PLANT CELLS

• A cell is the smallest unit that can carry on all of the processes of life

  
• Early scientists that led to the Cell Theory:

  • Anton Van Leeuwenhoek (1600s) developed the 1st mini microscope and observed pond water
  • Robert Hooke coined the term "cell" when he looked at slices of cork and dead plant cells
  • Robert Brown (1833) observed the nucleus
  • Matthias Schleiden (1838) stated all plants are made of cells
  • Theodor Schwann (1839) discovered all animals are made of cells
  • Rudolph Virchow (1855) stated all cells come from the division of preexisting cells
• Cell Theory:

  • All living things are composed of cells
  • Cells are the basic units of structure and function in living things
  • All cells come from pre-existing cells
• Characteristics that all living things share:

  • Consist of organized parts (cells)
  • Obtain energy from their surroundings
  • Perform chemical reactions
  • Change with time (evolution)
  • Respond to their environments
  • Reproduce
  • Maintain constant internal environment (homeostasis)
  • Share a common history
• Relationship between a cell's shape and its function:

  • Diversity of shapes reflects diversity of functions
  • Cell shape evolved to allow the cell to perform its function effectively
• Factors limiting the size most cells can obtain:

  • Limited by the relationship of the cell's outer surface area to its volume
  • Most cells range from 10-100µm
• Structurally speaking, cells can be Prokaryotes or Eukaryotes:

  • Prokaryotes have no nucleus, while Eukaryotes have a nucleus and organelles
• Parts of a Plant Cell:

  • Cell Wall, Plasma Membrane, Cytoplasm, Mitochondria, Dictyosomes, Endoplasmic Reticulum, Ribosomes, Microbodies, Plastids, Cytoskeleton, Vacuoles, Nucleus
• Cell Wall:

  - lies outside the cell membrane

  - made of fibers of cellulose (plants)

  - very porous

  - helps to protect and support the cell

  - gives rectangular shape to plant cells

  • Only in plants, bacteria, and fungi
  • Made of fibers of cellulose
  • Functions to protect and support the cell

  
• Cell Membrane:

  >Phospholipid bilayer: hydrophilic heads (water loving), hydrophobic tails (water fearing)- >Contains lipids, proteins (channels), and carbohydrate chains (identification cards)

  • Regulates what enters and leaves the cell
  • Contains lipids, proteins, and carbohydrate chains
  • Acts as a barrier between the cell and its environment

  
• Mitochondria:

  Double membrane: Cristae – inner folds, increase surface area

  Outer membrane for protection of organelle

  • Known as the "Powerhouse" of the cell
  • Produces ATP (cell energy) through cellular respiration
• Dictyosomes (Golgi bodies):

  Disk-shaped sacs that are stacked-up together in a flat or cup-shaped array close to ER.

  • Produce secretory vesicles for export or repair within the cell
• Endoplasmic Reticulum:

  -network of flattened sacs.

  -can be rough (with ribosomes) or smooth (without ribosomes)

  • Rough ER has ribosomes and is involved in protein synthesis
  • Smooth ER is involved in lipid synthesis
• Ribosomes:

  - little “dots”

  - small (25 nm) ball like structure

  - found free floating in cytoplasm or attached to rough ER

  - composed of RNA and protein

  • Synthesis of proteins in the cell
• Microbodies:

  Numerous spherical bodies about 0.5-1.5 µm in diameter

  • Include glyoxysomes and peroxisomes, isolating reactions involving hydrogen peroxide
• Plastids:

  Always have inner and outer membranes and an inner fluid called stroma

  • Include chromoplasts and leucoplasts, aiding in photosynthesis
• Cytoskeleton:

  • Maintains cell shape and provides internal support through microtubules, intermediate filaments, and microfilaments
• Vacuole:

  Pressure system for plants, prevents wilting.

  • Stores water, salts, proteins, and waste products in plants
• Nucleus:

  • Control center of the cell, containing the nuclear envelope, nucleoplasm, chromatin, and nucleolus
• components of cytosekeleton (in order)

  >microtubules >intermediate filament >microfilament