Organelles Flashcards
Peroxisomes
- Main sites of oxygen utilisation
- contain oxidative enzymes (- catalase, urate oxidase)
- perform oxidation reaction without generation of energy
- oxygen –> a plant toxin
-peroxisomes perform redox reactions - also important for B-oxidation
Autophagy
- The self-eating of cytosolic materials
- degrades damaged or unwanted proteins and organelles
-nucleation and extension
-closure - fusion with lysosomes
-digestion
Lysosomes
- Safe container for ‘lethal’ digestive enzymes
- acidic pH ~5.0
- proton gradient maintained by H+-pump
- fusion with late endosomes
–>endolysosome - fusion with phagosomes
–>phagolysosome - heterogeneous: hydrolytically active, low pH compartments
What materials if transported from lysosomes
Metabolites
What materials is transported to lysosomes
There are three major routes exist for the transport of molecules to lysosomes for digestion.
- Heterophagy (phagocytosis and endocytosis)
- autophagy
-KFERQ - dependent import of cytosol proteins
Functions of ER
- protein synthesis on rough ER (rER)
- protein processing (cleavage, glycosylation, disulphide bridge formation and prenylation)
- protein folding and assembly
-protein sorting & quality control
-biosynthesis of lipids (also for mitochondria and plastids)
-calcium storage for signalling
The different regions of the ER specialise in certain functions
ER-Golgi communication
- two way traffic
- ER does not communicate directly with secretory vesicles
- all onward traffic via Golgi
- Golgi-lock
Transport from the ER to the Golgi apparatus
ER to the cis Golgi network is transported by microtubules, protein cargo is transported in COPII- coated vesicles from the ER to the cis-Golgi
cis Golgi network to the ER the protein cargo transported by retrieval transport and coated in COPI-coat
Golgi Apparatus
- Consists of an Ordered Series of Compartments
- the cis FACE is the Golgi vesicle side
- trans FACE is the secretory vesicle side
Ordered series of compartments
ER –> Golgi
Sorting- phosphorylation of oligosaccharides on lysosomal proteins - cis Golgi network
Removal of Man - cis cisterna
Removal of man and addition of GlcNAc - medial cisterna
addition of Gal and addition f NANA - trans cisterna
sulfation of tyrosine’s and carbohydrates - sorting (lysosomes, plasma membrane and secretory vesicle)
Protein processing in the ER
cleavage of signal peptides
glycosylation of proteins
Folding and quality control of proteins in the ER
Other proteins called chaperones use energy to fold proteins into their proper shape
Only proteins that are properly folded and assembled can leave the ER
Biosynthesis of lipids in the ER
-almost all phospholipids synthesised in the ER
-transported as vesicles to destinations and plasma membrane
-lipid synthesis also for mitochondria and chloroplasts
-close physical relationship of ER and mitochondria and plasma membrane
The ER can exist without mitochondria, but mitochondria cannot exist without the ER
Endocytosis
contents are taken up from the outside
Exocytosus
Contents are released (secreted) to the outside
Main route by which organelles of the endomembrane system interact
- Endoplasmic Reticulum 2 way traffic to the Golgi
- Golgi 2 way traffic to the Secretory vesicles
- Golgi 1 way traffic to the Extracellular Space
- Golgi 2 way traffic to early endosome
- Golgi 2 way traffic to late endosome
- Late endosome 2 way same direction traffic to lysosome
- cytosol to lysosome
- Early endosome 2 way same direction traffic to late endosome
- Early endosome to recycling endosome to extracellular space
-Early endosome 2 way traffic to extracellular space
Nuclear envelope
A double membrane that encloses the nucleus, regulating material exchange between the nucleus and cytoplasm via nuclear pores
Nuclear pores
Protein complexes embedded in the nuclear envelop that control the passage of molecules like RNA and proteins between the nucleus and cytoplasm
Nucleolus
A dense region within the nucleus responsible for the synthesis and assembly of ribosomal RNA and ribosome subunits
Chromatin
DNA wrapped around histone proteins, which condenses to form chromosomes during cell division. It stores genetic information and regulates gene expression
Nucleoplasm
The gel-like substance within the nucleus that suspends chromatin and nucleolus, providing structural support and medium for molecular interactions
How molecules enter and leave the nucleus
Imported proteins carry a specific signal peptide: nuclear localisation signal (NLS)
Exported proteins also carry a specific signal peptide: nuclear export signal (NES)
Centrosome
Composed of two centrioles and surrounding matrix of proteins.
- structure: it consists of two perpendicular centrioles made of microtubules, surrounded by the pericentriolar material, which contains proteins important for microtubule nucleation.
-function: the centrosomes serves as the main microtubule organising centre, playing a key role in cell division by organising the mitotic spindle and regulating microtubule dynamics for cell shape and intracellular transport
Flagellum
Axoneme: A core structure made of nine outer microtubule doublets surrounding two central microtubules (9+2 arrangement)
Basal Body: Anchors the flagellum to the cell, similar to a centriole
Plasma membrane: Encases the flagellum, providing structural support
The coordinated movement of the axoneme microtubules allows the flagellum to enable cell motility.
Origin of eukaryotic nucleus
Thought to have originated from an infolding of the plasma membrane
Origin of flagellum
Originated from bacterial-like structures, such as bacterial pili or filaments
