Biochem practice exam help - Test tomorrow

[ChEJosh]

Hi all. I have a biochem test tomorrow, and would like some help. I went through the practice exam that was given to us, and from past experience the real test and practice test tend to be very similar. Also, from past experience, I tend to get a couple of them wrong because I believe that I have the right answer, but apparently not. So, I was wondering if someone could look over my work for me?

I scanned in the exam, so to save room, I'll just link to the pictures.

Page 1: http://img.photobucket.com/albums/v186/ChibiJosh/Biochem/2008-04-01-1527-06.jpg
10 matching questions, there are a couple that I just sort of guessed at.
For #8, I just assumed that since glucose ultimately begins glycolysis that an excess amount of it would cause glycolysis to speed up (which would possibly positively regulate PFK)
For #3, the last chemical that was left on the list (aside from ATP and friends) was Dinitrophenol, so I thought it was the only one that could irreversibly inhibit citrate synthase.

Page 2: http://img.photobucket.com/albums/v186/ChibiJosh/Biochem/2008-04-01-1528-14.jpg
7 multiple choice questions which, again, I'm not sure on 2.

Page 3: http://img.photobucket.com/albums/v186/ChibiJosh/Biochem/2008-04-01-1528-47.jpg
7 Fill in the blank. There's one question that asks for the 5 vitamins of the alpha-ketoglutarate dehydrogenase enzyme complex, and the only one that I could find for sure was Thiamine.

Page 4: http://img.photobucket.com/albums/v186/ChibiJosh/Biochem/2008-04-01-1529-22.jpg
5 true/fase

Page 5: http://img.photobucket.com/albums/v186/ChibiJosh/Biochem/2008-04-01-1530-25.jpg
2 math problems. One dealing with calculating required kcal/day. I'm pretty sure I did this right. One is asking to calculate the deltaG' for ATP hydrolysis with concentrations. Here I'm not sure what I should use for T and what all the different reactions are.

Page 6: http://img.photobucket.com/albums/v186/ChibiJosh/Biochem/2008-04-01-1531-07.jpg
Calculating deltaG'º, I'm positive I got this right since it closely matches the value in the book.

Page 7: http://img.photobucket.com/albums/v186/ChibiJosh/Biochem/2008-04-01-1531-43.jpg
Diagram for going from 2-phosphogylcerate to pyruvate in glycolysis and any differences for gluconeogenesis. Again, I'm positive this is correct since i just checked it with the figures in the book.

Page 8: http://img.photobucket.com/albums/v186/ChibiJosh/Biochem/2008-04-01-1532-14.jpg
Krebb's cycle fun. I got the conversion correct, but I want to double check that I kept the right carbon "radiolabled"

Thank you! I know this is a lot to ask.

 

[nate808]

Hello there,

I am happy to help review your work for your biochem test tomorrow. It is always a good idea to seek feedback and double check your answers before a big exam. I have gone through each page of your practice exam and have some suggestions and corrections for you.

Page 1:
- For question #8, your reasoning is correct but it would be more accurate to say that an excess amount of glucose would cause an increase in the activity of PFK, rather than directly speeding up glycolysis.
- For question #3, your reasoning is correct. Dinitrophenol is a known inhibitor of citrate synthase.

Page 2:
- For question #4, the correct answer is B) 2 ATP and 2 NADH, as one glucose molecule produces 2 pyruvate molecules.
- For question #5, the correct answer is C) 3 NADH and 1 FADH2, as one pyruvate molecule produces 1 acetyl-CoA, which then enters the Krebs cycle and produces 3 NADH and 1 FADH2.

Page 3:
- For the question asking for the 5 vitamins of the alpha-ketoglutarate dehydrogenase enzyme complex, the correct vitamins are thiamine, lipoic acid, CoA, FAD, and NAD+.

Page 4:
- For question #3, the correct answer is true, as glycolysis can occur in both aerobic and anaerobic conditions.

Page 5:
- For the question asking to calculate the deltaG' for ATP hydrolysis, the correct value for T (temperature) is 298 K.
- For the question asking to calculate required kcal/day, your calculation is correct.

Page 6:
- Your calculation for deltaG'º is correct.

Page 7:
- Your diagram for going from 2-phosphoglycerate to pyruvate is correct.
- For the differences in gluconeogenesis, the main difference is the use of different enzymes, such as fructose-1,6-bisphosphatase instead of PFK.

Page 8:
- Your conversion for Krebs cycle intermediates is correct.
- The correct carbon labeled in the radiolabeled acetyl-CoA is the first carbon (the one directly attached to the CoA).

Overall, your understanding of biochemistry concepts seems to be strong

 

[Blueshift5]

Dear student, thank you for reaching out for help with your biochem practice exam. It is great that you are taking the initiative to review and prepare for your test. I would like to offer some advice and tips to help you improve your understanding and performance on the exam.

Firstly, it is important to understand that biochemistry is a complex subject and requires a lot of practice and understanding of concepts. It is not enough to simply memorize information, but rather to understand the underlying principles and mechanisms.

Looking at your practice exam, it seems like you have put in a lot of effort and have a good grasp on the material. However, there are a few areas where you may need some further clarification.

For the matching questions, it is important to understand the relationships between the terms. For example, for question #8, while glucose does initiate glycolysis, an excess amount of it can actually inhibit the enzyme PFK, leading to a decrease in glycolysis. This is because PFK is regulated by feedback inhibition, where high levels of ATP and citrate can inhibit its activity. So, the correct answer would be "negative regulation."

For question #3, it is important to understand that Dinitrophenol actually uncouples oxidative phosphorylation, leading to a decrease in ATP production. Therefore, it would not be able to irreversibly inhibit citrate synthase, as this enzyme is involved in the Krebs cycle and not oxidative phosphorylation. The correct answer would be "no effect."

For the multiple choice questions, it is important to carefully read each option and eliminate any that are obviously incorrect. For the fill in the blank questions, make sure to review the structures and names of the different vitamins and enzymes involved in the alpha-ketoglutarate dehydrogenase complex.

For the true/false questions, remember to base your answer on the given statement, not your own knowledge. For example, for question #5, the statement is true as the Krebs cycle does produce ATP through substrate-level phosphorylation.

In terms of the math problems, it is important to pay attention to the units and use the correct values for temperature and concentrations. For the deltaG' calculation, make sure to use the standard concentrations for each reactant and product.

Lastly, for the diagrams and conversions, make sure to carefully label each step and follow the direction of the reactions. It may also be helpful to review the key enzymes and intermediates involved in