Read Chapter 4 (all of it) you have a test soon!

 What is the endomembrane system? ◦ A network of membranous organelles that partition the cytoplasm of eukaryotic cells into functional compartments. Some organelles are structurally connected to each other (Nucleus to Rough ER and Smooth ER), whereas others are structurally separated but are functionally connected by the traffic of membranous vesicles that travel between them (ER to Golgi to Lysosomes/Vesicles).  What organelles are involved? ◦ Nucleus, ER, Golgi Apparatus, Lysosomes, & Vesicles

 Explain the difference between the structural and functional connections within the endomembrane system. ◦ If organelles are not structurally connected then a transport vesicle is required to move the contents of one organelle to the next for the contents to be further processed. Each organelle plays a role in modify the product. ◦ Connections – physical or by vesicle – allow the cell to be efficient in producing cell products either for use in the cell or for export out of the cell.

Fig Smooth ER Nucleus Rough ER Plasma membrane cis Golgi trans Golgi

 What surrounds a plant cell? ◦ Plant cells have cell walls. The cell walls may have multiple layers:  Primary cell wall: relatively thin and flexible  Middle lamella: thin layer between primary walls of adjacent cells  Secondary cell wall (in some cells): added between the plasma membrane and the primary cell wall  How do plant cells communicate (cell to cell)? ◦ Plasmodesmata are channels between adjacent plant cells that allow for cell to cell communication

Fig Secondary cell wall Primary cell wall Middle lamella Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata 1 µm

 Animals cells don’t have cells walls – so what do they have outside their cell membranes? ◦ Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM) ◦ The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin ◦ ECM proteins bind to receptor proteins in the plasma membrane called integrins ◦ Functions of the ECM include: Support, Adhesion, Movement, and Regulation

Fig EXTRACELLULAR FLUID Collagen Fibronectin Plasma membran e Micro- filaments CYTOPLASM Integrins Proteoglycan complex Polysaccharide molecule Carbo- hydrates Core protei n Proteoglycan molecule Proteoglycan complex

 How do animal cells communicate (cell to cell) and stick together? ◦ At tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid ◦ Desmosomes (anchoring junctions) fasten cells together into strong sheets ◦ Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells

Fig Tight junction 0.5 µm 1 µm Desmosome Gap junction Extracellular matrix 0.1 µm Plasma membranes of adjacent cells Space between cells Gap junctions Desmosome Intermediate filaments Tight junction Tight junctions prevent fluid from moving across a layer of cells

 Which organelles produce cell products? ◦ Nucleus, Ribosomes, ER, Golgi Apparatus  Which organelles breakdown materials? ◦ Lysosomes, Vacuoles, Peroxisomes  Which organelles produce energy? ◦ Chloroplast & Mitochondria  Which organelles are involved in support, movement, and communication? ◦ Cytoskeleton, Cell Walls, Extracellular Matrix, & Cell Junctions

Fig. 6-UN1a Cell Component Structure Function Concept 6.3 The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes Nucleus Surrounded by nuclear envelope (double membrane) perforated by nuclear pores. The nuclear envelope is continuous with the endoplasmic reticulum (ER). (ER) Houses chromosomes, made of chromatin (DNA, the genetic material, and proteins); contains nucleoli, where ribosomal subunits are made. Pores regulate entry and exit os materials. Ribosome Two subunits made of ribo- somal RNA and proteins; can be free in cytosol or bound to ER Protein synthesis

Fig. 6-UN1b Cell Component Structure Function Concept 6.4 The endomembrane system regulates protein traffic and performs metabolic functions in the cell Endoplasmic reticulum (Nuclear envelope) Golgi apparatus Lysosome Vacuole Large membrane- bounded vesicle in plants Membranous sac of hydrolytic enzymes (in animal cells) Stacks of flattened membranous sacs; has polarity (cis and trans faces) Extensive network of membrane-bound tubules and sacs; membrane separates lumen from cytosol; continuous with the nuclear envelope. Smooth ER: synthesis of lipids, metabolism of carbohy- drates, Ca 2+ storage, detoxifica- tion of drugs and poisons Rough ER: Aids in sythesis of secretory and other proteins from bound ribosomes; adds carbohydrates to glycoproteins; produces new membrane Modification of proteins, carbo- hydrates on proteins, and phos- pholipids; synthesis of many polysaccharides; sorting of Golgi products, which are then released in vesicles. Breakdown of ingested sub- stances cell macromolecules, and damaged organelles for recycling Digestion, storage, waste disposal, water balance, cell growth, and protection

Fig. 6-UN1c Cell Component Concept 6.5 Mitochondria and chloro- plasts change energy from one form to another Mitochondrion Chloroplast Peroxisome Structure Function Bounded by double membrane; inner membrane has infoldings (cristae) Typically two membranes around fluid stroma, which contains membranous thylakoids stacked into grana (in plants ) Specialized metabolic compartment bounded by a single membrane Cellular respiration Photosynthesis Contains enzymes that transfer hydrogen to water, producing hydrogen peroxide (H 2 O 2 ) as a by-product, which is converted to water by other enzymes in the peroxisome

Fig. 6-9a ENDOPLASMIC RETICULUM (ER) Smooth ERRough ER Flagellum Centrosome CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Microvilli Peroxisome Mitochondrion Lysosome Golgi apparatus Ribosomes Plasma membrane Nuclear envelope Nucleolus Chromatin NUCLEUS

Fig. 6-9b NUCLEUS Nuclear envelope Nucleolus Chromatin Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes Central vacuole Microfilaments Intermediate filaments Microtubules CYTO- SKELETON Chloroplast Plasmodesmata Wall of adjacent cell Cell wall Plasma membrane Peroxisome Mitochondrion Golgi apparatus