• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/29

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

29 Cards in this Set

  • Front
  • Back
What are the molecules in the Creb cycle from AcCoA to Oxaloacetate?
-AcCoA
-Citrate
-Isocitrate
-α-ketoglutarate
-Succinyl CoA
-Succinate
-Fumarate
-Malate
-Oxaloacetate
Do α or beta decarboxylations happen easily?
Beta decarboxylations happen easily and spontaneously.
What 3 enzymes are encompassed in the pyruvate dehydrogenase complex (PDC)?
E1, pyruvate decarboxylase (contains TPP)
E2, transacetylase (contains lipoic acid)
E3, dihydrolipoyl dehydrogenase (contains FAD)
What is the net reaction for PDH complex? Easily reversible?
Pyruvate- + NAD+ + CoASH (yields) acetyl-CoA + CO2 + NADH
(This reaction is kinetically and thermodynamically irreversible)
What is the most common vitamin deficiency in alcoholics? What is this needed for?
Thiamine- necessary to accomplish difficult α-decarboxylation reactions.
How is PDC (pyruvate dehydrogenase complex) regulated? What is active?
Regulated by phosphorylation/dephosphorylation. Phosphorylated PDC is inactive, dephosphorylated PDC is active.
What increases the dephosphorylation (activation) of PDC (pyruvate dehydrogenase complex)? What decreases the phosphorylation (inactivation) of PDC?
-Ca2+
-ADP and pyruvate
What increases the phosphorylation (inactivation) of PDC (pyruvate dehydrogenase complex)?
-NADH, AcCoA (recall that these are the products of pyruvate-->AcCoA)
Where is pyruvate converted to AcCoA?
In the mitochondria
What is Leigh syndrome? What is a sign of it?
-There is a defect in the PDC (pyruvate dehydrogenase complex). This prevents pyruvate from being converted to AcCoA, therefore all metabolism is anaerobic.
-First presents in neural tissue because it can't oxidize fatty acids.
-Lactic acid/pyruvate in urine, CSF, and blood
How does thiamine pyrophosphate (found in pyruvate decarboxylase, E1 in PDC) get around the problem of pyruvate being a α-keto acid?
-Thiamine loses a proton (pulled off by a base on the enzyme), creating a reactive carbon.
-The carbanion attacks the carbonyl carbon of pyruvate forming a covalent intermediate.
-This covalent intermediate looks more like a beta-keto acid, therefore the carboxyl group comes right off.
-E2 and E3 will do the rest of the reaction. :-)
What is the net yield from Steps 1-8 of the Creb cycle?
3NADH
1GTP
1FADH
What does the structure of citrate look like?
6 carbons structure with 3 carboxylic acids together.
What one enzyme in the Citric acid cycle is not found in the mito matrix?
Succinate dehydrogenase
What keeps the cycle turning? (3 things)
-NADH is being used up by muscles, pulling along.
-All intermediates available, pushing through.
-Energy of the reactions are favorable moving ahead. (MTF)
What 3 steps in the citric acid cycle release a large amount of free energy?
Step 1, creating citrate.
Step 3, creating alpha-ketoglutarate.
Step 4, creating succinyl CoA.

These are also the steps that regulation occurs.
What kind of enzyme is used if the reaction releases either NADH or FADH?
Dehydrogenase
What kind of enzyme is used if ATP or GTP is created or used?
A kinase.
What is the significance of transforming citrate to isocitrate?
Makes it a beta-ketone so CO2 comes right off. (Beta-decarboxylation)
What stimulates Step 3 of Creb cycle, forming alpha-ketoglutarate from isocitrate? What inhibits it?
-ADP, Ca2+ stimulates
-NADH inhibits
What does it mean that the TCA cycle is an amphibolic hub?
This means that the TCA cycle is involved in anabolic and catabolic processes. Within the cycle itself, it fluxuates between a 6C and a 4C molecule and it also sends intermediates to other anabolic pathways.
Besides continuing through the TCA cycle, where else can citrate go?
To fatty acid synthesis in the cytoplasm.
Besides continuing through the TCA cycle, where else can alphaketoglutarate go?
-Amino acid synthesis
-Produce neurotransmitters (GABA!)
Besides continuing through the TCA cycle, where else can succinyl CoA go?
To heme synthesis
Besides continuing through the TCA cycle, where else can malate go?
To gluconeogenesis in the liver.
Besides continuing through the TCA cycle, where else can oxaloaccetate go?
To amino acid synthesis
What is an anaplerotic reaction?
An anaplerotic reaction forms intermediates in the TCA cycle. The most important anaplerotic reaction is the conversion of pyruvate to oxaloacetate catalyzed by biotin-dependent pyruvate carboxylase. This provides oxaloacetate to react with AcCoA (normal pathway from pyruvate) to jumpstart the TCA cycle.
Once you've formed pyruvate through glycolysis, what two directions can it go into the TCA cycle?
It can either be converted to AcCoA by the PDC complex -or- it can be converted to oxaloacetate by biotin-dependent pyruvate carboxylase.
Besides pyruvate, what else can contribute AcCoA to the TCA cycle?
-Carbs
-Fatty acids
-Amino acids