Tutor profile: Alex S.

Compare and contrast the carbon cycle before and after the late 1700s.

Prior to the late 1700's humans had not created technology harvesting or needing fossil fuels to an extent that it would impact the carbon cycle. During the late 1700's (industrial revolution and thereafter) the use of fossil fuels has infiltrated the carbon cycle with an overabundance of carbon. The carbon stores are holding more carbon (unable to be pulled from the atmosphere at a higher rate) and therefore have stayed in the atmosphere longer at greater amounts. This has impacted the Earth's temperature and contributes to global climate change.

Compare and contrast prokaryotes and eukaryotes.

Prokaryotes such as bacteria, do not contain a nucleus. Eukaryotes, such as plant and animal cells do contain a nucleus. All cells contain ribosomes, DNA, cytoplasm, and a cell membrane.

During a long endurance race such as the Tour de France, cyclists experience a painful feeling in their muscles that inhibits performance. What substance causes this sensation in the muscles and describe what is occurring.

Cyclists are experiencing a build up of a substance called lactic acid in their muscles. This build-up occurs when cells are using up oxygen so quickly, there is not a sufficient amount left to perform aerobic respiration. The body then switches to anaerobic respiration which occurs in the cytoplasm. This process recycles NADPH while creating very little ATP.