Unit 3 Reflection

        In this unit, we explored cells and their processes of photosynthesis and cellular respiration. While prokaryotic, autotrophic cells were the original ones, after cyanobacteria evolved, there was enough oxygen for heterotrophs to prosper. According to the endocytotic theory, eukaryotes with different organelles evolved as a result of heterotrophs consuming smaller autotrophs and cyanobacteria through phagocytosis, and the consumed bacteria surviving and living in symbiosis, creating the organelles we see today. These organelles include many membrane-bound structures, including the nucleus, lysosomes, ribosomes, mitochondria, and chloroplasts. The cell membrane has also evolved to be semipermeable and to allow protein-facilitated transport. A similar method of transport--diffusion--plays an important role in the osmosis of water, which not only helps maintain equilibrium, but also makes processes such as photosynthesis and cellular respiration possible.

The organelles of a eukaryotic animal cell

        Photosynthesis uses carbon dioxide, water, and light in a series of light dependent reactions, diffusing the H+ ions from water across the thylakoid, and producing NADPH and ATP to be used in the Calvin cycle. The Calvin cycle produces sugar from carbon dioxide and the molecules formed in the light independent reactions. Cellular respiration does the opposite, breaking down glucose to form ATP for energy storage through glycolysis, the Krebs cycle, and the electron transport chain. This yields 36 ATP in total from 6 glucose and 6 oxygen molecules.
        In general, I found understanding the processes of photosynthesis and cellular respiration a big jump from the relatively simple concepts that we covered earlier. In addition, though I found diffusion natural, the complex tonicities of osmosis were confusing when I was first exposed to them. However, after completing several labs and going through the steps of the processes, I found all of these concepts much easier to grasp. The egg diffusion lab helped me understand the impact of hyper- or hypotonic solutions on the movement of water across a membrane, and the photosynthesis virtual lab helped me better correlate each factor of photosynthesis with its rate and output.

The egg diffusion lab showed the effects of tonicity with a semipermeable membrane

        I still feel that the cellular processes of energy are extremely complex with details, and I would like to explore the different steps, such as glycolysis and the Calvin cycle, more in depth. This would provide a better understanding of how exactly each molecule is formed and used throughout the process.