GED Science Practice

What is an essential structural component of living cells and a source of energy for animals?

1. Carbohydrate

2. Carbon Dioxide

3. Carbon Monoxide

4. Cartilage

The correct answer is: Carbohydrate

Carbohydrates play a crucial role as a structural component of living cells and serve as a significant source of energy for animals. They are organic molecules made up of carbon, hydrogen, and oxygen, typically following the general formula of (CH₂O)n. In cellular structures, carbohydrates are often found on cell surfaces where they help form glycoproteins and glycolipids, which are important for cell recognition and signaling. Moreover, carbohydrates are a primary energy source for most organisms. When animals consume carbohydrates, they are broken down into glucose, which is then utilized in cellular respiration to produce ATP (adenosine triphosphate), the energy currency of the cell. This process is vital for sustaining the various biological functions and activities of living organisms. The other options do not fulfill both criteria of being a structural component of living cells and serving as an energy source. Carbon dioxide, while essential for photosynthesis in plants, is not a source of energy for animals and does not contribute to cellular structure. Carbon monoxide is a toxic gas and doesn't provide any nutritional value or functional role in cells. Cartilage is a flexible connective tissue found in some animals but is not a source of energy or a fundamental structural component in the way carbohydrates are.