L8+9 biochem Flashcards
- conversion of pyruvic acid (end product of glycolysis) irreversibly to Acetyl-CoA, catalyzed by PDH complex (not a component of TCA)
- known as the link reaction between glycolysis and citric acid cycle.
- pyruvate transported into mitochondria via pyruvate transporter
Oxidative decarboxylation of Pyruvic acid
Pyruvate dehydrogenase complex
E1: needs TPP thiamine pyrophosphate as coenzyme
E2: needs lipoic acid (firmly attached=prosthetic group) and CoASH (free)
E3: need FAD (firmly attached to the enzyme) and NAD (free)
E1: Pyruvate decarboxylase (pyruvate dehydrogenase)
E2: Dihyrolipoyl transacetylase
E3: Dihyrolipoyl dehydrogenase
conversion of pyruvate to acetyl CoA via three steps:
a) Decarboxylation (E1)
B) Transfer of acetyl group to CoA (E2)
C) Oxidation (E3)
*End result: ___ NADH and __ ATP
*2 NADH used by ETC to produce 6 ATP
- more toxic than pentavalent form(replaces Pi)
- mechanism: forms a stable complex with thiol (SH) groups of lipoic acid leading to inhibition of enzymes that require lipoic acid as a coenzyme
- NEGATIVELY affects the brain and leads to DEATH
Triavalent arsenite
A)allosteric regulation
1-PDH complex is inhibited by its own product _____ and ____
B)covalent modification
1-PDH kinase: inhibits PDH complex by _____ of E1 (pyruvate dehydrogenase)
2-PDH kinase can also be regulated allosterically by high ATP, NADH, Acetyl CoA which ____ PDH kinase activity, WHILE high ADP and pyruvate will ___ PDH kinase activity
B1-phosphorylation
B2-induce, inhibit
- rare disorder
- **most common biochemical cause of congenital lactic acidosis
symptoms: neurodegeneration, muscle spasticity, neonatal (early)death
Pyruvate dehydrogenase deficiency (PDCD)
- occurs primarily in liver (90%), (10% in kidney) in fasting
- happens 50% during prolonged starvation
- in cytosol and mitochondria
- importance: maintain blood glucose level during fasting for more than 18 hours
- 6 ATP is consumes
Gluconeogenisis
during Anaerobic glycolysis in skeletal muscle, pyruvate is reduced to ______ by _______
this reaction serves 2 critical functions:
1- the LDH reaction requires ___ and yields NAD+ for use of glycolysis
2- the lactate produced will go to the blood, then liver where its converted to glucose then returned to blood for use of muscle this is called the ________
Lactate, LDH (lactate dehydrogenase)
1-NADH
2- Cori cycle
glycerol kinase is present only in ___ and ___ (not present in adipose tissue) + it catalyzes glycerol to DHAP
Liver and Kidney
glucogenic amino acids are the building units for _____
-they are deaminated giving pyruvate and oxaloacetate (Krebs cycle)
Protein (mainly muscle protein)
all amino acids can give glucose except ____ and ___
Leucine and lysine
***Q: any reaction with Acetyl CoA as the end product is ALWAYS _____
irreversible
***Q: the FA that contributes to gluconeogenesis?
odd chain FA only
the enzymes that are irreversible and require** 4 **enzymes unique to gluconeogenesis foe their reversal:
1- ________
2-________
3-________
1- PK
2- PFK1
3- glucokinase (hexokinase)
reversal of PK reaction by 2 enzymes :
1- __________ (in metabolism)
2-__________ (in cytosol)
1- pyruvate carboxylase
2- phosphoenolpyruvate carboxykinase (PEPCK)
