5.7.3

• Mitochondrial structure

  present in all types of eukaryotic cells

  • mitochondria envelope outer is smooth + inner is folded into cristae, giving it large surface area
  • embedded in the inner membranes are proteins that transport electrons, + protein channels associated with ATP synthase enzyme that allows protons to diffuse through them (electron transfer chain)

  
• mitochondrial structure 2

  • between inner + outer membrane of the envelope is the intermembrane space
  • the mitochondrial membrane matrix, enclosed in inner membrane, is semi-rigid + gel-like

  → contains mitochondrial ribosomes, looped mitochondrial DNA + enzymes for the link reaction + Krebs Cycle
• How the structure of mitochondria enables them to carry out their functions

  the matrix

  where the link reaction + Krebs Cycle take place

  contains :

  • enzymes that catalyse the stages of these reactions
  • molecules of the coenzymes NAD + FAD (flavine adenine dinucloetide)
  • oxoloacetate - the 4-carbon compound that accepts the acetyl group from the link reaction
  • mitochodnrial DNA - some of thwhich codes for mitochondrial enzymes + other proteins
  • mitochondrial ribsosmes, structurally similar to prokaryotic ribosomes
• How the structure of mitochondria enables them to carry out their functions

  The outer membrane

  phospholipid composition of the outer membrane is similar to that o membranes around other organelles in eukaryotic cells

  • it contains proteins, some form channels or carriers that allow passage of molecules , such as pyruvate, into the mitochondrion
• How the structure of mitochondria enables them to carry out their functions

  the inner membrane

  the lipid composition of the inner membrane differs from that of the outer membrane

  • this lipid bilayer is less permeable to small ions such as hydrogen ions (protons) than is the outer membrane
  • the cristae give a large surface area for the electron carriers + ATP synthase enzymes embedded in them
  • the electron carriers are protein complex arranged in electron transport chain

  → electron transport chains are involved in final stage of aerobic respiration, oxidative phosphorylation
• How the structure of mitochondria enables them to carry out their functions

  intermembrane space

  this is also involved in oxidative phosphorylation

  • the inner membrane is in close contact with the mitochondrial matrix , so the molecules of reduced NAD + FAD can easily deliver hydrogens to the electron transport chain
• the electron transport chain

  • each electron carrier protein contains a cofactor - a non-protein haem group that contains an iron ion
  • the iron ion can accept + donate electrons can become reduced (Fe2+) by gaining an electron + then become oxidised (Fe3+) when donating an electron to the next electron carrier

  → electron carriers proteins are oxido-reductase enzymes

  
• the electron transport chain 2

  • electron carriers also have a coenzyme that, using energy released from the electrons, pumps proteins from matrix to the intermembrane space
  • proton accumulates in the intermembrane space + a proton gradient forms across membrane

  →the proton gradient can produce a flow of protons through the channels in the ATP synthase enzymes to make ATP
• the ATP synthase enzymes

  • they are large + protrude from the inner membrane into the matrix

  → protons can pass through them