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Module 8 Lesson 4: Pentose Phosphate Pathway, Study notes of Biochemistry

The Pentose Phosphate Pathway (PPP), also known as the hexose monophosphate shunt, is a metabolic pathway parallel to glycolysis. Its primary functions are to produce NADPH, which is essential for biosynthetic reactions and antioxidant defense, and to generate ribose-5-phosphate, a precursor for nucleotide and nucleic acid synthesis. The pathway has two phases: Oxidative phase – converts glucose-6-phosphate into ribulose-5-phosphate, producing NADPH in the process. Non-oxidative phase – involves reversible interconversion of sugars, allowing cells to produce ribose-5-phosphate or feed intermediates back into glycolysis (like fructose-6-phosphate and glyceraldehyde-3-phosphate). The PPP is especially active in tissues involved in fatty acid synthesis (like liver and adipose tissue) and in red blood cells for maintaining reduced glutathione levels.

Typology: Study notes

2022/2023

Available from 05/25/2025

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Two
phases:
Oxidative
vs
non-oxidative
Nonoxidative
Oxidative
Main
products
->
NADPH
+
ribose
S-phosphate
phase
phase
Mr
T
NADPH
NAPPH
-
electron
donor
Reductive
blosynthesis
of
fatty
acids
+
stevolds
Repair
of
oxidative
damage
I
Ribosesphosphate
->
biosynthetic
precursor
of
nucleotides
in
the
case
here
are
writer
intere
Used
in
DNA+RNA
synthesis
or
synthesis
of
some
coenzymes
Precursors
Oxidative
Phase
Ribuloses,
phosphate
RiboseS-phosphate
low
-
so
are
Generates
NADPH
+
Pentose
Ribulose
-
5-phosphate
can
be
used
to
generate
ribose
-
5-phosphate
givgeny
genate
(shappn+
nt
for
DNA/RNA
as
well
as
xylulose
-
S-phosphate
for
non-
Nucleotides,
coenzymes,
nat
Oxidative
ppp
DNA,
RNA
noc/
lactone
*
NADPH
regulates
partitioning
Into
Glycolysis
lactonase
an
a
6-phosphogluconate
(meant
t
versus
Pentose
Phosphate
Pathway
*
a
0-
CH20H
nono.
ie"
phosphabetes
conopo..**
at
e
Glucose
coropa.
Bbsphase
-
the
internate
materia
CH2OPOS-
Xylulose
S-phosphate
Non-Oxidative
Phase
Glucosate
polysis,
A
*
Regenerates
G-G-P
from
R-5-p*
No
ATP
used
in
nonoxidative
phase
pentose
used
in
tissues
(requiring
more
NADPH
than
R-S-P)
phosphate
to
glucose
6
phosphate
such
as
liver
+
adipose
tissue
complete
conversion
of
ribose
-
5-
onosphate,
in
on
"
requires
6
RSP
to
make
5
G6P
pathway
*Non
oxidative
Phase
results
in
Net
Loss
of
Carbons,
but
not
energy
*
6-Phospho-
gluconolactone
oxidative
reactions
of
pentosephosphate
pathway
B
Ribose
----
one
nice
risen
oste
C
6C
"
S-phosphate
s
"
Isomerase
Wa
camerase
by
etolase
Adolase
v
phosphone
see
-
X
ylulose
Glyceraldehyde
Erythroes
fructose
s
/
>
NADPH
-
1
S-phosphate
a-phosphate
6-phosphate
fructose
16-
Ma
i
bisphosphatase
/7
Pentose
Ketolase"ancosphate
S-phosphate
dyceraldely
be
Xylulose
3-phosphate
T
phosphates
TC

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Two phases:Oxidative vs non-oxidative

Nonoxidative Oxidative

Main products -> NADPH + ribose S-phosphate phase phase

MrT^ NADPH

NAPPH -^ electron^ donor

Reductive blosynthesis of fatty acids + stevolds

Repair of^ oxidative^ damage

I

Ribosesphosphate ->^ biosynthetic precursor ofnucleotides^

in

the

case

here

are

writer

Used in DNA+RNA synthesis intere

or synthesis of some coenzymes Precursors

Oxidative Phase^

Ribuloses,

phosphate

RiboseS-phosphate

low-so

are

Generates NADPH+Pentose

Ribulose -^ ↓

givgenygenate 5-phosphate^ can^ be^ used^ to^ generate^ ribose^ -^ 5-phosphate

(shappn+nt for DNA/RNA as well as (^) xylulose - S-phosphate for (^) non- Nucleotides, (^) coenzymes, nat Oxidative^ ppp DNA,^ RNA noc/lactone^ *

NADPHregulates partitioning Into Glycolysis

lactonase (^) ana (^) 6-phosphogluconate(meantt (^) versus Pentose Phosphate (^) Pathway * a 0- (^) CH20H nono.

ie"

phosphabetes conopo..**

ate^ Glucose

coropa. Bbsphase

- theinternate

materia ↓

CH2OPOS-

Xylulose S-phosphate Non-Oxidative Phase^ Glucosate polysis,^ A

Regenerates G-G-P^ from^ R-5-p*^

No ATP used in nonoxidative phase

pentose (^) ⑪

used in tissues (requiring more NADPHthan R-S-P) phosphate to glucose 6 phosphate

such as liver + adipose tissue

complete conversion of ribose -^ 5-

onosphate,

inon

requires "

6 RSP to make (^5) G6P pathway *Non oxidative Phase results^ in Net^ Loss^ of^ Carbons,^ butnotenergy^ * 6-Phospho- oxidative reactions of^ gluconolactone pentosephosphate pathway B Ribose^ ---- onenicerisenoste C 6C (^) ↓

S-phosphate s^ "⑭

Isomerase Wa

camerase by^ etolase^ Adolasev ↑ phosphonesee^ - S-phosphate^ X^ ylulose Glyceraldehyde^ a-phosphateErythroes^ 6-phosphatefructose^ ⑤s/ >NADPH^ -^1

fructose 16- Ma

i

bisphosphatase /

⑲Ketolase"ancosphate Pentose S-phosphate^ Xylulose dyceraldely 3-phosphate be T TC phosphates