Glycolysis Steps

1

Hexokinase Reaction

• glucose to glucose 6 phosphate

• cat by hexokinase

• one atp invested - hydrolysis drives reaction

• coupled rxn rly thermo favorable - irreversible

• not committed bc intermediate for multiple paths - glycogen, pentosphosphate

2

Phosphoglucose Isomerase Reaction

Glucose 6 Phosphate to Fructose 6 phosphate

• reversible

• aldose to ketose

• pyranose to a furanose

3

Phosphofructose Kinase Reaction

• comitted step of glycolysis

• 2nd ATP invested

• highly regulated and irreversible

Convert fructose 6 phosphate to fructose 1 6 bisphosphate

4

Aldolase Reaction

Fructose 16 bisphosphate to 2 3C molecules

1. glyceraldehydr-3-phosphate

2. Dihydroxyacetone Phosphate

• reversible

• GAD is the one going through glycolisis so need to make DHAP →: GAD

What are the irreverisble steps of glycolsis

1 3 10

Which steps of glycolisis require ATP input

1 3

5

Triosephosphate Isomerase Reaction

Dihydroxyacetone Phosphate → Glyceraldehyde-3-Phosphate

• most efficient enzyme only limited by the diffusion rate of reactant basically instant

• even tho G greater than zero product formation occurs because GAD conc is kept low since its rapidly converted in the next step driving equilibrium toward product formation

6

GAD Dehydrogenase Reaction

Glyceraldehyde-3-Phosphate → 1,3- Biphosphoglycerate

NAD+ to NADH - redox reactions generates electrons, phosphate free not from atp added

AsO43- is a strong inhibitor bc it resembles PO43- , competitive inhibition

redox and phosphorlaytion

every time you see dehydrogenase what does that mean

redox reactions electron transfer

7

Phosphoglycerate Kinase Reaction

Dephosphoralation

Synth ATP through substrate level phosphorlyation

1,3 bisphosphate glycerate to 3-glycerophosphate

1,3- biphosphoglycerate a highe energy molecule that drives reaction forward

end of 7 step energy breaks even

8

Phosphoglycerate Mutase Reaction

3-phosphoglycerate → 2-phosphoglycerate

-rearrangent, increase in energy from having negative phosphate move closer to the negative carboxyl group

9

Enolase Reaction

2-phosphoglycerate → phosphoenolpyruvate

• high energy enol product drives ADP to ATP

• dehydration yields water as a product

10

Pyruvate Kinase reaction

phosphoenolpyruvate → pyruvate

really high energy drives ADP to ATP - phosphate transfer

last ATP molecule

what is pyruvate finally oxidized to

CO2- when there is sufficient oxygen supply - allows for generation of more atp molecules way later on

what is gluconeogenisis and its starting materials

generation of glucose from smaller carbon molecules

pyruvate from glycolysis

oxaloacetate from. citric acid cycle

when do we use gluconeogensis

prolonged starvation - after glycogen is depleated, then resort to gluconeogenisis

where does gluconeogenisis happen and why that location

Liver - basically just trying to keep the brain alive

where does glycolisis happen

cytosol

what three steps are different in gluconeogenisis

1 3 10 - the irreversible rxns of glycolysis

first step of gluconeogenisis

Pyruvate to phosphoenolpyruvate - super endergonic so coupled w ATP and GTP hydrolisis

Pyruvate —→ (pyruvate carboxylase - cytosol and mito, defects) + ATP + HCO3- → Oxaloacetate → PEP carboxykinase + GTP -→ PEP + CO2

7th step of gluconeogenisis

fructose16bisphosphatase ATP to ADP + Pi

last step of gluconeogenisis

glucose 6 phosphatase

how many ATP molecules does gluconeogenisis for the synthesis of one glucose

6 ATP molecules

what is feedback inhibition

concentration of product inhibits the upstream enzyme

why can ATP inhibit PFK-1

the purpose of glycolysis is to generate glucose and ATP molecules, if theres already a high conc of product, no sense to make more

• ATP binds allosterically

Why does a high concentration of ADP and AMP

means ATP is low, signals the need for energy production, cell needs energy

why does a high conc of PEP in bacteria inhibit PKF-1

feedback inhibition, end product accumulates signalnig upsream theres an accumulation to stop

regulation of glycolisis in mammals

citrate - even more downstream than pyruvate

AMP

ATP

What makes fructose-2,6-bisphosphate

PFK-2

What are the current two active sites on PFK-1 for

ATP Citrate AMP

In bacterial PFK1 what were the two regulatory sites for

PEP

Current structure of a PFK-1 in mammals

fused dimers from a homotetramer with one active site, one regulatory site for ATP, one regulatory site for citrate, and one regulatory site for fructose-2,6-bisphosphate which is an activator made by PFK-2

What does pfk-2 generate fructose-2,6-bisphosphate from

fructose 6 phosphate , costs one ATP molecule

What does Fructose-2,6-bisphosphate inhibit and what does it activate

inhibits = fructose-1,6-bisphosphatase in gluconeogenisis

activates = PFK-1 in glycolysis

What are the two domains of the PFK-2

kinase and phosphatase domains that regulate fructose 26 bisphosphate levels by

which domain turns glycolysis on and gluconeogenisis off

Kinase domain

which domain of PFK 2 do you want on to promote gluconeogenisis and turn off glycolysis

phosphate domain on , reduce conc of fructose 2,6 bisphosphate

how do you inhibit the kinase domain of pfk-2

phosphoralating it

how can we know when our body needs glycolysis or gluconeogenisis to happen for PFK-2 to act accordingly

trhough signal transduction pathways

G protein coupled receptor signal transduction pathway

1. signaling mol binds to embedded g protein coupled receptor

2. binding of receptor induces a conformatoin change opening the interior binding pocket

3. G protein binds to the open binding pocket of receptor and upon assocation, the alpha unit of the g protein releases a GDP, and gets a GTP

4. when it gets a GTP, the alpha unit is activated dissociated from the Beta and gamma subunits

5. the activated G protein activates adenylayte cyclase

6. adenylate cyclase catalyzes the conversion of ATP to cAMP

7. cAMP is a secondary messenger that activates protein kinase A

8. Protein kinase a two reg units cAMP binds and two catalytic units are released and phosphoralates downstream proteins, providing the cellular response

fight or flight mechanism of signal transduction pathway mobilization of energy

• uses signal transduction pathway to mobilize glucose

• when body is under threat we release signaling molecules - epinephrine and noepinephrine - body will know its time to release glucose

B-adregenic recetpor recieves epinephrine as signaling molecule

changes conf of receptor and intracellular binding pocket opens

G protein binds, GDP released and GTP picked up and a unit activates and dissociates

A unit activates adenylase cyclate

adenylate cyclase catalyzes ATP to cAMP

cAMP binds to regulatory domain ofPKA and releases active catalytic domain of PKA

catalytic domain of PKA phosphorylates Glycogen Phosphoralase to release and mobilziing glucose for response

What is the enzyme responsible for mobilizing glucose from glycogen in the B-adregenic signal transduction pathway

Glycogen Phosphorylase - cleaves glucoses from large glycogen polymer

how to turn off the g protein coupled receptor signal transduction pathway

a subunit hydrolyzes the gtp in it to gdp making it inactive again

despite turning of the a subunit, theres still a high conc of adenylate cyclase, what do you do ab this

second point to turn off is through reducing the concentration of cAMP through phosphodiesterase, converts cAMP to AMP

what converts cAMP to AMP

phosphodiesterase - stopping signal trans path

what stops the secondary messenger in the g protein coupled receptor trans path

phosphodiesterase by cAMP-AMP

two ways to stop signal transductin g protein

phosphodiesterase cAMP to AMP decreasing conc and hydrolyzing gtp to gdp in a unit of g protein

what are the two things caffeine do

blocking adenosine receptors to curb the sedative effects on the cns

phosphodiesterate is inhibited to cAMP levels are maintained so epinephrine signals keep going through and their efefct is felt

Glycogen synthesis

• branch off glycolysis pathway

• branches from glucose-6-phosphate synthesis step

• in liver bc no feedback inhibition

• when glucose levels are high

• cost a UTP - adding a glucose onto a growing glycogen requires a lot of energy

Glucose 6 phos → Glu 1 phos via phosphoglucomutase

Glu 1 phos + UTP —> UDP-glucose + pyrophosphate (exergonic and drives reaction)

UDP- glucose transfers to a growing glycogen onto the non reducing end catalyzed by glycogen synthase

difference in hexokinase between liver and m.

feedback inhibition in muscle of glu 6 phos while the liver doesn’t have that and won’t be inhibited

all glucose will be converted to glu 6 phosphate regardless of the conentration there already

Glycogen synthesis takes place in the liver

enzyme for glu 6 phosphate to glu 1 phosphate

phosphoglucomutase

What senses high levels of glucose and what does it start

insulin - signal to start glycogen synthesis and promote glucose uptake in cells

receptor tyrosine kinase path

how does insulin signal tranductoin cascade work

receptor tyrosine kinase

receptor binds to signaling insulin activates by autophosphorlyatoin - activating the intracellular. domain

receptor has two binding sites

the activated kinase phosphorylates downstream kinases allowing signal transduction

eventually activates PKB and PKC

what is the inhibitor that gets phosphoyrlated of glycogen synthase

GSK

how does PKB activate glycogen synthesis

PKB phosphorylates GSK (an inhibitor of glycogen synhtase) so glyocgen production goes

how does PKC activated glycogen synthesis

stimulates the translocation of glucose transpotrer incraese cellular uptake of glucose

what does insulin do to PFK-2

stimulates dephosphorylatoin. of PFK2 - kinase acitvity → glycolisis to create ATP for energy for glycogen synthesis

Pentose phosphate pathway

• on 24/7

• produce 2 NADH and one ribulose 5 phosphate

• oxidative stage and non oxidative stage

• oxidative is the whole pathway with the first step producting an nadph cat by G6P dehydrogenase

• non oxidative convertd to metabolites to stuff that can be used in glycolsis

how does NADPH act as the ultimate reducing power in the cell

glutothione directy reduces whatever then goes to naph to be fixed

why if u dont have Glucose-6-phosphate dehydrogenase will ur cells breakdown

nothing to fight against the oxidative species leads to cell breakdown because no NADPH

all the pathways stemming from glu 6 phos

glycolisis, pentose phosphate pathway, glycogen snythesis, glucose reabsorption