Botany

• Functions of the plasma membrane

  • Compartmentalization
  • Scaffold for biochemical activities
  • Selectively permeable barrier
  • Transport
  • Response to external stimuli
  • Intercellular interaction
  • Energy transduction
• Ernest Overton (1890)

  Used plant root hairs into hundreds of different solutions containing diverse solute
• Ernest Overton's discovery

  The more lipid soluble the solute, the more rapidly it would enter the root hair cells
• Ernest Overton's conclusion


  The dissolving power of the outer boundary layer of the cell matched that of a fatty oil
• Gorter & Grendel (1925)


  First proposal of the idea that cell membrane is made up of a lipid bilayer

  
• Gorter & Grendel's experiment

  Extracted lipid from human erythrocyte and measured the amount it will take to cover the surface area of water with the actual ratio of 2:1
• Gorter & Grendel's conclusion

  The plasma membrane contained a bimolecular layer of lipids with the polar groups of each layer directed outward towards the aqueous environment
• Hugh Davson and James Danielli (1935)


  Plasma membrane was also lined on both its inner and outer surface by globular proteins, and the lipid bilayer was also penetrated by protein-lined pores which could provide and entrance and exit for polar solutes
• Sandwich model


  Phospholipid bilayer between two layers of protein with pores for molecules to travel through
• S. Jonathan Singer and Garth Nicholson (1972)


  They proposed the fluid mosaic model of the plasma membrane, where the bilayer is present in a fluid state and individual lipid molecules can move laterally, presenting a dynamic structure in which the components are mobile and capable of engaging in various types of interaction

  
• Chemical composition of the plasma membrane

  • Phospholipids (built on a glycerol backbone, amphipathic)
  • Phosphatidic acid (just phosphate group)
  • Sphingolipids (amphipathic, derivative of sphingosine)
  • Cholesterol (missing from most plant & all bacteria cell membranes, can influence activity of particular membrane proteins, physical state of membrane, role in health & disease, precursors for chemical messengers)
• Phospholipids


  • Most membrane phospholipids are built on a glycerol backbone (not triglycerides, but diglycerides), amphipathic character
• Sphingolipids


  • Amphipathic & similar in structure with phosphoglycerides, derivative of sphingosine (an amino alcohol that contains long a long hydrocarbon chain)
• Cholesterol


  • Smaller and less amphipathic, interfere with movement of phospholipid fatty acid tails
• Membrane proteins


  • Glycoproteins (play an important role in mediating interactions of cell with other cells & non-living environment, sorting of membrane proteins to different cell compartments)
  • Integral proteins (transmembrane proteins, as receptors, channels/transporters, agents that transfer electrons)
  • Peripheral proteins (weak electrostatic bonds, can usually be solubilized by extraction with aqueous salt solutions, located in cytosolic surface, forming a fibrillar network, provides mechanical support for the membrane, anchorage of integral proteins)
• What was the sandwich method proposed by Davson and Danielli?

  Hydrophilic zone, Hydrophobic zone, Hydrophilic zone
• Botany


  Greek word: Botane, meaning ‘grass’, ‘fodder’ or ‘pasture’
• Aspects of Botany


  • Physiology
  • Structure
  • Genetics
  • Ecology
  • Distribution
  • Classification
  • Economic importance
• Theophrastus is known as the "Father of Botany"
• Works by Theophrastus


  • Historia Plantarum
  • On the Causes of Plants
• Germination, cultivation, and propagation are key topics in Botany
• City of Alexandria was significant in the history of Botany
• Sheets of papyrus were used for anatomical, obstetric, surgical, and botanical illustrations in the third century B.C.
• De Materia Medica


  On Medical Material, a guidebook with 600 plants and around 1000 medicines derived from them
• Pedanius Dioscorides authored De Materia Medica
• During a brief period, the search for knowledge in Botany became stagnant
• The revival of learning during the European Renaissance renewed interest in plants
• Johannes van Helmont's experiment

  1. Measure uptake of water in a tree

  2. Disproved ancient Greek theory

  3. Plants gain mass by taking minerals from soil
• Johannes van Helmont's experiment

  1640
• Robert Hooke


  Coined the term ‘cell’ and published ‘Micrographia’
• Robert Hooke was the first to describe ‘living cells’ with his own microscope
• Anton van Leeuwenhoek's observations

  • Rainwater
  • Pondwater
  • Scrapings from his own teeth
• Animalcules


  Minute moving objects now referred to as protozoa, yeasts, and bacteria
• “Nullius in verba” means "Take nobody’s word for it"
• John Ray's Historia Plantarum became an important step toward modern taxonomy
• Rudolf Camerarius


  Established plant sexuality and authored De Sexu Plantarum Epistola
• Stephen Hales established plant physiology as a science
• Stephen Hales' published works

  • Vegetable Staticks
  • Experiments on nutrition and respiration of plants
• Carolus Linnaeus is known as the "Father of Taxonomy"
• Taxonomy


  Science of identification, nomenclature, description, and classification of organisms