Endomembrane System & Energy Production

1. Endomembrane System & Energy Production • The endomembrane system is an internal membrane system within the cell that carries out a variety of functions such as: • synthesis of proteins and their transport • metabolism and movement of lipids • the detoxification of poisons. • The membranes of the system are either directly in contact with each other or can communicate through the formation of vesicles (enclosed sacs made of membrane material). • There are 5 major compartments: • endoplasmic reticulum (smooth&rough), • golgi apparatus, • Lysosomes • vacuoles.

2. Endoplasmic Reticulum(ER) • largest of the endomembrane systems (over 1/2of the total) • contains a network of tubes called cisternae (contains the inner lumen) • connected to the nuclear envelope separating the cytosol from the inner lumen (much like our digestive system) • self proliferating making its components from precursors (pieces of phospholipids) found in the cytosol • 2 distinct compartments smooth & rough

3. Smooth ER • Cisternae are rich in enzymes that carry out specialized tasks • Functions • Synthesis of lipids • oils, phospholipids, & steroids • cells that produce and secrete these will be "rich" in smooth ER • Metabolism of carbohydrates • Detoxification of drugs and poisons • primary area is in the liver • detoxification occurs through adding hydroxyl functional groups (increases water solubility) • increased used (drugs & alcohol) causes proliferation of smooth ER in the liver which increases tolerance through faster clearance • Storage of calcium ions • stored in muscle for use in contraction

4. Rough ER • growing chain of polypeptides is threaded into the cisternae lumen from the ribosome • makes secretory proteins called glycoproteins (proteins with a carbohydrate covalently bonded) • makes membrane proteins that are anchored by hydrophobic attraction • once completed the proteins are transported through vesicles to their destination

5. The Golgi Apparatus (shipping & receiving) • Consists of flattened sacs of cisternae • 2 distinct sides - CIS (receiving)&TRANS (shipping) • each side has different polarity and thickness • CIS face is close to the ER to receive incoming vesicles • packaged vesicles leave from the trans face • Site of ER product modification (may modify the glycoprotein to make it better suited for its final destination) • Produces its own polysaccharides to be fused with plasma membranes • molecular identification tags (phosphate groups or external molecules) aid in delivery to the correct location

6. Lysosomes • A sac of hydrolytic enzymes • made in the rough ER & modified in the golgi • Acidic in nature • Special inner membrane with a 3D conformation that resists auto digestion • Can carry out intracellular digestion via phagocytosis (enfolding of membrane around an object) of membrane bound food vacuoles • Digestion products (simple sugars, amino acids, & other monomers) pass back to the cytosol via exocytosis

7. Vacuoles • Food storage structures in plants, protist, and fungal cells. • Contain hydrolytic enzymes much like lysosomes • Can be specialized in different animals to perform specific functions • Contractile vacuole • protists use this structure to maintain salinity by adding and removing water • Central vacuole • found in mature plants • enclosed in a specialized membrane called a tonoplast • enclosed material is called sap not cytosol • can be used to store molecules, ions, waste, pigments, or anything needed for growth • plays a major growth role

8. Mitochondria • transform energy from their environment to be used by the host organism. They produce their own energy, are mobile, and divide (bud) to create new structures. • found in all Eukaryotes • site of cellular respiration • produces ATP through redox reactions in the mitochondrial membranes • the # of mitochondria present is based on the cell's (organism's) need for energy • has a smooth outer membrane and a folded inner membrane called cristae • contains its own DNA & ribosomes in the mitochrondrial matrix (an enclosed area in the inner membrane)

9. Chloroplasts • transform energy from their environment to be used by the host organism • specialized member of the plastid family (chromoplasts & amyloplasts) • contain the green pigment chlorophyll • function in the photosynthetic production of sugar • consists of many flattened sacks called thalokoids (stacks are called granum) • fluid outside is called the stroma (contains the DNA & ribosomes)

10. Peroxisomes • Structures is much like lysosomes. • Produce peroxide (H2O2) for the breakdown of fatty acids by oxidation for use in the mitochondria. • Also found in the liver as sites of detoxification. • Glycoxysomes are specialized structures in plant seeds that convert fatty acids to sugar used as a source of energy • Cannot self replicate - product of lipids from the ER, proteins from the cytosol, & lipids made in the peroxisomes • they may split (bud) once the necessary parts are assembled and the size is sufficient