I remember flipping through sports channels on the TV one day and coming across a rugby game. I watched it for only a few minutes before continuing my search for something else. Why? It had nothing to do with rugby per se; there’s no doubt it’s a very athletic and physical game, and the players were impressive athletes. However, I know nothing about the sport and its rules, and because of that I could not appreciate what was going on and what was trying to be accomplished.
The same thing goes for cellular metabolism and the various pathways that are involved. Metabolism is not an easy subject to master, partly because that in order to appreciate their purpose, how they are regulated, and how they connect to other pathways, one is required to learn the details of each pathway. When I took introductory metabolism back in 1977, one way that I familiarized myself with these pathways was to write them out on paper, including pathway intermediates, enzymes and products. I repeated this many times so that eventually I was able to ingrain the details of each pathway. This information ultimately allowed me to “see the bigger picture” of metabolism, including how the pathways connected with each other, and how they were regulated by hormones, metabolite concentrations, etc.
With any activity, the more fun and interesting it is the more likely one is to regularly engage in it. This was the motivation behind developing interactive exercises for several metabolic pathways. The availability of eLearning software such as Adobe Captivate facilitated the development of such activities that make interacting with the material more enjoyable and entertaining. Student feedback on these activities has been very positive, including the confidence-building positive feedback they receive when they drag the correct answer to a drop area, click on the right box, or identify the correct allosteric regulators for a particular enzyme.
Our testing of these activities has indicated that they are best viewed on a laptop or desktop computer. They are too elaborate or “busy” to view on a mobile phone. They will work to some degree on an iPad or tablet, but you may find you have to work a bit harder since some of the buttons don’t always respond when tapped on the first time or two. If you choose to view these on your iPad/tablet, please use full-screen mode. Also, since sounds are used to indicate success or failure, please ensure that the Audio on your device is turned On.
I hope you enjoy these activities and find them useful as you explore the beauty of metabolism. Your feedback is welcome; they can be shared with us using the contact info provided on this site.
We consume carbohydrates everyday in the form of breads, desserts pastas, vegetables, fruits, and sugary drinks, and together they provide about 50% of our total caloric intake. Much of this carbohydrate is made up of glucose, and Glycolysis is the pathway whereby glucose is converted to pyruvate, in the process producing ATP. This pathway connects to many other metabolic pathways, and thus plays a central role in intermediary metabolism. Thus, a solid understanding of this pathway, and how it is regulated, will be helpful as you explore other metabolic pathways. Hopefully you find this activity on glycolysis helpful in deepening your understanding of this central pathway.
There are several tissues or cells in our body, such as the brain and red blood cells, that derive all their energy needs primarily from glucose. It is for this reason that several metabolic pathways exist to ensure that blood glucose levels remain sufficient even when we don’t eat for long periods of time, such as during a good night’s sleep. One of these is Gluconeogenesis, a pathway that occurs in liver and kidney whereby glucose is synthesized from non-carbohydrate molecules such as pyruvate and lactate. The glucose produced is released from the cells where it is made into the blood stream, contributing to the maintenance of blood glucose levels. This interactive exercise will improve your understanding of this important metabolic pathway.
Pentose Phosphate Pathway
The Pentose Phosphate Pathway is one of the pathways that branches off glycolysis. The two major products of this pathway are NADPH and ribose 5-phosphate, the latter being the pentose phosphate for which the pathway is named. NADPH is a source of reducing power that is needed for the synthesis of a number of biomolecules, including cholesterol and fatty acids. The ribose 5-phosphate is used in the synthesis of DNA and RNA. Not surprisingly, this pathway occurs in just about all tissues in the body due to the importance of its products to the cell. I hope you enjoy testing your knowledge of this pathway through this interactive exercise.
Glycogen is a storage form of glucose, and thus provides an important source of fuel when needed. Not surprisingly, the synthesis and degradation of glycogen are tightly controlled by both allosteric regulators and hormones. The study of these two pathways has led to many general insights into signaling pathways and mechanisms of enzyme regulation. Have fun as you work your way through this interactive exercise!
Citric Acid Cycle
The Citric Acid Cycle is a pathway whereby nutrients are converted to high-energy compounds, with the energy ultimately being captured in the form of ATP. Hans Krebs was responsible for constructing the complete picture of this cycle in 1937, which is why this pathway is also known as the Krebs Cycle. The elucidation of this pathway was so important for our understanding of cellular metabolism that Hans Krebs received the Nobel Prize in Physiology and Medicine in 1953 to recognize his achievements. Take your time going through this exercise; it will be worth the effort!
Mahatma Gandhi fasted on 17 different occasions during India’s freedom movement, with the longest lasting 21 days. He was able to go this long without eating because his body took advantage of the fatty acids stored as triacylglycerol in adipose tissue. Fatty acids are the most energy-rich nutrient that we metabolize because they are so highly reduced. Fatty acids are metabolized through an iterative process called β-oxidation. Because fatty acids are such an essential fuel, it is important to have a good understanding of how they are broken down and how the energy from them is captured. I hope this exercise facilitates your appreciation for this critical process.
Professor Bill Roesler
Department of Biochemistry
University of Saskatchewan
Saskatoon, SK Canada S7N 5E5