Biology: Cell Biology & Signaling
Free MCAT study guide — Biological and Biochemical Foundations of Living Systems
Cell Structure
| Organelle | Function | Key Details |
|---|---|---|
| Nucleus | DNA storage, transcription | Double membrane, nuclear pores |
| Rough ER | Protein synthesis (secretory) | Ribosomes on surface |
| Smooth ER | Lipid synthesis, detox | No ribosomes |
| Golgi | Modify, sort, package proteins | cis (ER side) → trans (membrane side) |
| Mitochondria | ATP production | Double membrane, own DNA, cristae |
| Lysosome | Intracellular digestion | Acidic (pH ~5), hydrolases |
| Peroxisome | H₂O₂ metabolism, β-oxidation | Very long chain fatty acids |
Cell Cycle
Key Point: p53 = 'guardian of the genome' — arrests cell cycle or triggers apoptosis. Rb prevents G1→S transition until phosphorylated by Cyclin-CDK.
Cell Signaling
Key Point: GPCRs → G proteins → adenylyl cyclase (cAMP) or PLC (IP₃ + DAG). RTKs → Ras-MAPK pathway.
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