AP Biology class blog for discussing current research in Biology

Tag: cellular respiration

Climate Change’s Toll On Fish

What if I told you that by 2080 almost 80% of the world’s oceans will be suffocating from a lack of oxygen due to climate change. It seems like every year we get yet another grim fact that if we do not act by a certain time it will be too late. This is the reality for all the world’s oceans.

Multiple studies have shown that the mesopelagic zone (from 656 to 3,281 ft below sea level), the area that holds the most fish in the ocean, is the most vulnerable since it is not as enriched with oxygen as are the upper layers of the ocean. This is also because the most algae is decomposed in the mesopelagic zone, which absorbs oxygen.

You may be wondering how climate change actually affects oceanic wildlife. As the earth warms, its waters warm with it causing there to be less dissolved oxygen in the water. This issue on top of there being less oxygen already in the mesopelagic zone means a lot of death amongst fish. Fish, like us human beings, need oxygen to perform cellular respiration in order to survive. Similar to what we learned in class, fish intake oxygen and release carbon dioxide. However, they do this process in a slightly different way than us humans. Fish have gills which are positioned at the sides of its body. Water passes over the gills, specifically the gill filaments, and is filtered in as oxygen. There are also blood capillaries located very close to the surface of the gills so that the fish can take in as much oxygen as needed and release carbon dioxide smoothly. The overall goal of this process is to make ATP, in order for the fish to stay alive. However, in this time of climate crisis where oceans are undergoing deoxygenation, fish are struggling to stay alive and this can actually have effects on us.

A lot of the fish that are at stake include some essential to our nutrition. Fish is a key source of protein for us and without it our health might be at risk. Additionally, many of the fish who are in the danger zone are commercial fish which we buy and sell, so businesses will be severely hurt from this crisis.

It is clear that climate change is having a tremendous effect not only on marine wildlife, but also on our economy. 58 years might sound like many, but our time is now to make change. What do you think about this crisis?

Group of fish near the beach of Sharm El Naga

Nobel Prize awarded to Researchers for Key Discoveries in Cellular Respiration

Recent findings about the change in oxygen levels in cells show new important factors about oxygen that translate to one’s well-being. William G. Kaelin Jr., Sir Peter J. Ratcliffe and Gregg L. Semenza discovered how cells can “sense and adapt to changing oxygen availability,” and are now being awarded the Nobel Prize in Physiology or Medicine. Oxygen is a crucial aspect to how a cell’s functionality. Mitochondria in cells use oxygen to aid in converting food into ATP (energy), a process known as cellular respiration.

A representation of the reaction of cell respiration.


Gregg Semenza wanted to further look into the rise of levels of the hormone erythroprotein (EPO), a response to low levels of oxygen, or hypoxia. He found that “oxygen sensing mechanisms were present in virtually all tissues, not only in the kidney cells where EPO is normally produced.” While Semenza analyzing cultured liver cells, Semenza found a protein complex that was unknown to science. He named unidentified DNA segment the “hypoxia-inducible factor (HIF).”

Over the course of 24 years, Semanza continued to explore aspects of HIF and found two different DNA-binding proteins, now named “HIF-1a and ARNT.” Researchers worked with Semanza in finding out which parts of the HIF assist in cellular respiration. While Semenza and Ratcliffe were researching regulation of EPO, Kaelin Jr. was researching von-Hippel-Lindau’s disease (VHL). Kaelin Jr.’s research showed that VHL gene “encodes a protein that prevents the onset of cancer,” and that cancer cells lacking a functional VHL gene have “abnormally high levels of hypoxia-related genes.” But when the VHL gene was reintroduced into cancer cells, “normal levels were restored.” Eventually, Kaelin Jr. and his team found that VHL needs HIF-1a for degradation at normal oxygen levels.

Kaelin Jr. and Ratcliffe both published articles that center around protein modification called prolyl hydroxylation which “allows VHL to recognize and bind to HIF-1α degradation with the help of oxygen-sensitive enzymes.” The papers also wrote that the gene activating function of HIF-1α “was regulated by oxygen-dependent hydroxylation.” The researchers now had a much clearer idea of the effects of how oxygen is sensed within cells.

These groundbreaking finds give the science world more information about how oxygen levels are regulated in cells in physiological processes. Sensing oxygen levels is important for muscles during physical exercise, as well as the generation of blood cells and strength of one’s immune system.

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