The document summarizes the organelles and structures found inside neurons. It notes that neurons resemble other cells but have distinctive shapes. The main organelles in neurons are the nucleus, cell body, dendrites, axon, ribosomes, endoplasmic reticulum, Golgi complex, lysosomes, mitochondria, and peroxisomes. Protein synthesis occurs via mRNA transcribed in the nucleus and transported to ribosomes. The endoplasmic reticulum modifies and transports proteins, while the Golgi apparatus further modifies proteins before they reach their destination. Gene expression can be regulated by controlling mRNA stability and degradation.

2. Neurons resemble epithelial cell, except for their shape

3. Organelles inside neurons are almost the same as in any other cell Only plants

5. The nucleus has a double membrane with nuclear pores for the traffic of macromolecules: Transcription factors and Nucleic acids

6. Proteins are synthesized from mRNA synthesized in the nucleus and translocated to ribosomes

7. A specific transport mechanism is responsible for mRNA traslocation

8. An active transport system using GTP energy traslocates macromolecules in and out from the nucleus

10. Nuclear pores are typically made up by 8 subunits

11. RIBOSOMES Are produced in the nucleolus and transported to the extracllular space where some of them are taken by the endoplasmic reticulum (ER)

12. Ribosomes are not organelles, in the sense that do not have an internal and external sides separated by a lipid membrane. They are made up by two subunits. Their total composition is 2/3 RNA and 1/3 proteins

13. Complex mechanism of protein synthesis and folding

14. Once they are in the extranuclear space part of the ribosomes stay free in the cytosol, and part of them stick to the Endoplasmic Reticulum (ER)

15. The ER has two compartments: the “rough” ER and the “smooth” ER. The rough ER is characterized by the presence of long lines of ribosomes that are continuously producing proteins and sending them to other organelles Endoplasmic Reticulum

16. Specific intracellular stimuli induce the release of Ca +2 from the ER There are two separate Ca+2 stores: 1) IP3-gated 2) Ca +2 -gated (Ryanodine-dependent) Their activation transiently elevates [Ca +2 ] i , the cytosolic concentration of Ca +2 Another function of the Endoplasmic Reticulum:

17. Ribosomes in Cell Body and Dendrites

20. Once proteins are synthesized and folded they detach from ribosomes but are not ready yet to function, and need to be properly folded and further modified

21. Golgi apparatus

22. Transmembrane protein can cross the membrane many times

23. A series of enzymes starts to modify proteins when they are being synthesized (co-translational modifications)

26. Complex sugar chains are attached as a whole in the ER

27. Lipids are attached sometimes to the end of the protein, as an anchor to the cell membrane lipid bilayer. Sugar-lipid chains characterize extracellular proteins like Ach-esterase or NCAM cell adhesion molecules

28. Successive stages of further proteins modifications are performed in the Golgi apparatus, up to the transport of complete, functional proteins at their site of work

29. Even after proper folding and posttranslational modification they are often not ready yet and need to be assembled in various subunits, like for instance many membrane channels

30. DNA Protein Inactive Protein Inactive mRNA Primary RNA transcript mRNA mRNA 1 Transcriptional Control 2 RNA Processing Control 4 Translation Control 5 mRNA Degradation Control 6 Protein Activity Control 3 RNA Transport Control Cytosol Nucleus

31. Gene expression can be controlled by regulating mRNA stability The competition between mRNA translation and decay might be related to synaptic plasticity