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Glycolysis vs. Gluconeogenesis: A Comparative Analysis of Glucose Metabolism, Study notes of Biochemistry

Massachusetts College of Pharmacy & Health Sciences (MCPHS)Biochemistry

Glycolysis and gluconeogenesis are opposing metabolic pathways vital for glucose metabolism. Glycolysis, mainly in muscle and brain, breaks down glucose into pyruvate, producing ATP and NADH. Gluconeogenesis, primarily in the liver, synthesizes glucose from non-carbohydrate precursors like pyruvate, lactate, glycerol, and amino acids. This overview highlights key enzymes, regulatory mechanisms, and conditions under which each pathway operates, emphasizing their roles in maintaining blood glucose homeostasis during starvation, exercise, and low-carbohydrate diets. It details pyruvate conversion to phosphoenolpyruvate, including pyruvate carboxylase and phosphoenolpyruvate carboxykinase, and biotin's role as a CO2 carrier. It further explains how animals produce glucose from sugars and proteins but not fatty acids, and plants' and bacteria's ability to convert CO2 to carbohydrates via the Calvin cycle.

Typology: Study notes

2022/2023

Available from 05/25/2025

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bg1
Glycolysis
vs
Gluconeogenesis
Glycolysis
Gluconeogenesis
Glycolysis
occurs
mainly
in
the
muscle
+
brain
Glucose,
Jose
Gluconeogenesis
occurs
mainly
in
the
liver
nexokinase
2
pyruvate
+
4
ATP
+
2
GTP
+
2
NADH
+
2H
+
4
H,0
->
Glucose
+4
ADP+2GDP+6Pi+2
NAD
Opposing
pathways
that
are
both
thermodynamically
favorable
irbt
usb
a
n
rub
in
the
Operate
in
opposite
direction
End
product
of
one
Is
the
starting
compound
of
the
other
phosphate
Allows
generation
Reversible
reactions
->
both
pathways
of
glucose
when
glycogen
stores
are
depleted
->
starvation
VIgo4roUS
exercise
No
ATP
generated
during
gluconeogenesis
aclds
(no
fatty
acids)
physiologically
Irreversible
reaction
of
glycolysis
->
bypassed
in
gluconeogenesis
I
seusetra-avian
interestinent
Different
enzymes
in
different
pathways
necessary:
Brain,
nervous
system,
and
red
blood
cells
Gifferentials
regulate
event
of
futile
are
vertegnose
are
Metabolic
pathway;
results
in
generation
of
glucose
from
certain
non-carbohydrate
carbon
substrates
(2)
Pyruvate
Animals
produce
glucose
from
sugars/proteins
Blood
Animals
cannot
produce
glucose
from
fatty
colds
Ubiquitous
process
->
plants,
animals,
fungi,
bacteria
+
other
microorganisms
Process
occurs
during
periods
of
fasting,
starvation,
low-carbohydrate
are
"net
nee
diets/
Intense
exercise
Mammals
->
gluconeogenesis
is
believed
to
be
restricted
to
the
liver,
the
kidney,
the
Intestine,
muscle.
New
evidence
suggests
that
it
occurs
in
astrocytes
of
the
brain
CHIC
Begins
in
mitochondrial
Intermediate
of
->
citric
acid
cycle
path
from
pyruvate
to
phosphoenolpyruvate
leads
through
oxaloacetat e
I
Any
compound
that
can
be
converted
to
either
pyruvate
or
oxaloaceta te
can
Pyruvate
amino
therefore
serve
as
starting
material
for
gluconeogenesis
(alanine
+
aspartate)
ā†‘
Flucogenic
Glycerol
3-phospho-
acIds
ā†‘
Lactate
Triacyl-
CO2
can
also
yield
3
or
4
carbon
fragments
glycerols
fixation
plants
+
photosynthetic
bacteria
are
uniquely
able
to
convert
co,
to
carbohydrates
(Calvin
cycle)
pf2

Partial preview of the text

Download Glycolysis vs. Gluconeogenesis: A Comparative Analysis of Glucose Metabolism and more Study notes Biochemistry in PDF only on Docsity!

Glycolysis vs^ Gluconeogenesis

Glycolysis Gluconeogenesis

Glycolysis occurs^ mainly in^ the^ muscle^ +^ brain^ Glucose, Jose Gluconeogenesis occurs^ mainly^ in^ the^ liver^

nexokinase

(^2) pyruvate + 4 ATP + 2 GTP + 2 NADH + 2H^ + (^4) H,0 ->^ Glucose +4^ ADP+2GDP+6Pi+2 NAD Opposing pathways thatare^ both^ thermodynamically favorable irbtusb

an

rub

in

Operate in^ opposite direction the End (^) productof one Is the (^) starting compound of^ the other phosphate

Allows generation

Reversible reactions -> both pathways of^ glucose^ when^ glycogen

stores are^ depleted -> starvation

VIgo4roUS exercise

No ATP^ generated during gluconeogenesis (^) aclds (^) (no (^) fatty acids)

physiologically

Irreversible reaction of^ glycolysis ->^ bypassed in (^) gluconeogenesis I

seusetra-avian

interestinent

Differentenzymes in differentpathways necessary:Brain, nervous system, and^ red^ blood^ cells Gifferentialsregulateeventoffutileare vertegnose

are

Metabolic (^) pathway;results in (^) generation of (^) glucose from certain

non-carbohydrate carbon^ substrates

(2) Pyruvate

Animals (^) produce (^) glucose from (^) sugars/proteins (^) Blood Animals (^) cannot produce (^) glucose from (^) fatty colds Ubiquitous process ->^ plants,^ animals, fungi,^ bacteria^ +^ other microorganisms Process occurs (^) during periods of (^) fasting, starvation, (^) low-carbohydrate

are

"netnee

diets/ Intense^ exercise

Mammals -> (^) gluconeogenesis is believed to be restricted to the (^) liver, the (^) kidney,the (^) Intestine,muscle. New evidence (^) suggests thatit occurs in (^) astrocytes of^ the brain

CHIC

Begins in^ mitochondrial^ Intermediate^ of

-> citric^ acid^ cycle

path from (^) pyruvate to (^) phosphoenolpyruvate leads (^) through oxaloacetate (^) I Any compound^ thatcan^ be^ converted^ to^ either^ pyruvate^ or^ oxaloacetate^ can^ Pyruvate amino therefore serve as^ starting material^ for^ gluconeogenesis (alanine^ +^ aspartate)^ ā†‘

Flucogenic

Glycerol

3-phospho-

acIds ā†‘

can also Lactate^ Triacyl-^ CO

yield 3 or^4 carbon^ fragments (^) glycerols fixation

plants + photosynthetic bacteria are^ uniquely^ able^ to^ convert co, to^ carbohydrates^ (Calvin^ cycle)

Steps 1+^2 Pyruvate to^ Phosphoenolpyruvate

1ststep -> pyruvate carboxylase converts pyruvate to oxaloacetate

Bicarbonate (^) Pyruvate

8 Carboxylation^ using^ a^ blotin^ factor

  • ~ no-c_- +CH--, (^) Requires transportinto the mitochondria 10-

2nd Step -> Phosphoenolpyruvate carboxykinase converts oxaloacetate to PEP

car seat

phosphorylation from^ GTP^ +^ decarboxylation

AbP+Pi occurs^ in^ mitochondria/cytosol^ depending on^ the^ organism

Carbon is added^ - immediately removed^ from^ structure Blotin Is a (^) CO2 Carrier Guanosine attentionerat

a

Long (^) CO2blotinyl-Lys from site^ tether 1 to (^) site^ moves 2 HC05 - pyruvate carboxyminera at app isa cat.at I pyruvate carboxylase 0 - P0?

CH2 =C-C00-^ Pyruvate Carboxylase Reaction: Phosphoenolpyruvate FirstGluconeogenic Steps cofactor (^) blottn (^) covalently attached to (^) enzyme (^) through amide (^) linkage to s amino^ group of^ Lys residue^ forming bloting/enzyme Travel (^) through Mitochondria cytosolic S

*PEPS Reaction occurs 1n2 phases which occur at 2 differentsites in the enzyme

Carboxykinase CO

Catalytic Site^ 1,^ bicarbonate^ on^ is^ converted^ to^ Co, atthe^ expense of^ ATP CO2 reacts^ with^ biotin^ (forms^ carboxybloting-enzyme). Long arm^ composed minerariesministrar isa biotinanocossidechain cattained^ then^ carriesconotcurbobiotingienee

to catalytic site 2 enzyme surface. CO2 Is released + reacts with pyruvate, forms

oxaloacetate + regenerating blotinyl enzyme

Lactate Flexible arms -> Intermediates between (^) enzyme active^ sites Selectively permeable ->^ Inner^ mitochondrial^ membrane^ Blotin-^ dependentcarboxylation reactions^ (those^ catalyzed by proplony Malate, PEP+^ pyruvate (permeable) (^) CoA (^) carboxylase + acetyl-CoA carboxylase) Oxaloacetate cannotescape Oxaloacetate (^) can be utilized in citric acid (^) cycle (Krebs (^) cycle) * Pathways depend on the (^) availability oflactate or (^) pyruvate + the^ * oxaloacetate can be converted to^ PEP^ or malate^ to^ allow^ cytosolic requirements^ for^ NADHfor^ gluconeogenesis

transport to^ cytosol for gluconeogenesis