Concise Notes on Cells

Early Earth Conditions

  • Violent conditions with volcanic eruptions, lightning, and storms.
  • Atmosphere contained gases like CO<em>2CO<em>2, CH</em>4CH</em>4, NH<em>3NH<em>3, and H</em>2H</em>2.
  • These conditions favored the production of simple organic molecules like purines, pyrimidines, sugars, and amino acids.

Properties of Molecules

  • Amino acids polymerize into proteins.
  • Purines and pyrimidines polymerize into polynucleotides.
  • Polynucleotides can guide the formation of copies of their own sequence through base pairing.

Cell Theory

  • Cells are the fundamental units of life.
  • All organisms are composed of cells.
  • All cells come from pre-existing cells.

Microscopy

  • Smallest visible object: 0.2 mm (200 µm).
  • Resolution: ability to distinguish objects.
  • Light Microscope resolution: 0.2 µm.
  • Electron Microscope resolution: 0.2 nm.

Cell Size

  • Limited by surface area-to-volume ratio.
  • Surface area: interface with the environment.
  • Volume: space inside the cell.
  • Increasing volume decreases the surface area: volume ratio.

Cell Diversity

  • Prokaryotic Cells: No nucleus or membrane-bound organelles.
  • Eukaryotic Cells: Membrane-enclosed nucleus and organelles.

Prokaryotic Cells - shared features

  • Cytoplasm
  • Ribosomes
  • Nucleoid
  • Plasma membrane

Prokaryotic Cell Wall

  • Maintains cell shape.
  • Most bacteria cell walls contain peptidoglycan.
  • Some have an outer layer of lipopolysaccharide and protein.

Mycoplasma

  • Bacteria that lack a cell wall

Prokaryotic cell Capsule

  • Polysaccharide layer enclosing the cell wall
  • Not necessary for survival

Prokaryotic Cells - Internal Membranes

  • Cyanobacteria have internal membranes for photosynthesis.

Prokaryotic Cells - Flagella

  • Locomotory structures shaped like corkscrews

Prokaryotic Cells - Pili

  • Threadlike structures for adhesion and genetic material exchange

Prokaryotic Cells - Helical structure

  • Helical structure is responsible for maintaining the structure of the cell
  • Divide by binary fission

Prokaryotic Cells - Shapes

  • Rod shaped ("Bacillus")
  • Spherical ("Cocci bacteria")
  • Spiral shaped ("Spirillia")

Prokaryotic Cells - Inclusions

  • Deposits of lipids, starch, or glycogen within the cytoplasm

Prokaryotic Cells - Endospores

  • Dormant, resistant structures within vegetative cells
  • Resistant to environmental stresses.