respiration

• glycolysis

  • occurs in the cytoplasm
  • end products= 2 3 carbon pyruvate, 4 ATP, 2 NADH
• process of glycolysis

  1. first step requires 2 ATP. two phosphates attach to glucose to form hexose biphosphate
  2. molecule becomes unstable and splits in two triose phosphates
  3. another phosphate group is added to each triose phosphate to form 2 triose biphosphates
  4. 2 triose biphosphates are oxidised by the removal of hydrogen (dehydrogenation) to form 2 three carbon pyruvate molecules.
  5. NAD coenzymes accept the removed hydrogens- they are reduced to NADH
  6. four ATP are produced using phosphates from triose biphosphates
• the link reaction

  • occurs in the matrix of the mitochondria
  • end product= acetyl coenzyme A
• the link reaction process

  1. pyruvate enters by active transport via a specific carrier protein
  2. pyruvate undergoes decarboxylation and dehydrogenation
  3. the hydrogen removed is accepted by NAD to form NADH
  4. the two carbon acetyl group is bound by coenzyme A to form acetylcoA
• the krebs cycle process

  1. acetyl coA delivers an acetyl group and it combines with oxyloacetate to form citric acid
  2. citric acid undergoes decarboxylation and dehydrogenation to produce NADH and carbon dioxide. (this forms a 5 carbon compound)
  3. 5 carbon compound undergoes further decarboxylation and dehydrogenation to regenerate oxyloacetate
  4. 4 carbon molecule undergoes another reaction and the energy released is used to form ATP
  5. 4 carbon molecule transfers electrons and hydrogen to FAD to form FADH2 (dehydrogenation)
  6. 4 carbon molecule undergoes dehydrogenation to produce NADH.
• FAD

  • occurs in krebs cycle
  • accepts two hydrogens
  • FADH2 oxidised further along the electron transport chain
  • results in synthesis of 2 ATP
• NAD

  • occurs in all stages of respiration
  • accepts one hydrogen
  • NADH oxidised at start of electron transport chain
  • results in the synthesis of 3 ATP
• oxidative phosphorylation

  1. NADH and FAD deliver hydrogen atoms to the ETC. these dissociate into H+ and electrons
  2. energy is released as the electrons reduce and oxidise electron carriers. high energy electrons are used in ATP synthase
  3. the energy released is used to create a proton gradient. this leads to the diffusion of protons through ATP synthase (resulting in ATP synthesis)
  4. at the end of the ETC, electrons combine with H+ and oxygen to form H20
• outer mitochondrial membrane

  • separates the contents of the mitochondria from the rest of the cell. creates a cellular compartment with ideal conditions for aerobic respiration
• intermembrane space

  • proteins are pumped into this space by ETC. the same space is so small so the concentration builds up quickly
• cristae

  • projections of the inner membrane which increase the surface area available for oxidative phosphorylation
• matrix

  • contains enzymes for the krebs cycle and the link reaction. also contains mitichondrial DNA
• inner mitochondrial membrane

  • contains ETCs and ATP synthase
• obligate anaerobes

  • cannot survive in the presence of oxygen
  • prokaryotes
• facultative anaerobes

  • synthesise ATP by aerobic respiration if oxygen is present but can switch to anaerobic respiration in the absence of oxygen
  • yeast
• obligate aerobes

  • can only synthesise ATP in the presence of oxygen
  • mammals
• fermentation

  • process by which organic compounds are broken down into simpler inorganic compounds without the use of oxygen or the involvement of an electron transport chain
• alcoholic fermentation

  • occurs in yeast and some plant root cells
  • end products= ethanol and carbon dioxide
• lactate fermentation

  • occurs in animal cells
  • end product= lactate
• lactate fermentation process

  1. pyruvate takes the hydrogen from NADH, catalysed by the enzyme lactate dehydrogenase.
  2. pyruvate converted to lactate and NAD is regenerated
• lactate fermentation cannot occur indefinitely

  • reduced quantity of ATP produced wouldn't be enough to maintain vital processes for a long period of time
  • accumulation of lactic acid causes a fall in pH so proteins denature
• alcoholic fermentation process

  1. pyruvate converted to ethanal, catalysed by pyruvate decarboxylase
  2. ethanal accepts a hydrogen from NADH becoming ethanol
• lactate fermentation is reversible

  • lactic acid converted back into glucose in the liver (with presence of oxygen)
• respiratory quotient

  • CO2 produced/ O2 consumed
  • carbohydrates= 1.0
  • protein= 0.9
  • lipids= 0.7