Anabolic Metabolism I and II Flashcards Preview

Foundations 1 > Anabolic Metabolism I and II > Flashcards

Flashcards in Anabolic Metabolism I and II Deck (33):

What are the two shunts found in erythrocyte glycolysis?

Rapaport-Luberin shunt - generates 2,3 BPG which regulates oxygen binding to hemoglobin

generates NAD+ and NADH to reduce Fe3+ in hemoglobin to Fe2+


Describe the pentose phosphate pathway.

bypasses the first stage of glycolysis to generate NADPH for other reactions and pentose sugars such as ribose 5-phosphate for nucleotide synthesis


What is the key regulatory enzyme of the pentose phosphate pathway?

glucose 6-phosphate, NADPH is a strong product inhibitor


How do cells deal with superoxide radicals?

catalase, glutathioine oxidation, or iron oxidation


anabolic rections of the TCA cycle

amino acids and neurotransmitters from OAA and a-KG

heme synthesis from succinyl CoA

glucose from malate

fatty acids and cholesterol from citrate


anaplerotic reaction

a reaction that returns carbons to the TCA so that the cell can continue oxidizing acetyl CoA


What are the major anaplerotic reactions in a cell?

alanine and serine conversion to pyruvate, branched chian amino acids, propionyl CoA and glutamate from the blood


Why can't acetyl CoA be used in an anaplerotic reaction?

if acetyl CoA is used, there will be no net conversion to oxaloacetate, only a buildup of citrate


pyruvate carboxylase

uses a covalently attached biotin cofactor to convert pyruvate into oxaloacetate

positively regulated by high acetyl-CoA levels


Describe the process of fatty acid synthesis.

build up of citrate, export into the cytoplasm, conversion to OAA to generate acetyl CoA which is used for fatty acid synthesis, remaining malate goes back into pyruvate


Where does the NADPH equivalents necessary for fatty acid synthesis come from?

mainly from the pentose-phosphate pathway and the malate to pyruvate conversion


fatty acid synthase

single enzyme with three different domains and seven catalytic functions

antiparallel arrangement of the domains so that the exchange is happening between the different subunits and not within the subunit itself

synthesizes up to C16 fatty acids due to a stearic problem


elongation of fatty acids

condensation, reduction, dehydration, and reduction

acetyl-coA initiates synthesis and then malonyl CoA extends


desaturation of fatty acids

involves cytochrome b5, molecular oxygen, and NADH


How is fatty acid synthesis regulated to ensure that fatty acid metabolism isn't occuring at the same time?

inhibition of CPTI by malonyl CoA, preventing fatty acid import into the mitochondria


Describe the process of synthesizing ketone bodies.

synthesized when fatty acid levels are elevated during fasting, starvation or as the result of a high fat low carbohydrate diet


regulation of ketone body synthesis

increase CPTI activity increases fatty acid import, increase in beta-oxidation increases acetyl CoA leads to synthesis of ketone bodies


synthesis of triacylglycerols

glycerol-3-P is the first major contributor


glycerophospholipid synthesis

happens in the ER


cholesterol biosynthesis

start with acetyl CoA and acetoacetyl CoA, reduced by HMG-CoA reductase, generates squalene, lanestrol, and eventually cholesterol

improtant for membranes


What are the three irreversible reactions of glycolysis that need to be circumvented by gluconeogenesis?

carboxylation of pyruvate by pyruvate carboxylase

PFK-1 conversion of F-6-P to F-1,6-P

Glucose to G-6-P by hexokinase


conversion of pyruvate to PEP

can be done in the mitochondria by phosphoenolpyruvate carboxykinase (PEPCK) and then shuttled out

can also be done in the cytoplasm after OAA has been converted to malate or aspartic acid and shuttled out


Describe the gluconeogenesis pathway.

fructose 1,6-bisphosphatase is inhibited by AMP and activated by ATP, in liver and kidney, fructose 2,6-bisphosphate is an allosteric inhibitor


Describe the process of glycogen synthesis.

related to galactose pathway because UDP glucose generates UDP galactose


glucogenic amino acids

glutamate, arginine, histidine, glutamine, proline, aspartate, asparagine, tyrosine, phenylalanine, methionine, threonine, isoleucine, valine, threonine, tryptophan, glycine, alanine, serine, cysteine


ketogenic amino acids

threonine, lysine, leucine, isoleucine, tryptophane, phenylalanine, tyrosine, leucine


What amino acids form a-KG?

glutamate, arginine, histidine, glutamine, proline


What amino acids form oxaloacetate?

aspartate and asparagine


What amino acids form fumarate?

aspartate, tyrosine, phenylalanine


What amino acids form succinyl CoA?

methionine, threonine, isoleucine, valine


What amino acids form pyruvate?

threonine, tryptophan, glycine, alanine, serine, cysteine


What amino acids form acetyl CoA?

threonine, lysine, leucine, isoleucine, tryptophan


What amino acids form acetoacetate?

phenylalanine, tyrosine, leucine