ATP

• ATP allows for:

  • metabolism
  • movement (muscles contracting)
  • active transport
  • maintenance, repair and division of cells
  • production of substances (hormones and enzymes)
  • maintenance of core body temperature (homeostasis/heat energy loss during respiration)
• ATP can be produced as a molecule but energy cannot be produced - it cannot be created or destroyed, only transferred.
• Energy is released in the form of heat energy and ATP.
• Light energy is converted by plants into chemical energy (glucose) during photosynthesis. The chemical energy (in the form of organic molecules e.g. C₆H₁₂O₆) is converted into ATP during respiration. ATP is used by cells to perform useful work.
• ATP is a molecule that is made inside a cell and it stays within that cell to do 'work' (cannot leave).
• ATP stands for adenosine triphosphate.
• ATP structure consists of a nitrogenous adenine base, a ribose sugar and three phosphate groups.
• ADP stands for adenosine diphosphate.
• The process whereby ADP is converted back to ATP is called oxidative phosphorylation.
• Anabolic reactions are synthesising reactions which require energy from ATP hydrolysis.
• ATP has the ability to lose its terminal phosphate group and donate it to another molecule. The phosphate that breaks off is called an inorganic phosphate ion and releases about 30KJ mol⁻¹.

  ATP + H₂O -> ADP + Pi + E

  (hydrolysis reaction)
• The ATP hydrolase enzyme uses water to break down ATP into ADP.

  The ATP synthase (or ATPase) enzyme rebuilds ATP and releases a molecule of water in doing so.
• Phosphorylation is the process of adding a phosphate group to a molecule.
• Energy Coupling: ATP hydrolysis can be coupled to energy-requiring reactions within cells (e.g. active transport and protein synthesis).
• Catabolism is an exergonic (energy-releasing) process.
• Anabolism is an endergonic (energy-consuming) process.
• Photophosphorylation occurs in the chlorophyll during photosynthesis.
• Oxidative phosphorylation occurs in the mitochondria during the electron transport chain (part of respiration).
• Substrate-level phosphorylation occurs when phosphate groups are transferred from donor molecules to ADP.
• The condensation reaction ATP synthesis can also be referred to ADP phosphorylation.
• ATP properties:

  • nucleotide derivative
  • metabolic reactions in cells require a constant and steady supply of ATP
  • three phosphate ions play a significant role in energy transfer (phosphorylation)
  • phosphates are inorganic because they don't contain C atoms
  • is a small and soluble molecule that can be transported easily around the cell
  • can be rapidly resynthesised
• ATP functions:

  • releases energy in small amounts so nothing is wasted
  • immediate source of energy for biological processes (only one bond is hydrolysed to release energy)
  • can transfer energy to another molecule by transferring one of its phosphate ions
  • ATP cannot pass out of the cell so the cell always has an immediate energy supply
• ATP can be recycled 1000-1500 times a day.
• 𝘼𝙏𝙋 𝙑𝙎 𝙂𝙇𝙐𝘾𝙊𝙎𝙀:

  • cells do not overheat from wasted heat energy and are less likely to run out of resources when using ATP
  • both energy sources can move around in the cytoplasm with ease to provide energy for chemical reactions within the cell
  • glucose would need several bonds to be broken down to release all of its energy
  • ATP can transfer energy to another molecule via phosphorylation
  • ATP cannot leave the cell whereas glucose can
  • the total quantity of ATP is approximately 0.10mol/litre in an adult
• ATP is produced during cellular respiration from the coupling of an inorganic phosphate ion to an ADP.
• The ATP molecule is a nucleotide derivative. It consists of three components: a purine base (adenosine) and a pentose sugar (ribose), which form the nucleoside component, and three phosphate groups, which attach to the 5' carbon of the pentose sugar.
• ATP releases its energy during hydrolysis. Water is split and added to the terminal phosphate group resulting in ADP + Pi. For every mole of ATP hydrolysed 30KJ of energy is released. Note that energy is released during the formation of bonds not the breaking of chemical bonds.
• ATP is produced in the mitochondria.
• The ATP/ADP system is similar to a rechargeable battery because it alternates between a high (ATP) and low (ADP) energy state.
• How is an ATP molecule formed from its component molecules?

  Requires ATP synthase

  ADP + Pi forms ATP in a condensation reaction

  ATP is composed of a ribose sugar, nitrogenous adenine base, and three phosphate groups
• Give two ways in which ATP is a suitable energy source for cells to use.

  1. releases energy instantaneously
  2. releases relatively small amounts of energy so that only a little energy is lost as heat
• Why would glucose be an unsuitable respiratory substrate in an artificial ATP production investigation?

  • cannot cross mitochondrial membranes
  • is used/broken down in the cytoplasm (not the mitochondria)
• Why does oxygen concentration change during ATP synthesis?

  A water molecule (H20) is lost during synthesis.
• When glucose is respired what happens to the energy which is not incorporated into ATP?

  Released as heat.
• Why is less energy produced during anaerobic respiration?

  Glucose is only partly broken down (into lactate).