Metabolic Pathways of
Carbohydrates
By
Hasnat Mueen
1
, Contents
1 Introduction: ....................................................................................................................... 1
2 Glycolysis: ......................................................................................................................... 2
2.1 Significance: ................................................................................................................ 2
2.2 Types of Glycolysis (and net ATPs): .......................................................................... 2
2.2.1 Aerobic glycolysis: .............................................................................................. 3
2.2.2 Anaerobic glycolysis:........................................................................................... 3
2.3 Reactions of Glycolysis:.............................................................................................. 3
2.3.1 Energy investment phase: .................................................................................... 3
2.3.2 Splitting phase:..................................................................................................... 4
2.3.3 Energy generation phase: ..................................................................................... 5
2.4 Fate of pyruvate:.......................................................................................................... 6
3 Tricarboxylic Acid Cycle (Kreb’s Cycle or Citric Acid Cycle): ....................................... 7
3.1 Sources of Precursor of Acetyl CoA: .......................................................................... 8
3.2 Important Steps of TCA cycle:.................................................................................... 8
3.3 Electron Transport Chain: ........................................................................................... 9
4 Gluconeogenensis: ........................................................................................................... 10
4.1 Importance:................................................................................................................ 10
4.2 Substrates: ................................................................................................................. 10
4.3 Reactions of gluconeogenesis: .................................................................................. 11
4.3.1 Conversion of pyruvate to phosphoenolpyruvate: ............................................. 11
4.3.2 Conversion of fructose 1,6-bisphosphate to fructose 6-phosphate: ................... 12
4.3.3 Conversion of glucose 6-phosphate to glucose .................................................. 12
4.4 Gluconeogenesis from amino acids: ......................................................................... 12
4.5 Gluconeogenesis from glycerol:................................................................................ 12
4.6 Gluconeogenesis from lactate (Cori cycle): .............................................................. 12
i
, 5 Glycogenesis: ................................................................................................................... 13
5.1 Steps of Glycogenesis: .............................................................................................. 13
5.1.1 Synthesis of UDP glucose:................................................................................. 13
5.1.2 Synthesis of primer to initiate glycogenesis: ..................................................... 13
5.1.3 Glycogen synthesis by glycogen synthase: ........................................................ 14
5.1.4 Branch Formation: ............................................................................................. 14
6 Glycogenolysis:................................................................................................................ 14
6.1 Steps of glycogenolysis: ............................................................................................ 14
6.1.1 Shortening of Glycogen chain: .......................................................................... 15
6.1.2 Removal of branches: ........................................................................................ 16
6.1.3 Formation of glucose 6-phosphate and glucose: ................................................ 16
7 Pentose Phosphate Pathway: ............................................................................................ 16
7.1 Importance:................................................................................................................ 17
7.2 Various reactions in HMP pathway: ......................................................................... 17
8 Glucuronic Acid Pathway: ............................................................................................... 18
8.1 Various involved steps/reactions:.............................................................................. 18
9 Galactose metabolism: ..................................................................................................... 19
10 Fructose Metabolism:....................................................................................................... 20
10.1 Fructokinase pathway: ........................................................................................... 20
10.2 Sorbitol pathway of fructose production: .............................................................. 21
11 Metabolism of Amino sugars: .......................................................................................... 22
12 Glyoxylate Cycle: ............................................................................................................ 22
12.1 Reactions of the Cycle: .......................................................................................... 23
13 References: ....................................................................................................................... 24
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Carbohydrates
By
Hasnat Mueen
1
, Contents
1 Introduction: ....................................................................................................................... 1
2 Glycolysis: ......................................................................................................................... 2
2.1 Significance: ................................................................................................................ 2
2.2 Types of Glycolysis (and net ATPs): .......................................................................... 2
2.2.1 Aerobic glycolysis: .............................................................................................. 3
2.2.2 Anaerobic glycolysis:........................................................................................... 3
2.3 Reactions of Glycolysis:.............................................................................................. 3
2.3.1 Energy investment phase: .................................................................................... 3
2.3.2 Splitting phase:..................................................................................................... 4
2.3.3 Energy generation phase: ..................................................................................... 5
2.4 Fate of pyruvate:.......................................................................................................... 6
3 Tricarboxylic Acid Cycle (Kreb’s Cycle or Citric Acid Cycle): ....................................... 7
3.1 Sources of Precursor of Acetyl CoA: .......................................................................... 8
3.2 Important Steps of TCA cycle:.................................................................................... 8
3.3 Electron Transport Chain: ........................................................................................... 9
4 Gluconeogenensis: ........................................................................................................... 10
4.1 Importance:................................................................................................................ 10
4.2 Substrates: ................................................................................................................. 10
4.3 Reactions of gluconeogenesis: .................................................................................. 11
4.3.1 Conversion of pyruvate to phosphoenolpyruvate: ............................................. 11
4.3.2 Conversion of fructose 1,6-bisphosphate to fructose 6-phosphate: ................... 12
4.3.3 Conversion of glucose 6-phosphate to glucose .................................................. 12
4.4 Gluconeogenesis from amino acids: ......................................................................... 12
4.5 Gluconeogenesis from glycerol:................................................................................ 12
4.6 Gluconeogenesis from lactate (Cori cycle): .............................................................. 12
i
, 5 Glycogenesis: ................................................................................................................... 13
5.1 Steps of Glycogenesis: .............................................................................................. 13
5.1.1 Synthesis of UDP glucose:................................................................................. 13
5.1.2 Synthesis of primer to initiate glycogenesis: ..................................................... 13
5.1.3 Glycogen synthesis by glycogen synthase: ........................................................ 14
5.1.4 Branch Formation: ............................................................................................. 14
6 Glycogenolysis:................................................................................................................ 14
6.1 Steps of glycogenolysis: ............................................................................................ 14
6.1.1 Shortening of Glycogen chain: .......................................................................... 15
6.1.2 Removal of branches: ........................................................................................ 16
6.1.3 Formation of glucose 6-phosphate and glucose: ................................................ 16
7 Pentose Phosphate Pathway: ............................................................................................ 16
7.1 Importance:................................................................................................................ 17
7.2 Various reactions in HMP pathway: ......................................................................... 17
8 Glucuronic Acid Pathway: ............................................................................................... 18
8.1 Various involved steps/reactions:.............................................................................. 18
9 Galactose metabolism: ..................................................................................................... 19
10 Fructose Metabolism:....................................................................................................... 20
10.1 Fructokinase pathway: ........................................................................................... 20
10.2 Sorbitol pathway of fructose production: .............................................................. 21
11 Metabolism of Amino sugars: .......................................................................................... 22
12 Glyoxylate Cycle: ............................................................................................................ 22
12.1 Reactions of the Cycle: .......................................................................................... 23
13 References: ....................................................................................................................... 24
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