How's it going everyone? One mnemonic you can use to remember the role of GLUT4 is that GLUT4 is released when you are "GLUTtonous 4 sugar," meaning GLUT4 is mobilized when blood sugar is high.
A person has a nonsense mutation in a gene that codes for glucagon? Which cells of the pancreas expresses this gene? A. villi cells B. alpha cells C. beta cells D. most islet cells of the pancreas A person has a proliferative tumor in the delta cells of the pancreas? How is Growth hormone activity affected? A. GH levels are lower since somatostatin is always produced at high levels B. GH levels are higher since somatostatin is produced at high levels C. GH levels are lower since somatostain is produced at abnormally low levels D. GH levels are higher since somatostain is produced at low levels. Where's GLUT-4 located? What about GLUT-2's location? Answers: B, A, muscle cells/adipocytes, liver/pancreas
Hi, thanks for the video. I do have a question regarding the example question. Since the cancer is in the pancreas, why is it resulting in a high amount of GLUT4, not GLUT2? Is this because insulin only regulates GLUT4?
Hello, great question! GLUT2 is found on the beta-islet cells of the pancreas itself, partly as a way of "sensing" how much glucose we have in the blood. The beta-islet cells release insulin after that "sensing." If we have a tumor of the beta-islet cells of the pancreas (often called an insulinoma), we get high circulating levels of insulin. One of insulin's effects in the body is to increase the mobilization of GLUT4 channels to the cell membrane on skeletal muscle and adipocytes to take up glucose from the extracellular space. This lowers the blood sugar. While you're right that there might be more GLUT2 just because there are more beta-islet cells, this doesn't explain the low blood sugar levels, which are a result of increased insulin production. Let me know if that helps!
@@medcatmcatThanks for replaying. Can you please check if I understand it correctly: the cancer of the beta cells of the pancreas produces excessive amount of insulin, causing a drop in the blood sugar level. In response to this drop, the body needs to secrete GLUT4 to uptake more sugar because GLUT4 is most “insulin sensitive”. For the sake of MCAT, is GLUT4 the only glucose transporter for glucose uptake? I just looked up online and it seems like all GLUT can also uptake sugar, but only GLUT4 is considered “insulin regulated”.
You're very welcome. It is more along these lines: 1) A proliferation of beta-islet cells results in more insulin being made and secreted into the blood to reach the rest of the body. 2) Insulin binds to extracellular receptors on skeletal muscle and fat cells, causing GLUT4 receptors to be mobilized to the cell membrane of the skeletal muscle and fat cells. 3) Glucose from the blood goes into the skeletal muscle and fat cells through the GLUT4 transporter. In other words, insulin's effect of causing low blood sugar is through GLUT4 (GLUT4 is not a response to low blood sugar). For your second question, no, GLUT4 is just one of many glucose uptake transporters. GLUT4 is unique as you noted in that it can be regulated by the amount of insulin we have.
I have only skimmed the video (shame on me :( ), but GLUT1 and 4 are also expressed in the cardiac muscle. I don't believe you're mentioning this. Is there a reason?
Correct, I don't mention this! I don't mention it because it is historically unlikely to be tested on the MCAT. Further, given that it is not tested on Step 1 nor taught in many medical schools (which is much more detailed in biology), I'd be shocked to see it tested on the MCAT.
RBCs still need ATP! If they don't have it, a whole number of pathologies can result. They get the ATP through glycolysis, which starts with glucose. One example (not MCAT relevant, but you'll learn in med school) is pyruvate kinase deficiency, a genetic condition that results in anemia. There's not enough ATP to support the RBC membrane, and as a result, the RBCs get destroyed.
How's it going everyone? One mnemonic you can use to remember the role of GLUT4 is that GLUT4 is released when you are "GLUTtonous 4 sugar," meaning GLUT4 is mobilized when blood sugar is high.
Another good one is GLUT2 for 2 much blood sugar
The MCAT world has a new legend in the making
😂😁
This is a pretty good video! I have two sets of review books and neither one mentioned the glucose transporters whatsoever! So, thank you.
I believe Kaplan discusses glucose transport in their section before glycolysis! In case you wanted to take a look at that.
A person has a nonsense mutation in a gene that codes for glucagon? Which cells of the pancreas expresses this gene?
A. villi cells
B. alpha cells
C. beta cells
D. most islet cells of the pancreas
A person has a proliferative tumor in the delta cells of the pancreas? How is Growth hormone activity affected?
A. GH levels are lower since somatostatin is always produced at high levels
B. GH levels are higher since somatostatin is produced at high levels
C. GH levels are lower since somatostain is produced at abnormally low levels
D. GH levels are higher since somatostain is produced at low levels.
Where's GLUT-4 located?
What about GLUT-2's location?
Answers: B, A, muscle cells/adipocytes, liver/pancreas
Need more people like you at the NHS!
Thank you Boris, very cool!
Hi, thanks for the video.
I do have a question regarding the example question. Since the cancer is in the pancreas, why is it resulting in a high amount of GLUT4, not GLUT2? Is this because insulin only regulates GLUT4?
Hello, great question! GLUT2 is found on the beta-islet cells of the pancreas itself, partly as a way of "sensing" how much glucose we have in the blood. The beta-islet cells release insulin after that "sensing." If we have a tumor of the beta-islet cells of the pancreas (often called an insulinoma), we get high circulating levels of insulin. One of insulin's effects in the body is to increase the mobilization of GLUT4 channels to the cell membrane on skeletal muscle and adipocytes to take up glucose from the extracellular space. This lowers the blood sugar.
While you're right that there might be more GLUT2 just because there are more beta-islet cells, this doesn't explain the low blood sugar levels, which are a result of increased insulin production.
Let me know if that helps!
@@medcatmcatThanks for replaying. Can you please check if I understand it correctly: the cancer of the beta cells of the pancreas produces excessive amount of insulin, causing a drop in the blood sugar level. In response to this drop, the body needs to secrete GLUT4 to uptake more sugar because GLUT4 is most “insulin sensitive”.
For the sake of MCAT, is GLUT4 the only glucose transporter for glucose uptake? I just looked up online and it seems like all GLUT can also uptake sugar, but only GLUT4 is considered “insulin regulated”.
You're very welcome. It is more along these lines:
1) A proliferation of beta-islet cells results in more insulin being made and secreted into the blood to reach the rest of the body.
2) Insulin binds to extracellular receptors on skeletal muscle and fat cells, causing GLUT4 receptors to be mobilized to the cell membrane of the skeletal muscle and fat cells.
3) Glucose from the blood goes into the skeletal muscle and fat cells through the GLUT4 transporter.
In other words, insulin's effect of causing low blood sugar is through GLUT4 (GLUT4 is not a response to low blood sugar).
For your second question, no, GLUT4 is just one of many glucose uptake transporters. GLUT4 is unique as you noted in that it can be regulated by the amount of insulin we have.
@@medcatmcat Got it. Thanks again for your help!
I have only skimmed the video (shame on me :( ), but GLUT1 and 4 are also expressed in the cardiac muscle. I don't believe you're mentioning this. Is there a reason?
Correct, I don't mention this! I don't mention it because it is historically unlikely to be tested on the MCAT.
Further, given that it is not tested on Step 1 nor taught in many medical schools (which is much more detailed in biology), I'd be shocked to see it tested on the MCAT.
@@medcatmcat alright, thx for clarifying :)
Hey MedCat, why do RBC’s need glucose? They don’t have mitochondria 😅
RBCs still need ATP! If they don't have it, a whole number of pathologies can result. They get the ATP through glycolysis, which starts with glucose.
One example (not MCAT relevant, but you'll learn in med school) is pyruvate kinase deficiency, a genetic condition that results in anemia. There's not enough ATP to support the RBC membrane, and as a result, the RBCs get destroyed.
@@medcatmcat ah thank you so much, appreciate it
I think better on ketones🙂
Many do!