Difficulty: Easy
Correct Answer: Glycogen
Explanation:
Introduction / Context:
The human body needs a way to store extra energy for later use when food is not immediately available. Glucose is the primary simple sugar used by cells for energy, but the body cannot keep large amounts of free glucose circulating in the blood. Instead, it stores glucose in the form of a larger polymer. This question tests your knowledge of which storage form the human body uses and distinguishes it from other carbohydrates such as sucrose, cellulose, and starch, which you may encounter in everyday foods and plant structures.
Given Data / Assumptions:
Concept / Approach:
Glycogen is a branched polymer of glucose that serves as the storage form of carbohydrate in animals, including humans. It is stored mainly in the liver and skeletal muscles. When blood glucose levels fall or when muscles need extra energy, glycogen is broken down into glucose and released into the bloodstream or used directly in the muscles. Sucrose is a disaccharide commonly known as table sugar and is found in plants and food, not as a storage polymer in human tissues. Cellulose is a structural carbohydrate in plant cell walls and cannot be digested by humans. Starch is the storage form of glucose in plants, not in animals.
Step-by-Step Solution:
1. Recall that the body maintains blood glucose in a narrow range and cannot store large amounts of free glucose without causing serious problems.2. The liver and muscles help by converting surplus glucose into a storage form.3. In animals, this storage form is glycogen, a highly branched polysaccharide composed entirely of glucose units.4. When the body needs energy between meals or during exercise, enzymes break glycogen back down into glucose for use in cellular respiration.5. Sucrose, cellulose, and starch have important roles in plants or in the human diet but are not the form in which human tissues store glucose.6. Therefore, the only correct answer for the storage form of glucose in the human body is glycogen.
Verification / Alternative check:
Physiology and biochemistry textbooks describe glycogenesis as the process by which glucose is converted to glycogen for storage, and glycogenolysis as the reverse process through which glycogen is broken down when energy is needed. They list the liver glycogen store as a buffer for blood glucose and muscle glycogen as a local energy reserve during intense exercise. Nutritional information about plant foods describes starch as the main storage carbohydrate in plants and cellulose as indigestible fiber, which confirms that these substances are not used by the human body as its internal glucose store. This supports the conclusion that glycogen is the correct answer.
Why Other Options Are Wrong:
Option A, sucrose, is incorrect because sucrose is an external dietary sugar, not a storage polysaccharide in human tissues. Option C, cellulose, is wrong since it is used by plants for structural support and passes through the human digestive system as fiber without being stored as energy. Option D, starch, is the storage form of glucose in plants, such as potato tubers and cereal grains, but in animals starch from food is broken down into glucose and then converted into glycogen, not stored as starch inside the body.
Common Pitfalls:
Students sometimes confuse starch and glycogen because both are glucose polymers. A useful distinction is that starch is plant storage and glycogen is animal storage. Another pitfall is assuming that any sugar found in food, such as sucrose, could be the storage form in the body, which is not the case. Careful reading of the phrase in the human body in the question helps steer you toward glycogen as the correct answer.
Final Answer:
In human physiology, glucose is stored mainly in the form of glycogen in the liver and muscles for later energy use.
Discussion & Comments