Pepsin enzymes can then digest dietary in the lumen of the stomach

Pepsin enzymes can then digest dietary proteins in the lumen of the stomach. Pepsin in a protease digesting the proteins into smaller peptides. It is produced by the chief cells of the stomach in the form of a proenzyme called pepsinogen. A proenzyme or a zymogen is basically inactive and needs a biochemical change to become an active enzyme. This biochemical change is brought about by the acidic environment of the stomach by the secretion of the hydrochloric acid by the parietal cells in the stomach lining.

4.) metal

"-the movement of carbon from the nonliving environment into living things and back to the environment

-carbon is the essential component of proteins, fats, and carbohydrates (which make up all organisms)

-carbon exists in air, water, and living organisms

-producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis

-bacteria in the atmosphere cycles through the system in filtration units

-in cellular respiration, carbon is released back into the atmosphere as carbon dioxide

-some carbon is stored in limestone (forming one of the largest "carbon sinks" on earth)

-largest carbon reservoir on earth= limestone

-carbon stored in the bodies of organisms as fat, oils, or other molecules may be released into the soil or air when the organism dies

-this may form deposits of coal, oil, or natural gas (fossil fuels, which increased the atmospheric carbon dioxide)

-fossil fuels store carbon left over from bodies of organisms that died millions of years ago

-they are located in the surface of earth, deep within the earth and beneath the ocean floor."    

i think that it is plants