Discuss the energy value of carbohydrates?

Value ??? Human metabolism is driven by the energy release from glucose. The easiest dietary source is various forms of carbohydrates that are easily broken down into glucose. However, the body can convert protein and fat into glucose in more complex reactions. Excess carbohydrates are stored eventually as fats. Carbohydrates provide no usable parts to maintain cell walls, or other body needs.

Great question for Wikipedia. It is determined by burning the item of interest and calculating how much heat it produces. This is measured in calories. Look up definition of calorie by googling. As i recall the amount of energy needed to raise the temperature of 1 gram of water 1 °C (now usually defined as 4.1868 joules). Good luck on your test.