carbohydrate metabolism, Glycolysis, metabolic process of carbohydrates, EMP pathway, Embden- Meyerof-Paranas pathway, cabohydrate metabolic process for study, A presentation on cabohydrate metabolic process i.e. Glycolysis

1. Glycolysis
EMBDEN – MEYERHOF – PARANAS PATHWAY
EMP PATHWAY
OR
OR

2. Defination
The process in cell metabolism by which carbohydrates and sugars,
especially glucose, are broken down, producing ATP and pyruvic acid and
two "high energy" electron carrying molecules of NADH.
CHO
C
C
C
C
CH OH2
OH
H
OH
OHH
H
H
HO
GLUCOSE + 2NAD +2Pi + 2ADP 2 PYRUVATE+ 2NADH+2ATP+2H
+
2NAD +2Pi + 2ADP
2
CH C
O
C
O
O
+
-
+
2

3. GLYCOLYSIS
Glycolysis is the central pathway for the glucose catabolism in which
glucose(6 carbon compound) in converted into pyruvate (3 carbon
compound) through a sequence of 10 steps.
Glycolysis takes place in both aerobic and anrobic organisms & is the first
step towards glucose metabolism.
Glycolysis is also known as Embden – Meyerhof – Paranas pathway or
EMP pathway.
In words, the equation is written as:-
Glucose+ Adenosine diphosphate + Phosphate + Nicotinamide adenine
dinucleotide
Pyruvate + Water + Adenosine triphosphate + Nicotinamide adenine
dinucleotide + Hydrogen ions
Glycolysis can be considered as a two part process:-
1. Energy investment phase – require two ATP molecules to produce high
energy intermediates.
2. Energy pay out phase – The intermediate is metabolized, producing four
ATP molecules and two NADH molecules.

4. GLUCOSE
GLUCOSE-6-PHOSPHATE
FRUCTOSE-6-PHOSPHATE
FRUCTOSE1,6-BIPHOSPHATE
GLYCERALDEHYDE 3-PHOPHATE
DIHYDROXYACETONEPHOSPHATE
+
STEPS OF GLYCOLYSIS
2 MOLECULE
3 CARBON
(6 C)
(6 C)
(6 C)
(6 C)
(6 C)
(6 C)
1,3-BIPHOSPHOGLYCERATE
3-PHOSPHOGLYCERATE
2-PHOSPHOGLYCERATE
(2M, 3C)
(2M, 3C)
PHOSPHOENOLPYRUVATE
(2M, 3C)
(2M, 3C)
GLYCERALDEHYDE 3-PHOPHATE
PYRUVATE(2M, 3C)
2Pi
ATP
ADP
ATP
ADP
2NAD
NADH+H
2
+
2 ADP
2 ATP
+
2 H O
2 ADP
2 ATP
1
2
3
4
5
7
6
8
9
10
1ST STEP
(6 C)
(6 C)
2ND STEP

5. STEP 1- Phosphorylation of Glucose
Energy investment phase
 The enzyme hexokinase phosphorylates (adds a
phosphate group at 6th position of glucose) glucose in the
cell's cytoplasm.
 This step is also accompanied by considerable loss of
energy as heat.

6. STEP 2- Isomerization of Glucose -6- phosphate
 The enzyme phosphoglucoisomerase or
phosphohexoisomerase converts glucose -6-phosphate
into its isomer fructose 6-phosphate.
 This reaction involves a shift of the carbonyl oxygen from
C1 to C2, thus converting an aldos.

7. STEP 3- Phosphorylation of Fructose -6- phosphate
 The enzyme phosphofructokinase uses another ATP molecule to
transfer a phosphate group to fructose 6- phosphate to form fructose
1, 6-bisphosphate.
 The phosphate is transferred from ATP so some amount of energy is
lost in the form of heat.

8. STEP 4- Cleavage of Fructose 1,6- diphosphate
 The enzyme aldolase splits fructose 1, 6-bisphosphate into two sugars
that are isomers of each other. These two sugars are dihydroxyacetone
phosphate and glyceraldehyde phosphate.
 This step involves the unique cleavage of the C-C bond in the fructose 1,
6-bisphosphate.

9. STEP 5- Isomerization of Dihydroxyacetone phosphate
 The enzyme triose phosphate isomerase rapidly inter- converts the
molecules dihydroxyacetone phosphate and glyceraldehyde phosphate.
 Glyceraldehyde phosphate is removed / used in next step of Glycolysis.

10. • Net result for steps 4 and 5:
Fructose 1,6-bisphosphate↔ 2 molecules of
Glyceraldehydes phosphate (C3H5O3P1)

11. STEP 6- Oxidative phosphorylation of Glyceraldehyde 3-phosphate
 Step 6 is one of the three energy-conserving or forming steps of glycolysis.
 The glyceraldehyde 3-phosphate is converted into 1,3-bisphosphoglycerate
by the enzyme glyceraldehyde 3-phosphate dehydrogenase
(phosphoglyceraldehyde dehydrogenase).
 In this process, NAD+ is reduced to coenzyme NADH by the H– from
glyceraldehyde 3-phosphate.
 Since two moles of glyceraldehyde 3-phosphate are formed from one mole
of glucose, two NADH are generated in this step.

12. STEP 7- Transfer of phosphate from
1,3-diphosphoglycerate to ADP
 This step is the ATP-generating step of glycolysis.
 It involves the transfer of phosphate group from the 1, 3-
bisphosphoglycerate to ADP by the enzyme phosphoglycerate kinase, thus
producing ATP and 3-phosphoglycerate.
 Since two moles of 1, 3-bisphosphoglycerate are formed from one mole of
glucose, two ATPs are generated in this step.

13. STEP 8 – Isomerization of 3- phosphoglycerate
 The 3-phosphoglycerate is converted into 2-phosphoglycerate due to
the shift of phosphoryl group from C3 to C2, by the enzyme
phosphoglycerate mutase.
 This is a reversible isomerization reaction.

14. STEP 9 – Dehydration of 2- phosphoglycerate
 In this step, the 2-phosphoglycerate is dehydrated by the action of
enolase (phosphopyruvate hydratase) to phosphoenolpyruvate.
 This is also an irreversible reaction where two moles of water are lost.

15. STEP 10–Transfer of phosphate from phosphoenolpyruvate
 This is the second energy-generating step of glycolysis.
 Phosphoenolpyruvate is converted into an enol form of pyruvate by the
enzyme pyruvate kinase.
 The enol pyruvate, however, rearranges rapidly and non-enzymatically to
yield the keto form of pyruvate (i.e. ketopyruvate). The keto form
predominates at pH 7.0.
 The enzyme catalyzes the transfer of a phosphoryl group from
phosphoenolpyruvate to ADP, thus forming ATP.

16. Significance of Glycolysis
1. The glycolytic pathway is employed by all tissues for the
breakdown of glucose to provide energy in the form of ATP.
2. Important pathway for the production of energy especially under
anaerobic conditions.
3. It is crucial for generation of energy in cells without mitochondria.
4. It forms products that are intermediates for other metabolic
pathways.
5. Glycolysis interfaces with glycogen metabolism, the pentose
phosphate pathway, the formation of amino sugars, triglyceride
synthesis (by means of glycerol 3-phosphate), the production of
lactate (a dead-end reaction), and transamination with alanine.

17. ATP generation
 During Stages I and II of glycolysis, two ATP molecules are consumed
and four ATP molecules are synthesized.
 Thus, the net energy yield in glycolysis is two molecules of ATP per
molecule of glucose fermented.
 However, maximal ATP yield from oxidation of glucose is 36 to 38 ATP.
 The maximum yield of ATP per glucose molecule depends on coupling of
glycolysis with the citric acid cycle by means of pyruvate dehydrogenase.