Respiration

• What is the word equation for respiration?

  Glucose + oxygen -> carbon dioxide + water
• What is the symbol equation for respiration?

  C6H12O6 + 6O2 -> 6CO2 + 6H2O
• What is meant by oxidation?

  Gain of oxygen

  Loss of hydrogen

  Loss of electrons
• What is meant by reduction?

  Loss of oxygen

  Gain of hydrogen

  Gain of electrons
• Where does glycolysis occur?

  In the cytoplasm
• Describe glycolysis

  -Glucose is phosphorylated into glucose phosphate to make it more reactive

  -This requires hydrolysis of 2 ATP -> 2ADP + 2Pi

  -Glucose phosphate splits into 2x triose phosphate

  -Each triose phosphate oxidised into pyruvate

  -This requires reduction of NAD into reduced NAD using a dehydrogenase enzyme

  -4 ATP molecules are made from 4 ADP + Pi - this makes 2 net ATP
• Where does link reaction occur?

  Mitochondrial matrix
• Describe the link reaction

  -Pyruvate is actively transported to the mitochondrial matrix

  -Pyruvate is then oxidised which reduces NAD to reduced NAD using a dehydrogenase enzyme

  -Pyruvate is also decarboxylated to acetate which forms a carbon dioxide

  -Coenzyme A is added to acetate to form acetyl coenzyme A
• Where does the Kreb's cycle occur?

  MItochondrial matrix
• Describe the Kreb's cycle

  -Acetyl coenzyme A (2C) combines with 4C to form 6C, releasing coenzyme A

  -6C is decarboxylated, releasing carbon dioxide, forming 5C

  -6C is also oxidised, reducing NAD to reduced NAD using a dehydrogenase enzyme

  -5C is decarboxylated, releasing carbon dioxide, reforming 4C

  -5C is also oxidised, reducing 2NAD to 2 reduced NAD and reducing FAD to reduced FAD, using dehydrogenase enxymes

  -Substrate level phosphorylation also occurs to produce ATP from ADP + Pi
• Where does the electron transfer chain take place?

  On the mitochondrial cristae
• Describe the electron transfer chain

  -NADH and FADH are oxidised to release electrons

  -The electrons move along carrier proteins in the cristae in a series of redox reactions

  -Energy is released as the electrons move down

  -The energy is used to actively transport protons into the intermembrane space

  -A proton gradient is established, so protons diffuse back into the matrix through ATP synthase = chemiosmosis

  -ATP synthase produces ATP from ADP + Pi = oxidative phosphorylation

  -Oxygen is the final electron acceptor and forms water
• Where does the 2nd stage of anaerobic respiration in animals occur?

  In the cytoplasm
• Describe the 2nd stage of anaerobic respiration in animals

  -Pyruvate is reduced to lactic acid

  -Reduced NAD is oxidised to NAD, which is regenerated to be used again in glycolysis
• Where does the 2nd stage of anaerobic respiration in yeast and plants occur?

  In the cytoplasm
• Describe the 2nd stage of anaerobic respiration in yeast and plants

  -Pyruvate is reduced to ethanol

  -Decarboxylation releases CO2

  -Reduced NAD is oxidised to NAD, which is regenerated to be used again in glycolysis
• What are the stages of aerobic respiration?

  Glycolysis

  Link reaction

  Kreb's cycle

  Electron transfer chain
• What are examples of other respiratory substrates that aren't glucose?

  Lipids

  Proteins
• Describe how lipids are used as a respiratory substrate

  -Lipids are hydrolysed to glycerol and fatty acids

  -Glycerol (3C) is phosphorylated and converted to triose phosphate, which enters glycolysis

  -Fatty acids are broken down into 2 carbon fragments and hydrogen ions

  -The 2C fragments are converted into acetyl coenzyme A, which enters the Kreb's cycle

  -The H+ are used in oxidative phosphorylation
• Describe how proteins are used as a respiratory substrate

  -Proteins are hydrolysed to amino acids

  -Each one is deaminated (amine group removed)

  -2C fragments are converted into acetyl coenzyme A, which enters the Kreb's cycle

  -3C fragments are converted into triose phosphate, which enters glycolysis

  -4 and 5C fragments enter the Kreb's cycle
• Describe how to measure the rate of respiration using DCPIP / methylene blue

  -A known mass of yeast cells is mixed with a known concentration of glucose

  -A known concentration of DCPIP is added and it takes place of NAD

  -DCPIP accepts electrons and becomes reduced, changing from blue to colourless

  -The time it takes for the solution to become colourless is measured
• Why is a respirometer left for 30 minutes?

  -Allows rate of respiration to stabilise

  -Allows time for gases to reach equilibrium

  -Allows for expansion of gases
• Describe how a respirometer works

  -O2 is used in respiration

  -CO2 is produced but is absorbed by KOH solution

  -Volume and pressure of gases decrease, so the coloured liquid moves toward the organism's chamber down a pressure gradient
• How is the volume of oxygen measured?

  πr2h
• Describe a respirometer to measure the volume of CO2 produced in anaerobic respiration in yeast and plants

  -Cover organisms with a thin layer of oil to prevent O2 from diffusing through

  -CO2 is made which increases the pressure and volume of gases in the organism's chamber

  -Coloured liquid moves away from the organisms