Water and Ions

• Hydrogen Carbonate?

  Natural Buffer

  
• Phosphate?

  1. Phospholipids in cell membranes2. Nucleic Acids3. Adenosine Triphosphate (ATP)
• Nitrate?

  1. Amino Acids2. Nucleic Acids (DNA and RNA)3. Chlorophyll

  
• Potassium?

  Function of neurones (nerve cells)

  
• Magnesium?

  1. Chlorophyll

  
• Iron?

  1. Heamoglobin2. Electron carriers in respiration.

  
• Calcium in animals?

  1. Bones and Teeth2. Blood Clotting3. Muscle Contraction

  
• Calcium in plants?

  Form calcium pectate, middle lamella of plant cell walls.

  
• What is an ion?

  Atoms that have lost or gained electrons and so have a positive or negative charge.
• Examples of buffers

  1. Hydrogencarbonate ions2. Albumin (blood protein)3. Haemoglobin (blood protein)
• What are buffers?

  Chemicals that resist changes to pH (keep pH constant)
• Why does pH need to be kept constant in the body?

  Proteins are very sensitive to pH.Enzymes, hormones etc..are made of protein.Proteins have a very specific 3D shape that needs to be maintained.If the pH does not suit the protein this shape changes and the protein will not function.

  
• Hydrophobic?

  Water hating molecules that will not dissolve in water.

  
• Hydrophilic?

  Water loving molecules that will dissolve in water.

  
• 2 reasons why water is a valuable solvent.

  1. Cell reactions take place in an aqueous (watery) solution.2. Helps with transport around organisms.
• What percentage of cells is made of water?

  50-90%
• Why is water an excellent solvent?

  Solvents dissolve a wide range of substances.Polar (charged) molecules like glucose and amino acids dissolve in water as the polar water molecules form clusters around them.

  
• What are Hydrogen bonds and why do they form in water?

  Hydrogen bonds are the attraction between the negative Oxygen of one water molecule and the positive Hydrogen of another water molecule.

  
• Why is water polar?

  In H₂O there is an uneven distribution of charge and Hydrogen has a slightly positive charge and Oxygen has a slightly negative charge.

  
• Where does most Hydrogen and Oxygen exist in living organisms?

  Exists as water

  
• What are the three most abundant elements in living organisms?


  1. Carbon2. Hydrogen3. Oxygen