Respiration

Relate the structure of a mitochondriion to it’s funtion[6] #

Describe how the structure of a mitochondrion is related to its function. [8]

• double membrane ;
• inner membrane
  • folded or cristae ;
  • increased or large, surface area ;
  • has, ATP synthase or stalked particles ;
  • has carrier (proteins) or cytochromes ;
  • (site of) ETC or oxidative phosphorylation/chemiosmosis ;
• intermembrane space
• has low pH or high concentration of protons ;
• accepts protons from ETC ;
• proton gradient between intermembrane space and matrix or protons move from intermembrane space to matrix;
• ref. to ATP synthesis;
• matrix
  • contains enzymes;
  • site of, link reaction or the Krebs cycle;
• outer membrane
  • presence of carriers for, pyruvate or reduced NAD ;
  • e.g. ribosomes or DNA.

Outline the process of anaerobic respiration in both mammal and yeast cells. [8] #

• general
  • reduced NAD produced in glycolysis ; A glycolysis described
  • small amount of ATP produced in glycolysis ;
• in yeast cells
  • pyruvate converted to ethanal ;
  • carbon dioxide released / decarboxylation ;
  • ethanal, reduced / accepts H ;
  • by reduced NAD ;
  • ethanol formed ;
• in mammalian cells
  • pyruvate converted to lactate ;
  • by reduced NAD ;
  • in, liver / muscle, cells ;
• reversible in mammal / irreversible in yeast / single step in mammal / more than 1 in yeast / reoxidised NAD allows glycolysis to continue / named enzyme

Explain how the reduced NAD is oxidised under anaerobic conditions in mammalian muscle tissue and in yeast.[6] #

• Muscle
  • pyruvate converted to lactate; A lactic acid
  • hydrogen combines with pyruvate;
  • lactate dehydrogenase;
• Yeast
  • pyruvate converted to ethanal;
  • release of carbon dioxide / decarboxylated;
  • hydrogen combines with ethanal;
  • ethanal converted to ethanol;
  • alcohol dehydrogenase;

Explain the role of NAD in aerobic respiration. [6] #

• coenzyme;
• for dehyrogenase;
• reduced;
• carries electrons;
• and protons/H+/H/hydrogen;
• from Krebs cycle;
• and from glycolysis;
• to cytochromes/electron transfer chain;
• reoxidised/regenerated;
• ATP produced;
• 3/2.5 (molecules of ATP) per reduced NAD;

Explain the different energy values of carbohydrates, lipid and proteins as respiratory substrates [6] #

• lipid > protein > carbohydrate ;
• A lipid has more energy than either protein or carbohydrate
• comparative figures ;
• kJ g-1 / per unit mass ;
• more hydrogen atoms in molecule, more energy ;
• lipid have more, hydrogen atoms / C-H bonds ;
• (most) energy comes from oxidation of hydrogen to water ;
• using reduced, NAD / FAD ;
• in ETC ;

Describe the process of glycolysis[8] #

• (glucose) phosphorylated by ATP ;
• raises energy level / overcomes activation energy ;
• hexose bisphosphate ;
• lysis / splitting, of, glucose / hexose ;
• breaks down to two TP ;
• 6C(2) x 3C ;
• dehydrogenation / description ;
• 2 NAD reduced formed (from each TP to pyruvate formed) ;
• 4 ATP produced / net gain of 2 ATP ;
• pyruvate produced ;
• reduced NAD to oxidative phosphorylation / redox ;

Describe the main features of the Krebs Cycle. [8] #

• matrix;
• of mitochondrion;
• acetyl CoA combines with oxaloacetate;
• to form citrate;
• 4C to 6C;
• decarboxylation/produce CO₂;
• dehydrogenation/oxidation;
• 2CO2 released;
• reduced NAD produced;
• reduced FAD produced;
• ATP produced;
• series of steps/intermediates;
• enzyme catalysed reactions;
• oxaloacetate regenerated;

Describe how ATP is synthesised by oxidative phosphorylation [8] #

Describe the process of oxidative phosphorylation in the mitochondria[8]

• reduced, NAD / FAD ;
• passed to ETC ;
• inner membrane / cristae ;
• hydrogen released (from reduced, NAD / FAD) ;
• split into electrons and protons ;
• electrons pass along, carriers / cytochromes ;
• ref. energy gradient ;
• energy released pumps protons into intermembrane space ;
• proton gradient ;
• protons pass through (protein) channels ;
• ATP synthase / stalked particles ;
• (ATP produced from) ADP and inorganic phosphate ;
• electron transferred to oxygen ;
• addition of proton (to oxygen) to form water / (oxygen) reduced to water ;