BSC (2.2) Endomembrane system

Powerpoint for endomembrane system

Endomembrane system

Group of membrane-bound structures within a eukaryotic cell that function as a continuum: Contains; Nucleus, Golgi apparatus(Gogli), Lysosomes

Central Dogma of endomembrane system

Double stranded DNA to single stranded RNA (Transcription): Single stranded RNA to ribosomes and proteins (Translation)

Nucleus

Command center of the cell: Where DNA as chromosomes is located: Membrane bound: Site of transcription and RNA modification and maturation: Normally only ONE per cell unless cell is actively dividing

Perinuclear space

Gap between membranes that surrounds nucleus

Nuclear Membranes

Double-membrane with perinuclear space: Allows separation of mRNA from translational machinery: Allows modification and maturation of mRNA before it is translated into proteins: Covered with octameric pores that allow mRNA OUT and nuclear proteins IN

Nuclear Pores

Located in nuclear membrane, these are membrane protein openings: Small ions and molecules can pass through this passively: Large proteins and RNA require active transport

Endoplasmic Reticulum

Complex mass of membranes with cytoplasm of cell: Extension of nuclear membranes and perinuclear space

Rough ER

imbedded with ribosomes: makes cisternae: is literally rough: Roles are- ribosomes synthesize excreted proteins(stored in cisternae or vesicle), modify proteins (Glycosylation of proteins), delivery of membrane associated proteins, often interacts with golgi

Smooth ER

No ribosomes: makes tubules: Roles are- tissue)specific uses), storage of carbohydrates, detoxification reactions in the liver, synthesizes much of the new membrane material, modification of existing molecules

Relation of golgi and ER

often adjacent in cytoplasm of cell: both membrane producers- membranes have sides, vesicles are produced inside out, vesicle fuses with surface and excreted proteins are released and integral proteins are added along with membrane.: ER often performs first steps in modification which is later finished in golgi

Golgi Apparatus

complex collection of membrane: Has polarity (cis and trans surfaces): Responsible for secretion(very prominent in cells that serve secretory functions such as epithelial cells: Modifies structures previously synthesized in thr ER: Activity starts closest to ER and ends closer to the cell membrane

Golgi Apparatus locations

Cis face is near the center of the cell, often adjacent to ER: Trans face is nearer the cell membrane

Lysosome

Contains digestive enzymes used to degrade macromolecules or organelles: originates in ER but enzymes are activated in Golgi: important in macrophages for degradation of particles acquired via phagocytosis: used to degrade organelles(autophagy)

Protein targeting

Proteins need to get to the cell compartments: Signal sequences in the amino acid sequence of the protein which determines where the protein will eventually become localized: other proteins assist by recognizing the signal sequence and directing it to the correct location (integral vs cytoplasmic proteins)