Part 2 - lecture 3.2 Exam Flashcards
(36 cards)
What are fatty acids structure?
R-COOH that can be short - very long, branched or unbranched, saturated or unsaturated, essential or non-essential (CH3 - (CH2)n - COOH)
What separates double bonds in FAs?
Methylene CH2 groups
Where are odd and even carbon FAs found?
Even are most common in biological systems - odd are mostly used for energy
What are oxidized forms of FAs?
Have alpha-OH and used structurally - only made as intermediates during energy production and specific functions
What do FAs use to make branched chain acids?
Methyl groups
What are the length of short, medium, long and very long chain FAs?
Short = <6 and medium 6-10 … milk rich is C4-C10 FAs, long is 12-18 and very long is 20-24
What is the approved nomenclature of FAs?
First number is length of C chain and 2nd is number of double bonds, parentheses are the location of double bonds
Ex) 18:2(9,12) - 18C long with 2 double bonds at carbon 9 and 12
What do most FAs in humans occur as?
Triglycerides - as esters of glycerol when stored
What are neutral fats?
Triglycerides of three OH groups on glycerol molecules esterified with a FA
What does milk contain that is important?
C4-C10 short and medium chain FA that get directly absorbed by enterocytes - essential FAs that are easy to digest and contain essential AAs - glucose and essential vitamins, minerals and antibodies
What makes triglycerides efficient for storing energy as a means other than glycogen?
Hydrophobic nature and highly reduced state (more protons and less oxygen)
Does glycogen or triglycerides give more energy?
Triglycerides by weight give more ATP
Are most de novo synthesized FAs in humans saturated or not?
Saturated or just one DB
What FAs are higher mammals not able to synthesize and make them essential?
Omega-3 or omega-6 with double bonds near methyl end of molecule - linoleic and linolenic acid
What is the first FA to be synthesized and how are the rest made?
Palmitic acid (C16) - modified to give all other AA
What synthesizes FAs?
AcCoA produced from glucose and some AA is transported from mitochondrion to cytosol for FA synthesis – 2C units added to activated carboxyl end by fatty acid synthase and rest of 2C units added as malonyl-CoA by acetyl-CoA carboxylase
Where are the FA synthesis enzymes found and what are their names?
FA synthase and acetyl-CoA carboxylase – in cytosol
What is the major source of AcCoA for FA synthesis?
Glucose making pyruvate in PDH reaction in matrix of mitochondria
How does AcCoA get to cytosol?
OOA from pyruvate is made into citrate which can get across membrane where it is cleaved into AcCoA and OOA again (requires 1 ATP)
What happens to OOA in cytosol to get back to mitochondria?
Reduced to Malate by NADH (from glycolysis) and malate dehydrogenase – malate decarboxylated by NADP malic enzyme to reproduce pyruvate – gives NADPH to be used for FA synthesis
What does C16 production require (palmitate)?
8 AcCoA + 8 NADPH – other 6 must come from PPP
What is the committed/rate limiting step of FA synthesis?
Activation of AcCoA to malonyl-CoA by Acetyl-CoA carboxylase – biotin coenzyme to transfer CO2 – requires ATP
What is the regulation of Acetyl-CoA Carboylase?
Allosteric: activated by citrate, inhibited by palmitoyl-CoA
Hormonal: active when dephosphorylated meaning it is activated by insulin and deactivated by glucagon
What is fatty acid synthase?
A multifunctional enzyme with two identical subunitseach with 6 enzymes and an acyl carrier protein (ACP) - growing FA chain continually bound andtransferred between ACP and ACP synthase (first enzyme domain)
