Which of the following are carbohydrates?
A glycogen, cellulose, ATP
B sugar, glucose, steroids
C glucose, glycogen, waxes
D sugar, glucose, starch
The Correct Answer and Explanation is :
The correct answer is D: sugar, glucose, starch.
Explanation
Carbohydrates are one of the four main macromolecules essential for life, primarily serving as a source of energy and playing a key role in the structure of cells. They are organic compounds made up of carbon, hydrogen, and oxygen, typically in a ratio of 1:2:1. Carbohydrates can be classified into three main categories: sugars (simple carbohydrates), oligosaccharides, and polysaccharides (complex carbohydrates).
Sugar refers to simple carbohydrates, which can be classified as monosaccharides or disaccharides. Glucose, a monosaccharide, is one of the most important sugars for energy production in living organisms. It serves as the primary energy source for cells and is crucial in cellular respiration.
Starch is a polysaccharide, which means it is composed of many glucose units linked together. It is the primary storage form of carbohydrates in plants, allowing them to store energy for later use. When consumed, starch is broken down into glucose molecules, which can then be used for energy.
On the other hand, glycogen (option A) is a storage form of carbohydrates in animals but is also classified as a polysaccharide. Cellulose is a structural polysaccharide found in plant cell walls and is not digestible by humans, serving primarily a structural function. ATP (adenosine triphosphate) is not a carbohydrate; rather, it is the primary energy carrier in cells.
In option B, steroids are lipids, not carbohydrates, and while sugar and glucose are carbohydrates, the presence of steroids disqualifies this option. In option C, waxes are also lipids, and therefore, glucose and glycogen cannot be considered carbohydrates within that context.
In summary, the carbohydrates listed in option D—sugar, glucose, and starch—are essential components of nutrition and energy metabolism, highlighting their critical role in biological systems.