Phospholipid structure

1. Phospholipid structure Amphipathic molecule (phosphatidyl choline) hydrophobic part: fatty acids hydrophilic part: phosphate & choline

2. Membrane structure

3. Membrane components

4. Transmembrane proteins

5. Intercellular structures Desmosomes “spot welds”, dense proteins (cytoplasm & intercellular) fibers (intermediate filaments) extend across cells epithelial cells (especially skin), cardiac intercalated disks Tight junctions cell “collar”, block large molecules, no lateral protein movement epithelial cells Gap junctions cell-cell communication, small molecules (<1000 MWt) cardiac intercalated disks, smooth muscle

6. Desmosomes “spot welds”, dense proteins (cytoplasm & intercellular) fibers (intermediate filaments) extend across cells epithelial cells (especially skin), cardiac intercalated disks fig 3-10a

7. Tight junctions cell “collar”, block large molecules, no lateral protein movement epithelial tissue (esp. kidney, gut) paracellular pathway between cells fig 3-10b

8. Gap junctions cell-cell communication, small molecules (<1000 MWt) cardiac intercalated disks, smooth muscle fig 3-10d

9. Epithelial cell fig 3-10c

10. Protein ligand interaction Proteins could be: Ligands would be: enzymes substrates, allosteric regulators receptors chemical messengers transporters transported substances transcription factors transcription regulators any of above drugs

11. Protein-ligand binding properties Specificity: binding depends on ligand size, shape, charge Affinity: strength of binding: i.e. [ligand] at 50% binding Saturation: there is a finite number of binding sites Competition: structurally similar molecules can compete for binding

12. Specificity binding depends on ligand size, shape, charge fig 3-27 fig 3-26

13. Specificity protein Y specificity greater than protein X specificity fig 3-28

14. Affinity strength of binding: i.e. [ligand] at 50% binding fig 3-29

15. Affinity & saturation strength of binding: i.e. [ligand] at 50% binding fig 3-30

16. Affinity (different proteins) strength of binding: i.e. [ligand] at 50% binding fig 3-31

17. Affinity (different ligands) strength of binding: i.e. [ligand] at 50% binding

18. Protein-ligand binding properties Specificity: binding depends on ligand size, shape, charge Affinity: strength of binding: i.e. [ligand] at 50% binding Saturation: there is a finite number of binding sites Competition: structurally similar molecules can compete for binding and remember: the protein can be an enzyme, receptor, transporter, etc.

19. Regulating binding site properties a. Allosteric modulation reversible binding at another (“allo-”) site can be activation or inhibition

20. Regulating binding site properties a. Covalent modulation chemical alteration of the protein can be activation or inhibition

21. Metabolism (pathways)

22. Metabolism (key) Key: A: glycogenesis, B: glycogenolysis, C: glycolysis, C+D: anaerobic glycolysis (lactic acid fermentation), E: gluconeogenesis, F: irreversible step (pyruvate dehydrogenase), G: protein synthesis, H: proteolysis, I: lipogenesis, J: lipolysis, K: Krebs cycle, L: urea synthesis, M: ketogenesis Anabolic pathways: A, G, I Catabolic pathways: B, C, E, F, H, J, K Liver only: E, L, M Mitochondrial: K Ribosomal: G Smooth endoplasmic reticulum: I

23. Energy content