Biochemie P1 Flashcards
(38 cards)
Where does glycolysis take place?
Cytoplasm
Where does oxidation of pyruvate and subsequent ATP synthesis take place?
mitochondria
In anaerobic metabolism, why is pyruvate converted to lactate?
- Pulls the rxn forward (reduces the concentration of pyruvate)
- Regenerate NAD+ for more rounds of glycolysis (reoxidize NADH)
What are the most important users of ATP in the body?
- Ion pumps - Na+/K+ pump, SERCA pump (pumps Ca2+ into ER lumen), PMCA pump (pumps Ca2+ out of the cell)
- Contractile/motor proteins which drive muscle contraction
What occurs in the mitochondrial matrix?
- PDH (pyruvate dehydrogenase)
- CAC enzymes
Most of the oxidative metabolism occurs within the matrix or within the inner leaflet of the inner mitochondrial membrane.
What occurs in the inner mitochondrial membrane?
- ETC enzymes
- ATP synthase
How many mitochondria in RBCs?
none.
Where does heart obtain most of its pyruvate?
a. glycolysis
b. lactate dehydrogenase
c. pentose phosphate pathway
d. catabolism of pye
Lactate dehydrogenase - b/c in the heart, the H form of lactate dehydrogenase predominates. This favors conversion of lactate to pyruvate.
How does pyruvate move into the mitochondrial matrix?
through membrane transporters. Because remember that glycolysis occurs in the cytoplasm (glucose –> pyruvate), so we need to figure out a way for pyruvate to enter the mitochondrial matrix.
What is the PDH complex composed of?
3 distinct enzymes
What are the 5 bound co-factors of PDH complex?
- TPP
- Lipoic acid
- CoA
- FAD
- NAD+
(TLC FN)
Which co-factor ultimately accepts the carbons of pyruvate?
CoA
What does the PDH reaction start with?
Pyruvate + CoA + NAD+
What are the products of the PDH reaction?
Acetyl CoA + NADH + H+ + CO2
NAD+ is used in ____ rxns generally (catabolic or anabolic)
Catabolic reactions, often used in OXIDATIVE reactions
What is the major consequence of aerobic glucose catabolism?
production of NADH and FADH2
What is the cytosolic ratio of NAD+ to NADH?
1000:1 NAD+: NADH
This is because catabolism is an oxidizing process. We need to couple it to a reducing process (NAD+ to NADH) so we have a lot of NAD+. This drives oxidation of the substrate (pyruvate)
What is the cytosolic ratio of NADPH: NADP+?
100:1 NADPH:NADP+
Because NADPH is used in anabolic reactions (building molecules) - we need to couple it to an oxidation of NADPH so therefore we have more NADPH (reduced form) so we can oxidize it.
Lactate dehydrogenase is a mechanism for converting:
a) NADH –> NAD+
b) NAD+ –> NADH
NADH –> NAD+
What are the 4 B vitamins that PDH requires to do its job?
- TPP (Vitamin B1/thiamine pyrophosphate): fx: acetyl carrier
- CoA (Vitamin B5/pantothenic acid) - fx: acetyl carrier
- FAD (Vitamin B2/riboflavin) - fx: electron carrier
- NAD+ (Vitamin B3/niacin) - fx: electron carrier
What are the steps of the PDH reaction?
- Pyruvate loses CO2, and the acetyl group remains. Acetyl group passed to TPP.
- Acetyl group gets passed from TPP to lipoic acid
- Lipoic acid passes the acetyl group to CoA.
- At this point, lipoic acid is reduced, and needs to be reoxidized. So, FAD+ –> FADH2 (reduction).
- FADH2 needs to be oxidized to FAD. So, NAD+ –> NADH. NADH then goes to ETC –> ATP.
What regulates PDH?
Indirect allosteric regulation. Directly regulated by phosphorylation.
- Substrates (pyruvate, NAD+) or signs of energy need (ADP) activate PDH. This happens by ADP, NAD+, activating a phosphatase, which activates PDH.
-Products (Acetyl CoA, NADH) or signs of energy abundance (ATP) inhibit PDH. This happens by ATP activating the kinase, which inhibits PDH.
What are the 3 steps of ethanol metabolism, and where does it occur?
-Ethanol metabolism occurs in the liver.
Steps:
1) Ethanol gets oxidized to acetaldehyde. [occurs in CYTOPLASM]
2) Acetaldehyde gets oxidized to acetate [occurs in MATRIX]
3. Acetate coupled to CoA through thiokinase. Produces Acetyl CoA, which can feed into Citric Acid Cycle. [occurs in MATRIX]
PDH is an ______ process.
a) oxidative
b) reductive
Oxidative process
