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Glycolysis

Glycolysis is a central metabolic pathway responsible for the breakdown of glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance and plays a vital role in generating free energy Free energy Enzyme Kinetics for the cell and metabolites for further oxidative degradation. Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance primarily becomes available in the blood as a result of glycogen breakdown or from its synthesis Synthesis Polymerase Chain Reaction (PCR) from noncarbohydrate precursors ( gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis) and is imported into cells by specific transport proteins Transport proteins Proteins and Peptides. Glycolysis occurs in the cytoplasm and consists of 10 reactions, the net result of which is the conversion of 1 C6 glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance to 2 C3 pyruvate molecules. The free energy Free energy Enzyme Kinetics of this process is harvested to produce adenosine Adenosine A nucleoside that is composed of adenine and d-ribose. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter. Class 5 Antiarrhythmic Drugs triphosphate (ATP) and nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway hydride (NADH), key energy-yielding metabolites. The overall stoichiometry of the pathway is: glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance + 2 Pi + 2 ADP + 2 NAD NAD+ A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway+ > 2 pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O (H+: hydrogen ion, Pi:  phosphate Phosphate Inorganic salts of phosphoric acid. Electrolytes ion, NAD NAD+ A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway+: nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway).

Last updated: Jul 21, 2021

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Steps 1–5: 1st Half of Glycolysis

The 1st half of glycolysis requires an energy investment of 2 adenosine Adenosine A nucleoside that is composed of adenine and d-ribose. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter. Class 5 Antiarrhythmic Drugs triphosphate (ATP) molecules and serves to convert the hexose glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance into 2 trioses. The process consists of 5 steps:

  1. Glucose → glucose 6-phosphate (G6P)
    • Hexokinase (HK) transfers a phosphoryl group from ATP onto the 6th carbon of glucose to form G6P.
      • Requires magnesium (Mg2+) as a cofactor 
      • Requires ATP
    • In the liver, this step is catalyzed by glucokinase (an enzyme with the same function but lower glucose affinity), helping the liver serve as a blood glucose “buffer.”
  2. G6P → fructose-6-phosphate (F6P)
  3. F6P → fructose-1,6-biphosphate (FBP)
    • Phosphofructokinase (PFK-1) phosphorylates F6P on C1, yielding FBP.
    • Requires Mg2+ as a cofactor
    • Requires ATP
    • This is a rate-determining reaction in glycolysis, therefore a regulated step
  4. FBP → glyceraldehyde 3-phosphate (GAP) + dihydroxyacetone phosphate Phosphate Inorganic salts of phosphoric acid. Electrolytes (DHAP)
    • Aldolase Aldolase Becker Muscular Dystrophy cleaves the 6-carbon FBP into 2 different 3-carbon molecules, GAP and DHAP. 
    • The reaction is an aldol cleavage with an enolate intermediate stabilized by resonance.
  5. DHAP → GAP
    • Triose-phosphate isomerase (TIM) interconverts DHAP and GAP to allow DHAP to proceed through glycolysis. 
First half of glycolysis

The first 5 steps (first half) of the glycolysis pathway

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Steps 6–10: 2nd Half of Glycolysis

The 2nd half of glycolysis converts the triose GAP to pyruvate, with the concomitant generation of 4 ATP and 2 nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide A coenzyme composed of ribosylnicotinamide 5′-diphosphate coupled to adenosine 5′-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway hydride (NADH) per 2 GAP. Thus, the energy investment of steps 1–5 is paid back twice here. In certain cell types and conditions, these 5 steps are the predominant source of ATP: 

  1. GAP → 1,3-bisphosphoglycerate (1,3-BPG)
    • Glyceraldehyde-3-phosphate Glyceraldehyde-3-phosphate An aldotriose which is an important intermediate in glycolysis and in tryptophan biosynthesis. Pentose Phosphate Pathway dehydrogenase (GAPDH) catalyzes the phosphorylation Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Post-translational Protein Processing and oxidation of GAP, yielding 1,3-biphosphoglycerate (1,3-BPG). 
    • 1,3-BPG is the 1st high-energy intermediate in glycolysis.
    • Produces 2 NADH from nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide A coenzyme composed of ribosylnicotinamide 5′-diphosphate coupled to adenosine 5′-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway ( NAD NAD+ A coenzyme composed of ribosylnicotinamide 5′-diphosphate coupled to adenosine 5′-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway+) and a phosphate Phosphate Inorganic salts of phosphoric acid. Electrolytes ion (Pi)
      • Under aerobic conditions, oxidation of NADH at the respiratory chain regenerates NAD NAD+ A coenzyme composed of ribosylnicotinamide 5′-diphosphate coupled to adenosine 5′-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway+ and produces additional ATP.
      • Under anaerobic conditions, additional reactions are required to regenerate NAD NAD+ A coenzyme composed of ribosylnicotinamide 5′-diphosphate coupled to adenosine 5′-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway+.
  2. 1,3-BPG → 3-phosphoglycerate
    • Phosphoglycerate kinase (PGK) converts 1,3-BPG to 3-phosphoglycerate (3PG). 
    • Requires Mg2+ as a cofactor
    • Produces ATP
    • The GAPDH and PGK reactions are coupled to allow the energetically unfavorable GAPDH reaction to be “pulled forward” by the highly favorable PGK reaction.
  3. 3PG → 2-phosphoglycerate
    • Phosphoglycerate mutase (PGM) converts 3PG to 2-phosphoglycerate (2PG) by transferring the functional group phosphate Phosphate Inorganic salts of phosphoric acid. Electrolytes from C3 to C2.
    • Generates a 2,3-bisphosphoglycerate (2,3-BPG)–enzyme complex
  4. 2PG → phosphoenolpyruvate (PEP)
    • Enolase dehydrates 2PG to phosphoenolpyruvate (PEP). 
    • PEP is the 2nd high-energy intermediate formed in glycolysis.
  5. PEP → pyruvate

Net reaction: glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance + 2 Pi + 2 ADP + 2 NAD NAD+ A coenzyme composed of ribosylnicotinamide 5′-diphosphate coupled to adenosine 5′-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). Pentose Phosphate Pathway+ → 2 pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O

Second half of glycolysis

The last 5 steps (last half) of the glycolysis pathway.

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Regulation of Glycolysis

  • Glycolysis operates continuously in most tissues, with a varying rate according to the needs of the cell.
  • Factors that induce glycolysis repress gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis (the reverse of glycolysis) and vice versa because gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis is reciprocally regulated. 
  • Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin and glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions are the main hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types that control the fluxes of glycolysis and gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis.
  • Optimal pathway regulation is achieved by controlling reactions with a large negative free energy Free energy Enzyme Kinetics change, of which there are 3 in glycolysis.
Regulation of glycolysis

An overview of the regulation of glycolysis. Activators of hexokinase (HK), phosphofructokinase-1 (PFK-1), or pyruvate kinase (PK) are marked in green. Metabolites that inhibit these enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes are marked in red.

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Hexokinase (HK)

  • Regulates step 1 of the pathway
  • Negatively regulated by excess G6P
  • Not relevant when glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance is derived from glycogen, as glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance is released from glycogen as G6P

Phosphofructokinase

  • PFK-1 is the primary flux control point for glycolysis; regulates step 3
  • FBPase catalyzes the reverse step to PFK-1 in gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis, and the 2 enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes are reciprocally regulated.
    • When PFK-1 is inhibited and FBPase is activated, flux is shifted from glycolysis to gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis.
  • PFK-1 is allosterically inhibited by ATP, an indicator Indicator Methods for assessing flow through a system by injection of a known quantity of an indicator, such as a dye, radionuclide, or chilled liquid, into the system and monitoring its concentration over time at a specific point in the system. Body Fluid Compartments of energy abundance.
  • PFK-1 is allosterically activated by adenosine Adenosine A nucleoside that is composed of adenine and d-ribose. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter. Class 5 Antiarrhythmic Drugs monophosphate (AMP) and adenosine Adenosine A nucleoside that is composed of adenine and d-ribose. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter. Class 5 Antiarrhythmic Drugs diphosphate (ADP), indicators of energy scarcity.
  • PFK-1 is allosterically inhibited by citrate.
  • PFK-1 is potently allosterically activated by fructose-2,6-bisphosphate (F2,6P).
    • F2,6P has the opposite effect on the opposing step in gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis.
    • F2,6P is synthesized and degraded by a bifunctional enzyme called PFK-2/FBPase-2, whose activity is controlled by many allosteric effectors and hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types.
    • F6P promotes F2,6P synthesis Synthesis Polymerase Chain Reaction (PCR), activating glycolysis.
    • In the fed state Fed state Energy Homeostasis: insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin stimulates PFK-2/FBPase-2 dephosphorylation → increasing F2,6P levels → increasing glycolytic flux
  • Catecholamines Catecholamines A general class of ortho-dihydroxyphenylalkylamines derived from tyrosine. Adrenal Hormones (via cyclic AMP) inhibit glycolytic enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes HK, PFK-1, PFK-2 (which produces fructose 2,6 bisphosphate), and PK. 

Pyruvate kinase (PK)

  • Regulates step 10 (last) of the pathway
  • Allosterically activated by FBP, indicating accumulation of upstream glycolytic intermediates: results in “pulling” through the glycolytic pathway
  • Allosterically inhibited by ATP, indicating plentiful energy supply
  • In the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy, allosterically inhibited by alanine Alanine A non-essential amino acid that occurs in high levels in its free state in plasma. It is produced from pyruvate by transamination. It is involved in sugar and acid metabolism, increases immunity, and provides energy for muscle tissue, brain, and the central nervous system. Synthesis of Nonessential Amino Acids, a precursor for gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis

Clinical Relevance

  • Galactosemia Galactosemia Galactosemia is a disorder caused by defects in galactose metabolism. Galactosemia is an inherited, autosomal-recessive condition, which results in inadequate galactose processing and high blood levels of monosaccharide. The rare disorder often presents in infants with symptoms of lethargy, nausea, vomiting, diarrhea, and jaundice. Galactosemia: defective metabolism of the sugar galactose Galactose An aldohexose that occurs naturally in the d-form in lactose, cerebrosides, gangliosides, and mucoproteins. Deficiency of galactosyl-1-phosphate uridyltransferase causes an error in galactose metabolism called galactosemia, resulting in elevations of galactose in the blood. Lactose Intolerance. Clinical manifestations begin when milk feeding is started. Infants develop lethargy Lethargy A general state of sluggishness, listless, or uninterested, with being tired, and having difficulty concentrating and doing simple tasks. It may be related to depression or drug addiction. Hyponatremia, jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice, progressive liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy dysfunction, kidney disease, cataracts, weight loss Weight loss Decrease in existing body weight. Bariatric Surgery, and susceptibility to bacterial infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease (especially E coli). Intellectual disability Disability Determination of the degree of a physical, mental, or emotional handicap. The diagnosis is applied to legal qualification for benefits and income under disability insurance and to eligibility for social security and workman’s compensation benefits. ABCDE Assessment may develop if the disorder is left untreated. The mainstay of management is exclusion of galactose Galactose An aldohexose that occurs naturally in the d-form in lactose, cerebrosides, gangliosides, and mucoproteins. Deficiency of galactosyl-1-phosphate uridyltransferase causes an error in galactose metabolism called galactosemia, resulting in elevations of galactose in the blood. Lactose Intolerance from the diet.
  • Hereditary fructose intolerance Hereditary fructose intolerance An autosomal recessive fructose metabolism disorder due to deficient fructose-1-phosphate aldolase activity, resulting in accumulation of fructose-1-phosphate. The accumulated fructose-1-phosphate inhibits glycogenolysis and gluconeogenesis, causing severe hypoglycemia following ingestion of fructose. Prolonged fructose ingestion in infants leads ultimately to hepatic failure and death. Patients develop a strong distaste for sweet food, and avoid a chronic course of the disease by remaining on a fructose- and sucrose-free diet. Disorders of Fructose Metabolism: deficiency of fructose-1-phosphate aldolase Aldolase Becker Muscular Dystrophy. Symptoms begin after ingestion of fructose (fruit sugar) or sucrose so presents later in life. Presents with failure to gain weight, vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia, hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia, liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy dysfunction, and kidney defects. Children with the disorder do very well if they avoid dietary fructose and sucrose.
  • Fructose 1,6-diphosphatase deficiency: associated with impaired gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis. Symptoms include hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia, intolerance to fasting, and hepatomegaly. Emergent treatment of hypoglycemic episodes with glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance rich IV fluids IV fluids Intravenous fluids are one of the most common interventions administered in medicine to approximate physiologic bodily fluids. Intravenous fluids are divided into 2 categories: crystalloid and colloid solutions. Intravenous fluids have a wide variety of indications, including intravascular volume expansion, electrolyte manipulation, and maintenance fluids. Intravenous Fluids and avoidance of fasting are the mainstays of therapy. Severe cases may require glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance supplementation to avoid hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia.
  • Glycogen storage diseases Glycogen Storage Diseases A group of inherited metabolic disorders involving the enzymes responsible for the synthesis and degradation of glycogen. In some patients, prominent liver involvement is presented. In others, more generalized storage of glycogen occurs, sometimes with prominent cardiac involvement. Benign Liver Tumors: deficiency of enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes responsible for glycogen degradation. Depending upon which enzyme is affected, these conditions may affect Affect The feeling-tone accompaniment of an idea or mental representation. It is the most direct psychic derivative of instinct and the psychic representative of the various bodily changes by means of which instincts manifest themselves. Psychiatric Assessment the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy, muscles, or both. There are several clinically significant glycogen storage diseases Glycogen Storage Diseases A group of inherited metabolic disorders involving the enzymes responsible for the synthesis and degradation of glycogen. In some patients, prominent liver involvement is presented. In others, more generalized storage of glycogen occurs, sometimes with prominent cardiac involvement. Benign Liver Tumors with differing presentations. 
  • Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance 6-phosphate dehydrogenase deficiency ( G6PD G6PD Pentose Phosphate Pathway): a genetic disorder that occurs almost exclusively in males and mainly affects red blood cells Red blood cells Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology, causing hemolysis and hemolytic anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types. Symptoms include dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea, fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia, tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children, dark urine Urine Liquid by-product of excretion produced in the kidneys, temporarily stored in the bladder until discharge through the urethra. Bowen Disease and Erythroplasia of Queyrat, palor, and jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice. Hemolytic anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types may be triggered by infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease, certain drugs (antibiotics,  antimalarials), and after eating fava beans.

The following are enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes of the glycolysis pathway that may be involved in congenital Congenital Chorioretinitis enzymatic defects:

  • Pyruvate kinase deficiency (most common)
  • Erythrocyte hexokinase
  • Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance phosphate Phosphate Inorganic salts of phosphoric acid. Electrolytes isomerase
  • Phosphofructokinase

These congenital Congenital Chorioretinitis enzymatic defects produce hemolytic anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types.

Hemolytic anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types: a group of anemias that are due to destruction or premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis clearance of RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology. Intrinsic abnormalities of the RBC lead to splenic clearance ( extravascular hemolysis Extravascular hemolysis Hemolytic Anemia). The chronic destruction of RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology can present as jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice, splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly, cholelithiasis Cholelithiasis Cholelithiasis (gallstones) is the presence of stones in the gallbladder. Most gallstones are cholesterol stones, while the rest are composed of bilirubin (pigment stones) and other mixed components. Patients are commonly asymptomatic but may present with biliary colic (intermittent pain in the right upper quadrant). Cholelithiasis, hematuria Hematuria Presence of blood in the urine. Renal Cell Carcinoma, and symptoms of anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types ( shortness of breath Shortness of breath Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea, fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia, syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope, and tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children).

References

  1. Voet D., Voet J. G., Pratt C. W. (2016) Voet’s Principles of Biochemistry Global Edition.
  2. Allen, G. K. (2020). First Aid for the USMLE Step 1.

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