Carbohydrates, Glycolysis/Gluconeogenesis, and TCA

Carbohydrates
1. Have generic formula Cn(H20)n
2. Functions
  1. Energy source and storage
  2. Structural component
  3. Informational molecules in cell-signaling
3. Structures to know
  1. Glyceraldehyde
    Annotations:
    - Triose sugar
  2. Ribose
    Annotations:
    - 5 carbon sugar, aldose, all OH's on the right
  3. Mannose
    Annotations:
    - C2 epimer of glucose
  4. Glucose
  5. Galactose
    Annotations:
    - C3 epimer of glucose
  6. Fructose
    Annotations:
    - ketose sugar
  7. Maltose
  8. Cellobiose
  9. Lactose
  10. Sucrose
  11. Cellulose
    Annotations:
    - polymer of cellobiose
  12. Chitin
  13. Starch
    Annotations:
    - has alpha 1-->6 brances every 20 residues
  14. Glycogen
    Annotations:
    - Branching alpha 1-->6 linkages about every 10 residues This allows rapid mobilization of glucose when needed
Glycolysis
1. Glucose is good fuel, can be stored in polymeric form
2. Versatile biochemical precursor
3. Can be stored as starch or glycogen
4. Short term energy needs met by glycolysis
5. Pentose phosphate pathway generates NADPH
6. Structural polysaccharides made from glucose
7. Hexokinase
  1. Phosphohexose Isomerase
    1. Phosphofructokinase
      1. Aldolase
        Triose Phosphate Isomerase
        GAP Dehydrogenase
        Phosphoglycerate Kinase
        Phosphoglycerate Mutase
        Enolase
        Pyruvate Kinase
        Acetyl CoA and TCA Cycle
        Lactate (anaerobic respiration)
        Fermentation (alcohols)
8. Key regulatory steps: 1, 3, 10 these steps are irreversible and have different enzymes in gluconeogenesis
9. Occurs mainly in the muscle and brain
TCA
1. Pyruvate dehydrogenase complex
  Annotations:
  - Made up of E1 (pyruvate dehydrogenase), E2 (dihydrolipoyltransacetylase), and E3 (dihydrolipoyldehydrogenase). They are associated together to help prevent intermediates from being diffused away.
  1. Citrate synthase
    1. Aconitase
      1. Isocitrate dehydrogenase
        a-Ketoglutarate dehydrogenase
        Succinyl-CoA Synthetase
        Succinate Dehydrogenase
        Fumarase
        Malate dehydrogenase
2. 3 key steps are 2, 4, and 5
3. Anaplerotic reactions replenish the cycle
  1. Channels reactants back into TCA
Regulation
1. One reaction in a pathway is almost always irreversible
2. Fatty acids can NOT be used for gluconeogenesis
3. Gluconeogenesis occurs mainly in the liver and kidneys
4. Steps 1,3, and 10 of gluconeogenesis are different than glycolysis
5. Very expensive but necessary since the brain, nervous system, and blood cells can only generate ATP from glucose
6. Lactate can be recycled in the liver and reoxidized to pyruvate which can be used in gluconeogenesis
7. When glycolysis is turned on, gluconeogenesis is off, and vice versa
8. When energy is low (large [AMP]) cell goes into glycolysis, when energy is high (large[ATP]) the cell goes into gluconeogenesis
9. Muscles consume glucose for energy production, liver maintains blood glucose homeostasis by removing or producing glucose depending on conditions
10. Insulin
  1. Released from pancreas in response to increased glucose in blood
11. Glucagon
  1. Released by pancreas in response to low blood glucose
  2. Active on liver and adipose tissue but NOT muscle and brain
    1. Epinephrine works on liver and muscles
  3. Stimulates liver to release glucose from glycogen stored in blood
12. Regulation of fructose 2,6-bisphosphate
  1. Fructose 2,6-bisphosphate is formed by PFK-2 and not formed by FBPase 2, F26BP inhibits FBPase-1 and gluconeogenesis and activates PFK-1 and glycolysis in high concentrations, activates FBPase-1 and gluconeogenesis and inactivates glycolysis in low concentrations

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Carbohydrates, Glycolysis/Gluconeogenesis, and TCA

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	Created by Sarah Emslie about 9 years ago