Phospholipid structure
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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

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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

“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

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

fibers (intermediate filaments) extend across cells

epithelial cells (especially skin), cardiac intercalated disks

fig 3-10a


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

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

cardiac intercalated disks, smooth muscle

fig 3-10d


Epithelial cell

fig 3-10c


Protein ligand interaction

Proteins could be:Ligands would be:

enzymes substrates, allosteric regulators

receptorschemical messengers

transporterstransported substances

transcription factorstranscription regulators

any of abovedrugs


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

binding depends on ligand size, shape, charge

fig 3-27

fig 3-26


Specificity

protein Y specificity

greater than

protein X specificity

fig 3-28


Affinity

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

fig 3-29


Affinity & saturation

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

fig 3-30


Affinity (different proteins)

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

fig 3-31


Affinity (different ligands)

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


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

a.Allosteric modulation

reversible binding at another (“allo-”) site

can be activation or inhibition


Regulating binding site properties

a.Covalent modulation

chemical alteration of the protein

can be activation or inhibition


Metabolism (pathways)


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


Energy content


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