Which of the following processes requires a proton gradient across a membrane?
a)simple diffusion
b)substrate level phosphorylation
c)endocytosis
d)oxidative phosphorylation
e)exocytosis

D)Oxidative Phosphorylation

Explanation:

Oxidative phosphorylation occurs when the reducing powers NADH and FADH2 are oxidized via an electron transport chain. During their oxidation, the protons are pumped across the inner mitochondrial membrane to generate the proton concentration gradient. This gradient drives the facilitated diffusion of protons through proton channels of the ATP synthase and phosphorylation of ADP into ATP. This process of ADP phosphorylation is called oxidative phosphorylation since the energy of the proton concentration gradient generated during oxidation of reducing powers drives the process.

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."