read chapter 4 (all of it) you have a test soon!
TRANSCRIPT
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
Endomembrane System
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.
Endomembrane System
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
Cell to Cell Connenction
Fig. 6-28
Secondary cell wallPrimary cell wall
Middle lamella
Central vacuole Cytosol
Plasma membranePlant 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
Cell to Cell Connection
Fig. 6-30
EXTRACELLULAR FLUID
Collagen
Fibronectin
Plasmamembrane
Micro-filaments
CYTOPLASM
Integrins
Proteoglycancomplex
Polysaccharidemolecule
Carbo-hydrates
Coreprotein
Proteoglycanmolecule
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
Cell to Cell Connection
Fig. 6-32
Tight junction
0.5 µm
1 µm
Desmosome
Gap junction
Extracellularmatrix
0.1 µm
Plasma membranesof adjacent cells
Spacebetweencells
Gapjunctions
Desmosome
Intermediatefilaments
Tight junction
Tight junctions preventfluid from movingacross 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
Organelle review
Fig. 6-UN1a
Cell Component
Structure
Function
Concept 6.3 The eukaryotic cell’s geneticinstructions are housed inthe nucleus and carried outby the ribosomes
Nucleus
Surrounded by nuclearenvelope (double membrane)perforated by nuclear pores.The nuclear envelope iscontinuous with theendoplasmic reticulum (ER).
(ER)
Houses chromosomes, made ofchromatin (DNA, the geneticmaterial, and proteins); containsnucleoli, where ribosomalsubunits are made. Poresregulate entry and exit osmaterials.
Ribosome
Two subunits made of ribo-somal RNA and proteins; can befree in cytosol or bound to ER
Protein synthesis
Fig. 6-UN1b
Cell Component
Structure
Function
Concept 6.4 The endomembrane systemregulates protein traffic andperforms metabolic functionsin the cell
Endoplasmic reticulum
(Nuclearenvelope)
Golgi apparatus
Lysosome
Vacuole
Large membrane-boundedvesicle in plants
Membranous sac of hydrolyticenzymes (in animal cells)
Stacks of flattenedmembranoussacs; has polarity(cis and transfaces)
Extensive network ofmembrane-bound tubules andsacs; membrane separateslumen from cytosol;continuous withthe nuclear envelope.
Smooth ER: synthesis oflipids, metabolism of carbohy-drates, Ca2+ storage, detoxifica-tion of drugs and poisons Rough ER: Aids in sythesis ofsecretory and other proteinsfrom bound ribosomes; addscarbohydrates to glycoproteins;produces new membrane
Modification of proteins, carbo-hydrates on proteins, and phos-pholipids; synthesis of manypolysaccharides; sorting ofGolgi products, which are thenreleased in vesicles. Breakdown of ingested sub-stances cell macromolecules, and damaged organelles for recycling Digestion, storage, wastedisposal, water balance, cellgrowth, and protection
Fig. 6-UN1c
Cell Component
Concept 6.5Mitochondria and chloro-plasts change energy fromone form to another
Mitochondrion
Chloroplast
Peroxisome
Structure
Function
Bounded by doublemembrane;inner membrane hasinfoldings (cristae)
Typically two membranesaround fluid stroma, whichcontains membranous thylakoidsstacked into grana (in plants) Specialized metaboliccompartment bounded by asingle membrane
Cellular respiration
Photosynthesis
Contains enzymes that transferhydrogen to water, producinghydrogen peroxide (H2O2) as aby-product, which is convertedto water by other enzymesin the peroxisome
Fig. 6-9a
ENDOPLASMIC RETICULUM (ER)
Smooth ER
Rough ERFlagellu
m
Centrosome
CYTOSKELETON:
MicrofilamentsIntermediate
filamentsMicrotubules
Microvilli
Peroxisome
Mitochondrion Lysosom
e
Golgiapparatus
Ribosomes
Plasma membrane
Nuclearenvelope
NucleolusChromatin
NUCLEUS
Fig. 6-9b
NUCLEUS
Nuclear envelopeNucleolusChromatin
Rough endoplasmic reticulum
Smooth endoplasmic reticulum Ribosome
s
Central vacuole
MicrofilamentsIntermediate filaments
Microtubules
CYTO-SKELETON
Chloroplast
PlasmodesmataWall of adjacent
cell
Cell wall
Plasma membrane
Peroxisome
Mitochondrion
Golgiapparatus