Most life on Earth gets energy from the Sun. This energy is in the form of radiant energy.

Chlorophyll, the green pigment in plant cells, uses the radiant energy to create chemical energy in food molecules. This happens in chloroplasts and is called photosynthesis. The base product is glucose, a simple sugar.

Image shows a chloroplasts with radiant energy going in and glucose going out

When people eat plants, for example a carrot, their bodies break down the complex molecules to glucose. The cells then must break the bonds in the glucose to release energy (ATP) that is used to grow and move. This process occurs in mitochondria in the cell and is called cellular respiration. It is a chemical energy transfer to another form of chemical energy.

Image shows a mitochondria with glucose going in and ATP going out.

Image shows a boy playing soccer

ATP is used to make muscles move. This is a transfer of chemical energy to mechanical energy.

Interactive exercise. Assistance may be required. Directions: Study the chart below. Use the columns that are filled in as clues to complete the remaining columns. Drag the terms into the correct location on the chart. The last column is to help relate what is happening in the body to man-made systems.