Fat metabolism Flashcards
Structure of a fatty acid?
hydrophilic carboxylic acid head
hydrophobic hydrocarbon tail
Function of adipocytes?
- control acid storage and used to provide energy during starvation
- Stored as triacyl
- Albumin is a good carrier of fatty acid
Where is fat derived from?
- Diet
- De novo synthesis in liver
- Hydrolyze storage deposits in adipocytes
Where are bile salts stored and generated?
Bile salts generated by liver and stored in gallbladder
What is the function of bile salts?
- Secreted into intestine during digestion to emulsify fat and fat soluble vitamins (A, D, E, K) digestion
What allows them to break down fat?
amiphilic allowing interaction with solute and triglyceride - are soluble form so lipases can break down
How are fats digested and absorbed?
- Triacylgylceride solubilized
- Taken up by enterocytes in intestine
- MonoACYLglycerols (MAG), DAG and free FA which join bile salts + lysophosphatidic acid (LPA) + fat soluble vitamins and form mixed micelles
- Absorbed by enterocytes –> triacylglycerol synthesized–> packaged in chylomicrons
- Chylomicrons from lacteals of intestine –>thoracic duct –>l. subclavian–> bloodstream
What does orlistat inhibit?
- Gastric and pancreatic enzymes
What is the first reaction of beta oxidation?
Fatty acid + ATP + HS-CoA –> acyl CoA + AMP + PPi
- ATP –> AMP breaks two high energy bonds
Acyl CoA Synthetase
Where does beta oxidation occur?
In outer mitocondrial membrane cartinine shuttle transports into matrix
Steps of the Cartinine shuttle:
see notes
Steps of the Beta oxidation cycle?
see notes
What is the final ATP yield?
129 ATP
What is the overall reaction?
palmitoyl CoA + 7 FAD + 7 NAD+ + 7 H2O + 7 CoA
–> 8 acetyl CoA + 7 FADH2 + 7 NADH
Why does beta oxidation and carb metabolism need to be balanced?
oxaloacetate is needed for entry
What are formed when fat breakdown dominates?
- Acetoacetate
- Acetone
- D-3-hydroxybutyrate
- formed by fusion of acetyl CoA
What is the overall reaction of lipogenesis?
Acetyl-CoA + 7 Malonyl-CoA + 14 NADPH + 14H+–> Palmitate (16C) + 7CO2 + 6H2O + 8 CoA-SH + 14NADP+
What are the steps of lipogenesis?
see notes
How are fatty acids longer than 16 carbons generated?
elongationof the acyl group occurs separately from palmitate synthesis in the mitochondria and endoplasmic reticulum (ER).
What enzyme desaturates fatty acids?
fatty acyl-CoA desaturases.
creates oleic acid and palmitoleic acid from stearate and palmitate, respectively, is called a Δ-9 desaturase
What are the types of acetyl CoA dehydrogenases?
- Short
- Medium
- 3-hydroxy
- Long
- Very long
- Catalyze initial step in each fatty acid beta oxidation cycle
Examples of inborn errors in metabolism?
Medium chain acyl coenzyme A dehydrogenase (MCADD)
- Autosomal recessive, predominantly seen in Caucasians - 1/10000 live births - Accounts for 1/1000 deaths from SIDS - If diagnosed - avoid fasting and have high carb diet - Part of heel prick test - Patients with loss of appetite may need IV Glu to make sure body doesn't depend on fatty acids for energy
Primary Carnitine deficiency:
- Autosomal recessive - Cartinine needed to get acyl group into membrane - Can be given as supplement to treat
