Respiration mechanism

• Glycolysis - Step 3

  2 Triose phosphate +2Pi + 4ADP + 2NAD → 4ATP + 2Pyruvate + 2NADH
• Glycolysis

  Glucose enters the cytoplasm via facilitated diffusion
• Glycolysis - Step 2

  Hexose bisphosphate → 2triose phosphate
• Glycolysis - Step 1

  • Phosphate is added to prevent the glucose molecule from leaving the cytoplasm of the cell via transport protein specific to glucose
• Glycolysis - Step 1

  1. Glucose + 2ATP → Hexose bisphosphate

  2. 2ATP → 2ADP + 2Pi

  3. Phosphorylation of glucose occurs
• Respiration

  Before any sort of respiration can occur, glycolysis needs to take place
• Aerobic Respiration - Step 2: Link reaction


  Pyruvate enters mitochondrial matrix via active transport + co - transport, but energy is not used but the co-enzymes: (CoA) and NAD: Pyruvate → 2Acetate + 2 $CO_2$ (decarboxylation) + H, NAD + H → NADH, Carbon dioxide is exhaled, 2 Acetate + 2 CoA → 2 Acetyl CoA, 2 pyruvate from glycolysis lose a carbon to form acetate and bond with coenzyme A(CoA) to form Acetyl CoA, Final products: 2Acetyl CoA, 2$CO_2$, NADH
• Glycolysis - Step 3

  • ATP produced this way is called substrate-level phosphorylation
  • Oxidation-reduction reaction occurs: triose phosphate is oxidised - loses hydrogen (+2H), NADH is reduced - gains lost hydrogen (2NADH formed)
• Aerobic Respiration - Step 3: The Krebs cycle

  Acetyl CoA + Oxaloacetate → Citrate + CoA, Citrate then undergoes a series of reactions producing products to reform oxaloacetate: Citrate undergoes decarboxylation, releases 2 CO2, a single ADP reacts with a phosphate group to produce ATP (substrate-level phosphorylation),

  Citrate undergoes oxidation/dehydrogenation - losing a hydrogen: 3NAD + 3H → 3 NADH, FAD + 2H → FADH2 (FAD, like NAD, is also a coenzyme), Overall yield: 2 ATP (as the process occurs twice for one glycolysis)
• Lactate

  Same as lactic acid except a hydrogen missing from the carboxylic acid part
• Anaerobic Respiration


  All of anaerobic respiration occurs in the cytoplasm
• NADH and FADH2 donates a pair of electrons to a channel protein and moves along channel proteins via oxidation-reduction reactions, what are the reactions that occur?

  
  

  NADH→ NAD + H+ + e-

  FADH2→ FAD + 2H+ +2e-
• Even though in high concentration lactate and ethanol are harmful, they ensure glycolysis can continue to produce a small amount of ATP and produce molecules that can be used in Aerobic respiration once oxygen becomes available
• Step 2a: Anaerobic Respiration in animals


  Pyruvate + H → Lactate, hydrogen provided by NADH from glycolysis and reform NAD to be used in glycolysis
• Recycling of NAD and FAD

  • NAD is recycled to be used in glycolysis, link reaction and the krebs cycle
  • FAD recycled to be used in the krebs cycle
• Respiratory substrates in terms of energy released

  • Lipids > proteins > carbohydrates
• Electrons in the final transfer chain react with oxygen and protons


  To prevent the passage of electrons from stopping and building up along the chain: 2e-+2H++O2→H2O
• Electron transfer chain


  • Proteins that gain energy from the oxidation-reduction reactions through the transfer of electrons generate for Active transport of protons
• Oxygen is the final electron acceptor in animals
• At the end of this stage, it is possible for a single glucose molecule to have produced >30 ATP molecules
• Respiratory quotient (RQ) values

  • Carbohydrates: 1
  • Proteins: 0.9
  • Lipids: 0.7
• A respirometer is used to find the Respiratory quotient (RQ) value
• Proteins and lipids take more oxygen to break down due to the proportion of C-H bonds present in the molecule which requires more oxygen to break
• Step 2b: Anaerobic Respiration in Plants and some microorganisms


  Pyruvate + H → Ethanol + CO2, hydrogen provided by NADH and NAD is reformed to be reused
• Energy is needed to actively transport protons back to maintain the proton gradient


  Electron transfer chain done via oxidation-reduction reactions
• ATP synthase and channel proteins

  Lie in a membrane between the intermembrane space and the matrix
• Energy is supplied to ATP synthase

  1. Via a proton gradient

  2. Intermembrane space contains lots of protons

  3. Matrix contains less protons

  4. Proton gradient is created (a specific type of electrochemical gradient)

  5. Protons diffuse through ATP synthase which provides energy for oxidative phosphorylation where ADP -> ATP
• Chemiosmosis

  Diffusion of ions across a partially permeable membrane from an area of high concentration to an area of low concentration
• Energy is needed to actively transport protons back


  To maintain the proton gradient from matrix to the intermembrane space
• Electron transfer chain done via oxidation-reduction reactions

  1. NADH and FADH2 donate a pair of electrons to a channel protein and move along channel proteins via oxidation-reduction reactions

  2. NADH→NAD+H++2e-, NAD is recycled to be used in glycolysis, link reaction and the krebs cycle

  3. FADH2→FAD+2H++2e-, FAD recycled to be used in the krebs cycle

  4. These proteins are the electron transfer chain

  5. The oxidation-reduction reactions responsible for transferring proteins generate the energy for Active transport
• Electrons will reach the end of the transfer chain

  1. Electrons in the final transfer chain reacts with oxygen and protons to prevent the passage of electrons from stopping and building up along the chain

  2. 2e-+2H++O2→H2O

  3. Oxygen is the final electron acceptor
• Complete the process for glycolysis:

  .

  A) Glucose

  B) hexose bisphosphate

  C) triose phosphate

  D) triose phosphate

  E) pyruvate

  F) pyruvate

  G) 2 ATP

  
• the overall yield of glycolysis?

  2 ATP
• Where does the krebs cycle occur?

  in the matrix of mitochondria
• finish labelling the diagram

  A) Oxoloacetate

  B) Acetyl CoA

  C) CO2

  D) CO2

  E) ADP + Pi