ch_15_b_glikoliz_ve_heksozlarin_yikimi_yonca_duman

8/3/2019 ch_15_b_glikoliz_ve_heksozlarin_yikimi_Yonca_Duman

1/58

Pentose Phosphate Pathwayor

Hexose Monophosphate

or

Phosphogluconate Oxidative

Pathway


2/58

Of particular importance in

some tissues is the oxidation

of glucose-6-phosphate to

pentose phosphates by the

pentose phosphate pathway.In this oxidative pathway,

NADP+ is the electronacceptor, yielding NADPH.


3/58

Rapidly dividing cells, such

as those ofbone marrow,skin, and intestinal mucosa,

RNA, DNA, and such

coenzymes as ATP, NADH,

FADH2, and coenzyme A.


4/58

In other tissues, the essential

product of the pentose

phosphate pathway is not the

pentoses but the electron donor

NADPH, needed for reductivebiosynthesis or to counter the

damaging effects of oxygenradicals.


5/58

Tissues that carry out extensivefatty acid synthesis (liver,

adipose tissue, lactatingmammary gland) or very active

syn es s o c o es ero ansteroid hormones (liver, adrenal

gland, gonads) require the

NADPH provided by thepentose

phosphate pathway.


6/58


7/58

The gonad is the organ that makesgametes. The

gonads in males are thetestes and the gonads in

females are theovaries. The product, gametes, are

haploid germ cells. For example,sperm and egg

cells are gametes. In addition to producting

gametes, the gonads are a combinedglandsproviding both exocrine and endocrine functions.

The male and female gonads producesteroidsex

hormones, identical to those producted by adrenal

cortical cells.


8/58


9/58

Endocrine system, all organs and tissuesthat release a class of substances called

hormones. The endocrine organs are

also called ductless glands or endocrineglands because their secretions are

.

The hormones secreted by the endocrine

glands regulate growth, developmentandfunctions of many tissues, and coordinate

the bodys metabolic processes.


10/58

The body doesn't have an exocrine system as

such, but there are numerous exocrine glands.Exocrine glands are glands which secrete their

products onto the skin or into body cavities. They

do this either directly, or indirectly via a ductwhich transports the secretions to the skin surface.

mucous secreting glands (goblet cells)

sweat glands

oil glands salivary glands

The liver (secretes bile)

the pancreas (synthesises digestive enzymes)


11/58

Erythrocytes and the cells of the

lens and cornea are directly exposed

to oxygen and thus to the damaging

free radicals generated by oxygen. Bymaintaining a reducing atmosphere

high ratio of NADPH to NADP+ and

a high ratio of reduced to oxidized

glutathione), they can prevent or undooxidative damage to proteins, lipids,

and other sensitive molecules.


12/58

The activity ofPentose

Phosphate Pathway is low in

nonlactating mammary glandandskeletal muscle.


13/58


14/58


15/58


16/58


17/58


18/58

Pentose Phosphate Pathway


19/58


20/58


21/58


22/58


23/58


24/58


25/58


26/58


27/58


28/58


29/58


30/58


31/58


32/58


33/58


34/58


35/58


36/58


37/58

Transketolase Reaction Transaldolase Reaction


38/58


39/58


40/58


41/58


42/58


43/58


44/58


45/58


46/58


47/58


48/58



49/58


for the Cells require both NADPH and RIBOSE

Glucose-6-P + 2 NADP+ + H2O Ribose-5-P + CO2 + 2 NADPH + 2H+


50/58

Overall reaction of the oxidative phase ofOverall reaction of the oxidative phase ofOverall reaction of the oxidative phase ofOverall reaction of the oxidative phase of

Pentose Phosphate PathwayPentose Phosphate PathwayPentose Phosphate PathwayPentose Phosphate Pathway

for the Cells require both NADPH and RIBOSE

Glucose-6-P + 2 NADP+

+ H2O

Ribose-5-P + CO2 + 2 NADPH + 2H+

In some tissues, the pentose phosphate pathway ends at this point. The netresult is the production of NADPH, a reductant for biosynthetic reactions,and ribose 5-phosphate, a precursor for nucleotide synthesis.


51/58

Overall reaction of the non-oxidative phase of

Pentose Phosphate Pathway when cells require both NADPH and RIBOSE

4 Ribose-5-PP 4 Xylulose-5-P

2 Ribose-5-P + 2 Xylulose-5-P 2 Sedoheptulose-7-P + 2 Gliseraldehyde-3-P

2Gliseraldehyde-3-P + 2Sedoheptulose-7-P 2Fructose-6-P + 2Erythrose-4-P

ry rose- - + y u ose- - ruc ose- - + sera e y e- -

2 Gliseraldehyde-3-P Fructose-1,6-PP

Fructose-1,6-PP + H2O Fructose-6-P + Pi

6 Ribose-5-P + H2O 5 Fructose-6-P + Pi

5 Fructose-6-P 5 Glucose-6-P

6 Ribose-5-P + H2O 5 Glucose-6-P + Pi


52/58

Oxidative Phase

6Glucose-6-P + 12NADP+ + 6H2O 6Ribose-5-P + 6CO2 + 12NADPH + 12H+

Non-Oxidative Phase

6 Ribose-5-P + H2O 5 Glucose-6-P + Pi

Overall reaction of Pentose Phosphate Pathway when cells requireboth NADPH and RIBOSE



53/58


54/58

Overall reaction of the non-oxidative phase of

Pentose Phosphate Pathway when cells require NADPH but not RIBOSE

6Glucose-6-P + 12NADP+ + 6H2O 6Ribose-5-P + 6CO2 + 12NADPH + 12H+

4 Ribose-5-PP 4 Xylulose-5-P

2 Ribose-5-P + 2 Xylulose-5-P 2 Sedoheptulose-7-P + 2 Gliseraldehyde-3-P

sera e y e- - + e o ep u ose- - ruc ose- - + ry rose- -

2 Erythrose-4-P + 2 Xylulose-5-P 2 Fructose-6-P + 2 Gliseraldehyde-3-P

2 Gliseraldehyde-3-P Fructose-1,6-PP

Fructose-1,6-PP + H2O Fructose-6-P + Pi

5 Fructose-6-P 5 Glucose-6-P

6Glucose-6-P + 12NADP+ + 7H2O 12 NADPH + 12H+ 6CO2 + 6 Pi


55/58


56/58

Overall reaction of Pentose Phosphate Pathway when cells require

Ribose but not NADPH

6 Glucose-6-P 5 Fructose-6-P

Fructose-6-P + ATP Fructose-1,6-PP + ADPFructose-1,6-PP 2 Gliseraldehyde-3-P

2 Fructose-6-P + 2 Gliseraldehyde-3-P 2 Xylulose-5-P + 2 Erythrose-4-P

2Erythrose-4-P +2 Fructose-6-P 2Sedoheptulose-7-P + 2Gliseraldehyde-3-P2Gliseraldehyde-3-P + 2Sedoheptulose-7-P 2 Ribose-5-P + 2 Xylulose-5-P

4 Xylulose-5-P 4 Ribulose-5-P

4 Ribulose-5-P 4 Ribose-5-P5 Glucose-6-P + ATP 6 Ribose-5-P + ADP


57/58

Overall reactions of Pentose Phosphate Pathways

a) Cells require both NADPH and RIBOSE


b) Cells require NADPH but not RIBOSE

Glucose-6-P + 12 NADP+ + 7 H2O 12 NADPH + 12 H+ + 6 CO2 + Pi

c) Cells require RIBOSE but not NADPH

5 Glucode-6-P + ATP 6 Ribose-5-P + ADP


58/58

When NADPH is forming

used for biosynthesis andglutathione reduction,[NADPH] rises andinhibits the first enzymein the pentose phosphate

pathway. As a result,more glucose 6-phosphate is available forglycolysis.

ch_15_b_glikoliz_ve_heksozlarin_yikimi_yonca_duman

Documents