Glycolysis and Gluconeogenesis PDF

Glycolysis is a metabolic pathway that occurs in the cytoplasm of most living cells, including bacteria, animals, fungi, and plants. It is the first step in cellular respiration, the process by which cells convert glucose into ATP, the primary energy currency of the cell. Key points about glycolysi...

Glycolysis is a metabolic pathway that occurs in the cytoplasm of most living cells, including bacteria, animals, fungi, and plants. It is the first step in cellular respiration, the process by which cells convert glucose into ATP, the primary energy currency of the cell. Key points about glycolysis: Input: Glucose, a six-carbon sugar. Output: Pyruvate, a three-carbon molecule; ATP (net 2 molecules); NADH (2 molecules). Process: Glycolysis is divided into two phases: the energy investment phase and the energy payoff phase. Location: Cytoplasm of the cell. Types: Anaerobic glycolysis (occurs in the absence of oxygen) and aerobic glycolysis (occurs in the presence of oxygen). Anaerobic glycolysis: End product: Lactate (in animals) or ethanol (in plants and microorganisms). Purpose: To generate ATP in the absence of oxygen. Drawback: Inefficient compared to aerobic glycolysis. Aerobic glycolysis: End product: Pyruvate, which enters the mitochondria for further oxidation in the Krebs cycle and electron transport chain. Purpose: To generate a much larger amount of ATP compared to anaerobic glycolysis. Significance of glycolysis: It is the primary pathway for glucose metabolism in most organisms. It provides ATP for cellular activities. It serves as a starting point for other metabolic pathways, such as the Krebs cycle and gluconeogenesis. Overall reaction of glycolysis: Glucose + 2 ATP + 2 NAD+ → 2 pyruvate + 2 ATP + 2 NADH + 2 H+ Image of glycolysis pathway: —- Gluconeogenesis: The Reverse of Glycolysis Gluconeogenesis is a metabolic pathway that synthesizes glucose from non-carbohydrate precursors such as pyruvate, lactate, glycerol, and certain amino acids. It primarily occurs in the liver and kidneys. Why is it important? Maintaining blood glucose levels: When blood sugar levels drop, gluconeogenesis helps to replenish them. Energy source: Glucose is a primary energy source for many tissues, especially the brain and red blood cells. Liver function: The liver plays a crucial role in maintaining glucose homeostasis, and gluconeogenesis is a key process in this regulation. Key steps of gluconeogenesis: 1. Pyruvate carboxylation: Pyruvate is converted to oxaloacetate in the mitochondria. 2. Oxaloacetate to phosphoenolpyruvate: Oxaloacetate is transported to the cytoplasm and converted to phosphoenolpyruvate. 3. Phosphoenolpyruvate to fructose-1,6-bisphosphate: Phosphoenolpyruvate is converted to fructose-1,6-bisphosphate. 4. Fructose-1,6-bisphosphate to fructose-6-phosphate: Fructose-1,6-bisphosphate is converted to fructose-6-phosphate. 5. Fructose-6-phosphate to glucose-6-phosphate: Fructose-6-phosphate is converted to glucose-6-phosphate. 6. Glucose-6-phosphate to glucose: Glucose-6-phosphate is converted to glucose, which is released into the bloodstream. Differences between glycolysis and gluconeogenesis: Direction: Glycolysis breaks down glucose, while gluconeogenesis builds it up. Location: Glycolysis occurs in the cytoplasm of most cells, while gluconeogenesis primarily occurs in the liver and kidneys. Energy requirement: Gluconeogenesis requires energy in the form of ATP and GTP. Irreversible steps: Some steps in glycolysis are irreversible, so gluconeogenesis must use alternative pathways to bypass these steps. Factors affecting gluconeogenesis: Hormones: Glucagon and cortisol stimulate gluconeogenesis, while insulin inhibits it.  Nutritional status: Fasting or low-carbohydrate diets can trigger gluconeogenesis. Exercise: Intense exercise can lead to increased gluconeogenesis to provide energy for muscles. In summary, gluconeogenesis is a vital metabolic process that ensures a steady supply of glucose for the body, especially during fasting or when dietary carbohydrate intake is limited.