Printable worksheet for the Citric Acid Cycle where students identify intermediates and enzymes.

The image provided is a worksheet for the Citric Acid Cycle (also known as the Krebs Cycle or TCA Cycle). The task involves identifying the intermediates and molecules involved in each step of the cycle. Below, I will solve the problem by filling in the blanks with the correct names of the intermediates and molecules.

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Step-by-Step Solution:

#### 1. Acetyl CoA Entry
- Acetyl CoA combines with Oxaloacetate to form Citrate.
- Intermediate: Citrate
- Enzyme: Citrate synthase

#### 2. Isomerization to Isocitrate
- Citrate is isomerized to Isocitrate.
- Intermediate: Isocitrate
- Enzyme: Aconitase

#### 3. Oxidative Decarboxylation to α-Ketoglutarate
- Isocitrate undergoes oxidative decarboxylation to form α-Ketoglutarate, releasing CO₂ and NADH + H⁺.
- Intermediate: α-Ketoglutarate
- Molecule: CO₂
- Enzyme: Isocitrate dehydrogenase

#### 4. Oxidative Decarboxylation to Succinyl-CoA
- α-Ketoglutarate undergoes oxidative decarboxylation to form Succinyl-CoA, releasing CO₂ and NADH + H⁺.
- Intermediate: Succinyl-CoA
- Molecule: CO₂
- Enzyme: α-Ketoglutarate dehydrogenase

#### 5. Conversion of Succinyl-CoA to Succinate
- Succinyl-CoA is converted to Succinate, releasing GTP (which is later converted to ATP).
- Intermediate: Succinate
- Molecule: GTP
- Enzyme: Succinyl-CoA synthetase

#### 6. Dehydrogenation to Fumarate
- Succinate is oxidized to Fumarate, releasing FADH₂.
- Intermediate: Fumarate
- Enzyme: Succinate dehydrogenase

#### 7. Hydration to Malate
- Fumarate is hydrated to form Malate.
- Intermediate: Malate
- Enzyme: Fumarase

#### 8. Oxidation to Oxaloacetate
- Malate is oxidized to Oxaloacetate, releasing NADH + H⁺.
- Intermediate: Oxaloacetate
- Enzyme: Malate dehydrogenase

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Final Answer:

Here is the completed worksheet with the intermediates and molecules filled in:

1. Acetyl CoA Entry:
- Intermediate: Citrate
- Enzyme: Citrate synthase

2. Isomerization to Isocitrate:
- Intermediate: Isocitrate
- Enzyme: Aconitase

3. Oxidative Decarboxylation to α-Ketoglutarate:
- Intermediate: α-Ketoglutarate
- Molecule: CO₂
- Enzyme: Isocitrate dehydrogenase

4. Oxidative Decarboxylation to Succinyl-CoA:
- Intermediate: Succinyl-CoA
- Molecule: CO₂
- Enzyme: α-Ketoglutarate dehydrogenase

5. Conversion of Succinyl-CoA to Succinate:
- Intermediate: Succinate
- Molecule: GTP
- Enzyme: Succinyl-CoA synthetase

6. Dehydrogenation to Fumarate:
- Intermediate: Fumarate
- Enzyme: Succinate dehydrogenase

7. Hydration to Malate:
- Intermediate: Malate
- Enzyme: Fumarase

8. Oxidation to Oxaloacetate:
- Intermediate: Oxaloacetate
- Enzyme: Malate dehydrogenase

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Explanation:

The Citric Acid Cycle is a central metabolic pathway that occurs in the mitochondria of eukaryotic cells. It plays a crucial role in cellular respiration by breaking down acetyl groups derived from carbohydrates, fats, and proteins into carbon dioxide and high-energy electron carriers (NADH and FADH₂). These electron carriers are then used in the electron transport chain to generate ATP.

Each step in the cycle is catalyzed by a specific enzyme, and the intermediates are the compounds formed at each stage. The cycle regenerates oxaloacetate, allowing it to accept another acetyl group from Acetyl CoA, thus continuing the cycle.

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Final Answer Box:

\[
\boxed{
\text{Citrate, Isocitrate, α-Ketoglutarate, Succinyl-CoA, Succinate, Fumarate, Malate, Oxaloacetate}
}
\]