Topic A3

Question 1

Glycolysis

Steps

Answer 1

Se på egne notater

• Glycolysis takes place in two stages

First stage:

• Preparatory process

Second stage:

• Common pathway for all sugars
• ADP is phosphorylated to ATP

Question 2

Glycolysis

Types

Answer 2

• The fate of pyruvate depends upon the environment
  
  • Aerob glycolysis:
    
    • ​Pyruvate enter mitochondria where it is completely oxidized to CO₂ and H₂O
  • Anaerobe glycolysis:
    
    • ​Pyruvate is coverted into lactate

Question 3

Glycolysis

Location

Answer 3

• Each cell type
• Liver (not as intensive)
• Cytoplasm
• Only aerobic:
  
  • Cardiac muscles
  • Brain
• Only anaerobic:
  
  • Skeletal muscles
  • Erythrocytes

Question 4

Glycolysis

Regulation

Answer 4

Allosteric:

• Hexokinase*
  
  • Glucose-6-P ⊖
• Phosphofructokinase (most important control element)
  
  • ATP ↑ ⊖
  • Citrate ⊖
  • Low pH ⊖
  • AMP ↑ ⊕
  • ADP ⊕
  • Fructose-2,6-P ⊕
• Pyruvate kinase*
  
  • ATP ⊖
  • Fructose-1,6-P ⊕
  • Ala (⟷ pyruvate) ⊖
  • AcCoA ⊖

Hormonal

• Insulin ⊕
• Glucagen ⊖
• Glucocorticoid ⊕

Glycolysis is stimulated when the energy charge of the cell is low

Question 5

Glycolysis

Energy balance

Answer 5

• Aerobe:
  
  • End product: pyruvate
  • Glucose: +6 ATP
  • Glycogen: +7 ATP
• Anaerobe:
  
  • End product: lactate
  • Glucose: +2 ATP
  • Glycogen: +3 ATP

Se på notater

Question 6

Glycolysis

Importance

Answer 6

• Significance: energy production
  
  • Anaerobic glycolysis: only way for anaerobe microbes to produce energy
  • Role of lactate in meat quality:
    
    • Normal pH:
    • Lactate ↑ → Ph ↓ → PSE (Pale Soft Exudative)
    • Lactate ↓ → Ph ↑ → DFD (Dark Firm Dry)

Question 7

The Pasteur effect

Answer 7

• Investigation of fermentation processes: In the presence of oxygen no lactate production coud be observed
  
  • Inhibition of anaerobe glycolysis by respiration
• NADH+H⁺ has a bigger affinity to respiratory chain than to lactate dehydrogenase in aerobic conditions
• If Ø O₂ (anaerobe conditions) - NADH+H⁺ will be used for lactate production from pyruvate
• Ie. if O₂ present → ø lactate
  
  • ​Except:
    
    • Tumor
    • Embrional cells
    • Retinal cells

Question 8

Cori cycle

Answer 8

• Lactate, the end product of glycolytic sequence under anaerobic conditions, diffueses through the membrane of muscle cells into the the blood
• In the end of the cycle, the decomposed glucose enters the blood and is taken up by skeletal muscle as the initial compound of glycogen synthesis