For my final posting, that is coincidently, my 50th post, I would like to share this animation video with you that explains the action of electron transport chain and formation of ATP in the mitochondria via oxidative phosphorylation. It has been a wonderful time people. Hope that you enjoy the video and happy studying!!!
Good day my Biochem peeps,
Enzyme Inhibition by FortuneFavorsPrep
In your revision, you must be like me where you are wondering why you can never remember the enzyme kinetics and the graphs seen in the different reversible inhibition methods. Well, I came across this video where the person explains competitive, non-competitive and uncompetitive inhibition.
The guy on this video gives a good summary of each method and gives the main features of each inhibition, the main effects on the Km and Vmax of the enzyme and the mechanism of action of the inhibitor. He then actively draws both the M-M curve and L-B plot for each of the inhibition described. He is showing you why there is a change in the value, how to draw it and what the plot and curve changes means.
This video is well explained and an incentive to studying the inhibition since it summarizes most of what you need to know on the topic for exams. I felt that this video was an apt summary of the topic and there were little flaws in the explanation or demonstration. However, I felt that explanation of mixed inhibition and irreversible inhibition should also be covered. There were also no examples of each type of inhibitor. Nevertheless, this does not take away from the efficacy of the video and I enjoyed it a lot since above all, it was a short video of about 15 minutes.
The main points of the video has been summarized below, however, I am strongly suggesting that you view this video since it will really help you, if you are still confused on the topic and you wanted a nice summary of the essentials of inhibition.
The video begins with a summary of inhibitors. He then begins to describe competitive inhibition and the fact that the inhibitor binds to the active site of the enzyme and competes with the substrate to bind. He illustrates the equation of the enzyme and substrate interaction and shows the effect of a competitive inhibitor on this process. The guy then goes on to explain the effect of this inhibitor on the affinity of the enzyme for the substrate and hence an increase in the Km value. He also mentions that this inhibition may be reversed or overcome by increasing the substrate concentration and hence does not affect the Vmax. Finally, he uses the M-M curve and L-B plot to illustrate what was explained in the text of the video. He drew the two graphs, which was good since it actually demonstrated the method and reason for the position of the points on the graphs.
Then he moved on to non-competitive and uncompetitive inhibition where he proceeded to explain the main points of these two types of inhibition and compared them to competitive inhibition. In summarizing non-competitive, he mentions that this inhibitor binds to a site other than the active site and changes the conformation of the enzyme. He links this to induced fit model mechanism of action and then compares this method to that of competitive inhibition. He then further details the change in the Vmax and Km. He aptly explains that non-competitive inhibition does not prevent the substrate from binding to the enzyme and therefore does not change the affinity of the enzyme for the substrate and hence the Km is changed. However, since it changes the conformation of the enzyme, it decreases the ability for product formation and hence decreases the rate of reaction of the enzyme. This means that Vmax is decreased. Finally, he ends this section by draw the L-B plot and shows the changes that the non-competitive inhibitor has on the enzyme kinetics.
This video ends with an explanation of uncompetitive inhibition. In this final segment, he illustrates again the graphs and show how there is a decrease in the Vmax and Km due to the inhibitor binding to the enzyme-substrate complex. However, he does not mention that this is a proportional decrease and goes into why there is a decrease in these values. He also does not mention that uncompetitive inhibitor may bind to the free enzyme at another site than the active site. But overall, the explanation and illustration was very helpful in visualizing and conceptualizing the topic.
Well, I really hope that this aids in your revision. A point to note is that this should not be taken as the only source on this topic and you should refer to Sir’s lectures and the textbook for further details. Happy studying until the next one….
Hey Biochem folks,
Glycolisis (Biochemistry) by Pitanja sa kolokvijuma Pomozimo kolegama
Here is another video that is focused on Glycolysis. This was a long video of just over 50 minutes and the content focused on a medical based knowledge. The lecturer kept focus on the essentials towards the general board exams for medical students and touched on the key aspects of the glycolytic pathway as well as physiological and pathophysiological points to link the biochemistry of glycolysis.
This video was quite informative and interesting, even though there was much content that was not applicable to our course. I felt that the lecturer’s explanation was comprehensive and easily understandable. However, there was little animation and pictures where sometimes there were periods of just looking at the same diagram as he spoke, that was a little monotonous. However, the content was excellent and the explanations were clear and concise. All of the information he mentioned in this video, I came about in my reading and preparation for the glycolysis blog posts and therefore, I found that this video was a well-summarized and integrative approach to the topic of glycolysis.
Even though, there was a lot of skipping through the stages of glycolysis, except for the irreversible stages, there was a good summary of each stage and the focus on the three regulatory enzymes as well as how these enzymes were regulated and the implications of their regulation, was very helpful. The lecturer clearly outlined the process, reasoning behind the regulation of the enzyme and the unique characteristics of the liver that facilitates a more dynamic glycolytic pathway.
The video, however, did not go into any detail on the fates of pyruvate but rather brushed through the two main pathways of producing lactic acid or acetyl-CoA. There was a general summary on lactic acid production and the implications on the human body. However, the applications of this knowledge to athletes and their increased conditioning that may overcome the lactic acid production with extraneous, vigorous exercise, was the highlight of that section. This application created a deeper understanding into the reasons for the physiological changes that occur due to exercise. A fascinating point was the importance of 2, 3-BPG to oxygen dissociation and it importance towards oxygen transport to foetuses in pregnant women.
In summary, this video was informative, interesting and easy to understand. Even though, the content was less applicable to our syllabus, it still provided accurate and well-integrated real life information on glycolysis. The lecturer was well articulated and seemed very knowledgeable in this topic. Overall, the video was good and I recommend that you look at it in your spare time. The major points of this video are summarized below, but I would suggest that you look for yourself.
The video begins with the lecturer talking about how glucose enters the cell. Glucose enters the cell through the GLUT transporters, as he mentioned and these transporters are tissue specific and have different Km values. This means that the affinity for glucose to enter different cells is dependent on different circumstances. As he continues, the lecturer mentions that GLUT 1 and 3 transporters are found in most cells and have a low Km of 1 mmol value, which means that glucose is able to diffuse steadily into cells. However, GLUT 2 are found in the liver and pancreas and have a high Km value and follows 1st order kinetics in that the increase in glucose concentration leads to increase diffusion through these transporters in to the cell. He also mentioned about GLUT 4 transporters that are found in skeletal muscle and adipose tissues that are insulin-dependent and so will facilitate glucose uptake in response to insulin release. Interestingly enough, these GLUT 4 transporters also are increased in muscle cells in response to increased exercise. So one may allude to the fact that increased GLUT 4 transporters in muscles means an increased demand for glucose to generate energy is critical to maintain functioning.
As the lecturer proceeds, he goes into depth of the process of glycolysis with the focus on the three irreversible, regulated steps of glycolysis. He mentions the importance of phosphorylation of glucose and the fact that that hexokinase required Mg ions as a co-factor. He also explains that there is another enzyme, glucokinase in the liver that performs this phosphorylation reaction to convert glucose to glucose 6-phosphate. Glucokinase is hormone-dependant and is able to trap all excess glucose in the blood into hepatocytes in response to insulin release. It was determined that hexokinase is inhibited by glucose 6-phosphate and therefore, when there is an accumulation of glucose 6-phosphate, it prevents hexokinase from converting anymore glucose. Therefore, the excess glucose is funnelled to the liver.
Next, the lecturer explains the importance of PFK-1 and how it is regulated. AMP is able to activate this enzyme and therefore increase its action to produce fructose 1, 6-bisphosphate. This is because, increase levels of AMP may occur when there is increase in exercise and hence there is more utilization of energy and so need to increase the rate of glycolysis to generate energy. ATP and citrate inhibit PFK-1 since these are both indicators of high energy states. When PFK-1 is inhibited, there is decrease in glycolysis and hence will not be able to go on to make fatty acids, which is essential to lipid production. Therefore in the liver, PFK-2 is present and produces fructose 2, 6-bisphosphate. This product over-rides ATP inhibition and forces PFK-1 to continue glycolysis in the liver. It is a very potent activator of PFK-1 to ensure that glycolysis ensues in the liver. This is essential to continue to utilize the high glucose levels in the blood. PFK-2 is driven by insulin.
Glucagon is also essential to the liver since there is inhibition of PFK-1 in the liver and decreases glycolysis and increases gluconeogenesis. This is critical for fasting states and resting states. The lecturer then explains the implications of these processes on persons with hyperglycaemia such as diabetics.
The lecture continues to explain some alternative pathways for dihydroxyacteone phosphate. He then goes on to proceed through the different stages in the energy generation phase of glycolysis. There is little focus on most of the stages in this phase by the lecturer except to note that glyceraldehyde 3-phosphate dehydrogenase generates NADH from the only oxidation reaction in the pathway and performs phosphorylation via an inorganic phosphate. There is a very brief explanation about substrate level phosphorylation. He also notes that in rbc, there is also the conversion of 1, 3-BPG to 2, 3-BPG.
The lecturer then focuses on the last stage of glycolysis catalysed by pyruvate kinase. It is noteworthy that phosphoenolpyruvate is the highest energy compound of the cell. PEP has twice the amount of energy of ATP. There was also discussion on the pyruvate kinase deficiency and the pathophysiology of the haemolytic anaemia that occurs from this deficiency. During this discussion, he explains the importance of glycolysis, NADH and NADPH to erythrocytes and why the blood glucose levels must be maintained at 5mmol.
The video continues to explain the production of lactate and the effects on the body as well as the case with athletes being able to intake high percentage of oxygen and therefore will have increased rates of glycolysis and increased rates of energy production through TCA and ETC. The lecturer then ties this concept into the oxygen transportation of rbc and the release of oxygen from haemoglobin and the importance of 2, 3-BPG. There is an explanation of oxygen saturation curve and the role of 2, 3-BPG. The video ends with the description of the physiology of oxygen transport from mother to foetus in pregnancy.
Hope you will enjoy it as much as I did. Until next posting….
Essential Biochemistry: Enzyme Inhibition
Hey my Biochem Peeps,
Check out this video presentation on the website listed above. This video gives a very good description of enzyme inhibition. It begins with an overall introduction on the mechanism of action of inhibitors, then delves into the two main categories of inhibitors (irreversible and reversible). For each category, it shows an interactive cartoon in which the mechanism of action is described. When describing the different reversible inhibitors, it gives description of the process and then explains why there is a change in the enzyme kinetics (Km and Vmax). There is also questions at the end of each section where you can test your knowledge of what was just taught.
I really liked this video since it gives a summarized idea of each inhibition and tells you all the important info. for each without you having to read it and figure it out. I like the interactive animation as well. I am sure that you will really enjoy looking at this since it is a good revision especially for the upcoming exam on Wednesday. The downside to this video is that it does not give you the M-M curve and L-B plot, but this is a minor setback and the simple and easy to follow text material makes up for this.
Some general instructions:
You need to click on the forward button at the bottom of the video to move through the sections but there is also a drop down menu at the top right hand corner that allows you to skip through to different sections
The review questions, you click on the answer and it tells you why it is right or wrong. This is an added bonus and gives you good assimilation of all the materials.
I hope that you enjoy. Keep good.
Mcgraw-Hill Higher Education Anatomy and Physiology Online Learning Centre
Animation: How Glycolysis works
Here is a little summary video of glycolysis that I found doing some research. It is not very detailed and just gives a general overview of the process of glycolysis but it explains the idea of glucose a 6C sugar being converted to pyruvate, a 3C sugar by a number of steps. The added perk of this video is that it has some MCQ below to test your understanding of the information just presented. The video is also clear and the animation is simple enough to follow. However, there is little mention of the enzymes involved and the intermediate products formed before you get to pyruvate, but it gives a general overview which, if you are not aware of the process, it will give some insight on the topic. This video also has the text below in case you do not fully understand the narration which is an added bonus. So check it out and see if you like it or not. Answer the questions too, it is a nice review of your knowledge of glycolysis. The link is posted above.
I was going through some animations about enzymes when I came across this short YouTube video on action of enzymes. It is not an in-depth analysis but rather a little cartoon to illustrate enzyme specificity and general action. It is a basic level but fun to watch anyway. Check it out.
YouTube video : Enzyme animation by henmomma