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Phospholipid structure. Amphipathic molecule (phosphatidyl choline) hydrophobic part: fatty acids hydrophilic part: phosphate & choline. Membrane structure. Membrane components. Transmembrane proteins. Intercellular structures. Desmosomes

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Phospholipid structure
Phospholipid structure

Amphipathic molecule (phosphatidyl choline)

hydrophobic part: fatty acids

hydrophilic part: phosphate & choline





Intercellular structures
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


Desmosomes
Desmosomes

“spot welds”, dense proteins (cytoplasm & intercellular)

fibers (intermediate filaments) extend across cells

epithelial cells (especially skin), cardiac intercalated disks

fig 3-10a


Tight junctions
Tight junctions

cell “collar”, block large molecules, no lateral protein movement

epithelial tissue (esp. kidney, gut)

paracellular pathway

between cells

fig 3-10b


Gap junctions
Gap junctions

cell-cell communication, small molecules (<1000 MWt)

cardiac intercalated disks, smooth muscle

fig 3-10d


Epithelial cell
Epithelial cell

fig 3-10c


Protein ligand interaction
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


Protein ligand binding properties
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


Specificity
Specificity

binding depends on ligand size, shape, charge

fig 3-27

fig 3-26


Specificity1
Specificity

protein Y specificity

greater than

protein X specificity

fig 3-28


Affinity
Affinity

strength of binding: i.e. [ligand] at 50% binding

fig 3-29


Affinity saturation
Affinity & saturation

strength of binding: i.e. [ligand] at 50% binding

fig 3-30


Affinity different proteins
Affinity (different proteins)

strength of binding: i.e. [ligand] at 50% binding

fig 3-31


Affinity different ligands
Affinity (different ligands)

strength of binding: i.e. [ligand] at 50% binding


Protein ligand binding properties1
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.


Regulating binding site properties
Regulating binding site properties

a. Allosteric modulation

reversible binding at another (“allo-”) site

can be activation or inhibition


Regulating binding site properties1
Regulating binding site properties

a. Covalent modulation

chemical alteration of the protein

can be activation or inhibition



Metabolism key
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



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