Module 6 ChatGPT Flashcards
Hormone-Sensitive Lipase (HSL)
An enzyme phosphorylated by PKA to become more active, playing a key role in converting diglycerides to monoacylglycerol plus free fatty acids during lipolysis
Adipose Triglyceride Lipase (ATGL)
The rate-limiting enzyme of triglyceride degradation, catalyzing the conversion of triglycerides to diglycerides and free fatty acids
Comparative Gene Identification-58 (CGI-58)
A protein that regulates ATGL by binding to it when released from perilipin 1 (PLIN1) upon PKA activation
Perilipin 1 (PLIN1)
A protein that binds to triacylglycerol droplets, regulating their degradation
Phosphorylation by PKA releases CGI-58, activating ATGL
Glyceroneogenesis
The process by which adipocytes resynthesize triglycerides from glycerol 3-P (derived from amino acids or lactate) and free fatty acids, reducing fatty acid export
Fatty acids during fasting are
Released into the blood during lipolysis, travel complexed with albumin, and are oxidized to CO2 and water in muscle cells for energy
Ketone Bodies
Produced by the liver from acetyl-CoA during prolonged fasting and released into the blood for use as an energy source
Gluconeogenesis from Glycerol
Glycerol derived from lipolysis in adipose cells is used by the liver as a carbon source during fasting to produce glucose
cAMP in Adipose Cell
A secondary messenger that increases in response to the decrease of insulin and increase of glucagon during fasting, stimulating lipolysis
PKA (Protein Kinase A)
An enzyme activated by increased cAMP levels that phosphorylates hormone-sensitive lipase (HSL), enhancing its activity in lipolysis
Monoacylglycerol Lipase
The enzyme that converts monoacylglycerol to free glycerol and a free fatty acid during lipolysis
Triglyceride Synthesis in Adipocytes
Occurs simultaneously with glyceroneogenesis to regulate the amount of fatty acids released into circulation by resynthesizing triglycerides from glycerol 3-P and free fatty acids
Fatty Acid Transport
Fatty acids released during lipolysis travel in the blood complexed with albumin and enter muscle and other tissues for oxidation to produce energy
beta-Oxidation
The metabolic process by which fatty acids are broken down in the mitochondria of cells to generate acetyl-CoA, which can be used to produce energy or ketone bodies during fasting
Liver Function During Fasting
The liver uses glycerol derived from adipose tissue lipolysis for gluconeogenesis, converting it into glucose to maintain blood sugar levels
Perilipins
A family of proteins that regulate the breakdown of stored fats in adipocytes by binding to lipid droplets and controlling access to lipases
Phosphatidic Acid
An intermediate in the synthesis of triacylglycerols and the precursor of glycerolipids found in cell membranes and blood lipoproteins
Glycerol 3-Phosphate (Glycerol 3-P)
The molecule providing the glycerol backbone for triacylglycerol synthesis, produced in the liver by glycerol kinase or from DHAP
Dihydroxyacetone Phosphate (DHAP)
A glycolysis intermediate converted to glycerol 3-P in the liver and adipose tissue, serving as a source of glycerol for triacylglycerol synthesis
Triglyceride Synthesis in Liver and Adipose Tissue
Involves the reaction of glycerol 3-P with fatty acyl-CoA to form phosphatidic acid, followed by dephosphorylation to DAG, and then formation of triacylglycerol
VLDL (Very Low-Density Lipoprotein)
Lipoprotein particle formed in the liver from triacylglycerol, cholesterol, phospholipids, and proteins, primarily apoB-100, which is necessary for lipid transport
Microsomal Triglyceride Transfer Protein (MTP)
A protein required for the assembly of both VLDL in the liver and chylomicrons in the intestine, crucial for lipid transport
Apolipoprotein B-100 (ApoB-100)
The major protein component of VLDL, encoded by the same gene as apoB-48, with a longer sequence that enables lipid transport in the blood
Apolipoprotein B-48 (ApoB-48)
A truncated version of apoB-100, resulting from RNA editing in intestinal cells, involved in the formation of chylomicrons for dietary lipid transport
Abetalipoproteinemia
A genetic disorder caused by the lack of MTP activity, leading to the inability to assemble chylomicrons and VLDL particles, affecting lipid absorption and transport
Lipoprotein Lipase (LPL)
An enzyme synthesized by adipose tissue, secreted into capillaries, and responsible for digesting triacylglycerols from chylomicrons and VLDL, releasing fatty acids
Insulin’s Role in Adipose Tissue
Stimulates LPL synthesis, glucose metabolism, glycolysis, and conversion of glucose to fatty acids, leading to increased triacylglycerol storage in adipose cells
Phosphofructokinase-1 (PFK-1)
A glycolytic enzyme activated by insulin through increased fructose 2,6-bisphosphate levels, promoting the conversion of glucose to pyruvate
Pyruvate Dehydrogenase (PDH)
An enzyme dephosphorylated and activated by insulin, allowing pyruvate from glycolysis to enter the TCA cycle for further oxidation in adipose cells
VLDL (Very-Low-Density Lipoprotein)
A type of lipoprotein made by the liver that transports endogenous triglycerides, cholesterol, and apolipoproteins in the bloodstream
VLDL Assembly
Occurs in the liver from triglycerides, cholesterol, and apolipoproteins, then processed in the Golgi complex before being secreted into the blood
VLDL Conversion
In the bloodstream, VLDL is converted into intermediate-density lipoprotein (IDL) and low-density lipoprotein (LDL)
VLDL vs Chylomicrons
VLDL particles are more dense than chylomicrons because they contain a lower percentage of triglycerides and more protein
Apolipoprotein CII
An apolipoprotein acquired by VLDL from HDL in the bloodstream, which activates lipoprotein lipase (LPL) to cleave triglycerides in VLDL
Lipoprotein Lipase (LPL)
An enzyme attached to capillary endothelial cells that cleaves triglycerides in VLDL and chylomicrons, producing fatty acids and glycerol
LPL Isozyme in Muscle
Has a low Km, allowing muscle to use fatty acids from VLDL and chylomicrons as a fuel source even at low blood concentrations of these lipoproteins
LPL Isozyme in Adipose Tissue
Has a high Km, making it most active after meals when blood levels of chylomicrons and VLDL are elevated, facilitating fat storage
IDL (Intermediate-Density Lipoprotein)
A lipoprotein particle generated after VLDL has been processed by LPL; can further lose triglycerides to become LDL
LDL (Low-Density Lipoprotein)
A lipoprotein formed from IDL that is rich in cholesterol and transports it to cells in the body
Chylomicrons
Lipoproteins synthesized in the small intestine that transport exogenous (dietary) lipids, containing more triglycerides and less protein than VLDL
VLDL and HDL Interaction
VLDL particles acquire apolipoproteins CII and E from HDL to become mature VLDL particles in the bloodstream
Apolipoprotein B48 vs B100
Chylomicrons contain apolipoprotein B48, while VLDL contains apolipoprotein B100, reflecting their different origins and roles in lipid transport
Nascent VLDL Particles
Newly synthesized VLDL particles that are not fully mature; they acquire additional apolipoproteins (CII and E) from HDL to become fully functional
Role of VLDL in Lipid Transport
VLDL primarily transports endogenous lipids (lipids synthesized by the body) from the liver to peripheral tissues
Triglyceride Content in VLDL
VLDL particles contain a lower amount of triglycerides compared to chylomicrons, making them denser and richer in protein content
Golgi Complex and VLDL
The Golgi complex processes VLDL before it is secreted into the bloodstream, ensuring proper assembly and functionality of the lipoprotein particles
Fatty Acid Storage in Adipose Tissue
Fatty acids derived from VLDL are stored in adipose tissue as triglycerides after being released by LPL and taken up by adipose cells
Endogenous vs Exogenous Lipid Transport
VLDL is responsible for transporting endogenous lipids synthesized by the liver, while chylomicrons transport exogenous lipids absorbed from the diet
Apolipoprotein E
A component of VLDL obtained from HDL, important for the recognition and uptake of VLDL remnants (such as IDL) by the liver
Chylomicron Remnants
The remnants left after chylomicrons have delivered dietary triglycerides to tissues; these are taken up by the liver for further processing
Apolipoprotein B100
The main protein of VLDL, required for its synthesis and stability, and also involved in the interaction with LDL receptors in peripheral tissues
VLDL Secretion by Liver
The liver secretes VLDL into the bloodstream after assembly, where it plays a critical role in distributing lipids throughout the body
HDL (High-Density Lipoprotein)
A lipoprotein that transfers apolipoproteins to VLDL and chylomicrons, helping them to mature and function properly in lipid transport
Cholesterol in VLDL
VLDL particles also carry cholesterol along with triglycerides, contributing to the distribution of cholesterol to tissues and eventually forming LDL
What are the two categories of amino acids
Amino acids are categorized into essential and non-essential Essential amino acids must be obtained from the diet, while non-essential amino acids can be synthesized by the body
What is the role of transaminases in amino acid metabolism
Transaminases transfer the amino group from an amino acid to a keto acid, facilitating the production of new amino acids and the metabolism of nitrogen
What is the significance of pyridoxine (vitamin B6) in transamination reactions
Pyridoxine acts as a cofactor for transaminases, enabling the transfer of amino groups during transamination reactions
What happens to ammonia in the liver
Ammonia is converted into urea in the liver through the urea cycle, which is then excreted in the urine to prevent toxicity
What is the Cori cycle
The Cori cycle involves the conversion of lactate produced in muscles back to glucose in the liver, which can then be reused for energy
What is the role of glutamate in amino acid metabolism
Glutamate can undergo oxidative deamination, releasing ammonia and converting to alpha-ketoglutarate, a key intermediate in the TCA cycle
What are glucogenic amino acids
Glucogenic amino acids are those that can be converted into glucose through gluconeogenesis
What are ketogenic amino acids
Ketogenic amino acids are those that can be converted into ketone bodies, which serve as an alternative energy source
What is hyperammonemia, and what are its effects
Hyperammonemia is an elevated level of ammonia in the blood, leading to neurological symptoms such as cerebral edema, asterixis, and coma
What is the most common urea cycle disorder
The most common urea cycle disorder is ornithine transcarbamylase (OTC) deficiency, which leads to hyperammonemia and elevated orotic acid levels
What are the key symptoms of phenylketonuria (PKU)
Symptoms of PKU include intellectual disability, light skin and hair, a musty odor, and eczema It is caused by a deficiency in phenylalanine hydroxylase
What is the treatment for phenylketonuria
Treatment includes a low-phenylalanine diet and supplementation with tyrosine In cases of malignant PKU, tetrahydrobiopterin supplements may be required
What enzyme deficiency leads to maple syrup urine disease
Maple syrup urine disease is caused by a deficiency in the branched-chain alpha-keto acid dehydrogenase complex (BCKD)
What are the symptoms of maple syrup urine disease
Symptoms include sweet-smelling urine, irritability, poor feeding, vomiting, lethargy, and in severe cases, cerebral edema and seizures
What is alkaptonuria, and what are its key symptoms
Alkaptonuria is caused by a deficiency in homogentisate oxidase, leading to dark urine, ochronosis (bluish-black pigmentation), and joint pain
What causes homocystinuria, and what are its symptoms
Homocystinuria is often caused by a deficiency in cystathionine beta-synthase, leading to marfanoid habitus, ectopia lentis, and increased risk of thrombosis
What is the difference between homocystinuria and Marfan syndrome
Homocystinuria causes downward lens dislocation and is associated with atherosclerosis, while Marfan syndrome causes upward lens dislocation and affects the aorta
What is the primary diagnostic test for cystinuria
The sodium cyanide nitroprusside test detects cystine in the urine, helping to diagnose cystinuria, which causes cystine kidney stones
What is the treatment for cystinuria
Treatment includes alkalinization of urine with potassium citrate or acetazolamide and, if necessary, chelation therapy with penicillamine
What is propionic acidemia, and what causes it
Propionic acidemia is caused by a deficiency in propionyl-CoA carboxylase, leading to the accumulation of propionic acid and metabolic acidosis
What is methylmalonic acidemia, and how is it diagnosed
Methylmalonic acidemia is caused by a deficiency in methylmalonyl-CoA mutase or vitamin B12 It is diagnosed by elevated methylmalonic acid levels
What are the symptoms of organic acidemia
Symptoms include vomiting, poor feeding, hypotonia, seizures, hepatomegaly, and metabolic acidosis
What is the role of lactulose in treating hyperammonemia
Lactulose acidifies the gut, converting ammonia to ammonium, which is then excreted, lowering blood ammonia levels
What are the metabolic consequences of a urea cycle defect
Urea cycle defects lead to hyperammonemia, which can cause neurological damage, seizures, and coma if untreated
What is the role of benzoate in the management of hyperammonemia
Benzoate binds with glycine to form hippurate, which is excreted in urine, helping to reduce ammonia levels in hyperammonemia
What is the clinical significance of a musty” odor in urine
A musty odor in urine is a characteristic sign of phenylketonuria (PKU), caused by the accumulation of phenylketones
What is the treatment approach for maple syrup urine disease
Treatment involves dietary restriction of branched-chain amino acids (valine, leucine, isoleucine) and thiamine supplementation
What causes ornithine transcarbamylase deficiency
Ornithine transcarbamylase deficiency is an X-linked recessive disorder caused by mutations in the OTC gene, leading to hyperammonemia
What are the primary features of alkaptonuria
Features include dark urine, ochronosis, and arthralgias, resulting from a buildup of homogentisic acid due to a deficiency in homogentisate oxidase
What is the role of the urea cycle in the body
The urea cycle converts toxic ammonia into urea, which is then excreted in the urine, preventing ammonia accumulation and toxicity
What is asterixis, and what condition is it associated with
Asterixis is a flapping tremor of the hands when the wrists are extended, commonly associated with hyperammonemia and hepatic encephalopathy
What dietary management is recommended for individuals with propionic acidemia
A low-protein diet is recommended, avoiding substances that metabolize into propionyl-CoA, such as isoleucine, valine, methionine, and threonine
What is the impact of homocystinuria on the cardiovascular system
Homocystinuria increases the risk of atherosclerosis and thrombosis, potentially leading to stroke, myocardial infarction, or thromboembolism
What are the key symptoms of methylmalonic acidemia
Symptoms include vomiting, lethargy, hypotonia, metabolic acidosis, and developmental delay, typically presenting in infancy
What enzyme is deficient in phenylketonuria (PKU)
Phenylketonuria is caused by a deficiency in phenylalanine hydroxylase, preventing the conversion of phenylalanine to tyrosine
What is the function of cystathionine beta-synthase
Cystathionine beta-synthase catalyzes the conversion of homocysteine to cystathionine, a key step in methionine metabolism
What is the cause of orotic aciduria, and how does it differ from OTC deficiency
Orotic aciduria is caused by a deficiency in uridine monophosphate synthase (UMPS) and is distinguished from OTC deficiency by the absence of hyperammonemia
What are the treatment options for homocystinuria
Treatment includes dietary modification, increasing intake of B6, B12, folate, and cysteine, depending on the specific enzyme deficiency
What is the importance of thiamine in amino acid metabolism
Thiamine (vitamin B1) is a cofactor for the branched-chain alpha-keto acid dehydrogenase complex, essential for the metabolism of branched-chain amino acids
What condition is characterized by a sweet-smelling” urine
Maple syrup urine disease is characterized by sweet-smelling urine due to the accumulation of branched-chain amino acids and their keto acids
