How does ATP yield from glucose oxidation differ between prokaryotes and eukaryotes, considering cytosolic NADH shuttles?

How does ATP yield from glucose oxidation differ between prokaryotes and eukaryotes, considering cytosolic NADH shuttles?

• A. In prokaryotes, glycolysis-generated NADH can feed the ETC directly, with variable ATP yield; in eukaryotes, cytosolic NADH must be shuttled; malate–aspartate shuttle yields about 2.5 ATP per NADH, glycerol-3-phosphate yields about 1.5 ATP per NADH; total roughly 30–32 ATP depending on shuttle.
• B. In prokaryotes, glycolysis-generated NADH must be oxidized by mitochondria; in eukaryotes, NADH feeds ETC directly; both yield exactly 30 ATP.
• C. There is no difference between prokaryotes and eukaryotes in ATP yield from glucose oxidation.
• D. Eukaryotes have higher ATP yield than prokaryotes due to uncoupling proteins.

Answer: (A)

The main idea is that where NADH electrons enter the respiratory chain determines how much ATP you can generate from glucose. In prokaryotes there are no mitochondria, so the NADH produced during glycolysis can feed the electron transport chain directly at the plasma membrane. That setup generally allows more complete coupling of oxidation to ATP and leads to a higher ATP yield per glucose, with numbers varying among organisms and conditions (often in the high 30s). In eukaryotes, glycolysis happens in the cytosol, but the respiratory chain is in mitochondria. The cytosolic NADH from glycolysis must be shuttled into the mitochondria before it can be oxidized. Different shuttles give different ATP yields per NADH. The malate–aspartate shuttle transfers electrons with about 2.5 ATP produced per NADH, while the glycerol-3-phosphate shuttle yields only about 1.5 ATP per NADH. Because of these differences, the total ATP per glucose in eukaryotes typically falls around 30–32 ATP when malate–aspartate is used (and around 30 ATP with glycerol-3-phosphate). So, the prokaryotic situation can produce more ATP from glucose due to direct NADH entry into the ETC, whereas eukaryotes have a lower, shuttle-dependent yield, commonly about 30–32 ATP per glucose.

The main idea is that where NADH electrons enter the respiratory chain determines how much ATP you can generate from glucose. In prokaryotes there are no mitochondria, so the NADH produced during glycolysis can feed the electron transport chain directly at the plasma membrane. That setup generally allows more complete coupling of oxidation to ATP and leads to a higher ATP yield per glucose, with numbers varying among organisms and conditions (often in the high 30s).

In eukaryotes, glycolysis happens in the cytosol, but the respiratory chain is in mitochondria. The cytosolic NADH from glycolysis must be shuttled into the mitochondria before it can be oxidized. Different shuttles give different ATP yields per NADH. The malate–aspartate shuttle transfers electrons with about 2.5 ATP produced per NADH, while the glycerol-3-phosphate shuttle yields only about 1.5 ATP per NADH. Because of these differences, the total ATP per glucose in eukaryotes typically falls around 30–32 ATP when malate–aspartate is used (and around 30 ATP with glycerol-3-phosphate).

So, the prokaryotic situation can produce more ATP from glucose due to direct NADH entry into the ETC, whereas eukaryotes have a lower, shuttle-dependent yield, commonly about 30–32 ATP per glucose.