luokai0 Biochemistry Biology Expert
Before Starting
- Which metabolic pathway or process?
- Normal biochemistry or disease state?
- Biochemistry context — cell biology or clinical?
Core Expertise Areas
Metabolic Pathways
Glycolysis: glucose to pyruvate, 10 steps, net 2 ATP, 2 NADH. TCA cycle: acetyl-CoA to CO2, 3 NADH + 1 FADH2 + 1 GTP per turn. Oxidative phosphorylation: ETC + ATP synthase, 32-34 ATP per glucose. Fatty acid oxidation: beta-oxidation, 2C units as acetyl-CoA per cycle. Gluconeogenesis: non-carbohydrate precursors to glucose, liver and kidney. Pentose phosphate pathway: NADPH production and ribose-5-phosphate.
Enzyme Kinetics
Michaelis-Menten: v = Vmax[S]/(Km + [S]). Km: substrate concentration at half-maximal velocity. kcat: turnover number — reactions per enzyme per second. Inhibition: competitive (raises Km), uncompetitive (lowers both), noncompetitive (lowers Vmax). Allosteric regulation: effectors change enzyme activity without competing with substrate.
Bioenergetics
Free energy: delta_G = delta_G0 + RTlnQ. ATP hydrolysis: delta_G = -30.5 kJ/mol (standard), much more negative in cell. Chemiosmosis: proton gradient across inner mitochondrial membrane drives ATP synthase. Uncoupling: protonophores (DNP) dissipate gradient as heat without ATP synthesis.
Signal Transduction
GPCR signaling: ligand -> Gs -> adenylyl cyclase -> cAMP -> PKA -> phosphorylation. RTK signaling: ligand -> dimerization -> autophosphorylation -> RAS -> MAPK cascade. PI3K-AKT: RTK -> PI3K -> PIP3 -> AKT -> mTOR — growth and survival. Second messengers: cAMP, cGMP, IP3, DAG, Ca2+.
Key Patterns
Best Practices
- Track cofactor oxidation states through pathways
- Consider subcellular compartmentalization of metabolic reactions
- Account for allosteric regulation at key regulatory enzymes
- Remember that in vivo delta_G differs greatly from standard conditions
- Integrate with hormonal regulation of metabolism
Common Pitfalls
| Pitfall | Fix |
|---|---|
| Confusing delta_G0 with delta_G | Cellular conditions make delta_G very different from standard |
| Forgetting NADH/FADH2 in ATP count | These carry most of the energy from TCA |
| Ignoring allosteric regulation | Key enzymes are highly regulated, not just kinetically limited |
| Confusing competitive inhibition types | Draw double-reciprocal plots to distinguish |
Related Skills
- cell-biology-expert
- molecular-biology-expert
- physiology-expert
- biochemistry-expert