Glycolysis and Krebs Cycle!

[Milad]

Greetings and salutations!

 

I am absolutely worried that the following assignments are wrong in some way. Could you guys help me out, on this one my teacher at school isnt very responsive to these kind of things... MY anaswers seem ok but i dont know...

 

BTW Why do we exhale 12 times a minute im still quite unsure

 

Glycolysis

 

1. In one sentence, what occurs to the glucose molecule during glycolysis?

Glycolysis is the splitting of sugar (glucose).

2. Why is glycolysis divided into two phases?

Glycolysis is divided into 2 major phases: Energy Investment and Energy Production. In Energy investment 2 ATP molecules are used up, and in Energy Production 4 ATP molecules are produced. This gives off a net worth of 2 ATP molecules produced from Glycolysis.The reason for this split is the fact that the first 5 steps need energy first(2 ATP molecules) to convert glucose into Glyceraldhyde 3-phosphate molecules. Where in the next 5 steps the Glyceraldhyde 3-phosphate molecules are converted to pyruvrate molecules in order produce ATP. Therefore, there is an energy investment phase and an energy payoff phase.

3. What are enzymes and what role do they play in glycolysis?

Enzymes are catalytic proteins that lower the activation energy in reactions, in order for them to proceed at a faster rate. In each of Glycolysis’s 10 steps, a specific enzyme catalyze the reaction. For instance the enzyme hexokinase phosprylates glucose transforming it into glucose-6-phosphate.

4. Show the balanced chemical equation for the formation of ATP from ADP. Be sure to indicate "energy" as a reactant or product.

ATP+H20->ADP+P+energy ΔG=-30.5 kj/mol

5. Show the balanced chemical equation for the formation of ADP from ATP. Be sure to indicate "energy" as a reactant or product.

ADP+P+energy->ATP+H2O

6. Which of the above two reactions must occur more often in glycolysis? Why?

The hydrolysis of ATP in order to provide energy for the reaction to continue/occur.

7. What molecule is eventually produced by glycolysis? How many?

2 Pyruvrate Molecules

8. What else does glycolysis produce?

2NADH

 

 

Krebs Cycle

 

1. What two molecules, produced by glycolysis, does the Krebs cycle begin with?

2 Acetyl-CoA

2. Where does the Krebs’s cycle occur?

In the Mitochondrial Matrix

3. What must be present in order for the Krebs’s cycle to begin?

Oxygen and 2 Acetyl-CoA

4. Why do we exhale 12 times per minute?

That’s how long it takes for the Krebs cycle to go through 12 times (and produce 24 CO2 molecules) – which are eliminated through exhalation. Every exhalation represents one Krebs cycle process throughout the body

5. For each molecule of glucose, how many pyruvate molecules are formed? How many carbon atoms are in each pyruvate molecule?

For Each molecule of Glucose, 2 pyruvate molecules are formed. Each pyruvate molecule is made up of 3 carbon atoms

6. What is the total number of carbon dioxide molecules formed during the Krebs cycle?

2 Carbon Dioxide Molecules are formed.

7. What high energy compounds are produced during the Krebs cycle? How many of each are produce from a molecule of glucose? (Hint: be careful here - track the number of pyruvates).

2 ATP Molecules, 6 NADH, 2 FADH2, and 4 CO2 molecules

[Mr Skeptic]

4. Show the balanced chemical equation for the formation of ATP from ADP. Be sure to indicate "energy" as a reactant or product.

ATP+H20->ADP+P+energy ΔG=-30.5 kj/mol

5. Show the balanced chemical equation for the formation of ADP from ATP. Be sure to indicate "energy" as a reactant or product.

ADP+P+energy->ATP+H2O

 

I think you got those backwards.

 

6. Which of the above two reactions must occur more often in glycolysis? Why?

The hydrolysis of ATP in order to provide energy for the reaction to continue/occur.

 

Didn't you say the overall reaction produces ATP? Might want to explain that one better.

 

4. Why do we exhale 12 times per minute?

That’s how long it takes for the Krebs cycle to go through 12 times (and produce 24 CO2 molecules) – which are eliminated through exhalation. Every exhalation represents one Krebs cycle process throughout the body

 

Wouldn't that only make sense if the Kerbs cycles occur in sync?

[Milad]

Thank you. However Im still completely confused about why we exhale 12 times a minute?

[Mr Skeptic]

Thank you. However Im still completely confused about why we exhale 12 times a minute?

 

My guess would involve lung capacity, but somehow that seems like it would be a little off from the other questions. We breathe as much as we need to maintain the blood oxygenated and mostly clear of CO2, be it 12 times a minute, more, or less.

[dttom]

Glycolysis:

1) You are not wrong but I regard your sentence to be too brief; I would say it is a series of enzymatic process to convert glucose to pyruvate with the generation of NADH and ATP.

2) You should not answer like that, I feel that you are just rephrasing the description, but the question prompts you the reason, at least the answer should include ideas like making glucose inclusive inside cell, activation of glucose molecule .etc.

3) First, enzyme would not lower the activation energy, it just provides an alternative pathway with a lower activation energy, you should see it is not to compare activation energies for different pathways. Second, which is a rather minor problem, words like 'in order to' should be prevented as this might lead others to think it to be purposeful.

4,5,6) Mr. Skeptic has pointed them out.

7,8) Don't forget other 'energetic' molecules.

 

Krebs Cycle:

3) 'to begin' is different from 'to be sustained', oxygen is the final electron receivers (final oxidant) in electron transport chain which begins with intermediates in Krebs Cycle.

4) This should be a wrong statement, it varies amongst people.

7) To be precise it should be GTP instead of ATP.

Edited February 4, 2010 by dttom

[Mr Skeptic]

For the exhalation question, the only thing that makes sense to me now would be that it is hinting at basal metabolic rate.