IB SL Biology: Cells

IB SL Biology: Cells

1. Cell Theory

   • 1. All living organisms are composed of cells
     • 2. Cells are the smallest unit of life
       • 3. Cells come from pre-existing cells
   • Proof
     • One sealed soup container: no decay
     • Other open soup container: decay
     • Bacteria in air

2. Multicellular organisms

   • Differentiation
     • Cells specialise in different functions
       • Genes needed to specialise
         • Once specialised, cell is committed
   • Exhibits emergent properties
     • More than sum of parts - complex interations

3. Unicellular

   • Single cell = all functions of life
     • Amoeba
     • Euglena
     • Chlorella

4. Stem Cells

   • Retain ability to differentiate along different pathways
   • Small number of embryonic cells still retained by adult body
     • Potential for tissue repair
       • Cord blood for leukaemia
       • Skin grafts
       • Heart regeneration
       • Therapeutic use: bone marrow transplant as a result of chemotherapy

5. Cell Size

   • SA:Vol ratio
     • Smaller animals - poor
       • Heat loss - big issue
     • Bigger animals - good
     • Lungs + gills

6. Prokaryotic Cells

   • "Before the nucleus"
   • Cell Wall
     • Prevents damage
       • Retains structure
   • Plasma Membrane
     • Controls entry and exit of substances
   • Cytoplasm
     • Site of biochemical reactions
   • Pili
     • Hair-like structure
       • Connect bacteria together
   • Flagella
     • Propels cells
   • Ribosomes
     • Synthesise proteins
       • Translation of messenger RNA
         • 70 S
   • Nucleoid
     • Naked DNA
   • Binary fission

7. Eukaryotic Cells

   • Nucleus
     • Stores genetic information
       • Chromosomes
         • Strands of DNA associated with protein
           • 4+
   • Mitochondria
     • Carry out aerobic respiration
   • Lysosome
     • Stores digestive enzymes
   • Rough endoplasmic reticulum
     • Synthesises proteins for secretion from cell
   • Golgi Apparatus
     • Processes proteins before secretion
   • Plasma Membrane
     • Controls entry and exit of substances
   • Free ribosomes
     • Synthesise proteins for use in the cytoplasm
       • 80 S