Fatty Acid Synthesis and Regulation Quiz
44 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What initiates the rate limiting step in fatty acid synthesis?

  • Oxidation of fatty acids
  • Conversion of acetyl CoA to malonyl CoA (correct)
  • Formation of citrate from pyruvate
  • Conversion of malonyl CoA to acetyl CoA

Which component is essential for the activity of acetyl-CoA carboxylase?

  • NADPH
  • Biotin (correct)
  • Malonyl CoA
  • Citrate

How many carbon atoms does palmitate consist of, which is produced by fatty acid synthase?

  • 14
  • 18
  • 20
  • 16 (correct)

Which metabolic pathway is a source of NADPH for fatty acid synthesis?

<p>Pentose Phosphate Pathway (A)</p> Signup and view all the answers

What is the structural characteristic of the fatty acid synthase complex?

<p>Dimeric structure (D)</p> Signup and view all the answers

Which of the following provides acetyl CoA for fatty acid biosynthesis?

<p>Oxidation of pyruvate (A)</p> Signup and view all the answers

What is the primary function of malic enzyme in fatty acid synthesis?

<p>Production of NADPH (B)</p> Signup and view all the answers

During fatty acid synthesis, which of the following is increased by each cycle of the fatty acid synthase reaction?

<p>Carbon chain length by 2 carbons (A)</p> Signup and view all the answers

What role does acetyl CoA carboxylase play in fatty acid metabolism?

<p>It regulates both fatty acid synthesis and degradation. (A)</p> Signup and view all the answers

During starvation, which hormone is primarily responsible for activating lipolysis in adipose tissues?

<p>Epinephrine (B)</p> Signup and view all the answers

How does insulin affect acetyl CoA carboxylase activity?

<p>It deactivates the enzyme through dephosphorylation. (A)</p> Signup and view all the answers

What is the effect of palmitoyl CoA on acetyl CoA carboxylase?

<p>It inhibits the enzyme. (B)</p> Signup and view all the answers

Which factor does NOT contribute to the activation of acetyl CoA carboxylase?

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

Which statement accurately describes the short-term regulation of fatty acid synthesis?

<p>It includes covalent modification and allosteric regulation. (B)</p> Signup and view all the answers

Which metabolic state results in increased malonyl CoA formation?

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

What is the role of AMP in the global regulation of acetyl CoA carboxylase?

<p>It activates protein kinases. (B)</p> Signup and view all the answers

Which of the following statements about Acetyl CoA is true?

<p>Acetyl CoA is converted to fatty acids and is regulated by dietary intake. (C)</p> Signup and view all the answers

Which enzyme is considered the rate limiting step in fatty acid synthesis?

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

Where does the biosynthesis pathway for fatty acids primarily occur?

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

What initiates the elongation phase during fatty acid synthesis?

<p>Formation of acetyl ACP and malonyl ACP (C)</p> Signup and view all the answers

Which hormones are involved in the regulation of carboxylase activity?

<p>Insulin, epinephrine, and glucagon (A)</p> Signup and view all the answers

What is the major building block for the synthesis of triacylglycerols in most tissues?

<p>Glycerol-3-phosphate (D)</p> Signup and view all the answers

Which process occurs in adipose tissue to produce glycerol-3-phosphate?

<p>Conversion of dihydroxyacetone phosphate (D)</p> Signup and view all the answers

What prevents the synthesis of triacylglycerols in adipocytes when glucose is low?

<p>Decreased insulin levels (D)</p> Signup and view all the answers

Which of the following describes the process of triacylglycerol synthesis?

<p>Addition of 3 acyl groups from Acyl-CoA to glycerol-3-phosphate (D)</p> Signup and view all the answers

What is the yield of energy from triglycerides compared to carbohydrates and proteins?

<p>9 kcal/g for triglycerides, 4 kcal/g for carbohydrates and proteins (D)</p> Signup and view all the answers

What is the role of Glycerol Kinase in triglyceride synthesis?

<p>To convert free glycerol to glycerol-3-phosphate (B)</p> Signup and view all the answers

Which component is produced from glucose through glycolysis that is essential for triacylglycerol synthesis?

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

Which enzyme is responsible for the conversion of malonyl CoA to malonyl ACP?

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

During which step does the actual reduction of keto-acyl-ACP to hydroxyacyl-ACP occur?

<p>Step 5 (C)</p> Signup and view all the answers

What is the byproduct of the condensation reaction in fatty acid synthesis?

<p>CO2 (A)</p> Signup and view all the answers

What occurs during the dehydration step of fatty acid synthesis?

<p>Elimination of H2O from β-hydroxybutyryl ACP (B)</p> Signup and view all the answers

Which compound serves as the initial substrate in the fatty acid synthesis pathway?

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

What is the role of ACP (Acyl Carrier Protein) in the fatty acid synthesis process?

<p>To bind and carry acyl groups throughout synthesis (A)</p> Signup and view all the answers

Which step involves the transfer of the acetyl group to ACP?

<p>Step 2 (D)</p> Signup and view all the answers

What is the significance of the fatty acid synthase enzyme being coded by a single gene?

<p>It ensures coordinated expression of all enzyme components involved. (A)</p> Signup and view all the answers

What initiates the elongation phase of fatty acid synthesis?

<p>Formation of acetyl ACP and malonyl ACP (D)</p> Signup and view all the answers

Which enzyme catalyzes the conversion of acetoacetyl ACP to D-3-hydroxybutyryl ACP?

<p>ß-ketoacyl ACP reductase (D)</p> Signup and view all the answers

What is the product of the dehydration of D-3-hydroxybutyryl ACP?

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

Which reducing agent is used during the reduction of crotonyl ACP to butyryl ACP?

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

Which domain of the multifunctional enzyme complex contains the acyl carrier protein?

<p>Domain 2 (B)</p> Signup and view all the answers

What is the result of the final reaction in fatty acid synthesis involving palmitoyl-ACP?

<p>Palmitate and HS-ACP (B)</p> Signup and view all the answers

What type of reaction links acetyl ACP and malonyl ACP to form acetoacetyl ACP?

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

Which enzyme is responsible for catalyzing the condensation of butyryl ACP with malonyl ACP?

<p>Acyl-malonyl ACP condensing enzyme (D)</p> Signup and view all the answers

Flashcards

Lipogenesis

The process of converting acetyl CoA into fatty acids.

Acetyl-CoA Carboxylase (ACC)

A key enzyme in lipogenesis that converts acetyl CoA to malonyl CoA, the building block for fatty acids.

Conversion of Acetyl CoA to Malonyl CoA

The rate-limiting step in fatty acid synthesis. It involves the addition of a carbon dioxide molecule to acetyl CoA, forming malonyl CoA.

Fatty Acid Synthase (FAS)

A multi-enzyme complex that catalyzes the elongation of fatty acid chains, two carbons at a time. It contains 7 enzymes and an acyl carrier protein (ACP).

Signup and view all the flashcards

Acyl Carrier Protein (ACP)

A molecule that carries fatty acid intermediates during the synthesis process.

Signup and view all the flashcards

NADPH

A key source of reducing power (electrons) for fatty acid synthesis.

Signup and view all the flashcards

Citrate

The molecule that is shuttled out of mitochondria and converted to malonyl CoA for fatty acid synthesis.

Signup and view all the flashcards

Acetyl CoA

A molecule formed inside mitochondria but cannot leave freely. It is a precursor for fatty acid synthesis.

Signup and view all the flashcards

Fatty acid synthesis in bacteria

The main process of fatty acid synthesis in bacteria, involving a series of steps with specific enzymes.

Signup and view all the flashcards

Loading

An important step in fatty acid synthesis where acetyl- and malonyl- groups are transferred from CoA to ACP.

Signup and view all the flashcards

Condensation

A step in fatty acid synthesis where a 2-carbon unit from malonyl-ACP is added to acetyl-ACP, forming a 4-carbon keto-acyl-ACP.

Signup and view all the flashcards

Reduction

The process of converting keto-acyl-ACP to hydroxyacyl-ACP using NADPH as a reducing agent.

Signup and view all the flashcards

Dehydration

The removal of water from hydroxyacyl-ACP to form enoyl-ACP.

Signup and view all the flashcards

Reduction

The process of reducing the double bond in enoyl-ACP to form a fully saturated 4-carbon acyl-ACP using NADPH.

Signup and view all the flashcards

Pantothenic acid

A component of ACP that plays a role in fatty acid synthesis.

Signup and view all the flashcards

Fatty Acid Elongation: Step 1

The first step in fatty acid elongation involves attaching acetyl CoA and malonyl CoA to the ACP (acyl carrier protein).

Signup and view all the flashcards

Condensation Reaction

Acetyl ACP and malonyl ACP condense to form acetoacetyl ACP, a four-carbon intermediate.

Signup and view all the flashcards

Reduction: Step 1

Acetoacetyl ACP is reduced to D-3-hydroxybutyryl ACP using NADPH as the reducing agent.

Signup and view all the flashcards

Reduction: Step 2

Crotonyl ACP is reduced to butyryl ACP, the final product of the first elongation cycle.

Signup and view all the flashcards

Elongation Cycle

The synthesis process repeats, adding two carbons at a time, until a 16-carbon palmitoyl group is formed.

Signup and view all the flashcards

Final Step: Hydrolysis

Palmitoyl-ACP is hydrolyzed to release palmitate, a saturated fatty acid with 16 carbons.

Signup and view all the flashcards

Fatty Acid Synthase Complex

The fatty acid synthase complex is organized with multiple domains, each containing specific enzymes for the elongation process.

Signup and view all the flashcards

Acetyl CoA carboxylase

A crucial enzyme that catalyzes the irreversible conversion of acetyl-CoA to malonyl-CoA, the building block for fatty acid synthesis.

Signup and view all the flashcards

Fatty acid synthesis

The process of synthesizing fatty acids from acetyl-CoA. It primarily occurs in the cytoplasm of the cell.

Signup and view all the flashcards

Glycerol-3-phosphate

The major building block for the synthesis of triacylglycerols in tissues other than adipose tissue.

Signup and view all the flashcards

Fatty Acid Degradation

A process where stored fats (triglycerides) are broken down into fatty acids and glycerol, releasing energy.

Signup and view all the flashcards

Pentose Phosphate Pathway

This pathway provides reducing power (NADPH) and building blocks for fatty acid synthesis, happening in the cytoplasm.

Signup and view all the flashcards

Malonyl-CoA

A regulatory metabolite that inhibits the transport of fatty acids into the mitochondria, thus promoting fatty acid synthesis.

Signup and view all the flashcards

Insulin

A hormone responsible for promoting the storage of energy by increasing fatty acid synthesis, also activates ACC.

Signup and view all the flashcards

Glucagon and Epinephrine

Hormones that promote the breakdown of stored energy (fat) by inhibiting fatty acid synthesis, also inactivates ACC.

Signup and view all the flashcards

Phosphorylation

A mechanism regulating enzyme activity by adding a phosphate group, often affecting enzyme activity (in this case, inhibiting ACC).

Signup and view all the flashcards

Glucagon

A hormone that stimulates the breakdown of stored fat (lipolysis) by increasing the activity of hormone-sensitive lipase.

Signup and view all the flashcards

Epinephrine

A catecholamine hormone that also stimulates lipolysis, acting similar to glucagon.

Signup and view all the flashcards

Palmitoyl CoA

A long-chain fatty acid that inhibits fatty acid synthesis by regulating the enzyme acetyl-CoA carboxylase, a key step in making fatty acids.

Signup and view all the flashcards

AMP

A low-energy signal that activates fatty acid synthesis by stimulating the enzyme acetyl-CoA carboxylase which leads to the creation of fatty acids.

Signup and view all the flashcards

Dihydroxyacetone phosphate (DHAP)

The glycerol backbone of triacylglycerol is synthesized from this molecule, which is produced during glycolysis.

Signup and view all the flashcards

Glycerol kinase

This enzyme is responsible for converting glycerol to glycerol-3-phosphate in the liver, providing the backbone for triacylglycerol synthesis.

Signup and view all the flashcards

Study Notes

Fatty Acid Synthesis Overview

  • Fatty acid synthesis is the creation of fatty acids.
  • It primarily occurs in the cytoplasm of specialized cells like liver, adipose tissue, and lactating mammary glands.
  • It is a crucial pathway for energy storage in the form of triglycerides.

Stages of Fatty Acid Synthesis

  • Transport of Acetyl CoA: Acetyl CoA, a product of carbohydrate and amino acid breakdown, is exported from mitochondria into the cytoplasm via the citrate transport system.
  • Carboxylation of Acetyl CoA: Acetyl CoA is converted to malonyl CoA by the enzyme acetyl CoA carboxylase. This is a critical, irreversible rate-limiting step in the entire synthesis process.
  • Assembly of the Fatty Acid Chain: Fatty acid synthase (FAS), a multi-enzyme complex, catalyzes the elongation of the carbon chain by two carbons at a time. This involves a series of reactions including condensation, reduction, dehydration, and another reduction.

Requirements for Fatty Acid Synthesis

  • Enzymes: Fatty acid synthase (FAS), a multi-enzyme complex, and acetyl-CoA carboxylase, also a multi-enzyme.
  • Coenzymes and cofactors: Biotin, NADPH, and Mn++.
  • CO2: bicarbonate, and ATP provide the carbon dioxide source and energy.

Sources of NADPH

  • NADPH is created by transferring a molecule of acetyl CoA from mitochondria to the cytosol within the malic enzyme.
  • The pentose phosphate pathway also contributes to NADPH production.

Regulation of Fatty Acid Synthesis

  • Short-term regulation: Allosteric and/or metabolic regulation; covalent modification
  • Long-term regulation: Acetyl CoA carboxylase (ACC), Fatty acid synthase (FAS), ATP-citrate lyase).
  • Hormonal regulation: Insulin promotes synthesis while glucagon and epinephrine inhibit synthesis.
  • Dietary regulation: Carbohydrate-rich diets promote synthesis, and prolonged periods with low glucose can reduce it.
  • Allosteric regulation: Citrate stimulates and palmitoyl CoA inhibits acetyl CoA carboxylase.

Significance of Fatty Acid Synthase

  • High efficiency of fatty acid production.
  • Lack of permeability barriers.
  • Single gene coding for good coordination of enzymes.

Synthesis of Triglycerides

  • The major precursor for triacylglycerol synthesis, in tissues other than adipose tissue, is glycerol-3-phosphate.
  • Adipocytes lack glycerol kinase, therefore dihydroxyacetone phosphate, produced during glycolysis, is their precursor for triacylglycerol synthesis.
  • Adipocytes must oxidize glucose in order to store fatty acids.

Synthesis of Glycerol 3-Phosphate

  • There are multiple pathways for the production of glycerol-3-phosphate, one dependent on glucose availability, the other independent.

Breakdown of Triglycerides

  • Triglycerides are broken down to release fatty acids and glycerol for energy.
  • Glycerol and fatty acids can be used in various metabolic pathways in different tissues.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Lec1 Fatty Acid and Triglycerides PDF

Description

Test your knowledge on the key aspects of fatty acid synthesis and its regulation. This quiz covers topics such as the rate limiting step, acetyl-CoA carboxylase activity, and the metabolic pathways involved. Perfect for students studying biochemistry or related subjects.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser