Anaerobic Metabolism: Glycolysis Quiz

Anaerobic Metabolism: Glycolysis

• Anaerobic metabolism is the conversion of glucose to pyruvate in the glycolysis pathway
• The glycolysis pathway occurs in the cytosol and involves 10 soluble enzymes
• The pathway is present in all tissues and has multiple functions, including energy trapping (ATP synthesis), and providing intermediates for fat and amino acid synthesis

Structure and Function of Glucose and Glycogen

• Glucose is a monosaccharide that is an immediate energy source for glycolysis
• Glycogen is a polysaccharide that serves as a medium-term fuel source
• Glycogen is stored in tissue stores and has low osmolarity
• Glucose can be synthesized from non-carbohydrate sources through gluconeogenesis

Glycolysis: Key Points

• Glycolysis is the conversion of glucose to pyruvate
• The pathway occurs in the cytosol and involves 10 soluble enzymes
• The pathway has multiple functions, including energy trapping (ATP synthesis), and providing intermediates for fat and amino acid synthesis
• Glycolysis is a key pathway for ATP production in all tissues

Sources of Glucose for Glycolysis

• Glucose can be obtained from dietary sugars and starch
• Glucose can be broken down from stored glycogen in the liver
• Glucose can be recycled from lactic acid, amino acids, or glycerol

Summary Diagram of the Glycolysis Pathway

• The glycolysis pathway can be divided into 4 stages: activation, splitting, oxidation, and ATP synthesis
• The pathway involves 10 reactions, with key enzymes and intermediates including hexokinase, phosphofructokinase, aldolase, and pyruvate kinase

Activation Stage of Glycolysis

• The activation stage involves the conversion of glucose to fructose 1,6-bisphosphate
• The stage requires the use of 2 ATP molecules
• Key enzymes involved in this stage include hexokinase, phosphohexose isomerase, and phosphofructokinase

Splitting Stage of Glycolysis

• The splitting stage involves the conversion of fructose 1,6-bisphosphate to glyceraldehyde 3-phosphate and dihydroxyacetone phosphate
• The stage involves the action of the enzyme aldolase
• The stage results in the splitting of the 6-carbon sugar into two 3-carbon units

Oxidation Stage of Glycolysis

• The oxidation stage involves the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate
• The stage involves the action of the enzyme glyceraldehyde 3-phosphate dehydrogenase
• The stage results in the removal of 2H atoms and the production of NADH

ATP Synthesis Stage of Glycolysis

• The ATP synthesis stage involves the conversion of 1,3-bisphosphoglycerate to pyruvate
• The stage involves the action of the enzymes phosphoglycerate kinase, phosphoglycerate mutase, and enolase
• The stage results in the synthesis of 2 ATP molecules

Yields of ATP from Glycolysis

• The net yield of ATP from glycolysis is 2 ATP molecules
• However, the pathway can yield 4 ATP molecules in the later stages, resulting in a net gain of 2 ATP molecules
• Further ATP molecules can be produced through mitochondrial metabolism

Anaerobic Glycolysis

• Anaerobic glycolysis occurs in the absence of oxygen
• In anaerobic glycolysis, pyruvate is converted to lactate in order to regenerate NAD+
• The reaction is catalyzed by lactate dehydrogenase

Regulation of Glycolysis

• The glycolysis pathway is regulated by allosteric control and hormonal control
• One example of allosteric control is the inhibition of phosphofructokinase by ATP

Specialised Functions in Tissues

• In skeletal muscle, glycolysis provides ATP for intense exercise
• In red blood cells, glycolysis is the only pathway for ATP production
• In the brain, glycolysis is a major source of ATP

Warburg Effect

• The Warburg effect is the phenomenon of tumour cells preferring anaerobic glycolysis, even in the presence of oxygen
• The effect is named after Otto Warburg, who first described it over 90 years ago