IB SL Biology: Cells

Cell Theory
1. 1. All living organisms are composed of cells
  1. 2. Cells are the smallest unit of life
    1. 3. Cells come from pre-existing cells
2. Proof
  1. One sealed soup container: no decay
  2. Other open soup container: decay
  3. Bacteria in air
Multicellular organisms
1. Differentiation
  1. Cells specialise in different functions
    1. Genes needed to specialise
      1. Once specialised, cell is committed
2. Exhibits emergent properties
  1. More than sum of parts - complex interations
Unicellular
1. Single cell = all functions of life
  1. Amoeba
  2. Euglena
  3. Chlorella
Stem Cells
1. Retain ability to differentiate along different pathways
2. Small number of embryonic cells still retained by adult body
  1. Potential for tissue repair
    1. Cord blood for leukaemia
    2. Skin grafts
    3. Heart regeneration
    4. Therapeutic use: bone marrow transplant as a result of chemotherapy
Cell Size
1. SA:Vol ratio
  1. Smaller animals - poor
    1. Heat loss - big issue
  2. Bigger animals - good
  3. Lungs + gills
Prokaryotic Cells
1. "Before the nucleus"
2. Cell Wall
  1. Prevents damage
    1. Retains structure
3. Plasma Membrane
  1. Controls entry and exit of substances
4. Cytoplasm
  1. Site of biochemical reactions
5. Pili
  1. Hair-like structure
    1. Connect bacteria together
6. Flagella
  1. Propels cells
7. Ribosomes
  1. Synthesise proteins
    1. Translation of messenger RNA
      1. 70 S
8. Nucleoid
  1. Naked DNA
9. Binary fission
Eukaryotic Cells
1. Nucleus
  1. Stores genetic information
    1. Chromosomes
      1. Strands of DNA associated with protein
        4+
2. Mitochondria
  1. Carry out aerobic respiration
3. Lysosome
  1. Stores digestive enzymes
4. Rough endoplasmic reticulum
  1. Synthesises proteins for secretion from cell
5. Golgi Apparatus
  1. Processes proteins before secretion
6. Plasma Membrane
  1. Controls entry and exit of substances
7. Free ribosomes
  1. Synthesise proteins for use in the cytoplasm
    1. 80 S

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