Fatty Acid Synthesis Mechanisms
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Questions and Answers

What is the primary function of the microsomal pathway in fatty acid elongation?

  • To activate fatty acids into fatty acyl CoA
  • To elongate existing long-chain fatty acid molecules (correct)
  • To produce fatty acids shorter than 16 carbons
  • To synthesize triacylglycerols from fatty acids and glycerol

What molecule acts as the acetyl donor in the microsomal pathway of fatty acid elongation?

  • Glycerol-3-phosphate
  • Malonyl CoA (correct)
  • Dihydroxyacetone phosphate
  • Palmitate

During myelination of nerves, which fatty acid lengths are primarily produced by the microsomal pathway?

  • C10-C16
  • C26-C28
  • C18-C20
  • C22-C24 (correct)

What is the main function of glycerol-3-phosphate in lipogenesis?

<p>It provides the glycerol backbone for triacylglycerol synthesis (A)</p> Signup and view all the answers

What is the primary role of insulin in lipogenesis?

<p>It stimulates glycolysis, leading to increased dihydroxyacetone phosphate production (D)</p> Signup and view all the answers

Which hormone is primarily responsible for inhibiting lipogenesis and stimulating lipolysis during fasting?

<p>Glucagon (A)</p> Signup and view all the answers

In which tissue(s) is lipogenesis primarily regulated by the interplay of insulin and glucagon?

<p>Liver and adipose tissue (C)</p> Signup and view all the answers

What is the primary cause of fatty liver disease?

<p>Imbalance between triacylglycerol synthesis and export (B)</p> Signup and view all the answers

What is the main product of the cytoplasmic pathway of fatty acid synthesis?

<p>Palmitate (16C) (D)</p> Signup and view all the answers

What enzyme is key in regulating the cytoplasmic pathway of fatty acid synthesis?

<p>Acetyl CoA carboxylase (D)</p> Signup and view all the answers

Which of the following conditions inhibits fatty acid synthesis?

<p>Increased glucagon levels (C)</p> Signup and view all the answers

What is formed when acetyl CoA is activated during fatty acid synthesis?

<p>Malonyl CoA (C)</p> Signup and view all the answers

Where does fatty acid synthesis take place within the cell?

<p>Cytosol (C)</p> Signup and view all the answers

Which of the following substrates is NOT required for fatty acid synthesis?

<p>Glycerol (A)</p> Signup and view all the answers

What role does citrate play in fatty acid synthesis?

<p>Stimulator of acetyl CoA carboxylase (B)</p> Signup and view all the answers

What are the main reactions involved in fatty acid synthesis?

<p>Condensation, Reduction, Dehydration, and Reduction (C)</p> Signup and view all the answers

Flashcards

Cytoplasmic Fatty Acid Synthesis

The production of fatty acids in the cytoplasm of cells, primarily producing palmitate (16C).

Fatty Acid Synthesis Pathway (Cytoplasm)

The process of adding two-carbon units to a growing fatty acid chain, repeating until a 16-carbon fatty acid is formed. This process happens in the cytoplasm.

Fatty Acid Synthase Complex

The enzyme complex responsible for fatty acid synthesis in the cytoplasm. It binds to acetyl CoA, malonyl CoA, and other substrates needed for the process.

Insulin's Role in Fatty Acid Synthesis

The hormone that stimulates fatty acid synthesis by increasing the activity of key enzymes involved in the process.

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Glucagon and Epinephrine's Role in Fatty Acid Synthesis

Hormones that inhibit fatty acid synthesis by decreasing the activity of key enzymes, leading to increased breakdown of stored fat.

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Long-Chain Acyl CoA in Fatty Acid Synthesis

A long-chain fatty acid that inhibits its own production by acting as a feedback mechanism. It signals that enough fatty acids have been made.

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Citrate's Role in Fatty Acid Synthesis

A molecule that stimulates acetyl CoA carboxylase, a key enzyme in fatty acid synthesis, promoting the process.

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Microsomal Fatty Acid Synthesis

The pathway that elongates existing long-chain fatty acids (C10-C16) by adding 2-carbon units, primarily found in the endoplasmic reticulum.

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Malonyl CoA in Fatty Acid Synthesis

A molecule involved in both cytoplasmic and microsomal fatty acid synthesis. It provides the two-carbon units used for elongation.

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Lipogenesis

A process that involves the synthesis of triacylglycerols, the main form of stored fat. It uses fatty acids and glycerol.

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Glycerol Phosphate Production

The process of converting dihydroxyacetone phosphate, a product of glycolysis, into glycerol phosphate, a key component of triacylglycerols.

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Insulin's Role in Lipogenesis

A hormone that stimulates lipogenesis after a meal, increasing the availability of glycerol phosphate for triacylglycerol synthesis.

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Anti-insulin Hormones' Role in Lipogenesis

Hormones like glucagon that inhibit lipogenesis, promote fat breakdown (lipolysis), and counteract insulin's effects.

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Fatty Liver Disease

A condition where fat accumulates excessively in the liver, leading to potential damage and complications.

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Normal Liver Fat Content

The normal percentage of fat content in liver cells.

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Fatty Liver Development

The ratio of triacylglycerol synthesis to triacylglycerol export that determines the accumulation of fat in the liver.

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Study Notes

Fatty Acid Synthesis

  • There are two mechanisms for fatty acid synthesis: cytoplasmic and microsomal.
  • The cytoplasmic system (extra-mitochondrial) or de novo pathway produces palmitate (16C) as its main product.
  • This pathway takes place in the cytosol of many tissues, including the liver, adipose tissue, lung, and kidney.
  • It requires acetyl CoA, NADPH+H, and a group of enzymes called fatty acid synthase complex.

Fatty Acid Synthesis Pathway

  • Stage 1: Transport of acetyl CoA out of the mitochondria into the cytoplasm via citrate, which is cleaved into oxaloacetate and acetyl CoA.
  • Stage 2: Activation of acetyl CoA to form malonyl CoA.
  • Stage 3: Repetitive addition and reduction of two-carbon units to synthesize C16 fatty acid on an acyl carrier protein.

Regulation of Fatty Acid Synthesis

  • Insulin stimulates fatty acid synthesis.
  • Glucagon and epinephrine inhibit fatty acid synthesis through cyclic AMP and stimulate lipolysis.
  • Long-chain acyl CoA inhibits fatty acid synthesis.
  • Citrate stimulates fatty acid synthesis through stimulation of acetyl CoA carboxylase.

Microsomal Pathway

  • This pathway is responsible for the elongation of existing long-chain fatty acid molecules (C10-C16) derived from palmitate and dietary fatty acids.
  • It requires malonyl CoA as an acetyl donor and NADPH+H as a coenzyme.
  • This system is active during myelination of nerves, providing C22 and C24 fatty acids for sphingolipids.

Lipogenesis

  • Lipogenesis is the synthesis of triacylglycerols from fatty acids (acyl CoA) and glycerol (glycerol-3-phosphate).
  • Steps:
    • Activation of fatty acids into fatty acyl CoA.
    • Synthesis of glycerol phosphate in liver, kidney, intestine, and muscle.
    • Synthesis of triacylglycerol by reaction between acyl CoA and glycerol phosphate.

Regulation of Lipogenesis

  • After a meal, lipogenesis is stimulated by insulin, which stimulates glycolysis, providing dihydroxyacetone phosphate that is converted into glycerol phosphate in adipose tissue.
  • During fasting, lipogenesis is inhibited by anti-insulin hormones (e.g., glucagon), which inhibit lipogenesis and stimulate lipolysis.

Fatty Liver

  • Fatty liver disease is a build-up of fats in the liver, which can damage the organ and lead to serious complications.
  • Normally, liver cells contain only 5% of fats.
  • Fatty liver is formed when fat levels increase above 5% in liver cells due to an imbalance in the rate of triacylglycerol synthesis and export.

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Related Documents

Fatty Acid Synthesis PDF

Description

Understand the two mechanisms of fatty acid synthesis, including cytoplasmic and microsomal pathways, and their products and locations in the body.

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