Plant Cell Organelles PDF

Organelles That Are Different in Plants and Animals I. Plant organelles II. Animal organelles Organelles that are the same in plants and animals This is a review from your Introductory Biology Course. Please review Chapter 4and 5 in Raven (test your knowledge using Table 4.2 on page 81)....

Organelles That Are Different in Plants and Animals I. Plant organelles II. Animal organelles Organelles that are the same in plants and animals This is a review from your Introductory Biology Course. Please review Chapter 4and 5 in Raven (test your knowledge using Table 4.2 on page 81). It is your responsibility to know and understand the structure and function of the following 1. Plasma Membrane 2. Cytoplasm 3. Nucleus Nuclear envelope including continuity with endoplasmic reticulum Nuclear pores Nuclear lamina Chromatin including DNA and Histones Nucleolus 4. Ribosomes 5. The Endomembrane System Endoplasmic Reticulum—Rough endoplasmic reticulum and smooth endoplasmic reticulum Golgi apparatus Secretory vesicles and endosomes Lysosomes (sometimes called lytic vacuoles in plants) 6. Lipid droplets 7. Microbodies---Peroxisome, Glyoxisomes 8. Double membrane organelles---Mitochondria 9. The cytoskeleton Actin filaments (mircro0filaments) Intermediate filaments Microtubules (tubulin) and microtubule organizing center 10. Cell surface extension Flagella 11. Cytoskeleton of microtubules and microfilaments I. Unique Organelles of the Plant Cell The Cell Wall  The Cell Wall Never found in animals Lies outside the plasma membrane Composed of cellulose and polymers that add rigidity and strength Two types of cell walls Primary Cell Wall Secondary Cell Wall The cell wall is composed of polysaccharides and proteins Cell wall polysaccharides are classified into four groups Cellulose Hemicellulose Pectins Glycans Cellulose Is the major fibrillary component Polymer of β(1,4) glucose  Found in disaccharides, glycogen, starch Found in Cellulose 1,4 α glycosidic bonds are formed when the OH on the carbon-1 is below the glucose ring; while 1,4 β glycosidic bonds are formed when the OH is above the plane Unlike other matrix macromolecules that are ER/Golgi derived cellulose is synthesized by a plasma membrane Cellulose is synthesized by cellulose synthase, plasma membrane-embedded enzymes Cellulose synthase is embedded in the plasma membrane Is a rosette like structure of 6 subunits The synthesis of cellulose does not occur via the ER and Golgi  18 unbranched, parallel chains of β (1,4) glucose pack tightly together by extensive H bonding to form a macrofibril that becomes coated in glucan that also hydrogen bond with each other Microfibrils are insoluble in water and have a high tensile strength 24 to 36 parallel microfibrils pack together to form a macrofibril Hemicellulose Β(1,4) glucose backbone with a heterogeneous group of attached polysaccharides that bind to the surface of cellulose in order to link the microfibrils into a network Synthesize in RER and Golgi and secreted in vesicles Together with pectins makes up the matrix polysaccharides Pectins Soluble fiber Principal chemical component of pectin is galacturonic acid -a sugar acid derived from galactose Form a gel in which cellulose is embedded Forms interlocking matrix that controls spacing of macrofibrils and porosity Provides the cell wall with the ability to resist compression Glycans Polysaccharides consisting of many monosaccharides linked glycosidically increase the tensile strength of the cellulose Run parallel to the cellulose macrofibrils Primary Cell Wall Usually less than 1µm Characteristic of young growing cells The main chemical components of the primary plant cell wall include cellulose in the form of organized microfibrils Microfibrils crisscross The cell wall contains two groups of branched polysaccharides, the pectins (provides the cell wall with the ability to resist compression) and cross-linking glycans  The primary cell wall is rich in pectins with smaller amounts of cellulose and hemicellulose Enables the cell to elongate more easily-primary cell wall expansion extended by Physical forms generated from turgor pressure within central vacuole creating an outward directed force Acid induce loosening of the cell wall H+-ATPase in the plasma membrane release H+ that loosen the non-covalent adhesions between wall polysaccharides  The Secondary Cell Wall Deposited on the inner surface of the primary cell wall Thicker and stronger than the primary cell wall because lignin replace much of the pectins Lignin is a group of polymers of aromatic alcohols that are hard and impart considerable strength to the structure of the secondary wall. Highly cross-linked Lignin also makes plant cell walls less vulnerable to attack by fungi The Middle Lamella Shared by neighboring cells and cements them firmly together. Associated with the primary cell wall Punctuated by communicating junctions-plasmodesmata, that penetrate the middle lamella as well as the primary Middle lamellae between 2 cells needed and secondary cell walls, providing pathways for transporting cytoplasmic molecules from one cell to another. The cell wall of mature plant cells is composed of a primary cell wall, a middle lamellae, and a secondary cell wall Plasmodesma Junctional complexes between ta adjacent cells Penetrate middle lamellae, primary cell wall and secondary cell wall Membrane lined channel fill with cytoplasm and a central membrane rod derived from the ER--desmotubule Allows free movement of molecules between neighboring cells Cytokinesis The separation of the daughter cells by the reformation of plasma membrane for each daughter cell and the formation of a cell plate Cell plate is a wall-like structure that separates new daughter cells At telophase of mitosis a network of microtubules and F actin form a phragmoplast where cytokinesis will take place In the phragmoplast the microtubules are aligned with the –end toward the chromosomes at the poles and the + end toward the mid-zone  Microtubule Organizing Center Microtubule nucleation and initiation occur at a microtubule organizing center (MTOC) Made of a multi-protein complex containing γ-tubulin Does not contain centrioles The Endomembrane System The endomembrane system Plays a role in secretory processes, membrane recycling, cell cycle and storage Set of internal membranes continuous with the outer nuclear membrane and associated with the plasma membrane Composed of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, vacuoles, vesicles, lysosomes/lytic vacuoles, endosomes and the plasma membrane The plasm membrane regulates transport into and out of the cell Endosomes are vesicles derived from endocytosis of the plasma membrane that process or recycle the contents Also derived from the endomembrane system Oil bodies, protein bodies, peroxisomes, and glyoxysomes Vacuoles Membrane enclosed organelles containing vacuolar sap-water, inorganic ions, sugars, organic acids, and pigments brought in by specific membrane transporters-instead of cytoplasm Vacuolar membrane or tonoplast contains proteins and lipids that were synthesized in the ER and processed in the Golgi Central vacuole Central Vacuole Large membrane bound (tonoplast) vacuole Stores proteins, pigments and waste material Have water channels that maintain the tonicity of the cell Plants grow by expanding the central vacuole creating a physical force that pushes outward  Lytic vacuoles/lysosomes Heterogeneous morphology Involved in protein trafficking, membrane recycling, and protein digestion Protein bodies are derived from lysosome Larger and less numerous than in animals Contain hydrolytic enzymes- hydrolases  Oil bodies-store triglycerides Surrounded by a lipid monolayer Protein bodies-store proteins especially in seeds Peroxisomes, and Glyoxysomes Peroxisomes Contains enzymes that oxidize organic substrates to water Reactions first generate hydrogen peroxide (H2O2) Most plants have 2 types of peroxisomes One type in leaves where they participate in photorespiration Photorespiration occurs in the Calvin cycle when Rubisco uses oxygen instead of carbon dioxide to produce 1 molecule of 3 phosphoglycerate and 1 molecule of a 2 carbon phosphoglycerate (with CO2 yield would be 2 molecules of 3 phosphoglycerate-a 3 carbon compound). Enzymes in peroxisomes can oxidize 2-phosphoglycerate to glycine. One type in germinating seeds where they convert fatty acids into sugars-glyoxysomes Glyoxysome A type of peroxisome Found in oil rich storage organs of the seed Oxidize fatty acids to sugars Independently Dividing Semiautonomous Organelles Mitochondria Plastids Chloroplasts Plastids In plastids the lipid composition is almost entirely glycosylglycerides In plants and animals the most prominent lipid in the plasma membrane are phospholipids Types Chloroplasts-have a high concentration of carotenoids-yellow, red and orange pigments Leucoplasts- non-pigmented, specialized secretory tissue One type is the amyloplast-starch storage abundant in shoots and roots In the root specialized leucoplasts serve as gravity sensors that direct root growth downward In secretory tissues make volatile molecules that Chloroplasts Sites of photosynthesis Have three membranes Outer chloroplast membrane Inner chloroplast membrane Thylakoid membranes Proteins and chlorophyll and carotenoids for photosynthesis are embedded in the thylakoid membranes Stacks of thylakoids from grana Adjacent grana are connected by unstacked membranes called stromal lamellae The fluid filled compartment inside the thylakoid  Like mitochondria chloroplast divide by nuclear fission Flagella A circular array of nine fused pairs of microtubules , doublets, surrounding two central single microtubules, singlets. 9+2 axonemal structure Originate from a basal body- a structure with a similar structure to centrioles The only motile cells produced in land plants are male gametes, sperm Non-seed plants (ferns and mosses), Ginkos, and Cycads have flagellated sperm but other gymnosperms (ex pines) and flowering plants do not flagellated sperm travel through the water to reach another plant's egg. Organelles Unique to Animal Cells Extracellular matrix Collagen. Elastin, Fibronectin, and laminin fibers embedded into proteoglycans (core proteins that are covalently attached to glycosaminoglycan groups)  Centrioles Paired cylindrical organelles composed of the protein tubulin Nine sets pf microtubule triplets Pair sit at right angles to each other Self replicating In with cilia or flagella, basal bodies, have the same structure form as centrioles Often associated with the Centrosome A microtubule organizing center associated with centrioles The centrosome is composed of two centrioles, connected by interconnecting fibers and surrounded by the pericentriolar material (PCM). Microtubules are nucleated from the PCM and the appendages of the maternal centriole. Cilia and flagella Organelle of movement A circular array of nine fused pairs of microtubules , doublets, surrounding two central single microtubules, singlets. 9+2 axonemal structure Originate from a basal body (same structure as centriole) Cilia are shorter and more numerous than flagella.  Difference Between Cilia And Flagella Cilia Flagella The number of cilia is comparatively more The number of flagella is comparatively less (typically ranges in the thousands) (usually ranges from 1 to 8) Cilia are usually shorter in length Flagella are comparatively longer in length The beating pattern of cilia is very The beating pattern of flagella whip-loike complicated – It can move in a wide range motion of motions Flagella are of three types: bacterial Cilia are of two types: non-motile (in flagella, archaeal flagella and eukaryotic sernory organs ) cilia and motile cilia flagella Intermediate Filaments Tough, fibrous filaments 8-10nm in diameter network in the cytoplasm extending from a ring surrounding the nucleus to the plasma membrane Various types of intermediate filaments based on the proteins-ex. vimentin, keratin, neurofilaments, lamins Not present in plants Function of intermediate filaments Creates cell cohesion and prevent the acute fracture of cell sheets under tension because they are flexible and resistant. Allows cells to adhere to the extracellular matrix. Providing structure for internal organelles, and other cytoskeletal elements integrating them together Involved in the establishment of cell shape Cell Junctions Nuclear Lamina composed of intermediate filaments-lamins- and membrane associated proteins. In plants other proteins replace the lamins Tight junctions Protein complex between 2 cells that creates a seal to prevent leakage of material between the cells--paracellular permeability in vertebrates only made of proteins plasma membrane protein family of claudins associated with adapter proteins and actin Adherens junctions Interact with actin cytoskeleton and cadherins to support cell- cell adhesion Desmosomes Adhesive junctions Formed by superfamily of cadherin proteins association with the PM and adapter proteins with intermediate filaments Gap junctions Communicating junctions Made of 6 connexon proteins that form a pore in on cell and connect with a similar set in an adjacent cell Focal Adhesions Focal adhesions interact with integrins and actin filaments to promote adhesion between cells and the extracellular matrix Hemidesmosomes Associated with integrins that interact with intermediate filaments to anchor the cell to the cellular extra cellular matrix