exam questions

• Outer mitochondrial membrane not permeable to H+ ions, explain the importance of this feature of the membrane (4)

  -       To stop H+ diffusing out of mitochondrion 

  -       Thus, maintaining a high conc of H+ in the intermembrane space 

  -       So, hydrogen ions can move down the electrochemical gradient by chemiosmosis 

  -       To synthesise ATP
• Explain why some ATP is broken down during glycolysis (3)

  -       For the phosphorylation of glucose, breakdown of atp releases phosphate which is used to create 2 triose phosphate molecules 

  -       Breakdown of atp also provides energy to break down the glucose
• Explain the role of carrier molecules in the electron transport chain (3)

  -       Receive hydrogen from reduced NAD or FAD

  -       Break hydrogen into protons and electrons 

  -       Electrons transferred by a series of redox reactions 

  -       Energy released is used to pump hydrogen protons into intermembrane space
• Deduce what happens to lactate in liver cells (2)

  -       Lactate is oxidised into pyruvate 

  -       Pyruvate converted to glucose or not 

  -       Pyruvate can be used in link reaction, glucose can be used in glycolysis 
• Devise an investigation using this apparatus to determine whether an increase of 10 °C doubles the rate of respiration in yeast (4)

  -       Choose any 2 temps between 10 and 40 degrees 

  -       Control variable- PH of solution, yeast concentration 

  -       Record the distance travelled by the coloured liquid in a set time 

  -       Calculate rates by dividing distance travelled by time 

  -       Data collected during the initial rate of reaction/before a factor other than temperature becomes limiting
• Explain the need for reduced NAD to be oxidised in a mitochondrion (2)

  -       So that hydrogen can be delivered to the electron transport chain 

  -       To allow chemiosmosis/ATP synthesis 

  -       To regenerate NAD
• Explain why anaerobic respiration cannot continue for long in muscle cells (3)

  -       Lactate builds up 

  -       Which must be oxidised into carbon and water 

  -       This created an oxygen debt within the muscle cells 

  -       Only a small amount of ATP is released during anaerobic respiration
• State 2 things that can happen to lactate after it is produced (2)

  -       Oxidised back into pyruvate that can enter the Krebs cycle 

  -       Converted into glucose by the liver cells for respiration
• Describe the role of the coenzymes in the synthesis of ATP

  -       NAD and FAD are reduced by the addition of hydrogen 

  -       The coenzymes transfer hydrogen ions to the inner mitochondrial membrane 

  -       Which is the site of the electron transport chain 
• Explain why the link reaction is described as an oxidative decarboxylation reaction (2)

  -       Pyruvate is oxidised/removal of hydrogen atom 

  -       Pyruvate also loses a carbon atom as co2
• Explain 3 advantages of anaerobic respiration (3)

  -       Allows for short and quick bursts of energy

  -       Muscle fibres are still able to contract in low oxygen conditions 

  -       ATP is still produced when the availability of oxygen is low 
• Describe the mechanism by which ATP is formed in the mitochondria (6)

  -       Respiration produces reduced NAD and FAD

  -       Hydrogen atoms are donated by reduced coenzymes 

  -       Hydrogen atoms are split into h+ protons and electrons 

  -       Electrons move down ETC via a series of redox reactions 

  -       Energy used to actively transport protons across the inner mitochondrial membrane 

  -       This creates an electrochemical gradient between intermembrane space and matrix 

  -       Protons diffuse down gradient through the channel protein, ATP synthase