This worksheet guides students through the steps of the Krebs Cycle, including Pyruvate Oxidation and the final products of cellular respiration.

Here is the completed worksheet with all blanks filled in, based on standard biology curriculum for the Krebs Cycle (also known as the Citric Acid Cycle or TCA Cycle).

---

Pyruvate Oxidation

Pyruvate enters the mitochondrion from the cytoplasm.
One carbon atom is removed via decarboxylation and
CO₂ is removed using NAD⁺. Coenzyme A (CoA) becomes attached to the remaining two atoms, creating Acetyl CoA, which then enters the Krebs cycle.

> *Explanation:* Pyruvate (3 carbons) from glycolysis enters the mitochondrial matrix. It loses one carbon as CO₂ (decarboxylation), and the remaining 2-carbon fragment (acetyl group) binds to CoA, forming Acetyl CoA. NAD⁺ is reduced to NADH during this process.

---

Krebs Cycle

Acetyl CoA enters the cycle and then combines with Oxaloacetate to make the six-carbon compound Citrate. During the eight steps of the Krebs cycle,
Citrate undergoes a number of reactions, releasing CO₂ and Energy carriers (NADH, FADH₂) in a number of steps. Oxaloacetate is eventually converted into Oxaloacetate so it can be used again during the Krebs cycle.

> *Note: The last blank should say “Oxaloacetate is regenerated” — so the correct phrasing is:*
>
> Oxaloacetate is eventually regenerated so it can be used again during the Krebs cycle.

> *Explanation:* Acetyl CoA (2C) + Oxaloacetate (4C) → Citrate (6C). Through a series of redox, decarboxylation, and substrate-level phosphorylation reactions, two CO₂ molecules are released per acetyl CoA, and energy carriers (3 NADH, 1 FADH₂, and 1 ATP/GTP) are produced. Oxaloacetate is regenerated at the end to accept another acetyl CoA.

---

Products of the Krebs Cycle

1. CO₂ is released as waste.
2. NADH and FADH₂ move to the next stage of cellular respiration.
3. Energy is released in the form of ATP (or GTP). A glucose molecule produces 2 molecules of Acetyl CoA because two molecules of Pyruvate are created from each molecule of Glucose.

> *Explanation:* For every glucose molecule, glycolysis produces 2 pyruvates → each pyruvate becomes 1 Acetyl CoA → so 2 turns of the Krebs cycle occur per glucose. Each turn produces 3 NADH, 1 FADH₂, 1 ATP (or GTP), and 2 CO₂. Therefore, total per glucose: 6 NADH, 2 FADH₂, 2 ATP, 4 CO₂.

---

✔ Final Completed Worksheet Answers:

---

Pyruvate Oxidation
Pyruvate enters the mitochondrion from the cytoplasm.
One carbon atom is removed via decarboxylation and
CO₂ is removed using NAD⁺. Coenzyme A (CoA) becomes attached to the remaining two atoms, creating Acetyl CoA, which then enters the Krebs cycle.

---

Krebs Cycle
Acetyl CoA enters the cycle and then combines with Oxaloacetate to make the six-carbon compound Citrate. During the eight steps of the Krebs cycle,
Citrate undergoes a number of reactions, releasing CO₂ and NADH/FADH₂ in a number of steps. Oxaloacetate is eventually regenerated so it can be used again during the Krebs cycle.

*(Note: Some versions may list "energy carriers" or specify "NADH and FADH₂" — both acceptable.)*

---

Products of the Krebs Cycle
1. CO₂ is released as waste.
2. NADH and FADH₂ move to the next stage of cellular respiration.
3. Energy is released in the form of ATP. A glucose molecule produces 2 molecules of Acetyl CoA because two molecules of Pyruvate are created from each molecule of Glucose.

---

📌 Summary Diagram Notes (for the boxes in the cycle diagram):

The diagram shows the Krebs cycle with arrows indicating inputs/outputs. Typical labels for the boxes would be:

- Input: Acetyl CoA + Oxaloacetate → Citrate
- Outputs per turn: 2 CO₂, 3 NADH, 1 FADH₂, 1 ATP (or GTP)
- Regenerated: Oxaloacetate

In many diagrams, the boxes represent:
- CO₂ (released at two steps)
- NADH (produced at three steps)
- FADH₂ (produced once)
- ATP/GTP (produced once)

But since the worksheet doesn’t ask to label the diagram boxes explicitly, we’ve focused on the text summaries.

---

✔ This completes the worksheet accurately according to standard biology education materials (e.g., Campbell Biology, Nelson textbooks).

Let me know if you’d like a labeled diagram explanation too!