Lecture02.Plantcells.pdf

Unit 02.Plant Cells Prof. Ross D. Vasquez, PhD. AY 2023-2024 First Term  Content Topics Overview of Cells Membranes Basic Cell Types Plant Cells Fungal Cells Association of Cel...

Unit 02.Plant Cells Prof. Ross D. Vasquez, PhD. AY 2023-2024 First Term  Content Topics Overview of Cells Membranes Basic Cell Types Plant Cells Fungal Cells Association of Cells Unit 02.Plant Cells Cells: Concept basic structural and functional unit All living organisms are made up of cells Cells arise from preexisting cells Physiological processes are encountered and manifested at cellular level. e.g. respiration, digestion, growth and development. Cell Robert Hooke (1665) tiny compartments in cork tissue (cells) R. J. H. Dutrochet( 1824) osmosis, effect of light on plants Robert Brown (1833) nucleus, cytoplasmic streaming ( movt of cytosol and organelles), Brownian movt Matthias Schleiden (1838) Cofounder of cell theory, all plant parts are composed of cell Theodor Schwann (1839) cell theory Two basic types of cells 1. Prokaryote- cell without nucleus and other membrane bounded organelles e.g eubacteria, cyanobacteria and archaebacteria 2. Eukaryote – cell with nucleus and membrane bounded organelles. e. g. protists, fungi, plants, animals. * Animal cell- no cell wall, plastid, vacuole and glyoxysome  Membranes Cell Membranes or Plasmalemma Regulate passage of molecules in/out Divides cell into compartment Acts as surfaces w/c hold enzymes Exocytosis/ endocytosis Selectively permeable Dynamic and constantly changing As nature of membrane changes, nature of cell changes Fluid Mosaic Model: - As heterogenous memb, intrinsic proteins can diffuse laterally like lipids while other proteins are bound to adjacent proteins Composed of proteins (60%) and phospholipid bilayer (40%) All biological membranes are selectively or differentially permeable. Phospholipid bilayer: Small nonpolar molecules –gases, CO2, O2 Small uncharged polar molecules – H20, ethanol and urea Protein channel: Ions and charged molecules  Summary of Transmembrane Movement MEMBRANE TYPES Impermeable membrane Freely permeable membrane Selectively permeable TRANSMEMBRANE MOVEMENT Osmosis Facilitated Diffusion – hydrophilic, charges molecules Active transport – ATP expenditure Exocytosis Endocytosis  Selectively permeable Hydrophobic subs – cross membrane (oils, fats, greasy substances- simple diffusion) Charged substances – move through intrinsic proteins which act as channel (facilitated diffusion) Molecular pumps (protein) – bind molecule from 1 side and release it to the other using ATP ( Active Transport) A plant cell consists of three general parts: 1. Cell wall 2. Protoplast 3. Cell inclusion  Cell wall Protects the cellular contents and limits cell size Composed of cellulose (a polymer made up of molecules of the sugar, glucose is the most important Other important are lignins (sec. wall) which add rigidity, and waxes such as cutin (epidermis) and suberin (phellem or cork cells) which reduce water loss from cells.  Review: Cell wall All plant cells have cell walls except _______ of some seed plant Cellulose crystallized to form strong ________. Hemicellulose Produced by ________ (organelle), brought to cell wall by dictyosome vesicles. Primary cell wall is usually ______. (thin or thick?) Secondary cell wall- bet the primary cell wall and plasma membrane Thicker, impregnated with _______ The cell wall (types) are permanent not degraded nor depolymerized unlike microtubule/ microfilament _______ – made of pectin, attaches the wall to adjacent cell Plasmodesmata fine holes in primary walls, has plasma membrane, tubule (desmostubule) attached to ER Primary Pit Field – area w/ clustered plasmodesmata, increase transport of materials bet. Cells “All protoplasm w/in a plant is part of 1 interconnected mass called symplast” “Individuality of plant cell is diminished’’ Plant = symplast (Protoplasm)+ apoplast (intercellular space + wall) Apoplast – permits rapid diffusion of gases Cytoplasm- fluid portion containing the nucleus and the rest of the organelles; material left after the removal of nucleus and vacuole Nucleus more genetic material than prokaryotes plasmid. Histones with the deoxyribonucleic acid (DNA) to pack the genetic material into compact chromosomes. Nuclear envelope formed of a double membrane. The fluid portion is nucleoplasm (karyoplasm or karyolymph. The nucleolus synthesize RNA. The pores are called nuclear pores, for transport of substances fr nucleus to protoplasm Polysomes = ribosomes + mRNA Nucleoplasm Ass. Of DNA, enzymes, histones, RNA, water Chromatin = DNA + histone Nucleus & nucleoplasm are different in diff. ages of cell. Why? 1. Rapidly div cell= more DNA; 2. young cell = small w/ large nuclei 3. Mature cells = large with small nucleus  Endoplasmic reticulum (ER) Carries large mol like protein (not transported by diffusion) Syst of narrow tubes and sheets of membrane w/c form a network throughout the cytoplasm Rough ER – attached to ribosome Protein produced as storage product like legumes; remains in ER Protein to be secreted ( mucilage, nectar); detach, move to plasma memb, fuse with it and release its contents by exocytosis Smooth ER Lipid synthesis, membrane assembly Abundant in cells w/c prod large amt of fatty acids Cutin/ wax on epidermal cells, oil (palm , coconut, fragrances)  Dictyosomes Modifies material secreted by cell ( protein modification), ex.. Addtn of sugar to protein == glycoprotein Stacks of thin vesicles held together by flat/ curved array 2 faces: Forming face – where vesicles accumulate, embedded Maturing face – where vesicles are released, contents have been processed GOLGI Body Association of hundreds of dictyosmes Cisternae – stacks of wide thin flattened vesicle formed by ER vesicles w/c accumulated & fused together at 1 side of dictyosome.  Mitochondrion Cell respiration Circular DNA lacks histones, small ribosomes Respiration is mediated by enzymes bound to mitochondrial membrane Cristae- large sheets/ tubes formed by folded inner mitochondrial membrane Inner Mitochondrial mem- sel. Permeable; with pumps/ channels provides room for large # of enzymes Matrix – liq, where rxn takes place  Chloroplast Outer memb Inner memb, highly folded Stroma – inner fluid Ribosomes Circular DNA, not ass w/ histones Folding of Inner membrane forms:inc surface area, inc space for pigments insertion Thylakoid- single memb forming stacks of flattened vesicles called grana Sel. Permeable; conc of chem inside is diff from the stroma Leaf chloroplastids Grana – surrounded by liquid stroma Photosynthesis: Light reaction takes place in the grana CO2 is converted into CHO in the stroma  Leucoplastids – colorless plastids Amyloplast – stores starch. Aleuroneplast- stores protein Elaioplast – stores oils and fats; in tissues grown w/o light Leucoplastids – colorless plastids chromoplastids – colored plastids STORAGE PRODUCTS: Sugar is polymerized to starch grains inside chloroplast) Root, bark, wood (cant photosyn) Proplastid ---amyloplast ( store starch) Potato, yam, squash, starchy seeds STORAGE PRODUCTS: Highly colored chromoplast, produced from thylakoid when chloroplast produces high amt of colored lipids Fe – stored attached to protein (phytoferritin) in plastids (aleuroneplast or proteinoplast)  RNA- Ribonucleic acid Coding, decoding, regulation, expression of genes Microbodies are about 0.5 to 1.5 micrometer in diametes 2 types 1. Peroxisomes 2. Glyoxysomes Which is true about the cytosol? a. Aka hyaloplasm b. Clear substance composed of water, enzymes, chem. Precursors, reaction products in cytoplasm c. Has free ribosomes ( not attached to ER), skeletal structures ( microtubule, microfilaments) Cytoskeleton Network of fibers through out the cytoplasm Aids in cellular support and movement Composed of three components 1. Microtubules – 20 to 25 nm in diameter (alpha and beta tubulin) 2. Intermediate filaments (fibrous protein) 3. Microfilament – 3 t o 6 nm in diameter (g-actin) Flagella and cilia Elaborate microtubule arrangement in flagella and cilia Outer doublets ( has 2 arms of protein called Dynein) Sliding of 1 set of doublet cause the bending, alternate sliding ( beating motion) “9+2” arrangement Cilia – short, occur in grps Flagella – longer, in pair, single or in four Centrioles in animal cells only Centrioles in all animal cells and some fungal cells are associated with the formation of spindle fibers during cell interphase. Spindle fibers move the chromosomes during cell division. Vacuole Cont H20, salts and digestive enzymes Derived from small cavities scattered in the cytoplasm Cell sap (vacuolar sap),enclosed by the tonoplast ( vacuolar memb)- prevents leaking of waste back to cytoplasm Anthocyanin ( water sol pigment) In animal: Lysosome Functions 1. Maintain turgor pressure 2. Storage area for nutrients like K 3. Accumulation of toxic substances Vacuole Ergastic substances 1. crystals a. calcium carbonate b. calcium oxalate 2. starch and aleurone grains 3. nitrogenous inclusions – crystalloids or protein crystals 4. Granules / fibrous mat Calcium regulates activity of enzymes Plant cells regulate Ca conc in protoplasm by moving Ca into vacuole where it forms Ca oxalate crystals Crystals (CaC2O4) Raphides/ idioblast (gabi) Styloid (water hyacinth) Rosette (santan pula) Prismatic (Tradescantia spathacea ) Crystals (CaCO3) Cystolith – balete (Ficus) Crystal protect plants from animals Flower cells Petal cell – pigment attraction Scent cell- fragrance Nectary cell – sugar, attraction Stamen cell – indirectly involved in sperm cell prodtn Carpal cell (ovule) – egg cell Fruit cell – sugar, aroma, attraction of fruit eating animals Other types of cells Thank you for listening! Prepared by: Ross D. Vasquez, Ph.D.