1. Feeder pathways for glycolysis
Glycogen and starch
Maltose, lactose, trehalose, sucrose
Fructose, mannose, galactose

2. Catabolism of cellular glycogen
Glycogen phosphorylase catalyzes an attack by Pi on the (a1→4) glycosidic linkage that joins the last two glucose residues at a nonreducing end, generating glucose 1-phosphate and a polymer one glucose unit shorter.
14-10

3. Conversion of galactose to glucose 1-phosphate

4. Glycolysis Pentose phosphate pathway
Glucose 1-phosphate produced by glycogen phosphorylase is converted to glucose 6-phosphate by phosphoglucomutase, which catalyzes the reversible reaction
Glycolysis Pentose phosphate pathway

5. Dietary polysaccharides and disaccharides
are hydrolyzed to monosaccharides by
various enzymes

6. Galactosemia
In galactokinase deficiency galactosemia , high conc. are found in blood and urine. Infant develop cataracts, caused by deposition metabolite galactitol in the lens.
Transferase deficiency galactosemia is more serious; It is characterized by poor growth in children, mental deficiency and liver damage that may be fatal.

7. PENTOSE PHOSPHATE PATHWAY (Hexosemonophosphate Shunt)
To understand the function of the pentose phosphate pathway in production of NADPH and ribose precursors for nucleic acid synthesis.
Provides NADPH for biosynthesis
NADPH is used in cytosol for fatty acid synthesis

8. The pentose phosphate pathway is an alternate route for the oxidation of glucose.

9. Reactions of the pentose phosphate pathway occur in the cytosol in two phases
Oxidative non-reversible phase
Non-oxidative reversible phase
NADP+, not NAD +, is used as hydrogen acceptor
1st phase ; Oxidative Phase
This phase produces pentose phosphates and NADPH
- Glucose 6-phosphate undergoes dehydrogenation and decarboxylation to give a pentose, ribulose 5-phosphate, which is converted to its isomer, D-ribose 5-phosphate.
- Overall equation of 1st phase:
Glucose 6-phosphate + 2 NADP++ H2O
ribose 5-phosphate + CO2 + 2 NADPH + 2 H+

11. 2nd PHASE; Non-Oxidative Phase
Recycles pentose phosphate to glucose 6- phosphate.
Two enzymes that act in the interconversion of sugars are Transaldolase and Transketolase.
Transketolase- it catalyzes the transfer of a two carbon fragment from a ketose donor to an aldose acceptor.
Transaldolase- they carry out transfer of three carbon fragment from a keto donor to an aldose acceptor.

12. Non oxidative phase of HMP SHUNT

13. SUMMARY
Genetic defects in any of the three enzymes that catalyze conversion of galactose to glucose 1-phosphate result in galactosemias.
Entry of glucose 6-phosphate either into glycolysis or into HMP shunt is largely determined by the relative conc. of NADP+ & NADPH.