85 Questions
Where does de novo synthesis of fatty acids mainly occur?
Adipose tissue cells
What is the main source of mitochondrial Acetyl CoA production?
Oxidation of pyruvate
In the process of ACoA carboxylation to Malonyl CoA, which molecule is required for the carboxylation process?
Biotin
What substrates are used in de novo fatty acid synthesis?
Excess carbohydrates and proteins from the diet
Which enzyme is key in de novo fatty acid synthesis?
Acetyl Coenzyme A
What is the enzyme responsible for catalyzing the carboxylation of ACoA to Malonyl CoA?
Acetyl CoA carboxylase (ACC)
What is the primary end product of de novo fatty acid synthesis?
Palmitic acid
Which molecule allosterically activates Acetyl CoA carboxylase (ACC)?
Citrate
What stimulates ACC synthesis hormonally?
Insulin
In which organelle does the elongation of fatty acids occur?
Smooth endoplasmic reticulum
What type of fatty acids can be produced by adding cis double bonds in desaturation?
Polyunsaturated fatty acids
In the cytosol, how is citrate converted back to Oxaloacetate (OAA) and Acetyl CoA?
By ATP citrate lyase activity
What is the end product of fatty acid synthesis in eukaryotes?
Palmitate
Where do the carbons used in fatty acid synthesis come from?
Malonyl CoA
What is the role of the Pentose Phosphate Pathway in fatty acid synthesis?
Provides reductant NADPH
How does the presence of unsaturated fatty acids affect the melting temperature of lipids?
Decreases the melting temperature
Which type of fatty acids are generally found at position C-1 in triacylglycerols?
Saturated
What is the caloric value per unit mass of triacylglycerols compared to carbohydrates and proteins?
$9$ kCal/gm for TG, about $4$ kCal/gm for carbohydrate and proteins
Which tissue has the ability to use ketone bodies at high concentrations?
Brain cells
What is the main purpose of ketone bodies during fasting or prolonged exercise?
Provide an alternative energy source
What metabolic process stimulates the production of ketone bodies due to the excess of Acetyl CoA?
Ketogenesis
Which of the following is NOT a function of ketone bodies in the body?
Enhancing insulin secretion
What triggers the increased production of ketone bodies in the liver during fasting?
Mobilization of fatty acids from adipose tissue
How are ketone bodies utilized by peripheral tissues?
Oxidized to produce energy
What is the major pathway for fatty acid catabolism?
Beta-oxidation
Which enzyme is responsible for mobilizing fat through lipolysis?
Hormone-Sensitive-Lipase (HSL)
What inhibits the carnitine shuttle (CPT1) in fatty acid beta-oxidation?
Malonyl CoA
What is the role of the carnitine shuttle in fatty acid beta-oxidation?
To transport fatty-acyl-CoA into the mitochondria
Which compound is synthesized from lysine and methionine and helps transport fatty acids into mitochondria?
Carnitine
What does the first cycle of beta-oxidation produce?
1 Acetyl-CoA + 1 NADH + 1 FADH2
What is the main function of ATP citrate lyase in fatty acid synthesis?
Facilitates the conversion of citrate to oxaloacetate and Acetyl CoA
What is the effect of palmitoyl CoA on acetyl CoA carboxylase (ACC)?
It inhibits ACC
Which molecule serves as a negative feedback regulator of acetyl CoA carboxylase (ACC) activity?
Malonyl CoA
What stimulates acetyl CoA carboxylase (ACC) synthesis hormonally?
Insulin levels
In which pathway is acetyl CoA carboxylase (ACC) considered the rate-limiting step?
De Novo synthesis of fatty acids
What is the role of citrate in stimulating ATP citrate lyase activity?
Activates ATP citrate lyase by allosteric regulation
What are the final products after the full oxidation of 1 palmitoyl CoA?
ATP, CO2, H2O
What is the alternative fuel produced by the liver mitochondria from fatty acid oxidation?
Ketone bodies
Where are acetoacetate and ß-hydroxybutyrate transported for utilization in peripheral tissues?
Blood plasma
What can acetoacetate and ß-hydroxybutyrate be converted back into within peripheral tissue cells?
Acetyl CoA
What happens to acetone produced during ketone body metabolism?
Excreted through breath and urine
What is the end product of fatty acid synthesis catalyzed by fatty acid synthase in eukaryotes?
Palmitate (16:0)
What is the role of the Pentose Phosphate Pathway in fatty acid synthesis?
Provides reductant NADH
What is the caloric value per unit mass of triacylglycerols compared to carbohydrates and proteins?
9 kCal/gm for TG, about 4 kCal/gm for carbohydrate and protein
What type of fatty acids are generally NOT found at position C-2 in triacylglycerols?
Polyunsaturated
What decreases the melting temperature of lipids?
Presence of unsaturated fatty acids
How are newly synthesized fatty acids primarily stored in the body?
Triacylglycerols
Where does de novo fatty acid synthesis mainly occur?
Adipose tissue cells
Which of the following tissues can synthesize fatty acids in small quantities, besides liver, mammary glands, and adipose tissue cells?
Brain cells
What is the primary end product of de novo fatty acid synthesis?
Palmitic acid
Which organelle is key for providing Acetyl Coenzyme A (ACoA) as a substrate for fatty acid synthesis?
Mitochondria
Which enzymes in the smooth endoplasmic reticulum can cause desaturation of long-chain fatty acids by adding double bonds?
Desaturases
What is the main function of ketone bodies during fasting and prolonged exercise?
Save glucose
Which tissue has the ability to utilize ketone bodies at high concentrations?
Cardiac muscle
What stimulates the liver to produce high levels of ketone bodies during fasting?
Excess Acetyl CoA
Which molecule is produced when 3-hydroxybutyrate is oxidized in peripheral tissues?
Acetoacetate
What is the primary role of lipolysis in adipocytes?
Mobilize triglycerides
In which condition do ketone bodies increase, leading to their elevated use as an energy source by peripheral tissues?
Diabetes mellitus
What is the common compound that fatty acids are synthesized from and oxidized to?
Acetyl-CoA
Where are fatty acids oxidized and synthesized within the cell?
Both in the mitochondria
Under what conditions do physiological factors largely inhibit fatty acid oxidation?
High NADH/NAD+ ratio
Which process prevents 'futile cycling' by largely inhibiting fatty acid oxidation?
Fatty acid synthesis
What is the primary compound that connects the pathway for mobilization of fats with beta-oxidation?
Acetyl-CoA
What are the final products after the full oxidation of 1 palmitoyl CoA?
ATP, CO2, H2O
What are the primary ketone bodies formed in the adult liver mitochondria from fatty acid oxidation?
Acetoacetate, ß-hydroxybutyrate, Acetone
What can happen to acetone produced during ketone body metabolism?
It is exhaled through the lungs
Which tissues can receive transported ketone bodies for utilization?
Muscle and Brain
What is the alternative fuel that cells can derive from ACoA in peripheral tissues?
Acetyl CoA
What is the primary role of Hormone-Sensitive-Lipase (HSL) in the context of fat mobilization?
Promoting lipolysis
Which compound is required for the transport of fatty-acyl-CoA into the mitochondria for beta-oxidation?
Carnitine
What can cause decreased ability of tissues to use long-chain fatty acids as fuel?
Carnitine deficiencies
Which process can inhibit the transfer of newly synthesized fatty acids into the mitochondria for degradation?
Fatty acid synthesis
What is the rate-limiting step for transporting fatty-acyl-CoA into the mitochondria?
Carnitine shuttle activity
What is the main product generated in each cycle of fatty acid beta-oxidation?
$1$ acetyl-CoA + $1$ NADH + $1$ FADH2
What is the primary role of acetone in ketotic patients?
Causing a fruity smell on breath and urine
Why do ketone bodies save glucose during fasting?
By providing an alternative energy source for tissues
Where are ketone bodies primarily produced?
Liver
Why does the liver increase ketone body production during fasting?
To meet the energy demands of peripheral tissues
What stimulates the production of ketone bodies due to excess Acetyl CoA?
Exceeding oxidative capacity of the liver
How are ketone bodies utilized by peripheral tissues?
Supplying an energy source proportional to their blood concentration
What is the main role of ATP citrate lyase in the context of fatty acid synthesis?
Production of citrate from ACoA and oxaloacetate
Which molecule allosterically activates acetyl CoA carboxylase (ACC) in fatty acid synthesis?
Citrate
Which factor negatively regulates acetyl CoA carboxylase (ACC) activity in fatty acid synthesis?
Decreased citrate concentration
What is the primary requirement for the carboxylation of Acetyl CoA to Malony CoA in fatty acid synthesis?
ATP
What stimulates acetyl CoA carboxylase (ACC) synthesis in the context of fatty acid synthesis?
High-carbohydrate diet
Test your knowledge on the de novo synthesis of fatty acids, specifically focusing on where this process mainly occurs in the body. Learn about the key tissues involved and the role of essential fatty acids in the diet.
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