Glycolysis and the Krebs Cycle Part 1 PDF

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Glycolysis and the Krebs Cycle What reactions occur in the cell to turn glucose into carbon dioxide?

Why? Glucose is a high potential energy molecule. Carbon dioxide on the other hand is a very stable, low potential energy molecule. When a glucose molecule is converted to carbon dioxide and water during cellular respiration, energy is released and stored in high potential energy ATP molecules. The three phases of cellular respiration that oxidize the glucose molecule to carbon dioxide are glycolysis, the Link reaction and the Krebs cycle.

Model 1 – Glycolysis O

O– –

–

O

O

P O

C CH CH2 O P O–

O

–

H C CH CH2 O P O

–

O

Potential Energy

OH O Phosphoglyceraldehyde (PGAL) PGAL × 2

O

OH O 1,3-Bisphosphoglycerate (1,3-BPG)

2 NAD+ + 2 H+ + 2 Pi 2 NADH

2 ADP 2 ATP

OH O

Glucose

4 ADP 4 ATP

1, 3 BPG × 2

OH

O O– C C

OH OH OH Glucose

Pyruvate × 2

CH3

O Pyruvate

1. Refer to Model 1. a. What molecule from food is the primary reactant for glycolysis? the primary reactant for glycolysis is glucose.

b. How many carbon atoms are in that reactant molecule? there are six molecules in glucose

2. The carbon atoms from glucose end up in pyruvate molecules as a product of glycolysis. a. How many carbon atoms are in a pyruvate molecule? pyruvate has three carbon molecules.

b. How many pyruvate molecules are made from each glucose molecule? two pyruvate molecules are made from each glucose molecule.

Glycolysis and the Krebs Cycle

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3. Does the process of glycolysis require an input of energy? Provide specific evidence from Model 1 to support your answer. yes two atp molecules are needed/inputted in order to convert a glucose molecules two pgal molecules.

4. Refer to Model 1. Propose an explanation for why the author of this activity put PGAL at the highest point in the Model 1 diagram. the pgal molecule has higher potential energy then the glucose molecule, the energy from the atp molecule converting to adp has increased the potential energy of the pgal

5. Does pyruvate have more or less potential energy than glucose? Provide specific evidence from Model 1 to support your answer. glucose is at a higher level then pyruvate in model 1, making four atp as pgal is converting to pyruvate. meaning that pyruvate has less potential energy than glucose.

6. What is the net production of ATP by glycolysis? the net production of atp glycolysis is two because two atp's are needed and four are produced.

7. What molecule acts as an electron acceptor in glycolysis? nadh acts as a electron acceptor when pgal converts to 1,3 bpg

8. In the last steps of glycolysis 4 ATP molecules are produced. Analyze Model 1 to find the source of the four inorganic phosphates (Pi) that are added to the ADP molecules to make the four ATP molecules. Describe the origins of the four inorganic phosphates here. two groups of inorganic phosphate are added to the glucose molecule in the reaction that produces phosphoglyceraldehyde (pgal). two more inorganic phosphate groups are added to pgal in the reaction that produce 1,3 bisphosphoglycerate. the four (pi) groups are removed in the final steps that produce pyruvate.

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Model 2 – The Link Reaction Outer membrane

CO2

O –

O

Inner matrix

Inner membrane cristae

Coenzyme A (CoA) CoA

CH3 Pyruvate

C C O Pyruvate

Acetyl CoA

C

CH3

O Acetyl CoA

NADH NAD+

Cytoplasm

Mitochondrion

9. According to Model 2, where in a cell does the link reaction take place? the link reaction takes place in the inner matrix of the mitochondria

10. Consider the pyruvate molecule. a. Is the pyruvate molecule likely to move across the mitochondrial membranes by diffusion? (Your answer should include a comment about polarity.) no because pyruvate is polar and would not easily move through the non polar lipid bilayer.

b. Propose a method by which the pyruvate molecule moves across the mitochondrial membrane. pyruvate could move across the membrane through a protein carrier

11. During the link reaction, the pyruvic acid molecule is decarboxylated. What molecule is removed during this process? carbon dioxide is removed during the process during the link process.

Glycolysis and the Krebs Cycle

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12. Coenzyme A carries the remainder of the pyruvate molecule to the site of the Krebs cycle. a. What is the name of decarboxylated pyruvic acid? the name of the decarboxylated pyruvate acid is acetyl or acetate

b. How many carbons of the pyruvate molecule remain when is it attached to Coenzyme A? when the pyruvate molecule is attached to the coenzyme A only two carbn atoms remain.

c. When coenzyme A bonds to the decarboxylated pyruvic acid what molecule is produced? when coenzyme A bonds to the decarboxylated pyruic acid actyl-CoA is produced

d. The connection between Coenzyme A and the acetyl group is weak. How is this illustrated in Model 2? the connection between coenzyme A and the acetyl group is weak, this is represented between the double line

13. Has any ATP been used or produced during the link reaction? no atp is used or produced during the link reaction.

14. Have any other high potential energy molecules been produced during the link reaction? yes, one ndha molecule was produced

15. How many acetyl-CoA, carbon dioxide, and NADH molecules are produced in the link reaction for each glucose molecule that undergoes cellular respiration? for each glucose molecule that undergoes cellular respiration each glucose molecule makes two pyruvate molecules, two acetyl-CoA molecules, two carbon dioxide molecules, anad two ndha molecules. the link reaction happens twice for each glucose molecule.

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