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Chapter 23-25 and 27 (will be 60% of the content asked on final exam)
What is the main role of bile salts in fat digestion?
Bile salts emulsify triacylglycerol globules to produce a greater surface area, increasing lipase activity.
What happens to dietary fat after it is consumed?
Fat is minimally digested in the mouth and stomach, enters the small intestine where bile acids emulsify it, lipases break it down, and the products are absorbed into enterocytes to reassemble as triglycerides.
How is fatty acid transported into the mitochondrial matrix prior to beta-oxidation?
Through the acyl-carnitine/carnitine transporter after being converted to fatty acyl CoA.
What is the rate-limiting step for fatty acid transport into the mitochondria prior to beta oxidation?
The conversion of fatty acyl CoA to fatty acyl carnitine by CPT1/CAT1.
List the enzymes involved in beta-oxidation in order. What type of reaction does each perform?
Acyl-CoA dehydrogenase (Oxidation) 2. Enoyl-CoA hydratase (Hydration) 3. Hydroxyacyl-CoA dehydrogenase (Oxidation) 4. Thiolase (Cleavage).
What is the product of each round of beta-oxidation?
1 acetyl CoA, 1 NADH, 1 FADH2.
What stimulates lipolysis and when are these hormones active?
Glucagon activates lipolysis during fasting; epinephrine activates it during stress.
What condition can result from excessive ketone body production?
Ketoacidosis.
What are the three main ketone bodies?
Acetone, acetoacetate, and alpha-hydroxybutyrate.
What is the primary organ involved in cholesterol synthesis?
The liver.
What is the rate-limiting enzyme in cholesterol synthesis?
HMG-CoA reductase.
How does insulin regulate TAG synthesis?
Insulin activates TAG synthesis by promoting conversion of acetyl CoA into malonyl CoA and encouraging anabolic pathways.
What role does glycerol play after TAG hydrolysis?
Glycerol enters glycolysis, especially in the liver, where it is phosphorylated by glycerol kinase.
Describe the Glucose-Alanine Cycle.
It occurs during muscle breakdown, where pyruvate is converted to alanine, transported to the liver, converted back to pyruvate for gluconeogenesis, and glucose is returned to the muscles.
What are the two main types of amino acids based on their necessity?
Essential and nonessential amino acids.
What distinguishes glucogenic amino acids from ketogenic ones?
Glucogenic amino acids can be converted into glucose, while ketogenic amino acids can be converted into ketone bodies.
What factors can lead to high levels of urea in urine?
A high protein, very low carbohydrate diet.
What do zymogens require to become active?
Zymogens require proteolytic cleavage to become functional enzymes.
What is oxidative deamination?
It's the process where nitrogen is removed from an amino acid as ammonia, which is then processed into urea.
What is the main relationship between folic acid, THF, and homocysteine concerning cardiovascular disease?
Folic acid deficiency increases CVD risk; THF is necessary to convert homocysteine into methionine.
Which enzyme is involved in the transfer of nitrogen during transamination?
Aminotransferase.
Where in the body are BCAAs metabolized?
BCAAs are metabolized in the liver, muscle, adipose tissue, kidney, and brain.
What characterizes Maple Syrup Urine Disease (MSUD)?
Inability to degrade branched-chain amino acids leading to a buildup, with symptoms including a sweet urine smell, vomiting, convulsions, and potential mental retardation.
What are the starting substrates for the urea cycle?
Ornithine and carbamoyl phosphate.
What happens to succinyl CoA during amino acid metabolism?
It can enter the TCA cycle.
What is the function of lipoprotein lipase?
Lipoprotein lipase hydrolyzes triglycerides from lipoproteins to release fatty acids.
How does insulin influence the metabolism of fats and carbohydrates?
Insulin activates fat storage and promotes glycolysis while inhibiting lipolysis.
What are the essential amino acids?
Arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
What is the process by which ammonia is excreted in the body?
Through the urea cycle, converting ammonia to urea.
What is the role of THF in metabolism?
THF is a coenzyme involved in one-carbon metabolism, carrying methyl groups for various biosynthetic reactions.
What is ketoacidosis?
A condition caused by high levels of ketone bodies, resulting in low pH of blood.
What is the difference between transamination and deamination?
Transamination transfers the amino group from one amino acid to another, while deamination removes the amino group for excretion.
What is the role of biotin in fatty acid synthesis?
Biotin is a coenzyme required for the conversion of acetyl CoA to malonyl CoA in fatty acid synthesis.
Where does cholesterol synthesis occur within the cell?
Cholesterol synthesis occurs in the cytosol and endoplasmic reticulum of liver cells.
What is the significance of chylomicrons in lipid metabolism?
Chylomicrons transport dietary fats from the intestine to other tissues.
What does the HMG-CoA reductase enzyme do?
It catalyzes the rate-limiting step in cholesterol synthesis, converting HMG-CoA to mevalonate.
How is the activity of ACC regulated?
ACC is regulated by phosphorylation, with its activity being promoted by insulin and inhibited by glucagon.
What is the effect of high circulating levels of fatty acyl CoA on fatty acid synthesis?
High levels of fatty acyl CoA inhibit ACC and therefore fatty acid synthesis.
How do unsaturated fatty acids differ from saturated ones regarding energy yield?
Unsaturated fatty acids typically yield less energy than saturated fatty acids due to the difference in the number of bonds.
What role does citrate play in fatty acid synthesis?
Citrate transports acetyl CoA out of the mitochondria and activates ACC when present in high concentrations.
Where does the bulk of amino acid catabolism take place?
The liver is the primary site for amino acid catabolism.
What are the two types of protein degradation pathways in cells?
Proteosomal degradation and lysosomal degradation.
What is the function of alanine in the Glucose-Alanine Cycle?
Alanine is a transport molecule that carries amino groups from muscle to the liver for gluconeogenesis.
What is the primary cause of hyperammonemia in humans?
It is primarily caused by liver dysfunction, which leads to ineffective urea cycle activity.
What is the function of apolipoproteins in lipoprotein particles?
Apolipoproteins serve as structural components, receptor ligands, and activate enzymes in lipid metabolism.
Why is Vitamin B6 important for amino acid metabolism?
Vitamin B6 is a cofactor for aminotransferases involved in the transamination process.
How does glucagon affect carbohydrate metabolism during fasting?
Glucagon increases gluconeogenesis and glycogenolysis to raise blood glucose levels.
What are the two nitrogen sources for the urea cycle?
One nitrogen comes from carbamoyl phosphate and the other from aspartate.
What is meant by 'essential amino acids'?
Essential amino acids cannot be synthesized by the body and must be obtained from dietary sources.
What metabolic condition can arise from defects in BCAA catabolism?
Maple Syrup Urine Disease (MSUD) arises from defective catabolism of branched-chain amino acids.
What is the main outcome of the urea cycle?
The main outcome is the conversion of ammonia into urea for excretion.
Which hormones are involved in stimulating lipogenesis?
Insulin stimulates lipogenesis.
What process occurs in the mitochondrial matrix involving Acetyl-CoA during fasting?
During fasting, Acetyl-CoA is converted into ketone bodies.
What is the primary role of urea in the human body?
Urea serves as a primary means to excrete excess nitrogen from the body.
How can amino acids be involved in energy production?
Amino acids can be converted into intermediates for the Krebs cycle, contributing to ATP production.
What metabolic pathway is indicated by a diet high in protein and low in carbohydrates?
A ketogenic state where ketones are produced for energy.
What are the metabolic fates of nitrogen in terrestrial vertebrates?
Terrestrial vertebrates usually excrete nitrogen as urea.
How is cholesterol transported in the bloodstream?
Cholesterol is transported primarily by lipoproteins, such as LDL and HDL.
What is the role of insulin in fat metabolism?
Insulin promotes fatty acid synthesis and inhibits lipolysis.
Which enzyme is responsible for the oxidation of glutamate during amino acid degradation?
Glutamate dehydrogenase.
What is the fate of propionyl CoA in odd-chain fatty acid metabolism?
Propionyl CoA gets converted into succinyl CoA, which then entering TCA cycle.
Describe the connection between high homocysteine levels and cardiovascular disease.
High homocysteine levels can damage blood vessels and increase the risk of cardiovascular disease.
What are the two groups of BCAAs?
Valine, isoleucine, and leucine.
How can the liver impact blood glucose levels during fasting?
The liver can release glucose into the bloodstream through gluconeogenesis and glycogenolysis.
What reaction is catalyzed by aminotransferases?
Transamination, which transfers an amino group from an amino acid to a keto acid.
What characterizes the conditions under which oxidative deamination occurs?
Oxidative deamination occurs when nitrogen is removed from amino acids due to excess amino acids or during starvation.
