Biology Help please please please :-)?

Question

If plants make sugars and animals need sugar to survive, how is it that all plants do not taste sweet and all animals do not eat sugar directly?

Answer 1

The short answer:  Its not all just about sugar, its about carbohydrates (sucrose, glucose and starch)

Long answer:

Plants make carbohydrates (which is a category made up of sucrose, glucose or starch).  They make what we call sugar (glucose and sucrose) to be used immediately for energy.  However they store the rest as starch for long term energy usage.  Plants generally don't taste sweet because in the vascular tissue (stems, leaves, ect) there is no storage for the sugars, which in return is why there is often fruits that are high in sucrose and do taste sweet.

Animals usually don't eat sugar directly (however they probably would if given to them) because raw sugar carries almost no nutritional value.  Thus eating plants gives us a decent amount of carbohydrates in the form of different compounds.  Simply the same as we can not survive on eating sugar alone, but we could on salads.

Answer 2

Sugar is not the only thing plants make. They also make other carbon compounds like cellulose. Animals don't only need sugar, but also proteins, calcium, vitamins. All sugar does is provide energy, but energy is not very useful if the body to use it doesn't work well.