Water, ATP, and Inorganic ions

• ATP


  Adenosine triphosphate, the energy-carrying molecule that provides the energy to drive many processes inside living cells

  
• ATP


  • It is a phosphorylated nucleotide
  • It can have one, two or three phosphate groups attached to the adenosine
• AMP


  Adenosine monophosphate (one phosphate group)
• ADP


  Adenosine diphosphate (two phosphate groups)
• ATP


  Adenosine triphosphate (three phosphate groups)
• Hydrolysis of ATP


  1. Catalysed by the enzyme ATP hydrolase (ATPase)

  2. Converts ATP to ADP and inorganic phosphate

  3. Releases 30.8 kJ/mol of energy
• ATP synthesis


  1. Catalysed by the enzyme ATP synthase

  2. Combines ADP and inorganic phosphate to form ATP

  3. Requires energy input
• ATP


  • It is a universal energy currency
  • It is used in all organisms
  • It can be used for different purposes (reactions) and is reused countless times
• Water


  • Composed of hydrogen and oxygen atoms
  • A polar molecule due to uneven sharing of electrons

  
• Water


  • Forms hydrogen bonds between molecules
  • An excellent solvent
  • Has a high specific heat capacity
  • Has a high latent heat of vaporisation
  • Is less dense when a solid

  
• Water makes up 70-95% of the mass of a cell
• 71% of the Earth's surface is covered in water, making it a major habitat for organisms
• Metabolites


  Can be transported efficiently (except non-polar molecules which are hydrophobic)
• Water


  Due to its polarity it is considered a universal solvent
• Specific heat capacity


  • The amount of thermal energy required to raise the temperature of 1kg of that substance by 1 degrees celcius
  • Water's specific heat capacity is 4200 J/kg°C
• Water has a high specific heat capacity of 4200 J / Kg C meaning a relatively large amount of energy is required to raise its temperature
• High specific heat capacity of water

  Due to the many hydrogen bonds present in water. It takes a lot of thermal energy to break these bonds and a lot of energy to build them, thus the temperature of water does not fluctuate greatly
• Advantages of water's high specific heat capacity for living organisms

  • Provides suitable habitats
  • Able to maintain a constant temperature as water is able to absorb a lot of heat without big temperature fluctuations
  • Vital in maintaining temperatures that are optimal for enzyme activity
• Latent heat of vaporisation

  A large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate
• Advantage of latent heat of vaporisation for living organisms

  • Only a little water is required to evaporate for the organism to lose a great amount of heat
  • Provides a cooling effect for living organisms, for example the transpiration from leaves or evaporation of water in sweat on the skin
• Cohesion and adhesion


  • Hydrogen bonds between water molecules allows for strong cohesion between water molecules
  • Water is able to hydrogen bond to other molecules, such as cellulose, which is known as adhesion
• Advantages of cohesion and adhesion

  • Allows columns of water to move through the xylem of plants and through blood vessels in animals
  • Enables surface tension where a body of water meets the air
  • Enables water to move up the xylem due to transpiration
• An ion is an atom (or sometimes a group of atoms) that has an electrical charge
• Cation


  An ion that has a +ve charge
• Anion


  An ion that has a -ve charge
• Inorganic ion


  An ion that does not contain carbon
• Inorganic ions play an important role in many essential cellular processes
• Inorganic ions occur in solution in the cytoplasm and body fluids of organisms
• Some inorganic ions occur in high concentrations and others in very low concentrations
• The concentration of certain ions can fluctuate and can be used in cell signalling and neuronal transmission
• Hydrogen ions (H+)

  • Protons
  • The concentration of H+ in a solution determines the pH
  • There is an inverse relationship between the pH value and the hydrogen ion concentration
• Importance of hydrogen ion concentration

  • Essential for enzyme-controlled reactions, which are all affected by pH
  • The fluids in the body normally have a pH value of approximately 7.4
  • Maintenance of this normal pH is essential for many metabolic processes
  • Changes in pH can affect enzyme structure and cause denaturation
• Iron ions (Fe2+/Fe3+)

  • There are two versions of iron ions (known as oxidation states)
  • Iron (II) ions, also known as ferrous ions (Fe2+)
  • Iron (III) ions, also known as ferric ions (Fe3+)
• Roles of iron ions

  • Essential for binding oxygen in haemoglobin and myoglobin
  • Essential for the transfer of electrons during respiration and photosynthesis
• Sodium ions (Na+)

  • Required for the transport of glucose and amino acids across cell-surface membranes
  • Required for the transmission of nerve impulses
• Phosphate ions (PO43-)


  • Attach to other molecules to form phosphate groups, which are an essential component of DNA, RNA and ATP
  • Found in phospholipids, which are key components of the phospholipid bilayer of cell membranes

  
• Calcium ions (Ca2+)


  • Essential in the movement of organisms
  • Regulate the transmission of impulses from neurone to neurone
  • Stimulate muscle contraction
  • Activate many enzymes, making them key regulators in many biological reactions
  • Necessary for the formation of blood clots