2.1 The Structure & Functions of Eukaryotic Cells
Endoplasmic Reticulum Moves substances between the cytoplasm and nucleus in a network of inter-connected, complex system of channels & sacs (lumen) Ribosomes (RNA + proteins) synthesize protein and are either free-floating in the cytosol (proteins for use in cell) or attached to some ER (proteins excreted) Two types of ER –Rough endoplasmic reticulum or RER (ribosomes attached to the surface) –Smooth endoplasmic reticulum or SER (no ribosomes attached to the surface)
Rough Endoplasmic Reticulum Ribosomes attached to surface Manufactures proteins for use in membrane or for excretion from the cell. Sends them in vesicles to the Golgi Apparatus. Ribosomes, while still making proteins, differ in structure & mechanisms between eukaryotes and prokaryotes.
RER Micrograph
Smooth Endoplasmic Reticulum No attached ribosomes on the surface Has enzymes that help build molecules of lipids (ie: steroids & phospholipids) for use in the membrane. Sends them in vesicles to the Golgi Apparatus. SER also detoxifies drugs & alcohol and produces hormones (ie: sex hormones)
SER Micrograph
Endomembrane System Includes nuclear envelope, ER and the Golgi Apparatus. It synthesizes, modifies and transports cell products (ie: protein) The organelles are connected to each other by transport vesicles (membrane closed sacs for transport and storage)
Golgi Apparatus Moves substances from vesicles of the ER through a network of complex system of channels & sacs Stores or modifies proteins (CHO chains) from vesicles Involved in synthesis of plant cell wall Produces lysosomes Transports vesicles to cell membrane for excretion
Golgi Apparatus Function 1. Molecules arrive in vesicles from ER 2. Vesicles fuse with Golgi membrane 3. Molecules may be modified by Golgi 4. Molecules pinched-off in separate vesicle 5. Vesicle leaves Golgi apparatus 6. Vesicles may combine with plasma membrane to secrete contents
Golgi Apparatus Micrograph
Lysosomes & Peroxisomes Contains digestive enzymes to breakdown macromolecules. Lysosomes from GA and peroxisomes from ER Peroxisome functions; – catalyzing redox reactions –Breaks down toxic molecules –Contains catalase Lysosome functions; –Catalyze hydrolysis reactions –Breaks down old cell parts –Digests invaders
Vacuoles & Vesicles Membrane bound storage sacs (vesicles & vacuoles) or transport sacs (vesicles only) Larger vacuoles (ie; central) found only in plants Vesicles smaller & more common in animals Contents –Water –Food –Ions –Wastes –Macromolecules
Food Vacuole Micrograph
End of Part 2! (There’s more? …..oh joy…)
End Part 2