Carbohydrate Metabolism Overview

The complex process by which organisms break down, synthesize, and utilize carbohydrates like sugars and starches for energy and essential biological functions.

A metabolic pathway that breaks down glucose into pyruvate, producing a small amount of ATP and NADH. It occurs in the cytoplasm of most cells.

Metabolic processes that occur in the absence of oxygen, such as fermentation, to generate energy from glucose.

A type of anaerobic catabolism that converts pyruvate into ethanol and carbon dioxide, mainly found in yeast and some bacteria.

A type of anaerobic catabolism that converts pyruvate into lactate, often occurring in muscle cells during intense exercise.

A metabolic pathway that synthesizes glucose from non-carbohydrate precursors like lactate, amino acids, and glycerol, primarily in the liver.

A metabolic pathway that produces NADPH, a reducing agent essential for biosynthesis, and ribose-5-phosphate, a precursor for nucleotide synthesis.

An enzyme that catalyzes the first step of glycolysis, phosphorylating glucose to form glucose-6-phosphate.

An allosteric enzyme that catalyzes the second irreversible step of glycolysis, phosphorylating fructose-6-phosphate to form fructose-1,6-bisphosphate.

An enzyme that catalyzes the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate during glycolysis.

An enzyme that catalyzes the final step of glycolysis, transferring a phosphate group from phosphoenolpyruvate to ADP, producing ATP and pyruvate.

A concept where an enzyme changes its shape slightly upon binding its substrate, creating a more precise fit for catalysis.

An enzyme that catalyzes the conversion of pyruvate to oxaloacetate in the first step of gluconeogenesis, requiring biotin as a cofactor.

An enzyme that catalyzes the conversion of oxaloacetate to phosphoenolpyruvate in gluconeogenesis, an important step for glucose synthesis.

An enzyme that catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate in gluconeogenesis, a key step for glucose production.

An enzyme that catalyzes the dephosphorylation of glucose-6-phosphate to glucose in the final step of gluconeogenesis, releasing glucose into the bloodstream.

The phenomenon where cancer cells preferentially use glycolysis even in the presence of oxygen, producing lactate.

A reducing agent that is essential for biosynthesis, particularly in the pentose phosphate pathway, providing electrons for building molecules.

A precursor for nucleotide synthesis used in creating RNA and DNA, produced in the pentose phosphate pathway.

The inability to digest lactose due to a deficiency in lactase, the enzyme that breaks down lactose.

A metabolic process that occurs in the absence of oxygen to produce energy from glucose, often resulting in the production of alcohol or lactic acid.

A genetic condition where the enzyme glucose 6-phosphate dehydrogenase is deficient, causing a sensitivity to oxidative stress and potentially leading to hemolytic anemia.

A condition where harmful reactive oxygen species (ROS) damage cells and tissues, potentially leading to various diseases.

Harmful oxygen-containing molecules with unpaired electrons that can damage cells and tissues.

Clumps of denatured hemoglobin that form in red blood cells when glutathione is deficient, leading to potential cell lysis.

A condition where red blood cells are prematurely destroyed, leading to a deficiency of healthy red blood cells.

The coordinated, opposing control of two metabolic pathways, such as glycolysis and gluconeogenesis, ensuring balance.

A highly branched polymer of glucose that serves as a major form of carbohydrate storage in animals.

Glucose is the primary fuel source for most life forms because it's readily available under prebiotic conditions, is stable, and doesn't readily bind to proteins.

Glycolysis has two phases: the investment phase, where energy is used, and the payoff phase, where energy is generated, resulting in pyruvate, ATP, and NADH.

Hexokinase is an enzyme that traps glucose in the cell by phosphorylating it to glucose-6-phosphate, initiating glycolysis.

Induced fit is when hexokinase changes its shape upon binding glucose, creating a tighter fit and facilitating the reaction.

Pyruvate can be converted into lactate (anaerobic), ethanol (fermentation), or oxidized to form CO2 and H2O (aerobic).

The investment phase of glycolysis uses ATP to convert glucose to glyceraldehyde-3-phosphate, setting the stage for energy production.

The payoff phase of glycolysis generates ATP, NADH, and pyruvate by breaking down glyceraldehyde-3-phosphate.

Pyruvate, the product of glycolysis, can take three different paths depending on the availability of oxygen: aerobic metabolism, alcoholic fermentation, or lactic acid fermentation.

Metabolic processes that occur in the absence of oxygen. Examples include fermentation (alcoholic and lactic acid) which regenerate NAD+ for continued glycolysis.

Under anaerobic conditions, NADH is used to regenerate NAD+ so that glycolysis can continue. This is essential for energy production without oxygen.

Metabolic processes that use oxygen to completely oxidize pyruvate (via citric acid cycle & electron transport chain). Produces much more ATP than anaerobic processes.

A metabolic pathway that occurs in the mitochondria, where acetyl CoA (derived from pyruvate) is completely oxidized, producing electron carriers (NADH & FADH2).

A series of protein complexes embedded in the mitochondrial membrane that transfer electrons from NADH & FADH2, ultimately producing ATP through oxidative phosphorylation.

A step that connects glycolysis to the citric acid cycle, where pyruvate is converted to acetyl CoA, which can then enter the citric acid cycle.

Cataracts occur when galactose is converted to galactitol, which accumulates in the lens and disrupts water balance, causing clouding.

A sugar alcohol made from galactose, poorly metabolized and accumulates in the lens, causing cataracts.

It allows the body to produce glucose for essential functions, especially during fasting or strenuous exercise when glycogen stores are depleted.

The liver is the main site of gluconeogenesis, although some can occur in the kidneys.

Glucose is the primary fuel for the brain, and the only fuel for red blood cells.

Complete glycogen breakdown requires debranching enzymes to degrade the (1->6) linkages.

Enzymes responsible for breaking down the (1->6) linkages in branched glycogen molecules, allowing complete glucose release.

Carbohydrate breakdown happens in various parts of the cell, leading through different metabolic pathways from galactose to glucose-6-phosphate, fructose-6-phosphate, and ultimately to acetyl-CoA.

A key molecule in cellular metabolism, produced from the breakdown of carbohydrates, fats, and proteins, and used in the citric acid cycle for energy production.

Gluconeogenesis, the process of making glucose from pyruvate, requires energy input. It is unfavorable without coupling to favorable reactions.

Glycolysis and gluconeogenesis are regulated in a coordinated, opposing manner. When one is active, the other is typically turned off.

NADPH is a reducing agent, essential for biosynthesis, particularly in the pentose phosphate pathway. It provides electrons for building molecules.

The pentose phosphate pathway is found in various tissues like the liver, mammary glands, adrenal glands, and adipose tissue. It's also vital in red blood cells.

Metabolic pathway that synthesizes glucose from non-carbohydrate precursors like lactate, amino acids, and glycerol, primarily in the liver.

Certain enzymes are specific to gluconeogenesis including pyruvate carboxylase and glucose 6-phosphatase.

Gluconeogenesis is not simply the reverse of glycolysis, though they share some steps, because their overall free energy changes are different.

Pyruvate carboxylase converts pyruvate to oxaloacetate in the first step of gluconeogenesis using biotin.

PEPCK converts oxaloacetate to phosphoenolpyruvate, another important step for glucose synthesis.

Gluconeogenesis is regulated differently from glycolysis, ensuring balance between glucose production and utilization.

Glycerol can enter either the gluconeogenic or glycolytic pathway at dihydroxyacetone phosphate (DHAP), making it a flexible fuel source.

Most enzymes for gluconeogenesis are located in the cytoplasm, except for pyruvate carboxylase (in the mitochondria) and glucose 6-phosphatase (in the endoplasmic reticulum)