Lysosomes. Vacuoles. Phagocytosis. One cell engulfing another. forms a food vacuole. fuses with lysosome. Autophagy. Lysosomes use enzymes

Transcription

1 Lysosomes Phagocytosis One cell engulfing another forms a food vacuole fuses with lysosome Autophagy Lysosomes use enzymes to recycle the cell s own organelles and macromolecules Fig Nucleus 1 µm Vesicle containing two damaged organelles 1 µm Lysosome Lysosome Digestive enzymes Mitochondrion fragment Peroxisome fragment Lysosome Plasma Digestion Peroxisome Food vacuole Vesicle Mitochondrion Digestion (a) Phagocytosis (b) Autophagy Vacuoles A plant cell or fungal cell may have one or several vacuoles Food vacuoles formed by phagocytosis Contrac9le vacuoles found in many freshwater probsts, pump excess water out of cells Central vacuole Cytosol Central vacuoles found in many mature plant cells, hold organic compounds and water Nucleus Cell wall Chloroplast Central vacuole 5 µm 1

2 Mitochondria and Chloroplasts Mitochondria sites of cellular respirabon In plants too Chloroplasts in plants and algae only sites of photosynthesis Both change energy from one form to another Mitochondria and chloroplasts Mitochondria and Chloroplasts Are not part of the endo system Have a double Have proteins made by free ribosomes Contain their own DNA?! Endosymbiont theory h<p:// 2011/07/ htm h<p:// srep00013/full/srep00013.html Mitochondria Mitochondria in nearly all eukaryobc cells All have evolubonary descendants of mitochondria Cristae Folds of inner to increase surface area inner creates two compartments: inter space For H+ gradient of electron transport chain mitochondrial matrix For Krebs Cycle 2

3 Fig Inter space Outer Free ribosomes in the mitochondrial matrix Inner Cristae Matrix 0.1 µm Chloroplasts Chloroplast structure includes: Thylakoids membranous sacs, stacked to form a granum Stroma internal fluid Ribosomes Stroma Inner and outer s Granum Thylakoid 1 µm Peroxisomes Peroxisomes: Oxida9on Specialized metabolic compartments Bound by a single Oxygen used to break down different types of molecules H 2 O 2 by-product converted to water 3

4 Cytoskeleton Cytoskeleton network of protein fibers extending throughout the cytoplasm organizes the cell s structures and acbvibes anchors many organelles composed of three types of molecular structures: Microtubules Microfilaments Intermediate filaments Cytoskeleton: Support, Mo9lity, and Regula9on Cytoskeleton support the cell and maintain its shape motor proteins produce moblity PLAY vesicles can travel along monorails provided by the cytoskeleton Recent evidence suggests cytoskeleton may help regulate biochemical acbvibes Components of the Cytoskeleton Three main types of fibers make up the cytoskeleton: Microtubules thickest Intermediate filaments Medium sized diameter Microfilaments Thinnest also called acbn filaments 4

5 Centrosomes Microtubules and Cell Division Structure near nucleus from where microtubules grow a microtubule-organizing center In animal cells Centrosome Consists of two centrioles Centrioles Paired structures consisbng of nine triplets of microtubules arranged in a ring Centrioles Longitudinal section of one centriole Microtubules Microtubule 0.25 µm Cross section of the other centriole Most cells synthesize and secrete materials that are external to the plasma Extracellular Matrix These extracellular structures include: Cell walls of plants The extracellular matrix (ECM) of animal cells Intercellular juncbons cell wall Cell Walls of Plants extracellular structure disbnguishes plant cells from animal cells made of cellulose fibers embedded in other polysaccharides and protein protects the plant cell, maintains its shape, and prevents excessive uptake of water Prokaryotes, fungi, and a few probsts also have cell walls Bacteria - pepbdoglycan Fungi - chibn 5

6 The Extracellular Matrix (ECM) of Animal Cells Extracellular matrix (ECM) Animal cells lack cell walls but are covered by ECM made up of glycoproteins Collagen Proteoglycans fibronec9n Integrins Receptor proteins in the plasma to which ECM proteins bind FuncBons of the ECM: Extracellular Matrix Support Anchorage and separabon of different Bssues Adhesion Bind cells together within Bssues Movement Guide for cell migrabon in embryonic development RegulaBon PropagaBon of external sbmuli to nucleus Fig Collagen EXTRACELLULAR FLUID Proteoglycan complex Polysaccharide molecule Carbohydrates Fibronectin Core protein Integrins Plasma Proteoglycan molecule Proteoglycan complex Microfilaments CYTOPLASM 6

7 Intercellular Junc9ons Intercellular juncbons facilitate contact between neighboring cells in Bssues, organs, or organ systems adhere, interact, and communicate through direct physical contact Types Plasmodesmata Plants only Tight juncbons Desmosomes Gap juncbons Plasmodesmata in Plant Cells Plasmodesmata channels that perforate plant cell walls water and small solutes somebmes proteins and RNA can pass from cell to cell Plasma conbnuous from one cell to another Fig Interior of cell Cell walls Interior of cell 0.5 µm Plasmodesmata Plasma s 7

8 Tight Junc9ons, Desmosomes, and Gap Junc9ons 9ght junc9ons Leak-proof barrier Plasma s squeezed together DigesBve system Tight junctions prevent fluid from moving across a layer of cells Desmosomes anchoring juncbons fasten cells together into strong sheets rivets Tight junction Intermediate filaments Desmosome Gap junctions Gap junc9ons communicabng juncbons provide cytoplasmic channels between adjacent cells Space between cells Plasma s of adjacent cells Extracellular matrix You should now be able to: 1. DisBnguish between the following pairs of terms: magnificabon and resolubon; prokaryobc and eukaryobc cell; free and bound ribosomes; smooth and rough ER 2. Describe the structure and funcbon of the components of the endo system 3. Briefly explain the role of mitochondria, chloroplasts, and peroxisomes 4. Describe the funcbons of the cytoskeleton 5. Compare the structure and funcbons of microtubules, microfilaments, and intermediate filaments 6. Explain how the ultrastructure of cilia and flagella relate to their funcbons 7. Describe the structure of a plant cell wall 8. Describe the structure and roles of the extracellular matrix in animal cells 9. Describe four different intercellular juncbons 8