Gem - Ketogenic amino acids.pdf

Ketogenic Amino Acids are a group of amino acids that can be converted into ketone bodies in the liver when carbohydrate intake is limited. Ketone bodies are alternative energy sources for the brain and other tissues during fasting or low-carbohydrate diets. Key ketogenic amino acids: Leucine...

Ketogenic Amino Acids are a group of amino acids that can be converted into ketone bodies in the liver when carbohydrate intake is limited. Ketone bodies are alternative energy sources for the brain and other tissues during fasting or low-carbohydrate diets. Key ketogenic amino acids: Leucine Lysine Phenylalanine Tyrosine Conversion to ketone bodies: These amino acids are broken down into acetyl-CoA, which is then converted into acetoacetate and beta-hydroxybutyrate, the primary ketone bodies. Significance of ketogenic amino acids: Alternative energy source: Ketone bodies can provide energy for the brain and other tissues, especially during fasting or low-carbohydrate diets. Weight loss: Some people use ketogenic diets to promote weight loss by relying on ketone bodies for energy instead of carbohydrates. Neuroprotection: Ketone bodies have been shown to have neuroprotective effects, potentially beneficial for conditions such as Alzheimer's disease and epilepsy. Note: While ketogenic amino acids are beneficial in certain circumstances, excessive consumption can lead to imbalances in amino acid metabolism and other health issues. It is important to consult with a healthcare professional before adopting a ketogenic diet or making significant changes to your diet. – The Krebs cycle (also known as the citric acid cycle or tricarboxylic acid cycle) is a metabolic pathway that occurs in the mitochondria of eukaryotic cells and in the cytoplasm of prokaryotic cells. It is a key part of cellular respiration, the process by which cells convert glucose into ATP, the primary energy currency of the cell. Key points about the Krebs cycle: Input: Acetyl-CoA, a two-carbon molecule produced from the breakdown of carbohydrates, fats, and proteins. Output: Carbon dioxide, ATP, NADH, and FADH2. Process: A series of chemical reactions that involve the oxidation of  acetyl-CoA to carbon dioxide, producing energy in the form of ATP, NADH, and FADH2. Location: Mitochondria in eukaryotic cells, cytoplasm in prokaryotic cells. Steps of the Krebs cycle: 1. Acetyl-CoA enters the cycle: Acetyl-CoA combines with oxaloacetate to form citrate. 2. Citrate is converted to isocitrate: Citrate is isomerized to isocitrate. 3. Isocitrate is oxidized to alpha-ketoglutarate: Isocitrate is oxidized to alpha-ketoglutarate, producing NADH and carbon dioxide. 4. Alpha-ketoglutarate is oxidized to succinyl-CoA: Alpha-ketoglutarate is oxidized to succinyl-CoA, producing NADH and carbon dioxide. 5. Succinyl-CoA is converted to succinate: Succinyl-CoA is converted to succinate, producing ATP (or GTP in some organisms). 6. Succinate is converted to fumarate: Succinate is oxidized to fumarate, producing FADH2. 7. Fumarate is converted to malate: Fumarate is hydrated to malate. 8. Malate is converted to oxaloacetate: Malate is oxidized to oxaloacetate, producing NADH and regenerating the starting molecule of the cycle. Significance of the Krebs cycle: Energy production: The Krebs cycle produces a significant amount of ATP through oxidative phosphorylation. Intermediate production: The Krebs cycle also produces intermediates that are used in other metabolic pathways, such as amino acid synthesis and gluconeogenesis. Regulation: The Krebs cycle is regulated by various factors, including the availability of acetyl-CoA, the energy needs of the cell, and the levels of NADH and FADH2. Overall reaction of the Krebs cycle: Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi + H2O → 2 CO2 + 3 NADH + FADH2 + GTP + CoA Image of the Krebs cycle: —- Anaerobic Respiration is a type of cellular respiration that occurs in the absence of oxygen. It is a less efficient process than aerobic respiration, but it allows organisms to generate ATP in environments where oxygen is limited or unavailable. Key differences between aerobic and anaerobic respiration: Oxygen: Aerobic respiration requires oxygen as the final electron acceptor, while anaerobic respiration uses other electron acceptors, such as nitrate, sulfate, or carbon dioxide. ATP yield: Aerobic respiration produces significantly more ATP per glucose molecule than anaerobic respiration. End products: The end products of anaerobic respiration vary depending on the electron acceptor used. Common end products include lactate, ethanol, and carbon dioxide. Common types of anaerobic respiration: Lactic acid fermentation: In this process, pyruvate is converted to lactate, regenerating NAD+ for glycolysis to continue. This is common in muscle cells during intense exercise. Alcohol fermentation: In this process, pyruvate is converted to ethanol and carbon dioxide. This is common in yeast and some bacteria. Nitrate reduction: In this process, nitrate is reduced to nitrite or nitrogen gas. This is common in some bacteria. Sulfate reduction: In this process, sulfate is reduced to sulfide. This is common in some bacteria that live in anaerobic environments, such as swamps and sediments. Significance of anaerobic respiration: Survival in anoxic environments: Anaerobic respiration allows organisms to survive in environments where oxygen is limited or absent. Food production: Anaerobic respiration is used in the production of fermented foods, such as yogurt, cheese, and beer. Waste treatment: Anaerobic respiration is used in wastewater  treatment to break down organic matter. Overall, anaerobic respiration is a vital process for many organisms, allowing them to adapt to different environmental conditions and generate energy in the absence of oxygen. – Glucose Transporters are proteins embedded in the cell membrane that facilitate the transport of glucose across the membrane. They play a crucial role in maintaining glucose homeostasis in the body, ensuring that cells have a steady supply of glucose for energy. Types of Glucose Transporters: There are several types of glucose transporters, each with its own specific characteristics and functions: GLUT1: Found in most cells and is responsible for basal glucose uptake. GLUT2: Primarily expressed in the liver, pancreas, and kidney. It plays a role in glucose sensing and insulin secretion. GLUT3: Found in neurons and the placenta. It is highly efficient at glucose uptake, even at low glucose concentrations. GLUT4: Expressed in insulin-responsive tissues, such as muscle and adipose tissue. It is regulated by insulin, which promotes its translocation to the cell membrane to increase glucose uptake. GLUT5: Primarily found in the small intestine. It is responsible for fructose absorption. Functions of Glucose Transporters: Glucose uptake: Glucose transporters facilitate the movement of glucose from the extracellular space into the cell. Glucose sensing: Some glucose transporters, such as GLUT2, play a role in glucose sensing, which is important for regulating insulin secretion. Glucose homeostasis: Glucose transporters help to maintain glucose homeostasis by ensuring that cells have a steady supply of glucose for energy. Regulation of Glucose Transporters: The activity of glucose transporters can be regulated by various factors, including: Insulin: Insulin stimulates the translocation of GLUT4 to the cell membrane in insulin-responsive tissues, increasing glucose uptake. Glucose concentration: The activity of some glucose transporters, such as GLUT2, is influenced by the extracellular glucose concentration. Hormones: Other hormones, such as cortisol and glucagon, can also affect the activity of glucose transporters. In summary, glucose transporters are essential proteins that play a crucial role in glucose metabolism. They facilitate glucose uptake by cells, help to maintain glucose homeostasis, and are regulated by various factors. — The regulation of glycolysis is essential for maintaining cellular energy homeostasis. It ensures that glucose is metabolized at a rate that meets the cell's energy needs while avoiding excessive production of lactate or other waste products. Key regulatory factors: 1. Fructose-2,6-bisphosphate (F-2,6-BP): ○ A potent allosteric activator of phosphofructokinase-1 (PFK-1), the rate-limiting enzyme of glycolysis. ○ Its synthesis and degradation are regulated by the bifunctional enzyme PFK-2/FBPase-2. ○ Insulin stimulates the synthesis of F-2,6-BP, promoting glycolysis. ○ Glucagon inhibits the synthesis of F-2,6-BP, promoting gluconeogenesis. 2. ATP and AMP: ○ High ATP levels inhibit PFK-1, slowing down glycolysis. ○ High AMP levels activate PFK-1, stimulating glycolysis. ○ The AMP/ATP ratio is a sensitive indicator of the cell's energy status. 3. Citrate:  ○ A product of the citric acid cycle, citrate can inhibit PFK-1 when its concentration is high, indicating sufficient energy production. 4. Phosphofructokinase-2 (PFK-2): ○ Regulates the synthesis and degradation of F-2,6-BP. ○ Its activity is influenced by hormones (insulin and glucagon) and cellular energy status. 5. Hormones: ○ Insulin stimulates glycolysis by activating PFK-1 and promoting the synthesis of F-2,6-BP. ○ Glucagon inhibits glycolysis by inhibiting PFK-1 and promoting gluconeogenesis. Overall regulation: The regulation of glycolysis is a complex process that involves multiple factors working together to maintain cellular energy balance. The specific regulatory mechanisms can vary depending on the cell type and the physiological conditions.