Week 2- Cell Met II Flashcards
From what and where is acetyl coA produced?
From carbohydrates and fatty acids in the mitochondria
What are the 3 sources of fat?
Diet
De novo biosynthesis in the liver
Adipose tissue
Where are bile salts made?
Liver
Where are bile salts stored?
Gall bladder
How do bile salts pass into the small intestine?
Via the bile duct
What happens if there is a lack of bile salts?
Lack of fat absorption causing fatty poo (steatorrhea)
What is the name of the drug that reduces fat absorption and how does it work?
Orlistat- it inhibits proteases and lipases and used in the treatment of obesity (reduces fat absorption by around 30%)
How are lipids transported?
By lipoproteins
What are the 5 classes of lipoproteins?
Chlyomicrons, very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL), low density lipoproteins (LDL) and high density lipoproteins (HDL)
Describe the source and role of chylomicrons
Come from intestine, role is dietary fat transport
Describe the source and role of VLDL
Come from liver, role is endogenous fat transport
Describe the source and role of IDL
Come from VLDL, role is to be a precursor to LDL
Describe the source and role of LDL
Come from IDL, role is cholesterol transport
Describe the source and role of HDL
Come from liver, role is reverse cholesterol transport
What cells absorb fats in the small intestine?
Enterocytes
Describe the anatomy of chylomicrons
Contain triglycerides, acquire lipoproteins from HDL after release into bloodstream, also contain phospholipids
Describe the role and anatomy of lipoproteins
Transport hydrophobic molecules in aqueous environments, phospholipid monolayer contains cholesterol and apoproteins, inside there are cholesterol esters and triacylglycerides
Where are LDLs taken up and by what cells?
By macrophages in the liver
What is the difference between LDL and HDL?
LDL is bad cholesterol, it takes cholesterol to peripheral tissues
HDL is good cholesterol, it takes cholesterol from periphery to liver for use or disposal, lowing blood serum cholesterol levels
What is beta oxidation?
The oxidation of fatty acids to acetyl coA in mitochondria- fatty acids have a very high calorific yield so can provide almost half the bodies energy requirement (not inc the brain)
Describe the carnetine shuttle
Fatty acids are converted to an acyl coA species
Acyl coA couples with carnetine molecule to form acyl carnetine, this can be carried across the membrane (moved to and from matrix by enzyme translocase)
What is primary carnetine deficiency?
When the gene that codes for carnetine is absent so acyl coA cannot be carried across the membrane.
Symptoms include muscle weakness, cardiomyopathy and hypoglycemia
Treated by taking carnetine supplements
Describe the beta oxidation cycle
Acyl coA undergoes oxidation, hydration, oxidation and thiolysis to produce 1 acetyl coA and 1 acyl coA
The cycle continually removes 2C from acyl coA and on the final cycle 2 acetyl coA are formed
What is the equation for the beta oxidation cycle starting with palmitoyl coA?
Palmitoyl coA + 7FAD + 7CoA + 7NAD+ goes to 8 acetyl coA + 7NADH + 7 FADH2
What happens when acetyl coA production surpasses carbohydrate metabolism and why?
Carbohydrate metabolism produces oxaloacetate which is needed to allow acetyl coA to enter the TCA cycle. If not enough oxaloacetate is produced acetyl coA is converted to ketone bodies acetone, acetoacetate and D3 hydroxybutarate
What 2 enzymes are involved with fatty acid synthesis?
Acetyl coA decarboxylase and fatty acid synthase
How are fatty acids formed?
By decarboxylative condensation reactions involving acetyl coA and malonyl coA, after each round of elongation fatty acids undergo reduction and dehydration by sequential action of ketoreductase, dehydratase and enol reductase
What is the carrier in beta oxidation vs lipogenesis
CoA vs ACP
What provides reducing power in beta oxidation vs lipogenesis?
FAD/NAD+ vs NADPH
What is the location of beta oxidation vs lipogenesis?
Matrix vs cytoplasm
What is unusual about fatty acid synthesis in cancer?
Usually de novo synthesis is in the liver but in cancer cells there is evidence of it occurring. Targeting fatty acid synthase in cancer cells has shrunk tumors eg in ovarian cancer
What is medium chain acyl coA dehydrogenase? What occurs when there is a deficiency in it?
An enzyme that catalyses a step in beta oxidation. In deficiency, patients cannot go without food for 10/12 hrs, they must have a high carb diet to prevent dependency on fatty acids for energy.
