1 - Plant Cells and Tissues

• Components of All Cells:

  • Plasma Membrane
  • Cytoplasm
  • DNA
  • Nuclear Envelope
  • Chromatin and Chromosomes
  • Nucleolus
  • Ribosomes
• Components Unique to Eukaryotic Cells:

  • Endomembrane System
  • Endoplasmic Reticulum
  • Vesicles
  • Golgi Apparatus
  • Cytoskeleton
  • Mitochondria
  • Peroxisomes
• Components Unique to Plant Cells:

  • Cell Wall
  • Central Vacuole
  • Plastids
• Cell Wall:

  • Found in prokaryotes, fungi, and plants
  • Composed of cellulose
  • Rigid for structural support and cell shape
  • Middle lamella cements cells together
  • Types: Primary (thin) and Secondary (more rigid, developed, present in adult cells)
• Plasma Membrane:

  • Comprised of gel-like cytosol, cytoskeleton, and various chemicals
  • Fluid mosaic model
  • Hydrophilic head (phosphate group) and hydrophobic tail (fatty acids)
  • Contains proteins, simple sugars, amino acids, nucleic acids, and ions
  • Functions in protein synthesis and metabolic reactions
• Nucleus:

  • Contains DNA, the blueprint of the cell
  • Directs synthesis of ribosomes and proteins
  • Stores chromosomes in nucleoplasm
  • Parts include Nuclear Envelope, Nucleoplasm, Chromosomes, Chromatin, and Nucleolus
• Endoplasmic Reticulum:

  • Series of interconnected membranous sacs and tubules
  • Rough ER for protein synthesis, Smooth ER for lipid synthesis and membrane assembly
• Golgi Apparatus:

  • Sorts, tags, processes, and packages proteins and lipids
  • Acts as an assembly factory and is involved in cell wall formation
• Central Vacuole:

  • Regulates cell's water concentration for turgidity
  • Stores nutrients, wastes, and ions
  • Plays a role in cell expansion and osmosis
• Mitochondrion:

  • Powerhouse of the cell for energy conversion
  • Contains own DNA and ribosomes
  • Produces ATP using oxygen and producing carbon dioxide
• Chloroplast:

  • Types include Chromoplast and Leucoplast
  • Contains stroma, granum/grana, and thylakoid membrane for photosynthesis
• Microbodies:

  • Types include Peroxisomes and Glyoxisomes for oxidation and breakdown of fatty acids and amino acids
• Cytoskeleton:

  • Includes Microtubules, Microfilaments, and Intermediate filaments for cell division, organelle movement, and cell structure
• Plasmodesmata:

  • Extensions of plasma membrane connecting adjacent cells for transport
• Cell Types:

  • Parenchyma, Collenchyma, Sclerenchyma with different characteristics and functions
• Plant Tissues:

  • Simple tissue (1 type) and Complex tissue (more than one type)
  • Tissue systems: Ground, Dermal, Vascular
• Simple Tissues:

  • Parenchyma: most common, support, thin primary walls, abundant intercellular spaces, ability to divide
• In multicellular organisms, the distance for substances to enter cells is larger due to a higher surface area to volume ratio
• Multicellular organisms require specialised exchange surfaces for efficient gas exchange of carbon dioxide and oxygen
• The endodermis is the last layer before vascular tissue, found only in roots, responsible for the transport of water and solutes
• Transport mechanisms in plants include the Casparian strip, apoplastic route, symplastic route, transfer cells, and sieve elements
• Collenchyma provides support for young plants, is located beneath the epidermis, and has axially elongated cells with irregularly thickened primary walls
• Sclerenchyma provides support for mature plants with thickened secondary walls, is dead at maturity, and includes fiber and sclereid types like brachysclereids, macrosclereids, osteosclereids, trichosclereids, and filiform sclereids
• Xylem, a vascular tissue, transports water and minerals towards the inside/center of plants and includes tracheary elements like tracheids and vessel elements
• Tracheids are the main conducting cells in gymnosperms and primitive plants, have only pit pairs, no perforations, and end walls that are open with slits
• Vessel elements are major conduits of water in angiosperms, have perforations, are stuck end-to-end with pits connected, and allow direct water flow
• Phloem, another vascular tissue, transports food and sugar towards the epidermis and includes sieve elements like sieve-tube elements and sieve cells
• Sieve-tube elements are found in angiosperms, have sieve plates with companion cells, while sieve cells are in gymnosperms without sieve plates but with albuminous cells or Strasburger cells
• Secretory structures in plants include external structures like salt glands, hydathodes, nectaries, colleters, osmophores, and glandular trichomes
• Salt glands in halophytes secrete ions to regulate salt content, while hydathodes discharge liquid water with various substances from leaf tips or margins
• Nectaries release aqueous fluid with high sugar content, with floral nectaries for pollination and extrafloral nectaries for protection against herbivores
• Colleters produce sticky secretions for protection of meristem and young differentiating cells, with types like A, B, C, and D
• Glandular trichomes release lipophilic substances like terpenoids, fats, waxes, and essential oils, found on hairy leaves in plants
• Internal secretory structures in plants include oil cells, mucilage cells, resin ducts, kino veins, and laticifers, each with specific functions and characteristics
• Kino veins form frequently in the wood of the genus Eucalyptus which is a response to wounding or fungal infection