Acetyl CoA turned to Malonyl CoA

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In summary, in fatty acid synthesis, one acetyl unit enters the pathway directly from acetyl CoA, while the rest must be converted to malonyl CoA before entering. This process begins with carboxylation of acetyl CoA to form malonyl CoA, which then combines with acetyl CoA to start the cycle. The nascent fatty acid then continues to combine with malonyl CoA, with the decarboxylation of malonyl CoA providing the energy for the 2 carbon coupling. This entire process can be traced back to acetyl CoA, which is derived from pyruvate, CoA, and NAD+.
  • #1
sameeralord
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Hello everyone,

My note says in fatty acid synthesis, one acetyl unit enters the synthesis pathway directly but the remainder must be first converted to malonyl CoA.
I can understand the latter but why does one acetyl unit enter directly where did it come from? Thanks :smile:
 
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  • #2
It entered from or came from acetyl CoA. When acetyl CoA is carboxylated (with bicarbonate) it is known as malonyl CoA. This is catalyzed by acetyl CoA carboxylase. So you see that everything can be seen to originate with acetyl CoA which is derived from pyruvate, CoA and NAD+.

Malonyl CoA combines with acteyl CoA to start the cycle. Thereafter, the nascent fatty acid combines with more malonyl CoA since it's decarboxylation drives the energetics of the 2 carbon coupling.
 

1. What is the function of Acetyl CoA?

Acetyl CoA is a molecule that plays a crucial role in the metabolism of carbohydrates, fats, and proteins. It serves as a carrier of acetyl groups for various biochemical reactions in the body.

2. How is Acetyl CoA converted to Malonyl CoA?

The conversion of Acetyl CoA to Malonyl CoA is a two-step process. First, Acetyl CoA combines with carbon dioxide to form a 4-carbon molecule called citrate. This reaction is catalyzed by the enzyme citrate synthase. Next, citrate undergoes a series of reactions to produce Malonyl CoA, with the help of the enzyme citrate lyase.

3. What is the significance of Acetyl CoA turning into Malonyl CoA?

The conversion of Acetyl CoA to Malonyl CoA is a key step in the biosynthesis of fatty acids. Malonyl CoA serves as a building block for the formation of long-chain fatty acids, which are essential for the production of cell membranes, hormones, and energy storage molecules.

4. How does the body regulate the levels of Acetyl CoA and Malonyl CoA?

The levels of Acetyl CoA and Malonyl CoA are tightly regulated by a feedback mechanism. High levels of Malonyl CoA inhibit the enzyme that converts Acetyl CoA to Malonyl CoA, thus preventing an excessive buildup of fatty acids. Also, the presence of Malonyl CoA can suppress the enzyme that breaks down fatty acids, allowing for their accumulation in times of energy need.

5. Can Acetyl CoA be converted to other molecules besides Malonyl CoA?

Yes, Acetyl CoA can be converted to a variety of other molecules depending on the body's needs. It can be used to produce energy through the citric acid cycle, or it can be converted to ketone bodies to provide an alternative source of energy for the brain. Additionally, Acetyl CoA can be used to synthesize cholesterol, amino acids, and other important molecules in the body.

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