5.2 Respiration

• Why is respiration important?

  ● Respiration produces ATP (to release energy)

  ● For active transport, protein synthesis etc.
• Mitochondria structure:

  A) outer membrane

  B) cristae

  C) matrix

  D) small ribosomes

  E) circular DNA

  
• Summarise the stages of aerobic & anaerobic respiration

  Aerobic respiration

  1. Glycolysis - cytoplasm (anaerobic)

  2. Link reaction - mitochondrial matrix

  3. Krebs cycle - mitochondrial matrix

  4. Oxidative phosphorylation - inner mitochondrial membrane

  Anaerobic respiration

  1. Glycolysis - cytoplasm

  2. NAD regeneration - cytoplasm
• Describe the process of glycolysis

  1. Glucose phosphorylated to glucose phosphate

  ○ Using inorganic phosphates from 2 ATP

  2. Hydrolysed to 2 x triose phosphate

  3. Oxidised to 2 pyruvate

  ○ 2 NAD reduced

  ○ 4 ATP regenerated (net gain of 2)
• Explain what happens after glycolysis if respiration is anaerobic

  1. Pyruvate converted to lactate (animals &

  some bacteria) or ethanol (plants & yeast)

  2. Oxidising reduced NAD → NAD regenerated

  3. So glycolysis can continue (which needs

  NAD) allowing continued production of ATP
• Suggest why anaerobic respiration produces less ATP per molecule of

  glucose than aerobic respiration

  ● Only glycolysis involved which produces little ATP (2 molecules)

  ● No oxidative phosphorylation which forms majority of ATP (around 34 molecules)
• What happens after glycolysis if respiration is aerobic?

  Pyruvate is actively transported into the mitochondrial matrix
• Describe the link reaction

  1. Pyruvate oxidised (and decarboxylated) to acetate

  ○ CO2 produced

  ○ Reduced NAD produced (picks up H)

  2. Acetate combines with coenzyme A, forming Acetyl

  Coenzyme A

  Products per glucose molecule: 2 x Acetyl Coenzyme A,

  2 X CO2 and 2 X reduced NAD
• Describe the Krebs cycle

  1. Acetyl coenzyme A (2C) reacts with a

  4C molecule

  ○ Releasing coenzyme A

  ○ Producing a 6C molecule that

  enters the Krebs cycle

  2. In a series of oxidation-reduction

  reactions, the 4C molecule is

  regenerated and:

  ○ 2 x CO2

  lost

  ○ Coenzymes NAD & FAD reduced

  ○ Substrate level phosphorylation

  (direct transfer of Pi from

  intermediate compound to ADP)

  → ATP produced

  Products per glucose molecule: 6 x reduced NAD,

  2 x reduced FAD, 2 x ATP and 4 x CO2
• Glycolysis:

  A) 2 ATP

  B) 2 ADP + Pi

  C) 2 ADP + Pi

  D) 2 ATP

  E) 2 ADP + Pi

  F) NAD

  G) 2 ATP

  H) NAD

  I) NADH

  J) NADH

  
• Link reaction:

  A) NAD

  B) NADH

  C) CO2

  
• Krebs cycle:

  A) FADH

  B) FAD

  C) ATP

  D) ADP + Pi

  E) CO2

  F) CO2

  G) 3 NAD

  H) 3 FADH

  
• Describe the process of oxidative phosphorylation

  1. Reduced NAD/FAD oxidised to release H atoms → split into protons and electrons

  2. Electrons transferred down electron transfer chain

  ○ By redox reactions

  3. Energy released by electrons used in the production of ATP

  ○ Energy used by electron carriers to actively pump protons from matrix → intermembrane space

  ○ Protons diffuse into matrix down an electrochemical gradient, via ATP synthase

  ○ Releasing energy to synthesise ATP

  4. In matrix at end of ETC, oxygen is final electron acceptor

  ○ So protons, electrons and oxygen combine to form water
• Give examples of other respiratory substrates

  Breakdown products of lipids and amino acids, which enter the Krebs cycle. For example:

  ● Fatty acids from hydrolysis of lipids → converted to Acetyl Coenzyme A

  ● Amino acids from hydrolysis of proteins → converted to intermediates in Krebs cycle