Lecture 8 - The Endomembrane System 🟢 PDF

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Summary

Lecture Notes ...

Description

The Endomembrane System • List the components of the Endomembrane system, and describe the structure and function of each component • Describe the route taken by a secreted protein, from synthesis to export, and compare this to how non-secreted proteins are produced. 1. The Endomembrane system 2. ER, Golgi & Protein Secretion 3. Vacuoles 4. Lysosomes

Endomembrane system • Manufactures, sorts and distributes molecules ! • Physical continuity or vesicle transfer between components ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! Endoplasmic Reticulum (ER) (Inside - network)! ! Extensive membrane system ! • Continuous with nuclear membranes ! • Tubes and sacs

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Two kinds of ER:! !

Rough ER! • Sheet like ! • Rough appearance due to ribosomes ! !

Smooth ER! • Tubular ! • Smooth appearance (NO ribosomes)

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Functions of Smooth ER • Ca2+ ion storage (e.g. muscle contraction)! • Lipids synthesis (e.g. steroid sex hormones)! • Poison detoxification (e.g. alcohol)! !

Functions of Rough ER • Protein synthesis (secreted and membrane proteins)! • Glycosylation ! • Membrane synthesis ! ! ! ! ! ! ! !

Rough ER

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Many destinations for a completed protein (polypeptide)

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Proteins destined for secretion... • Have a hydrophobic signal peptide hat binds to a signal recognition particle (SRP)! • Translation is stopped

! ! ! ! ! ! ! ! ! ! ! ! ! ! Explain the roles of the ‘signal peptide’ and ‘signal recognition particle’ in targeting a protein to its final destination

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SRP attaches ribose to RER and translation starts again

Describe the process of glycosylation ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

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Golgi Apparatus • Sack of flattened sacs ! • Movement of proteins and flow of membranes ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

Functions of Golgi Apparatus • Completes glycosylation! • Sorts into vesicles ! • Makes polysaccharides

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Synthesis of membrane components and their orientation in the membrane

Model of an animal cell plasma membrane ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

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Carbohydrates attached on the OUTSIDE

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Vacuoles (in plants and fungi) ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

Arrow = Lysosome

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• Derived from ER and Golgi! • Hydrolytic enzymes! • Store ions and organic compounds

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Functions of Lysosomes Explain the functions of lysosomes and why they are important • Break down food etc following phagocytosis ! • Autophagy ! e.g. Digest old organelles ! • Break down toxic compounds ! ! !

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Lysosomes are critical to intracellular killing and digestion following phagocytosis

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Lysosomal storage disorder in dogs • Enzyme deficiency leading to lesions in many cell types ! • Complex sulphate polysaccharides not broken down properly in lysosomes...