All living things require energy to do the work necessary for survival and reproduction. But what is energy? Energy is simply the ability to do work, where work is done when a force moves an object. Let's consider your own needs (34) ______ a moment. You need energy to turn on and turn off your computer. You need energy to (35) ______ out of bed in the morning. And, yes, you need energy to reproduce. So where does energy come from and how do we use it? On Earth, energy ultimately comes from the sun. Plants use the sun's energy to make sugar. Organisms, (36) ______, use sugar as a source of energy to do work.

Plants use energy from sunlight to make sugar and oxygen from carbon dioxide and water. The process by (37) ______ carbon dioxide and water are (38) ______ to sugar and oxygen using sunlight is referred to as photosynthesis. This is an endergonic reaction, meaning energy is required by the reaction.

Specifically, energy is required to put the carbon dioxide and the water molecules together to form sugar. Sun provides the energy needed to drive photosynthesis, and some of the energy used to make the sugar is stored in the sugar molecule.

Let's consider your own needs (34) ______ a moment.