We can eliminate option a. Starch is the primary energy storage polysaccharide in plants, but not in humans. Thus, we can eliminate option d.

Identify the correct option

The only remaining option is glycogen. Glycogen is the main energy storage polysaccharide in humans and is stored primarily in the liver and muscles. Therefore, the correct answer is: b. glycogen.

Key concepts

Energy storage in humans

In humans, energy storage is crucial because it helps us maintain bodily functions when we aren't eating. Our body uses several mechanisms to store and release energy as needed. The primary forms of energy storage in our bodies are in the form of glycogen and lipids. When we consume food, the body converts excess glucose, a type of sugar, into glycogen or lipids for later use. Storing energy efficiently allows us to have reserves for times when immediate energy sources, such as food, are not available. The ability to store energy also helps stabilize blood sugar levels, ensuring our cells have a consistent energy supply.

Glycogen

Glycogen is a polysaccharide specifically used for storing energy in humans. It is often referred to as "animal starch" because it serves a similar purpose to starch in plants. Glycogen is predominantly stored in the liver and muscles.

• Liver: The liver acts as a central storage bank for glycogen. When needed, liver glycogen is converted back into glucose and released into the bloodstream, providing energy to the entire body.
• Muscles: Glycogen stored in muscle tissues is used primarily for muscle contraction and energy during physical activities.

Understanding glycogen's role is crucial because it helps us know how our bodies manage energy. For example, during exercise, muscles quickly deplete stored glycogen, which is why endurance athletes often "carb load" to increase their glycogen stores.

Lipid molecule

Lipid molecules play another critical role in energy storage, although they are not polysaccharides. Lipids are efficient energy storage molecules because they pack a large amount of energy within a small space. They are stored in our body as fat. When we need energy, such as during extended periods without food, our body converts fat into usable energy. Lipids are denser forms of energy storage compared to glycogen, meaning they can store more energy by weight. The role of lipids is not just limited to energy storage. They also have key roles in forming cell membranes and signaling pathways within the body. This makes lipids indispensable for both energy needs and essential cellular functions. Keeping lipids in balance supports overall health and wellbeing.