Glycolysis and gluconeogenesis: mnemonics | epomedicine (2023)

There is no need to memorize every step of the process. We will cover only the most important events.

One meaning:Glyco (Sugar) + Lysis (Breaking or Breaking)

B. Synonym:Embden-Meyerhof-Weg (EM-Weg)

C. Location:cytoplasm

D. Basic concepts of enzymes:

  • Kinase – adds or removes phosphate from substrate (uses ADP or ATP)
    • For phosphorylation (ATP is used): enzyme = "substrate" + kinase (e.g. hexokinase)
    • For dephosphorylation (ATP production): enzyme = “product” + kinase (e.g. pyruvate kinase)
  • Dehydrogenase: Oxidizes substrate, reduces electron acceptor (NAD+/NADP+ or FAD or FMN)
    • Converts aldehyde to alcohol

E. Key Concepts:

  1. 1 molecule of glucose (6 C) is converted into 2 molecules of pyruvate (2 x 3 C; aerobic) or lactate (2 x 3 C; anaerobic).
  2. During the initial cracking phase (6 C to 3 C) during the addition of phosphate to the substrate: Energy is consumed
  3. After splitting a 6C compound into two 3C compounds: 2 molecules are formed (energy is generated)
  4. Substrate phosphorylation consumes ATP: 1 at each step (no cleavage occurred)
    • Glucose zu Glucose-6-Phosphate (Glucokinase/Hexokinase) – 1 ATP
    • Fructose-6-Phosphate to Fructose-1,6-Biphosphate (Phosphofructokinase) – 1 ATP
  5. Dehydrogenation reaction (oxidative phosphorylation).: uses NAD to generate NADH (2 at each step - cleavage has already taken place)
    • Glycerinaldehyde-3-phosphate (G3P) zu 1,3-Bisphosphoglycerate (G3P-Dehydrogenase) + 2 NADH
  6. Substrate dephosphorylation produces ATP:2 in each step (the division has already been done)
    • 1,3 bisphosphoglycerato (1,3 BPG) zu 3-fosphoglycerato (fosfoglyceratoquinasa) + 2 ATP
    • Phosphoenolpyruvate (PEP) for Pyruvate (pyruvate kinase) + 2 ATP
  7. ATP net gain:
    • Aerobic: -1 ATP – 1 ATP + 2 ATP + 2 ATP + 2 NADH = 2 ATP + 2 NADH (1 NADH gives 2.5 ATP in the new concept depending on the shuttle or 3 ATP in the old concept) = 7 to 8 PTA
    • Anaerobic: -1 ATP – 1 ATP + 2 ATP + 2 ATP = 2 ATP (NAD+ is regenerated from NADH by the reduction of pyruvate to lactate by lactate dehydrogenase)
    • ATP generated directly by phosphorylation = substrate-level phosphorylation
  8. Irreversible reactions:
    • 3 out of 4 of the "kinase" reactions discussed above are irreversible.
    • Hexokinase/glucokinase, phosphofructokinase, and pyruvate kinase (irreversible due to very large negative ΔG)
    • These are potential sites for regulatory scrutiny (often this is because blockages could result in a pathway elsewhere
      for intermediate accumulation) and substrate availability (in this case glucose) is another general issue for regulation.
    • At each of these three points, glycolytic reactions are circumvented by alternative gluconeogenic reactions:
      • Hexoquinase/Glucoquinase by Glucose-6-Fosfatase
      • Phosphofructokinase during Fructose-1,6-Biphosphatase
      • Pyruvate kinase by pyruvate carboxylase and PEP carboxykinase

How does NADH make ATP?

  1. Glycolysis produces NADH in the cytosol.
  2. To produce ATP, it must be transferred to the electron transport chain within the mitochondria.
  3. NADH itself cannot cross the inner mitochondrial membrane.
  4. This is done by the malate-aspartate shuttle: Malate IN - Aspartate OUT (Malate enters and is oxidized to oxaloacetate, producing NADH, but it also cannot cross the mitochondrial membrane and therefore has to produce aspartate via a transamination, of way that aspartate enters the cytosol and regenerates oxaloacetate through the transamination reaction)

Glycolysis is aerobic except under the following conditions (where anaerobic glycolysis occurs):

  1. Decreased oxygen supply: renal medulla
  2. Few or no mitochondria: red blood cells
  3. Large increase in ATP requirement: skeletal muscle during exercise

E. Glucoquinasa (Hexoquinasa IV) vs. Hexoquinasa (Hexoquinasa I-III):

(Video) Glycolysis and Gluconeogenesis Mnemonic for Biochemistry

The difference between glucokinase and hexokinase I-III is that glucokinase only works at high concentrations of glucose. The liver, site of glycogen synthesis, has a homologous enzyme called glucokinase. This one has a high Km for glucose. This allows the brain and muscles to use the glucose before storing it as glycogen.

F. Entry of other sugars into glycolysis:

  1. fructose:
    • Fructose is phosphorylated by fructokinase (liver) or hexokinase (fat) at positions 1 and 6, respectively.
    • Fructose-6-phosphate is an intermediate product of glycolysis.
    • An aldolase-like enzyme acts on fructose-1-phosphate to produce DHAP and glyceraldehyde.
    • DHAP is an intermediate of glycolysis and glyceraldehyde can be phosphorylated to glyceraldehyde-3-P.
  2. Glycerin:It is phosphorylated to G-3-P, which is then converted to glyceraldehyde-3-phosphate.
  3. Galactose:
    • It has a somewhat complicated multi-step pathway to convert to glucose-1-phosphate.
    • gal → gal-1-P → UDP-gal → UDP-glc → glc-1-P.
    • When this pathway is interrupted due to a defect in one or more enzymes involved in the conversion of gal to glc-1-P, galactose accumulates in the blood and the subject suffers from galactosemia.

F. Regulation of Glycolysis:

1. Hexoquinasa:

  • Inhibition by accumulation of glucose-6-phosphate (feedback inhibition).
  • Glucose-6-phosphate is required for other metabolic pathways, including pentose phosphate shunting and glycogen synthesis. Therefore, the hexokinase step is not inhibited unless G-6-P accumulates (without regulation by downstream intermediates/metabolites).

2. Glucoquinasa:

  • No direct feedback inhibition as with hexokinase.
  • Induced by insulin and blood sugar and inactivated by glycogen.
  • Inactivated indirectly by fructose-6-phosphate (through induction of a protein that binds to and suppresses glucokinase).
  • Excessive consumption of fructose can cause an imbalance in liver metabolism, indirectly depleting ATP from liver cells.

3. Phosphofructokinase:

  • speed limit step
  • PFK-1 controls the entry of G6P into glycolysis; when the PFK-1 rate is reduced, G6P accumulates and is directed to glycogen synthesis or to the pentose phosphate pathway.
  • PFK-1 is allosterically regulated by:
    • Fructose-2,6-Bisphosphate: "well-fed" signal that stimulates PFK-1 in the liver (synthesized from F6P by PFK-2 when insulin levels are high; glucagon inhibits insulin and stimulates fructose bisphosphatase -two)
    • AMP: stimulates PFK-1 in muscle (inhibits fructose bisphosphatase and gluconeogenesis)
    • ATP and citrate: slow glycolysis when energy is plentiful (activates fructose bisphosphatase to form glucose)
  • Its equivalent enzyme (fructose biphosphatase-1) is the rate-limiting enzyme of gluconeogenesis.

4. Pyruvatequinase:

  • Innovative Stimulation: Fructose 1,6 Bisphosphate (prevents metabolic blockade when PFK is active)
  • Allosteric inhibition: ATP and alanine (biosynthetic product of pyruvate; mobilized from fasting muscle) - enable PEP accumulation and gluconeogenesis

Hormonal regulation:

1. Insulin (well-nourished state): Lowers blood sugar (stimulates glycolysis and inhibits glycolysis)

(Video) Glycolysis TRICK - How to remember GLYCOLYSIS FOREVER !!!

  • Stimulate glucokinase, PFK and pyruvate kinase (not hexokinase)
  • Inhibit the counterenzymes of gluconeogenesis, d. h glucose-6-phosphatase, fructose biphosphatase, pyruvate carboxylase and PEP carboxykinase

2. Glucagon (starvation): increase in blood sugar (inhibiting glycolysis and stimulating gluconeogenesis)

  • Inhibits glucokinase, PFK and pyruvate kinase (not hexokinase)

fasting state:↑ Glucagon → ↑ cAMP → ↑ Protein kinase A → ↑ FBPase-2, ↓ PFK-2
State:↑ Insulin → ↓ cAMP → ↓ Protein kinase A → ↓ FBPase-2, ↑ PFK-2

  • DAP forms glycerol-3-phosphate (G3P) by G3P dehydrogenase; G3P is involved in triglyceride synthesis and electron transport
  • In red blood cells: 2-3-BPG mutase forms 2,3-DPG from 1,3-BPG, which binds to the β chains of HbA and reduces oxygen affinity; shifts the oxygen dissociation curve to the right
  • Enolase is inhibited by fluorine.
  • PK deficiency: hemolytic anemia, elevated 2,3-BPG, absence of Heinz bodies (red blood cells lack mitochondria and rely on anaerobic glycolysis; PK deficiency results in decreased ATP, resulting in:
    • Loss of biconvex shape, which is destroyed in the spleen
    • decreased activity of the Na + K + ATPase pump, leading to loss of ionic balance and causing osmotic embrittlement

Gluconeogenesis begins 4 to 6 hours after the last meal and becomes fully active when liver glycogen stores are depleted, peaking after 5 to 7 days of fasting (it is not a source of energy for the liver; hepatocytes use beta oxidation to provide the energy needed for gluconeogenesis).

In gluconeogenesis, glucose is synthesized from non-carbohydrate precursors such as:

  1. Glycogenic amino acids (all except leucine and lysine)
  2. Lactate (produced by muscles during anaerobic glycolysis)
  3. Glycerin (produced by adipose tissue)
  4. Propionate (from odd-chain fatty acid beta oxidation, isoleucine oxidation, and cholesterol side chain)

The (large) liver and kidneys are important gluconeogenic tissues; the kidney contributes up to 40% of the total glucose synthesis in the fasted state and more in the fasted state. It does not occur in muscles because muscles lack glucose-6-phosphatase, so free glucose cannot be released.

Acetyl-CoA (produced by beta-oxidation of fatty acids in the liver after lipolysis during fasting) cannot be used as a substrate for gluconeogenesis, but is an allosteric activator of pyruvate carboxylase (converts pyruvate to oxaloacetate). for use in gluconeogenesis) and pyruvate dehydrogenase inhibitor (converts pyruvate to acetyl-CoA to enter the TCA cycle), pushing pyruvate towards gluconeogenesis.

Cahill cycle (alanine-glucose cycle): Glutamate (containing amino groups toxic due to breakdown of muscle protein) can be transported to the liver via conversion to glutamine, or it can transfer its amino group to pyruvate (product of glycolysis) via from the action of ALT (SGPT) to form alanine, which is then transported to the liver. In the liver, alanine is deaminated back to pyruvate. The amino group enters the urea cycle and the pyruvate enters gluconeogenesis. The glucose thus formed is transported back to the muscle for use.

Cori Cycle (lactic acid cycle):

First, the reaction of LDH to form lactate requires NADH and produces NAD.+which is then available for use by the glyceraldehyde-3-phosphate dehydrogenase reaction of glycolysis. Therefore, these two reactions are closely linked during anaerobic glycolysis. Second, the lactate produced by the LDH reaction is released into the bloodstream and transported to the liver, where it is converted to glucose. Glucose is then returned to the blood, where it is used by muscles for energy and glycogen stores are replenished. This cycle is calledheart cycle.

In muscle, glycolysis leads to the production of two units of ATP. However, the liver uses six units of ATP to carry out the process of gluconeogenesis. Cori's cycle also requires the initial supply of oxygen, without which it cannot start. Therefore, muscles eventually need a fresh supply of glucose and oxygen.

(Video) Glycogenesis Mnemonic for MCAT

When physical activity is very strenuous, muscle energy requirements exceed the ability of the Cori cycle to regenerate glucose from lactate. This leads to a condition known as lactic acidosis.


It involves cytosolic and mitochondrial enzymes.

The irreversible steps of glycolysis must be avoided with special gluconeogenic enzymes.

1. Pyruvate-carboxylase (mitochondrial):

In mitochondria, pyruvate is converted to oxaloacetate via pyruvate carboxylase. But, as mentioned above, the inner mitochondrial membrane is impermeable to oxaloacetate, so oxaloacetate must be converted to malate (through a malate-aspartate transport) to leave the mitochondria and reach the cytosol.

Activated by acetyl-CoA.

2. PEP carboxykinase (mitochondrial and cytosolic):

Activated by glucagon and cortisol.

3. Fructose-1,6-Biphosphatase (zytosolisch)

(Video) Gluconeogenesis Pathway Made Simple - BIOCHEMISTERY

4. Glucose-6-phosphatase (hepatocyte ER)

Glycolysis and gluconeogenesis: mnemonics | epomedicine (3)

dr. Sulabh Kumar Shrestha, MS Orthopedia

He is editor of the Orthopedics section of Epomedicina. Find and share easier ways to simplify complicated medical problems. She also loves writing poetry, listening to music and acting.


How do you memorize glycolysis mnemonics? ›

Ken Tao is the MedSchoolCoach expert on MCAT, and will help you remember glycolysis intermediates with the word trick: Girls get fine food; Gentlemen dine girls; Boys prefer to pick up pepperoni pizza.

What is a dirty mnemonic for glycolysis? ›

Using some basic ones I found, I tweaked them a bit while keeping them dirty, to help remember them better. Substrates: Gross, (Annoying) Guys Favor (Ass) Flab, But Dreamy, Gorgeous, (Nerdy) Boys (Always) Prefer Pretty, PEPpy, (Awesome) Princesses.

What are the 4 gluconeogenic enzymes that bypass the irreversible steps of glycolysis? ›

However, three reactions of glycolysis are highly exergonic, resulting in largely negative free-energy changes that are irreversible and must be bypassed by different enzymes. The enzymes unique to gluconeogenesis are pyruvate carboxylase, PEP carboxykinase, fructose 1,6-bisphosphatase, and glucose 6-phosphatase.

Do I need to memorize glycolysis for MCAT? ›

While you won't need to memorize each step of glycolysis and its related enzymes, it may be useful to be familiar with the function of each enzyme. Figure: An overview of glycolysis. Note that one molecule of glucose (a 6-carbon molecule) yields two molecules of pyruvate (a 3-carbon molecule).

What are the 10 steps of gluconeogenesis? ›

The gluconeogenesis pathway has four irreversible steps catalysed by the enzymes phosphoenolpyruvate carboxykinase, pyruvate carboxylase, glucose 6-phosphatase, and fructose 1,6-bisphosphatase, which is generally found in the liver, kidney, intestine, or muscle.

What is step 8 of glycolysis? ›

Step 8 of glycolysis:

In the eighth step, the remaining phosphate group in 3-phosphoglycerate moves from the third carbon to the second carbon, producing 2-phosphoglycerate (an isomer of 3-phosphoglycerate). The enzyme catalyzing this step is a mutase (a kind of isomerase).

What are the important things to remember about glycolysis? ›

The essential metabolic pathway of glycolysis involves the oxidative breakdown of one glucose into two pyruvate with the capture of some energy as ATP and NADH. Glycolysis is important in the cell because glucose is the main source of fuel for tissues in the body.

What is glycolysis kid friendly? ›

Glycolysis means ''glucose splitting'' and that is just what happens during this first step of cellular respiration. A glucose molecule hanging out in a cell is split in half to make two smaller molecules of a chemical called pyruvate. During this splitting some energy—two molecules of ATP—is made.

What are the 3 bypass steps of gluconeogenesis? ›

There are three irreversible steps in the gluconeogenic pathway: (1) conversion of pyruvate to PEP via oxaloacetate, catalyzed by PC and PCK; (2) dephosphorylation of fructose 1,6-bisphosphate by FBP; and (3) dephosphorylation of glucose 6-phosphate by G6PC.

Which three steps in glycolysis Cannot be directly reversed during gluconeogenesis? ›

3 irreversible steps in glycolysis: hexokinase; phosphofructokinase; pyruvate kinase. New enzymes are needed to catalyze new reactions in the opposite direction for gluconeogenesis.

Which three enzymes are present in glycolysis but not gluconeogenesis? ›

The gluconeogenesis pathway consumes ATP, which is derived primarily from the oxidation of fatty acids. The pathway uses several enzymes of the glycolysis with the exception of enzymes of the irreversible steps namely pyruvate kinase, 6-phosphofructokinase, and hexokinase.

How much of the MCAT is memorization? ›

Memory questions represent 25% of science questions on the MCAT.

Is the MCAT mostly memorization? ›

The MCAT is not a memorization test. Let me be more specific: it's much more about recall than it is about recognition. When you're prepping for the Psych/Soc section of the MCAT, you'll learn about different types of memory—sensory, working, procedural, episodic—how memory is stored, and how it's retrieved.

What is gluconeogenesis and glycolysis pathway? ›

Glycolysis is the pathway by which glucose degrades into lactate (LAC), gluconeogenesis is the pathway by which glucose is generated from pyruvate and/or LAC, and glycogenesis is the pathway by which glycogen is synthesised from glucose (Nordlie et al, 1999).

How many steps are different between glycolysis and gluconeogenesis? ›

Complete answer:
This process takes place when the cell energy is low.This process takes place when the cell energy is high.
It is a 10-step reversible reaction.It is a 11-step reaction which involves 2 irreversible reactions.
5 more rows
7 days ago

What is gluconeogenesis for dummies? ›

Gluconeogenesis is the metabolic process by which organisms produce sugars (namely glucose) for catabolic reactions from non-carbohydrate precursors. Glucose is the only energy source used by the brain (with the exception of ketone bodies during times of fasting), testes, erythrocytes, and kidney medulla.

What are the 4 products of glycolysis? ›

Glycolysis starts with one molecule of glucose and ends with two pyruvate (pyruvic acid) molecules, a total of four ATP molecules, and two molecules of NADH.

How many ATP steps are in glycolysis? ›

There are two phosphorylation reactions in glycolysis where ATP acts as phosphate donor. During the formation of glucose-6-phosphate from glucose and during the formation of fructose 1, 6-bisphosphate from fructose-6-phosphate.

What are the 4 end products of glycolysis? ›

Hence this takes place in both aerobic and anaerobic organisms. The final output or end product of Glycolysis is two molecules of pyruvate, ATP, NADH, and water.

Is step 7 in glycolysis irreversible? ›


Two phases of glycolysis. There are ten steps (7 reversible; 3 irreversible).

What are the three types of glycolysis? ›

Main Steps Involved In The Glycolysis Pathway

There are three main steps in glycolysis: substrate level phosphorylation, conversion of glucose-phosphate to fructose-phosphate, and the formation of two molecules of phosphate.

Is Step 10 of glycolysis irreversible? ›

Step 10: The final step in glycolysis is the enzymatic conversion of phosphoenolpyruvate to pyruvate by pyruvate kinase. Substrate level phosphorylation occurs in this irreversible step to generate 2 molecules of ATP.

What is the most important enzyme in glycolysis? ›

Introduction of PFK

It is the most important rate-limiting enzyme of glycolysis. PFK-1 catalyzes the conversion of fructose 6-phosphate and ATP to fructose 1, 6-bisphosphate, and adenosine diphosphate (ADP).

What is the most important step in glycolysis? ›

The most important regulatory step of glycolysis is the phosphofructokinase reaction. Phosphofructokinase is regulated by the energy charge of the cell—that is, the fraction of the adenosine nucleotides of the cell that contain high‐energy bonds.

What are the steps of glycolysis? ›

Glycolysis is divided into 3 stages:
  • Stage 1 (Priming stage)
  • Stage 2 (Splitting stage)
  • Stage 3 (Oxidoreduction-phosphorylation stage)
  • Energy Balance Sheet for glycolysis.

What is Glycogenesis in biology? ›

Glycogenesis is the process of storing excess glucose for use by the body at a later time. Glycogenolysis occurs when the body, which prefers glucose as an energy source, needs energy.

What are the 2 types of glycolysis? ›

Glycolysis occurs in both aerobic and anaerobic states. In aerobic conditions, pyruvate enters the citric acid cycle and undergoes oxidative phosphorylation leading to the net production of 32 ATP molecules. In anaerobic conditions, pyruvate converts to lactate through anaerobic glycolysis.

Does glycolysis require ATP? ›

Energy is needed at the start of glycolysis to split the glucose molecule into two pyruvate molecules. These two molecules go on to stage II of cellular respiration. The energy to split glucose is provided by two molecules of ATP.

Does glycolysis require oxygen? ›

Glycolysis, which is the first step in all types of cellular respiration is anaerobic and does not require oxygen. If oxygen is present, the pathway will continue on to the Krebs cycle and oxidative phosphorylation.

How do you memorize the structure of glucose? ›

The mnemonic SOS (Same, Opposite, Same) can be helpful to recall the stereochemistry in either D-glucose or L-glucose. It refers to the configurations of C-2, C-3, and C-4 relative to that of C-5 in an aldohexose.

What are the main difference points between glycolysis and gluconeogenesis? ›

It is a catabolic pathway i.e. glucose molecule is broken down in this process.It is an anabolic pathway i.e. glucose molecule is synthesized in this process.
Glucose is broken down to produce two pyruvate molecules.Two pyruvate molecules come together to form glucose.
3 more rows

How do you remember the difference between glucose glycogen and glucagon? ›

What is the difference between glucose, glycogen, glucagon and GlucoGen?
  1. Glucose is the sugar in our bloodstream that our body uses for energy.
  2. Glycogen is a stored form of energy. ...
  3. Glucagon signals the body to convert the stored glycogen back into glucose.
Jun 6, 2022

What is the mnemonic for carbohydrates? ›

Meet three women who want to help you remember the names of the simple sugars and complex carbohydrates. "Mona Glues Fruit to her Glasses."

How do you memorize structures in biochemistry? ›

“Simply” learn to speak the language, beginning with the vocabulary (e.g. structures of adenine, ribose and phosphate) and finishing off by talking in whole sentences (e.g. adenosinetriphopshate). The names of most molecules are already describing the structure!

Why does gluconeogenesis need 4 ATP? ›

The breakdown pathway of glucose in glycolysis yields 2 ATP and 2 NADH. So it takes 4 more energetic triphosphates of energy to make each molecule of glucose than can be obtained from glucose breakdown.

What is glycolysis very short answer? ›

A process in which glucose (sugar) is partially broken down by cells in enzyme reactions that do not need oxygen. Glycolysis is one method that cells use to produce energy.

What is a mnemonic to remember when insulin and glucagon are released? ›

Insulin Mnemonic (Ready, Set, Inject, Love)

What is the difference between glycolysis and gluconeogenesis in glucose metabolism? ›

Glycolysis is a catabolic process of glucose hydrolysis needed for energy and biosynthetic intermediates, whereas gluconeogenesis is a glucose production process important for maintaining blood glucose levels during starvation.

What are the major differences between gluconeogenesis and glycolysis What about glycogenesis and Glycogenolysis? ›

glycogenesis - the conversion of glucose into glycogen. glycogenolysis - the breakdown of glycogen into glucose. gluconeogenesis - the manufacture of glucose from non carbohydrate sources, mostly protein.


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