D2 post absorptive state Flashcards
what are the 2 major essential polyunsaturated fatty acids
linoleic acid [C18:2]
linolenic acid [C18:3]
what lipid soluble vitamins are only present in dietary fat and require fat for absorption
A, D, E, and K
3 types of fat in our diet and body
-triacylglycerols (triglycerides)
-phospholipids
-cholesterol
basic structure of triacylglyerols
3 fatty acids attached to a glycerol
basic structure of phospholipids
2 fatty acids and a head group attached to glycerol
basic structure of cholesterol
4 ring hydrocarbon
what does saturated and unsaturated mean
saturated= no double bonds
unsaturation= 1+ double bonds
what are the 4 common head groups of phospholipids
(glycerophospholipids)
-phosphocholine
-phosphoethanolamine
-phosphoserine
-phosphoinositol
what is digestion of fat carried out by
lipases
what carries out digestion of fat in the mouth
lingual lipase
what carries out digestion of fat in the stomach
gastric lipase
what carries out digestion of fat in the intestine
pancreatic lipase,
phospholipase
(absorption of fatty acids, glycerol, fats)
properties of lipids (FA)
hydrophobic
insoluble in aq environments
what transports FA around the body
lipoproteins
name of fatty acid oxidation
b-oxidation
what are the 5 major step names in the oxidation of fatty acids in the mitochondria
- activation
1a transport - oxidation
- hydration
- oxidation
- thiolysis
activation
to form a thioester bond with CoA
transport
into mitochondia
oxidation 1
2 H removed - double bond C=C
hydration
H2O added across double bond C=C
oxidation 2
C-OH converted to C=O
thiolysis
acetyl-CoA cleaved from activated end
what does the thiol group of coenzyme A form
a high energy thioester bond with the carboxylic acid group of the fatty acid
what is the energy source in the activation of fatty acids by CoA
driven by ATP and subsequent hydrolysis of pyrophosphate
(2 high energy bonds)
where are fatty acids transported to
mitochondria
what does the transport of activated fatty acids into mitochondria use as a carrier
carnitine
what is carnitine
an acyl-carrier that transports the fatty acyl chains
how much ATP does each round of b-oxidation produce
14 ATP
(2.5 NADH
1.5 FADH2
10 acetyl CoA)
how many rounds of oxidation does palmitate need
7
what is the total yield of ATP from complete breakdown of fatty acids
106
(14x7)+10=108 but 2 used to activate the fatty acid
what enzyme is required for the degradation of unsaturated fatty acids for one c=c double bond
cis-D 3-Enoyl CoA isomerase
what enzymes are required for the degradation of unsaturated fatty acids for two C=C double bonds
cis-D3-Enoyl CoA isomerase
2,4-Dienoyl CoA reductase
when can acetyl CoA only enter the TCA
if carbohydrate and fat metabolism are balanced
what occurs if fat metabolism predominates and why
shortage of oxaloacetate
because its used for gluconeogenesis (to make glucose) and hence an excess of acetyl CoA
if fat predominates what is acetyl-CoA converted to
ketone bodies
what do odd chain fatty acids yield at the end of the degradation
propionyl-CoA (3C)
what is propionyl-CoA converted into
succinyl-CoA by addition of bicarbonate (HCO3) which then enters TCA cycle
what 2 things are required for the degradation of odd chain fatty acids
ATP and vitB12
what is the daily glucose requirement of the brain of a typical human being
120g
how much glucose needed daily by the whole body
160g
how much glucose is found in body fluids
20g
how much glucose is stored in glycogen
190g
when is gluconeogenesis esp important
during period of starvation
what is gluconeogenesis and where does it mainly occur
conversion of pyruvate into glucose
in liver
major carbohydrate precursors are
lactate
propionate
aa
glycerol
where does lactate come from
rate of glycolysis exceeds the rate of oxidative metabolism
where does aa come from
breakdown of proteins
where does propionate and glycerol come from
hydrolysis of triacylglycerols
in what body parts are glucose 6 phosphate present in
liver and kidney
where in cells is glucose 6 phosphate located
membrane of ER
how many proteins are needed to transform glucose 6 phosphate into glucose
5
3 steps of converting glucose 6 phosphate to glucose
-G6P transported into ER
-G6P hydrolysed
-glucose and Pi transported into cytosol
what are the cofactors to fructose 1,6-biphosphatase
Mg2+
Mn2+
and/or Zn2+
what activates fructose 1,6-biphosphatase
citrate
can pyruvate be converted to phosphoenolpyruvate (PEP) by pyruvate kinase
no because the reaction is irreversible under intracellular conditions
how is the reversal of the reaction achieved (pyruvate conversion)
coupling of 2 rxns requiring ATP and GTP
where is pyruvate carboxylase localised
mitochondrium
what does pyruvate carboxylase carry as a prosthetic group
biotin
what does biotin function as
carrier for activated CO2
where is the activated carboxyl group transferred to to form what
pyruvate to form oxaloacetate
