Cellular Respiration

• Substrate - level phosphorylation


  When breakdown energy released is taken and used to stick a phosphate group onto ADP, producing ATP
• Electron carriers


  Small organic molecules that pick up electrons from one molecule and drop them off at another. Present in photosynthesis and cellular respiration
• NAD+ and FAD


  Two major electron carriers
• When NAD+ and FAD pick up electrons, they also get hydrogens, switching to slightly different forms. When they drop the electrons off, they go back to their original state
• Redox reactions


  Oxidation-reduction reactions
• Oxidation is when something loses electrons (getting a negative ion like oxygen). Reduction is when something gains electrons (losing a negative ion like oxygen).
• You can also have a redox reaction when two separate atoms enter a polar covalent bond, because one is still "gaining" electrons and the other is still "losing" them in respect to the way they were originally
• If a carbon-based molecule gains H+ or loses an O- it's been reduced . If a carbon-based molecule gains O- or loses H+ then it has been oxidized
• Molecules are at a higher energy state when associated with less electronegative atoms like C or H, and at a lower energy state when associated with more electronegative ions like O
• As glucose is broken down, the H atoms travel from glucose to oxygen, bringing the atoms down to a less excited state. The energy that is released during this process gets captured through cellular respiration in the form of ATP
• Glycolysis


  1st step of cellular respiration. When glucose gets broken down into two pyruvate molecules, where ATP is made and NAD+ is converted into NADH (carries electrons)
• Pyruvate


  3-carbon organic molecule synthesized when glucose is broken down during glycolysis
• Pyruvate oxidation


  2nd step of cellular respiration. When the pyruvates from glycolysis are sent to the mitochondrial matrix and broken down into acetyl CoA. CO2 is released and NADH is generated
• Acetyl CoA


  Two carbon molecule coenzyme A that is produced when pyruvates are broken down in the mitochondrial matrix
• Mitochondrial matrix


  Innermost compartment of the mitochondria
• Citric acid cycle


  3rd step of cellular respiration. When the acetyl CoA produced in pyruvate oxidation are combined with 4-carbon molecules, going through a series of chemical processes. At the end the 4-carbon molecule is regenerated, and ATP, NADH, and FADH2 are produced, and CO2 is emitted
• Oxidative phosphorylation


  4th step of cellular respiration. When NADH and FADH2 from earlier steps drop their electrons on the electron transport chain, returning to their original states of NAD+ and FAD. As the electrons release energy, they feed into the ATP H+ pump
• 4 steps of cellular respiration:

  • Glycolysis
  • Pyruvate oxidation
  • Citric acid cycle
  • Oxidative phosphorylation
• Electron transport chain


  Series of proteins and organic molecules found in the inner membrane of the mitochondria
• Oxidative phosphorylation


  Made up of chemiosmosis and the electron transport chain, ending in ATP synthesis
• Steps of oxidative phosphorylation

  • Delivery of electrons by NADH and FADH2
  • Electron transfer and protein pumping
  • Splitting up oxygen to form water
  • Gradient-driven synthesis of ATP
• Delivery of electrons by NAHD and FADH2


  When reduced electron carriers made earlier in cr drop off their electrons on the transport chain and revert to their original froms (NAD+ and FAD) (step 1 of op)
• Electron transfer and proton pumping


  Electrons release and lose energy as they are moved down the transport chain. Some of it is used to pump H+ protons from the matrix into intermembrane space, creating an electrochemical gradient (step 2 of op)
• Splitting of oxygen to form water

  Electron reaches the end of the chain, and 2 of them are added to molecular oxygen, which split in half and take up H+ to form water
• Gradient - driven synthesis of ATP

  H+ ions move down their gradient back into the matrix, going through ATP synthase, which harnesses their flow to synthesize ATP
• Carotenoids


  Orange or red pigments in plants that are released during the fall
• Electron transport chains are made up of membrane-embedded proteins and organic molecules, and mostly divided into four larger membrane protein complexes I - IV
• In eukaryotes, some of their electron transport chain has copies of molecules within the mitochondrial membrane. In prokaryotes, its components are found in the plasma membrane
• Protein complexes I III and IV have large drops in free energy of the electron leading to protons being pumped. Because FADH2 has more trouble letting go of electrons, it gives it off at complex II where protons are not immediately pumped
• NADH gives electron easily in redox reaction (has highly energetic electrons) so it drops them off direct at protein complex I of the electron transport chain, where its high level electron goes directly into giving off energy to pump protons
• NADH electrons are more energetic (easy to let go of) so they can be dropped off earlier in the transport chain and keep going for longer, whereas FADH2 is less energetic so it can't be dropped off as easily
• NADH turns into NAD+ and FADH2 turns into FAD+
• FADH2 contributes less than NADH because its electrons are weaker and bypass complex 1 so it pumps less protons
• Complex I


  Protein complex in the electron transport chain that NADH drops its electron off at. Flavoprotein (prosthetic group) receives the electron, and passes it off to Fe-S protein, then ubiquionine
• Prosthetic group


  Non-protein molecule tightly bound to a protein that is required for its activity, like flavoproteins
• Complex II


  Part of the e- transport chain that FADH2 gives its electrons to (and is also a part of, along with the enzyme that reduces it during the citric acid cycle). Passes e- off to Fe-S protein, then to ubiquionine, just like I
• Ubiquionine (Q)


  Mobile e- carrier that is used in the e- transport chain. It is given the electron at complexes I and II, then reduced to QH2 and travels through the membrane getting to complex III
• Cytochrome C (cyt C)


  e- carrier in the e- transport chain that carries the e- from complex III to complex IV, allowing the e- to release its energy to pump protons
• Complex III


  Protein complex containing Fe-S proteins and cytochromes. Electrons are transferred from one cytochrome to a Fe-S to another cytochrome to a carrier (cyt C) where it is brought to the last complex, pumping protons from the mitochondrial matrix to the intracellular space
• Cytochromes


  Family of related proteins with prosthetic groups containing heme groups (iron ions)