Lipid catabolism Flashcards
What are lipids?
Non-polar molecules, insoluble in water, soluble in organic solvents
Lipids serve as chemical messengers, energy sources, components of cell membranes, and precursors for hormones.
What are the main types of lipids?
Fats (triglycerides), phospholipids, steroids (hormones, cholesterol)
These types of lipids play various roles in biological functions.
How do carbohydrates compare to lipids in terms of energy release?
Carbohydrates release 4 Kcal/g, lipids release 9 Kcal/g
This indicates that lipids are more energy-dense than carbohydrates.
What is the structure of triglycerides?
Comprises three fatty acids esterified to glycerol
Triglycerides are the main form of stored energy in animals.
What is the first step in fatty acid mobilization?
Hormone Regulation
Adrenaline (epinephrine) is usually responsible for this activation.
What occurs during fatty acid activation?
Fatty acid reacts with ATP to form acyl adenylate and pyrophosphate (PPi)
This reaction drives the formation of acyl CoA.
What role does carnitine play in fatty acid metabolism?
Catalyzes the transfer of the acyl group to mitochondrial CoA-SH
This is crucial for transporting fatty acids into the mitochondria.
What are the four steps of beta-oxidation?
- Dehydrogenation
- Hydration
- Dehydrogenation
- Thiolytic cleavage
These steps facilitate the breakdown of fatty acids in the mitochondria.
What is produced after one cycle of beta-oxidation?
One molecule of acetyl CoA, NADH, FADH2
Each cycle shortens the fatty acyl-CoA by two carbon atoms.
What is the fate of acetyl CoA produced from beta-oxidation?
Enters the TCA cycle
Acetyl CoA is a key intermediary in the metabolic pathways.
How many ATP are produced from the complete oxidation of one mole of stearic acid?
120 moles of ATP
This is a higher yield compared to glucose.
True or False: Lipids are more readily digested than carbohydrates.
False
Carbohydrates are more easily digested compared to lipids.
What happens to fatty acids with odd numbers of carbon atoms during beta-oxidation?
They produce propionyl-CoA, which is converted to succinyl-CoA
Succinyl-CoA is an intermediate of the TCA cycle.
Fill in the blank: Acyl CoA must be transported into the mitochondria via the _______.
Carnitine shuttle
This shuttle is essential for fatty acid metabolism.
What is the energy yield from one molecule of acetyl CoA in the TCA cycle?
10 ATP
Acetyl CoA is an important fuel for the TCA cycle.
What is the net ATP yield from the complete oxidation of palmitoyl CoA?
106 ATP
This includes the ATP produced from acetyl CoA, NADH, and FADH2.
What is the ATP yield from 1 molecule of stearic acid?
120 ATP
What is produced from the final cycle of β-oxidation of fatty acids with odd numbers of carbon atoms?
1 molecule of propionyl-CoA
What does propionyl-CoA get converted to?
methylmalonyl-CoA
What is the rearrangement product of methylmalonyl-CoA?
succinyl-CoA
Where does β-oxidation take place besides mitochondria?
peroxisomes and glyoxysomes
What percentage of β-oxidation occurs in peroxisomes?
5-10%
What is the role of peroxisomes in lipid catabolism?
Shortens long chain fatty acids (22-24) for mitochondrial use
What is a key function of hypolipidemic drugs?
Stimulate β-oxidation in peroxisomes
What process is required to convert a cis double bond to a trans double bond in monounsaturated fatty acids?
cis-trans isomerisation
What enzyme is required for the first dehydrogenation reaction in the oxidation of monounsaturated fatty acids?
Acyl CoA Dehydrogenase
What is the initial product of β-oxidation?
Acetyl-CoA
What is the relationship between the number of carbon atoms in a fatty acid and the number of acetyl-CoA produced?
molecules of acetyl CoA produced = ½ the C atoms in the fatty acid
What condition leads to the formation of ketone bodies?
Excess of acetyl-CoA due to insufficient oxaloacetate
What are the two main ketone bodies formed from acetoacetate?
acetone and β-hydroxybutyrate
What condition is characterized by high levels of acetoacetate and acetone in the blood?
ketosis
What is ketoacidosis?
Lowering of blood pH due to high concentrations of acidic ketone bodies
What dietary conditions can lead to ketone body formation?
High intake of lipids and low intake of carbohydrates
What is the fuel source for the heart muscle and renal cortex during starvation?
Ketone bodies
Fill in the blank: Acetoacetate is converted into _______ molecules of acetyl CoA which then enters the TCA cycle.
2
True or False: Acetoacetate is preferred to glucose as a fuel source for heart muscle under normal physiology.
True
What is the process called when ketone bodies are formed from acetyl-CoA?
Ketogenesis
What are the four key terms related to the transport and oxidation of fatty acids?
- Acyl-CoA
- Acylcarnitine
- Carnitine
- β-oxidation
