Chapter 22 Fatty Acid and Triacylglycerol Metabolism

A comprehensive set of 300 flashcards based on Chapter 22, covering key topics in fatty acid and triacylglycerol metabolism for exam preparation.

What is the primary energy storage method used by birds such as the ruby-throated hummingbird?

Fats.

What processes are involved in fatty acid synthesis and degradation?

Fatty acid synthesis prepares for energy storage, while fatty acid degradation prepares for energy use.

By the end of Chapter 22, what should you be able to identify?

The repeated steps of fatty acid degradation.

What role do ketone bodies play in metabolism?

They serve as an alternate energy source.

How is the synthesis of fatty acids regulated?

Through various hormonal and physiological signals.

What are triacylglycerols?

Uncharged esters of fatty acids with glycerol.

Where is adipose tissue primarily stored?

Mainly in adipose tissue, and also stored by muscle for energy needs.

What are adipocytes?

Fat cells that make up adipose tissue.

What is the energy density of complete oxidation of fatty acids compared to carbohydrates and proteins?

38 kJ/g for fatty acids, compared to 17 kJ/g for carbohydrates and proteins.

What are lipases?

Intestinal enzymes that degrade triacylglycerols into free fatty acids and monoacylglycerol.

What are bile acids and how do they assist in digestion?

Amphipathic molecules that facilitate lipid digestion by lipases.

What are chylomicrons?

Lipoprotein transport particles composed of triacylglycerols, proteins, phospholipids, and cholesterol.

What happens to free fatty acids and monoacylglycerols after they are absorbed?

They are resynthesized into triacylglycerols and packaged into chylomicrons.

What are the three stages required for the use of fatty acids as fuel?

Mobilization, activation and transport, and breakdown into acetyl CoA.

What triggers the mobilization of triacylglycerols?

Hormonal control via lipases that catalyze hydrolysis.

Which hormones are involved in mobilizing fatty acids?

Glucagon and epinephrine.

What is the role of perilipin in fat mobilization?

Restructures the fat droplet to make triacylglycerols more accessible.

What enzyme initiates triacylglycerol mobilization?

Adipose triglyceride lipase (ATGL).

What is the main function of the liver in lipid metabolism?

Import, synthesis, storage, and secretion of lipids.

What does albumin do in the blood?

Transports fatty acids.

What is required for fatty acids to be oxidized?

They must be activated and linked to CoA.

What is the main function of acyl CoA synthetase?

Catalyzes the activation of fatty acids to form acyl CoA.

What is the initial step in the reaction catalyzed by acyl CoA synthetase?

Reaction of fatty acid and ATP to yield acyl adenylate.

How does the acyl adenylate form during fatty acid activation?

By a reaction between a fatty acid and ATP.

What transports long-chain activated fatty acids into the mitochondrial matrix?

Carnitine.

What is the role of carnitine acyltransferase I (CATI)?

Catalyzes the transfer of the acyl group from acyl CoA to carnitine.

What occurs during each round of fatty acid oxidation?

Acetyl CoA, NADH, and FADH2 are generated.

What is the β-oxidation pathway?

A process involving four repeated steps that degrade fatty acids.

What does each round of β-oxidation produce?

A shorter fatty acid chain and acetyl CoA.

What are the different dehydrogenase enzymes based on fatty acid chain length?

Long-chain, medium-chain, and short-chain acyl CoA dehydrogenases.

What happens to long-chain and branched fatty acids in peroxisomes?

They are oxidized to shorten them for better β-oxidation substrate.

What pathological conditions are associated with certain fatty acids?

Obesity, type 2 diabetes, and atherosclerosis from saturated and trans fats.

What are ketone bodies?

Water-soluble, transportable forms of acetyl units derived from fat metabolism.

What is the major site of ketone body production?

The liver.

How are acetoacetate and 3-hydroxybutyrate used as energy?

They are transported to tissues during fasting or diabetes.

What condition can result from excessive ketone body formation?

Diabetic ketoacidosis.

Why can't animals convert fatty acids into glucose?

Acetyl CoA cannot be converted into pyruvate or oxaloacetate.

What is the significance of increasing fatty acid synthase and ACC levels?

Occurs when fasted animals are fed high-carbohydrate, low-fat diets.

What are the major components of the fatty acid synthase complex?

Multiple enzymatic activity such as ketosynthase and acyl carrier protein.

How are fatty acids synthesized?

Through a series of reactions that involve malonyl ACP and acetyl ACP.

What is the committed step in fatty acid synthesis?

The formation of malonyl CoA from acetyl CoA.

Which proteins regulate acetyl CoA carboxylase activity?

AMPK and protein phosphatase 2A.

How does citrate influence ACC polymerization?

It facilitates the formation of active filaments.

What is adaptive control in fatty acid synthesis?

Regulation of enzymes required for fatty acid synthesis based on dietary fats.

What is the primary oxidative pathway that generates NADPH for fatty acid synthesis?

The pentose phosphate pathway.

What is the source of NADPH during the transfer of acetyl groups?

NADPH is generated as pyruvate is converted to oxaloacetate.

In what cellular compartments does fatty acid synthesis occur?

In the cytoplasm.

What are the essential fatty acids in the human diet?

Linoleate and linolenate.

How are eicosanoids related to fatty acid metabolism?

They are derived from polyunsaturated fatty acids like arachidonate.

What complex catalyzes the introduction of double bonds in fatty acids?

A membrane-bound complex in the ER.

What are the main functions of eicosanoids?

Stimulate inflammation, regulate blood flow, and modulate synaptic transmission.

How does insulin affect ACC activity?

It activates ACC by promoting dephosphorylation.

What effect does glucagon have on fatty acid metabolism?

It inhibits ACC activity and fat synthesis.

Why is malonyl CoA important in fatty acid metabolism?

It regulates fatty acid synthesis and inhibits fatty acid entry into mitochondria.

What happens to unsaturated fatty acids during β-oxidation?

They require additional steps for degradation.

What is the impact of acetyl CoA in the citric acid cycle?

It's metabolized alongside carbohydrates when in balance.

How are odd-chain fatty acids uniquely metabolized?

They can enter gluconeogenic pathways due to their carbon skeleton.

What is the role of malic enzyme in fatty acid synthesis?

Generates NADPH through the decarboxylation of malate.

What occurs during the reduction of acetoacetate?

It yields D-3-hydroxybutyrate.

What triggers the formation of ketone bodies during fasting?

Lack of oxaloacetate from carbohydrate degradation.

How does β-oxidation differ from fatty acid synthesis?

β-oxidation is oxidative, while synthesis is reductive.

What do ketone bodies serve as for the brain in times of starvation?

An alternative energy source.

What enzyme catalyzes the synthesis of malonyl CoA?

Acetyl CoA carboxylase.

What are the major types of eicosanoids derived from arachidonate?

Prostaglandins, thromboxanes, and leukotrienes.

What is the impact of diet on ACC levels?

Diet influences the synthesis of ACC and fatty acid synthase based on fat intake.

Which fatty acid is synthesized through a multi-enzyme complex in mammals?

Palmitate.

What is the effect of excessive consumption of trans fats?

Inhibits β-oxidation and promotes insulin resistance.

What enzyme's activity is altered by phosphorylation by AMPK?

Acetyl CoA carboxylase.

What is the structure of the fatty acid synthase complex in animals?

A homodimeric enzyme with multiple functional domains.

What is the main metabolic pathway for fatty acid degradation?

β-oxidation.

What is the function of acyl-carrier protein (ACP) in synthesis?

Attaches fatty acids during the synthesis process.

How does the synthesis of odd-chain fatty acids begin?

With propionyl ACP formed from propionyl CoA.

What does the term 'essential fatty acids' mean?

Fats that cannot be synthesized by the body and must be included in the diet.

What determines the oxidative state of fatty acids during metabolism?

The presence of enzymes like acyl CoA dehydrogenases.

Why are longer fatty acids synthesized in eukaryotes?

Through elongation reactions on the cytoplasmic side of the ER.

What is a key regulatory mechanism of fatty acid metabolism?

The interplay between synthesis and degradation based on cellular energy status.

What substrate does acetyl CoA combine with to enter the citric acid cycle?

Oxaloacetate.

What hormone plays a critical role in stimulating fatty acid synthesis through signaling?

Insulin.

What does excessive ketone body production in diabetes lead to?

Diabetic ketoacidosis.

What reaction is catalyzed by hydroxymethylglutaryl CoA synthase?

Formation of acetoacetate from acetyl CoA.

What does the energy yield from fatty acid oxidation rely on?

The number of acetyl CoA produced during the oxidation process.

What enzymatic pathway allows for the shortening of fatty acids in peroxisomes?

Beta-oxidation pathway adapted for very long-chain fatty acids.

How are eicosanoids synthesized from fatty acids?

Through specific enzymatic pathways that modify arachidonate.

What is the physiological significance of ketone bodies?

They provide an alternative energy source during fasting or low carbohydrate intake.

What is the role of fatty-acid binding proteins (FABPs) inside cells?

They transport free fatty acids to the cytosolic face of the smooth ER.

What is a disadvantage of consuming excessive polyunsaturated fats?

They can be easily oxidized and lead to undesirable health effects.

Which two enzymes are involved in converting malate to pyruvate while generating NADPH?

Malate dehydrogenase and malic enzyme.

What is the role of catalase in peroxisomes?

To degrade hydrogen peroxide into water and oxygen.

What metabolic conditions favor high levels of fatty acid synthase?

High carbohydrate intake and low-fat diet.

How does the presence of ATP influence ACC activity?

High ATP levels activate AMPK, inhibiting ACC activity.

What happens when malonyl CoA levels increase?

It inhibits fatty acyl-CoA entry into the mitochondria.

How do different fatty acid chain lengths affect enzymatic activity?

Different enzymes are required based on the chain length for oxidation.

What is the precursor for all eicosanoids?

Arachidonate.

What does

depend on the NADH/NAD+ ratio in the mitochondrial matrix.

How does starvation affect ketone body production?

Increases production due to excessive fatty acid mobilization from adipose tissue.

What pathway merges glycolysis and the citric acid cycle with fatty acid synthesis?

The pentose phosphate pathway.

What inhibits the activity of ACC during fatty acid synthesis?

Phosphorylation by AMPK.

What hormone can stimulate ACC and fatty acid synthesis?

Insulin.

What do fatty acids do once they are mobilized from adipose tissue?

They are transported to various tissues to be utilized as energy.

How do dietary fats affect insulin sensitivity?

Saturated and trans fats can impair insulin action.