Everything

Inorganic ions

Cations

Ions with positive charge.

• Calcium

  • Nerve impulse transmission

  • Muscle Contraction

  • Cofactor for enzymes

• Sodium

  • Generating nerve impulses

  • Muscle contraction

  • Co transport of glucose and amino acid

• Potassium

  • generating nerve impulses

  • Muscle contraction

  • Regulation fluid balance

• Hydrogen

  • Determines the pH of solutions

  • Used in photosynthesis reactions

• Ammonium

  • Source of nitrogen for plants

• Iron

  • Bind to oxygen within Haemoglobin

Anions

Ions with negative charge

• Chloride

  • Maintains blood pH in gas exchange

  • Cofactor for amylase enzyme

• Phosphate

  • Component of nucleotides and phospholipids

  • Bonds store energy in ATP

• Hydroxide

  • Determines the pH of solutions

• Nitrate

  • Source of Nitrogen

• Hydrogencarbonate

  • Maintains blood pH

Water

Structure

• Made up of one oxygen atom and two hydrogen atoms

  • Held together rby 2 covalent bonds

• Dipolar molecule

  • Oxygen is slightly negative

  • Hydrogen is slightly positive

• The partially positive hygen end of one water molecule attracts towards the partially negative oxygen end of another molecule.

  • This force of attraction is known as a hydrogen bond

Roles of water

• Solvent

  • Many substances dissolve in water

  • When an ionic compound is added to water the ions are spilt apart

    • The positive ions are attracted to the slightly negative oxygens

    • The negative ions are attracted to the slightly positive oxygens

  • Most biological reactions take place in solution

  • Dissolved substances can be transported around the body

• Temperature control

  • Water can buffer sudden temperature changes

  • High Specific heat capacity which means a lot of energy is needed to raise the temperature of 1g of water by 1°C.

    • Means that it is resistant to rapid changes in temperature

    • As many organisms are made up of water this allows the body to remain at a fairly stable temperature

  • The various hydrogen bonds between water molecules can absorb a lot of energy before being broken, so it takes a lot of energy to break the hydrogen bonds and heat the water.

• Cooling mechanism

  • Mammals use the evaporation of water in sweat to cool the skin

  • High latent heat of vapourisation caused by hydrogen bonding between water molecule also means that a lot of energy is needed to evaporate 1g of water.

  • This is useful of organisms because they cna use evaporation water as a method of cooling without losing too much water. When water evaporates from the surface of the skin it takes heat energy away from the surface cooling organsim down.

• Habitats

  • Many organisms can survive and reproduce in water

  • Creates a stable environment as it has a high specific heat capacity and high latent heat of vapourisation

  • At low temperatures water freezes to from ice

    • water molecules are held further apart in ice making it less dense than water

    • Ice floats and creates an insulating layer at the surface of pands and lakes

      • Water below this layer does not freeze

        • Allowing organisms within water to move and survive

• Metabolite

  • Many chemical reactions involve water

  • Hydrolysis reactions

    • Using water to break down complex molecules

  • Condensation reactions

    • Release water to join molecules together

  • Photosynthesis

    • Uses water as a raw material

• Transport

  • Organisms can use water to move substances

  • Cohesion between two water molecules & ashesion between water molecules and other molecules help water flow through organisms carrying substances along with it