respiration

• Pyruvate + NADH → (animals)

  Lactate + NAD

  
  

  (NAD allows for more glycolysis to occur)
• What happens during anaerobic respiration in animals?

  Pyruvate is reduced and NADH is oxidised to NAD releasing H. Pyruvate acts as the hydrogen acceptor and is converted to lactate
• What happens during exercise?

  Muscles carry out anaerobic respiration if there isn't enough oxygen available and oxygen debt occurs. This debt has to be repaid when exercise stops and oxygen becomes available again. Thus the lactate has to be oxidised in the liver back to pyruvate
• Pyruvate + NADH → (plants/yeast)

  Ethanol + Carbon Dioxide + NAD
• What happens during anaerobic respiration in plants/yeast?

  Pyruvate is decarboxylated to ethanal and then reduced to ethanol in a process called fermentation. This regenerates more NAD that can be used again in glycolysis
• Why does the build up of lactic acid in muscles lead to musicale fatigue?

  Lactic acid is toxic.

  -it lowers pH which interferes with the hydrogen bonding of proteins causing a change in the tertiary structure/active site. Therefore enzymes and proteins involved in muscle contraction and respiration are denatured
• Where in plants does anaerobic respiration occur?

  Roots in water logged soil
• How are lipids used in respiration?

  Lipids are hydrolysed into fatty acids and glycerol. Glycerol (3c) enters the glycolysis pathway and fatty acids are broken down in to many 2c fragments which are each converted to AcetylCoA in the link reaction
• How are proteins used in respiration?

  Proteins are hydrolysed into amino acids. The amino group (NH2) is removed in a process called deamination. The point at which it enters the respiratory pathway is dependant on the R group and the number of C atoms it contains
• What is the respiratory quotient?

  The ratio of oxygen taken in to carbon dioxide produced. It can determine the substrate used and if the reaction is aerobic/anaerobic

  
• What does a high RQ value indicate?

  Indicates that anaerobic respiration is occurring as more CO2 us being produced than oxygen being taken in
• What is the overall equation for respiration?

  C6H12O6 + 6O2 → 6H2O + 6CO2 + Energy (ATP)
• Where does glycolysis occur?

  cytoplasm
• What are the stages of glycoloysis?

  -phosphorylation of glucose to glucose phosphate using 2 ATP to ADP

  -this splits to form triose phosphate

  -the triose phosphate is oxidised to pyruvate with a net gain of ATP and NAD is reduced to NADH
• Why is ATP required for glycolysis?

  Glucose is a stable molecule, so ATP phosphorylates it thus lowering its activation energy and making it more reactive
• What is the role of NAD in the glycolytic pathway?

  Acts as a hydrogen acceptor so binds to hydrogen and is then able to release it later in other redox reactions and reduce other molecules
• What can happen next to the pyruvate produced in glycolysis in aerobic conditions?

  Pyruvate enters the mitochondrial matrix by active transport
• What can happen next to the pyruvate produced in glycolysis in anaerobic conditions?

  In an animal, pyruvate can be converted to lactate using reduced NAD or in a plant into ethanol
• What are the products of glycolysis per 1 molecule of glucose?

  -4 ATP molecules (2 net overall)

  -2 NADH

  -2 Pyruvate
• How does pyruvate enter the mitochondrial matrix for the link reaction?

  Active transport
• What happens during the link reaction?

  -pyruvate is decarboxylated releasing CO2

  -it is then oxidised to acetate producing reduced NAD

  -acetate combine with coenzyme A to produce acetylcoenzyme A
• What are the products of the link reaction?

  2acetyl CoA,

  2NADH

  2CO2
• Where does the link reaction happen?

  mitochondrial matrix
• What do decarboxylation reactions produce?

  carbon dioxide
• What do dehydrogenation reactions produce?

  NADH
• Describe the process of the Krebs cycle?

  1) Acetylcoenzyme A (2C), from the link reaction, combines with a 4 carbon molecule to produce citrate (6C).

  2) The 6c molecule loses CO2 and H to give a 4c molecule and a single molecule of ATP is made by substrate level phosphorylation

  3) The H is accepted by the carriers NAD and FAD thus reducing them

  4)The 4c molecule is reformed and can now combine with a new molecule of Acetyl CoA to begin the cycle again
• Where does the Krebs cycle occur?

  mitochondrial matrix
• What is produced in the Krebs cycle per AcetylCoA?

  3 NADH

  1 FADH2

  1 ATP

  2 CO2

  
  

  (this would be x2 overall as the cycle repeats twice)
• Where does substrate level phosphorylation occur?

  glycolysis and krebs cycle
• How is ATP generated in the krebs cycle?

  substrate-level phosphorylation

  
  

  -a method of forming ATP that involves the direct transfer of a phosphate group to ADP from a phosphorylated compound
• What happens during the electron transport chain?

  1. Reduced NAD and FAD (from Krebs cycle) are oxidised releasing H+ and e-

  2. Electron carriers in the membrane accept these high energy electrons

  3. The electrons move from one electron carrier to the next down an energy gradient

  4. Some energy is released and used to pump protons from the matrix into the inter membrane space

  5. There is now a high concentration of H+ in the inter membrane space.

  6. H+ flows down into the matrix through ATP synthase down an electrochemical gradient

  7. The ATP synthase uses the energy generated from the flow of hydrogen ions to synthesise ATP from ADP and Pi. This is known as chemiosmosis

  
  

  Oxygen accepts electrons and H+ Ions forming water
• What is the role of oxygen in the electron transport chain?

  Mops up the electrons and hydrogen ions at the end of the chain, forming water. It is often called the terminal electron acceptor.

  
  

  Without it, electrons would not be able to be passed along the electron carriers and the chain would come to a halt. Hydrogen ions and electrons would accumulate in the matrix.
• Where does the electron transport chain occur?

  inner membrane of mitochondria
• What is oxidative phosphorylation?

  This term refers to the mitochondrial process that uses oxygen and high energy electrons to produce ATP and water
• What are the products of the ETC (oxidative phosphorylation)?

  ATP

  H20

  NAD

  FAD
• Why can aerobic respiration not take place in the absence of oxygen?

  As oxygen acts as a terminal electron acceptor. It mops up the electrons and hydrogen ions at the end of the chain forming water
• What evidence supports the chemiosmosis theory?

  -There is a lower pH in the inter-membrane space than in the matrix, indicating a high conc of H ions in the inter-membrane space

  
  

  -There is a more negative water potential on the matrix side of the inner membrane indicating an electrochemical gradient due to more protons in the inter-membrane space compared to in the gradient creating a potential difference

  
  

  -Very little ATP is made in mitoblasts (mitochondria with outer membrane removed)