respiration

• ATP

  • phosphorylated nucleotide
  • 3 phosphate groups
  • adenine
  • ribose
  • nitrogenous base
• $atp+$$h2o=$$adp+$$pi+$$30.6kjmol$

  hydrolysis of atp
• glycolysis - occurs in cyptoplasm/cytosol

  glucose is broken down into 2 molecules of pyruvate
• process of glycolysis

  1. 2 phosphate groups are added to glucose. they come from the hydrolysis of 2 atp molecules. glucose cannot now leave the cell
  2. splitting of hexose bisphosphate into two triose phosphate molecules
  3. dehydrogenase enzymes remove hydrogen from triose phosphate, hydrogen transferred to reduced NAD
  4. in the process 2 molecules of atp are made, substrate level phosphorylation
• net products of glycolysis

  • 2 atp
  • 2 reduced nad
  • 2 pyruvate
• link reaction - occurs in mitochondrial matrix, pyruvate is actively transported into mitochondrion and converted into acetyl coenzyme A
• key facts of the link reaction

  • no atp produced
  • occurs twice for every molecule of glucose
• process of the link reaction

  1. the enzyme pyruvate decarboxylase removes carboxyl group which becomes carbon dioxide
  2. the enzyme pyruvate dehydrogenase removes hydrogen atoms which reduces coenzyme nad
  3. coenzyme A combines with acetate to form acetyl coenzyme A
• net products of the link reaction per glucose

  • 2 reduced nad
  • 2 carbon dioxide
  • 2 acetyl coenzyme A
• krebs cycle - occurs in mitochondrial matrix, series of reactions in which citrate is gradually changed into oxaloacetate
• process of the krebs cycle

  1. acetyl coenzyme a from the link reaction joins with ozaloacetate forming citrate, coenzyme released
  2. citrate is decarboxylated and dehydrogenated and a molecule of nad is reduced
  3. the 5c compound is decarboxylated and dehydrogenated to form a 4c compound and a molecule of nad is reduced
  4. the 4c compound id dehydrogenated and a molecule of fad is reduced
  5. the 4c compound is dehydrogenated and a molecule of nad is reduced. oxaloacetate is now regenerated
• dehydrogenated is to remove a pair of hydrogen atoms
• decarboxylated is to remove carbon dioxide
• key facts of the Krebs cycle

  • one true of the cycle for each molecule of acetate
  • occurs twice for every glucose molecule
• net products of the Krebs cycle

  • 2 atp from substrate level phosphorylation
  • 4 carbon dioxide
  • 6 reduced nad
  • 2 reduced fad
• oxidative phosphorylation - in the inner membrane of mitochondrial membranes. the formation of atp by adding a phosphate group to add in the presence of oxygen which is the final electron acceptor
• electron transport chain

  1. hydrogen atoms are removed from reduced nad and fad
  2. reduced nad and fad are oxidised whey they donate the hydrogen and therefore can be reused
  3. hydrogen atoms spilt into protons and electrons
  4. electrons are passed along the carrier until oxygen
• chemisosmosis

  1. as the electrons pass along the carriers, some energy is released which pumps the protons into the inter membrane space
  2. a proton gradient is created
  3. there is a higher concentration in the inter membrane space and so protons diffuse through atp synthase
• oxidative phosphorylation

  • as protons flow through atp synthase they drive the rotation of the enzyme to join adp+pi
  • electrons combine with oxygen which is the final electron acceptor
  • oxygen is reduced to water
• oxidative phosphorylation equation

  $2h^+$$+$$2e^-+$$0.5 oxygen=$$h20$
• anaerobic respiration

  if oxygen is absent as the final electron acceptor, there is no oxidative phosphorylation. reduced nad and fad are no regenerated and the link reaction and Krebs cycle stop
• alcoholic fermentation - for yeast and plants

  1. pyruvate is decarboxylated forming carbon dixoide and ethanal by the enzyme pyruvate decarboxylase
  2. nad accepts hydrogen from reduced nad which becomes deoxidised as ethanal is reduced to ethanol by the enzyme ethanol dehydrogenase
  3. regeneration of nad enables glycolysis to continue
  4. net 2 atp are produced by glycolysis
  5. nad doesn't enter mitochondria for oxidative phosphorylation
• lactate fermentation - muscles

  1. during vigorous excercsie not enough oxygen is available for aerobic respiration
  2. pyruvate accetps hydrogen from reduced nad and is converted to lactate by lactate dehydrogenase
  3. after exercise lactate is oxidised in the liver back to pyruvate
  4. net 2 atp produced
• oxygen debt

  oxygen needed to fully oxidise the lactate

  lactate fermentation cannot continue indefinitely as lactic acid causes a fall in pH denaturing proteins
• respiratory substrates - an organic substance that can be used in respiration.

  different substrates with more hydrogen atoms can generate more atp. there will be more protons for chemiosmosis
• respiratory substrates

  • lipid produces the most energy
  • protein when in dire need
  • carbohydrate produces the least energy
• respiratory quotient

  $carbon dioxide produced /oxygen consumed$
• respiratory quotient summary

  • the normal rq is between 0.7-1
  • res greater than 1 mean the organism is short of oxygen and is respiring anaerobically
  • plants some times have a low rq because the carbon dioxide released is used for photosynthesis
• respirometers - is the apparatus used to measure the rate of respiration of living organisms by measuring the exchange of carbon dioxide and oxygen
• process of a respirometer

  1. soda lime absorbs carbon dioxide
  2. any change in volume Is due to oxygen being absorbed
  3. less oxygen in the tube reduces the pressure in the other tube causing the coloured liquid in the capillary tube to rise
  4. the original level is measured and the diameter of the capillary tube is known then the volume of oxygen absorbed can be calculated