Week 7 GTP Metabolisum

Q: What are the three main precursors for gluconeogenesis?

Oxaloacetate, lactate, and amino acids.

Which enzyme converts pyruvate to oxaloacetate in gluconeogenesis, and where does this occur?

Pyruvate carboxylase occurs in the mitochondria and requires ATP.

What enzyme converts oxaloacetate to phosphoenolpyruvate (PEP), and what energy source does it require?

PEP carboxykinase (PEPCK); it requires GTP.

Which enzymes bypass the irreversible steps of glycolysis in gluconeogenesis?

Pyruvate carboxylase, PEPCK, fructose 1,6-bisphosphatase, and glucose 6-phosphatase.

Where do the steps of gluconeogenesis occur within the cell?

Initial steps (e.g., pyruvate to oxaloacetate) in the mitochondria; later steps in the cytoplasm.

Why does gluconeogenesis require ATP and GTP?

To overcome the energy barriers of glycolysis’s irreversible steps; it's an energy-consuming process.

Under what conditions is gluconeogenesis upregulated?

During fasting, low blood glucose, or carbohydrate deprivation.

What is required to "activate" fatty acids before oxidation, and where does this happen?

Coenzyme A (CoA), via acyl-CoA synthetase in the cytoplasm.

What is the purpose of fatty acid oxidation (beta-oxidation)?

To break down fatty acids into acetyl-CoA, which enters the citric acid cycle for energy production.

How are fatty acids transported into the mitochondria after activation?

Via the carnitine shuttle system (though not detailed, be aware it's needed for mitochondrial entry).

What role does acetyl-CoA play in metabolism?

It links fatty acid oxidation to the citric acid cycle and contributes to NADH/FADH2 production.

What are the major components of the electron transport chain (ETC)?

Complexes I–IV, electron carriers (NADH, FADH2), and ATP synthase (Complex V).

How does the ETC produce ATP?

By pumping protons to create a gradient used by ATP synthase in oxidative phosphorylation.

What are the main energy storage molecules in the body, and where are they stored?

Glycogen (in liver and muscle) for short-term energy; protein (in muscle) for longer-term energy.