Chap 4

Chap 4

1. Chemical composition of cell

   • Cells are composed of elements
     • Substance composed of only 1 kind of atom which cannot be broken down into simpler substances by chemical reactions
     • 25 essential elements
       • Major elements
         • Most common
         • 96% mass of human body
         • C Carbon
         • O Oxygen
         • N Nitrogen
         • H Hydrogen
         • Large amounts bcos
           • Cell contains a high percentage of water
           • Most compounds in the cell consist of carbon
       • Remaining 4%
         • Ca Calcium
         • Na Sodium
         • K Potassium
         • P Phosphorus
         • S Sulphur
         • Cl Chlorine
         • Mg Magnesium
       • Trace elements
         • Cu Copper
         • Fe Iron
         • I Iodine
         • Less than 0.01% of body mass
         • Needed in small amounts, but critical in maintaining healthy cells
       • Most exist as ions
   • Compound
     • A substance consisting of 2 or more elements chemically combined in a fixed ratio
     • Organic compounds
       • Contains carbon & hydrogen
       • Carbohydrates
         • C,H,O
       • Proteins
         • C,H,O,N,S,P
       • Lipids
         • C,H,O
       • Nucleic acids
         • C,H,O,P,N
       • Most are synthesised by the cell itself
     • Inorganic compounds
       • Non-living matter & no carbon
       • Water
       • Acids
       • Bases
         • Ex: Soaps, cleaners
       • Mineral salts
       • Obtained from external environments
   • Functions of elements in animal & plant cells
     • Functions