30 Questions
What is the first step in transporting fatty acids into the mitochondria for oxidation?
Combining with CPT1 on the outer membrane
Which enzyme is responsible for the final step before β-oxidation can begin in the mitochondria?
Carnitine:acylcarnitine translocase (CACT)
Which step of fatty acid breakdown corresponds to dehydration in fatty acid synthesis?
Hydration in the breakdown process
What type of fatty acids require additional enzymes for their oxidation due to their unsaturation or polyunsaturation?
Unsaturated and polyunsaturated fatty acids
Which molecule is a product of β-oxidation of fatty acids and plays a role in the electron transport chain?
FADH2
In fatty acid oxidation, what is the fate of NADH formed during the process?
Contribute to the electron transport chain
What is the main purpose of fatty acid oxidation in cells?
Produce Acetyl-CoA for energy production.
Which molecule is essential for transporting fatty acids into the mitochondrial matrix for beta-oxidation?
Carnitine
What is the function of Acetyl-CoA Carboxylase in fatty acid synthesis?
Convert acetyl-CoA to malonyl-CoA.
Which lipoprotein is responsible for transporting endogenous lipids in the bloodstream?
VLDL
What is the role of lipoprotein lipase (LPL) in lipid metabolism?
Release fatty acids from circulating triglycerides.
Which of the following is a necessary step for fatty acid activation before beta-oxidation?
Formation of malonyl-CoA.
What is the primary molecule produced by the liver that carries endogenous lipids?
Very Low Density Lipoproteins (VLDL)
Which enzyme is responsible for breaking down triglycerides in chylomicrons to release fatty acids for storage?
Lipoprotein lipase (LPL)
Which lipoprotein carries cholesterol from the liver to tissues for utilization?
Low Density Lipoproteins (LDL)
In fatty acid synthesis, where do the endogenous fatty acids primarily come from?
Glycogenolysis
Which lipoprotein is produced by the liver as empty shells?
High Density Lipoproteins (HDL)
What is the primary molecule responsible for transporting dietary fats from the intestines to tissues?
Chylomicron remnants
Where does dietary fat digestion primarily occur?
Small intestine
What is the primary function of micelles in lipid digestion and absorption?
To repackage and transport fatty acids into enterocytes
What is the role of bile salts in lipid digestion and absorption?
To emulsify dietary fats into smaller droplets
What is the end product of complete fatty acid oxidation?
Carbon dioxide and water
What are the carriers of fatty acids in the lymph?
Chylomicrons
What is the role of ketone bodies in metabolism?
To provide an alternative metabolic fuel
What is the net ATP yield from the complete oxidation of one molecule of palmitate?
106 ATP
During starvation, low carb intake, or diabetes, high levels of fatty acids are oxidized, leading to an accumulation of what compound?
Acetyl-CoA
What is the role of carnitine in fatty acid oxidation?
Carnitine is involved in the transport of fatty acids across the inner mitochondrial membrane.
What is the function of ketone bodies?
Ketone bodies are a source of energy for the brain and heart muscle.
In which tissue does fatty acid synthesis occur?
Liver
What is the role of VLDL in lipid transport?
VLDL transports fatty acids from the liver to peripheral tissues.
Study Notes
Fatty Acid Oxidation
- Fatty acid oxidation occurs in the mitochondrial matrix and requires the activation of fatty acids into fatty acyl-CoA.
- The process involves the transport of fatty acyl-CoA into the mitochondrial matrix, where it is converted into acetyl-CoA.
- Acetyl-CoA is then fed into the Krebs cycle, producing ATP, NADH, and FADH2.
- The electrons from NADH and FADH2 are passed through the electron transport chain, generating ATP.
- The net ATP yield from the complete oxidation of one fatty acid molecule (palmitate, C-16) is 26 ATP.
Fatty Acid Synthesis
- Fatty acid synthesis occurs in the liver and is the reverse of fatty acid oxidation.
- The process involves the conversion of acetyl-CoA into fatty acyl-CoA, which is then converted into fatty acids.
- Fatty acids are synthesized into triglycerides (TAGs) and packaged into very low-density lipoproteins (VLDL) for delivery to tissues.
- Fatty acid synthesis is regulated by the availability of acetyl-CoA, NADPH, and ATP.
Carnitine and Fatty Acid Oxidation
- Carnitine plays a crucial role in the transport of fatty acids into the mitochondrial matrix.
- Carnitine palmitoyl transferase 1 (CPT1) converts fatty acyl-CoA into acyl-carnitine, which is then transported into the mitochondrial matrix.
- Carnitine-acylcarnitine translocase (CACT) facilitates the transport of acyl-carnitine into the mitochondrial matrix.
- Carnitine palmitoyl transferase 2 (CPT2) converts acyl-carnitine back into fatty acyl-CoA.
- Deficiencies in carnitine transport or metabolism can lead to reduced energy production from fatty acids.
Lipid Metabolism
- Lipid metabolism involves the breakdown and synthesis of lipids.
- Dietary fats are broken down into fatty acids and glycerol, which are then absorbed into the bloodstream.
- Fatty acids are either used for energy production or stored in adipose tissue.
- Triglycerides are synthesized in the liver and packaged into VLDL for delivery to tissues.
Ketogenesis
- Ketogenesis occurs in the liver during states of starvation, low-carb intake, or diabetes.
- High levels of fatty acid oxidation lead to the production of acetyl-CoA, which is converted into ketone bodies.
- Ketone bodies are used as an alternate energy source for many tissues, including the heart, kidney, and brain.
- Ketone bodies can be transported in the blood to peripheral tissues.
Clinical Relevance
- Obesity is a result of energy intake exceeding energy expenditure.
- Excess energy is stored as TAGs in adipose tissue.
- Factors contributing to obesity include disturbances in physiological mechanisms, genetics, microbiome, lifestyle, environmental, and psychological factors.
- Primary carnitine deficiency and other disorders can lead to reduced energy production from fatty acids.
Test your knowledge on key concepts in metabolism including glycolysis, fatty acid oxidation, amino acid catabolism, and endogenous lipids. This quiz covers various metabolic pathways, enzymes, and important molecules involved in energy production and nutrient breakdown.
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