carbohydrates

• carbohydrates are the preferred fuel source of the nervous system
• monosaccharides are composed of carbon, hydrogen, and oxygen
• hexose structures: glucose, fructose, and galactose
• pentose structures: deoxyribose and ribose
• disaccharides are 2 monosaccharides joined by dehydration synthesis, creating covalent bonds
• the bond between monosaccharides in a disaccharide is glycosidic
• maltose is glucose + glucose
• sucrose is glucose + fructose
• lactose is galactose + glucose
• oligosaccharides have 2-6 sugars in a chain
• starch is the stored form of carbohydrates in plants
• fibre is part of the plant cell wall and cannot be digested by humans
• plants store glucose as amylose and amylopectin
• amylose is linear and has alpha 1-4 linkages
• amylopectin is branched with alpha 1-4, and branch points are alpha 1-6 every 24-30 residues
• cellulose is the major insoluble fibre in the diet
• cellulose consists of long chains of glucose molecules with beta 1-4 linkages, the linkages fold back together on themselves creating hydrogen bonds
• soluble fibre is fermented in the colon and protects gut flora
• the mouth has amylase that breaks down alpha 1-4 linkages, so does the small intestine
• glycogen is insoluble in water
• glycogen can readily be converted back to glucose in the liver
• when blood glucose increases, insulin is released from B cells in pancreas. insulin increases number of glucose transporters in skeletal muscle and adipose cells, increasing glucose uptake
• blood glucose increase causes glycogenesis and lipogenesis
• excess glucose is stored as triglyceride in adipose tissue
• glucagon targets the liver and adipose tissue
• glycogenolysis converts liver glycogen back to glucose
• gluconeogenesis is the making of new glucose in lover from non carb sources
• glycosidic bond is formed by the condensation of hydroxyl groups
• carbs have a higher potential for structural diversity than proteins or amino acids
• soluble fibre

  pectin, gums, beta glucans, some hemicelluloses
• insoluble fibres

  lignin, cellulose, some hemicelluloses
• hemicellulose is in most plant foods
• pectin is in fruit
• gums are used as food additives or thickeners in processed foods
• beta glucans are found in grains, seaweed, and mushrooms
• SCFAs promote the growth of intestinal epithelial cells and control their proliferation and differentiation
• liver stores 75-100g of glucose, and skeletal muscle stores 300-400
• high blood glucose concentrations can lead to dehydration
• chronically elevated BGL can lead to glycation
• 50% of calories should be from carbohydrates