Study your flashcards anywhere!

Download the official Cram app for free >

  • 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

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

89 Cards in this Set

  • Front
  • Back
Oxidation # of carbons in one glucose:
Oxidation # of carbons for 2 Pyruvate:
+4 (+2/2pyruvate)
Number of NAD+ reduced in pyruvate oxidation?
2 (1 molecule / pyruvate)
Oxidation # of carbons for 6 CO2:
+24 (+4/6CO2)
Number of NAD+/FAD reduced in CO2 oxidation?
10 NAD + 2 FAD = 12

(2 electrons per NAD or FAD)
Sequence of oxidation from CH4 to CO2:
CH4 -> CH3-OH / CH3NH2/ H2C=CH2
-> CH2=O -> HCOOH -> CO2
# electrons released in each oxidation:
Always present at an oxidation:
Enzyme that converts pyruvate to alanine:
-Cellular site
Alanine aminotransferase (ALT)
Coenzyme = PLP
Site = Cytosol
Enzyme that converts pyruvate to lactate:
-Cellular site
Lactate Dehydrogenase (LD)
Cell site: Cytosol
Enzyme that converts Pyruvate to Oxaloacetate:
-Cellular site
Pyruvate Carboxylase
-Mito matrix in liver/kidney
Enzyme that converts Pyruvate to AcCoA:
-Cellular site
Pyruvate dehydrogenase complex
-TPP, Lipoic acid, FAD
-Mito matrix
Enzyme that converts Pyruvate to Acetaldehyde -> Alcohol:
-Cellular site
Pyruvate decarboxylase
-Microbes only NOT MAMMALS
Why is Pyruvate so important?
It sits at a critical branchpoint with 4 possible fates:
What are the 4 fates of pyruvate? (things it can be converted to)
1. Alanine
2. Lactate
3. AcCoA
4. Oxaloacetate
Where is the energy in pyruvate?
-Its ability to be further oxidized
-The 2 NADH produced in glycolysis (G3P dehydrogenase)
What important factor determines the fate of pyruvate?
Whether oxygen is available or not.
What is the oxidation number of each molecule in going from methane to CO2 via methanol, formaldehyde, formic acid, CO2?
1. Methane = -4
2. Methanol = -2
3. Formaldehyde = 0
4. Formic acid = +2
5. Carbon Dioxide = +4
Back to the fates of pyruvate:
Why/when does pyruvate get converted to Lactate and Alanine?
When skeletal muscles don't get enough O2 like during intense exercise.
What 2 things need to happen during intense exercise?
1. Replenish NAD+
2. Resynthesize glucose (liver)
What is the body's simplest solution for achieving these goals?
1. Break down pyruvate to lactate
2. Send lactate to liver to make glucose
Why occurs in the similar process that converts pyruvate to L-alanine instead of lactate?
1. L-glutamate donates NH3 to pyruvate - makes L-alanine
2. NADH -> NAD+ at the same time; replenishes it for tissue.
How is L-Alanine useful?
Sent to the liver, it supports gluconeogenesis.
What is required for pyruvate to participate in gluconeogenesis in the liver?
Conversion to PEP via 2-step process
What is the first step in going from Pyruvate -> PEP?
Conversion to Oxaloacetate
What happens to pyruvate when oxygen is PLENTIFUL?
Gets oxidized to AcCoA
Why is AcCoA a very important irreversible step in biology?
How does the body prevent overproduction of AcCoA from glucose (depleting glucose)?
By tightly regulating the enzyme for the reaction - PDH complex.
What reaction with Pyruvate occurs in microbes but not mammals?
Where in the body does gluconeogenesis predominantly occur?
90% in liver
10% in kidney
What are the general characteristics of Pyruvate? (3 things)
1. Strong acid (pKa 2.5)
2. Simplest a-keto acid
3. Low concentration - always gets converted to something.
What really is the purpose of ALT?
To convert pyruvate to a product that is suitable for transport to the liver.
And the good byproduct of this conversion is:
Regeneration of NAD+ for the cell
What additional enzyme is necessary for the proper action of ALT?
Glutamate dehydrogenase (GDH)
3 good things accomplished by the ALT reaction:
1. NADH is oxidized to NAD+ and glycolysis can continue
2. L-alanine (pyruvate equiv) can make glucose in liver.
3. NH3 is converted to derivative for safe transport to liver; prevents toxicity.
How does LDH accomplish conversion of pyruvate to lactate?
By using NADH to donate a proton to C2 of pyruvate
What about LDH makes it a good enzyme for this conversion?
Its reactive site contains
-Arg to hold on to COO-
-His to donate proton to carbonyl oxygen -> -OH
How does NADH donate its H- to pyruvate?
The H- ion attacks C2 and bumps electrons up to grab on to histidine's proton.
What is important about NADH's participation in the LDH rxn?
Sterespecific - H donation comes from only one side of the NADH ring.
where is PDH complex located?
(pyruvate dehydrogenase)
In the mitochondrial matrix
What is PDH composed of?
(3 components)
E1. Pyruvate dehydrogenase
E2. Dihydrolipoyl transacetylase
E3. Dihydrolipoyl dehydrogenase
What 3 cofactors does PDH use?
1. TPP (thiamine pyrophosphate)
2. Riboflavin
3. FAD
What happens to Pyruvate in step 1 of PDH?
-Enzyme component
Enzyme = PDH
Cofactor = TPP
Pyruvate -> Hydroxyethyl TPP + CO2 (lost)
What happens to Hydroxyethyl TPP in step 2 of PDH?
-Enzyme component
Enzyme2 = Dihydrolipoyl transacetylase
-Hydroxyethyl TPP has neg charged carbon; attacks S of lipoamide
-Produces Acetyl-dihydrolipoamide
What happens in step three of PDH? What enzyme?
Still at Enzyme 2; CoA is incorporated into intermediate to produce Acetyl CoA.
How is the reduced lipoamide generated by Acetyl CoA production OXIDIZED to regenerate it?
By E3, dihydrolipoyl dehydrogenase
What cofactor and substrate is used by E3?
-FAD cofactor
-NAD+ substrate
Since NADH is produced in AcCoA production, this is obviously not something you want to be doing in strenuously exercising muscle.
What is special about lipoamide?
It has a long swinging arm that acts as a Lysine Tether to transport Acetyl group to active site for CoA addition
What type of reaction is catalyzed by PDH complex?
Oxidative decarboxylation
Is dihydrolipoamide good or bad?
Good if it can be regenerated, but you don't want to stay there. E3 better regenerate lipoamide if you want to keep producing AcCoA
What key role does PDH play in glucose metabolism?
Couples Glycolysis and TCA
3 goals accomplished by PDH:
1. Pyruvate -> AcCoA
2. Energy of oxidative decarboxylation is CAPTURED
3. Complex is regulated
In what 2 forms is the energy of the PDH complex captured?
1. NADH -> for further use
2. Hi energy thioester bond of AcCoA
Which components of PDH are reversible/irreversible reactions?
E1 = irreversible
(overall rxn is irreversible)

E2 and E3 = reversible
In what 2 ways is PDH regulated?
1. Feedback inhibition by NADH and AcCoA
2. Interconversion between active/nonactive forms
What form of PDH is
What makes these forms?
Active = DEphosphorylated
Nonactive = phosphorylated

PDH phosphatase/PDH kinase
Which enzyme turns on PDH?

Which enzyme turns it off?
PDH Phosphatase turns PDH on

PDH Kinase turns PDH off
What will make PDH Kinase act on PDH?
High Energy State metabolites:
Don't need Kreb's cycle
What will make PDH Phosphatase turn PDH on?
Low Energy State molecules:
-Insulin in adipose
Why does Insulin turn on PDH via PDH phosphatase?
B/c it signals high blood glucose; adipocytes need AcCoA to make fat.
What is the message Insulin gives adipose tissue in fed state?
-Turns on PDH phosphatase
-Turns on PDH
-Pyruvate -> AcCoA
-AcCoA -> FA biosynthesis
TPP is derived from:
Thiamine - vitamin B1
Deficiency of Thiamine leads to:
What is beriberi? who gets it?
Disorder w/ neurologic/CV symp.
-Far East people who eat rice
What term describes the condition of drinking ethanol rather than thiamine-containing foods?
Alcoholic Polyneuropathy
What does Thiamine deficiency in alcoholics irreversibly lead to?
Wernicke-Korsakoff Syndrome
What do all enzymes that require TPP (thiamine pyrophosphate) do?
Transfer activated aldehyde units
What are the 4 known Thiamine requiring mammalian enzymes?
-Transketolase (PPP)
-PDH (pyruvate mtbsm)
-a-Ketoglutarate Dehydrog (TCA)
-Branched chain of above (AA)
What is the substrate for all of these enzymes? In the last 3?
All use a ketone substrate
Last three involve a-ketoacid substrates.
How is Beriberi diagnosed?
RBC Transketolase assay
What is deficiency of E3?
Leigh's disease - less than 10 cases known
Rxn catalyzed by Pyruvate carboxylase?
Pyruvate -> Oxaloacetate
Coenzyme = Biotin
Substrate = ATP
What is the key feature of all Biotin-dependent enzymes?
Reaction occurs in 2 steps - first step attaches CO2 to biotin via ATP -> ADP + Pi
2 steps in Pyruvate carboxylase reaction:
1. HCO3 attached to Biotin via ATP cleavage
2. CarboxyBiotin + Pyruvate -> Oxaloacetat + Biotin
-Propionyl-CoA Carboxylase

-AcetylCoA Carboxylase

(both involved in FA metblsm)
What is the coenzyme used by Pyruvate Decarboxylase? What is this reaction specific to?
TPP - only in MICROBES
What is the Pyruvate decarboxylase reaction?
Just like PDH but no NAD used; NOT A REDOX
What does microbe Pyruvate decarboxylase produce?
Ethanol - in microbes in the human gut too.
When the bloodstream is cleared of glucose, but you're not fasting, what does the liver do?
Sends glucose to muscles (by breaking down glycogen)
What do the muscles do with glucose?
Glycolysis - which generates pyruvate first before TCA.
What do muscles do with Pyruvate?
If O2 available, TCA cycle.
If O2 unavailable, convert to lactate and alanine - less ATP gets made, but NAD+ regenerated.
What happens to Lactate and Alanine?
They're sent to the liver
What does the liver do with Lactate and Alanine?
Use it to remake pyruvate for gluconeogenesis
Which steps of gluconeogenesis require ATP?
-Pyruvate -> oxaloacetate
-Oxaloacetate -> PEP
-PEP -> Glucose
How does the liver generate ATP?
By breaking down fat -> AcCoA and using that for the TCA cycle
What is this shuttling of pyruvate breakdown products from skeletal muscle to liver called?
The cori cycle
How can the liver still run the TCA cycle when muscles are unable to b/c of anaerobic conditions?
The liver has more O2 in general.