2. Carbohydrate Digestion and Absorption.pdf

HNUT10010 HNUT10020 Human Nutrition 1: Understanding Nutrients Aifric O’Sullivan BSc, MSc, PhD UCD Institute of Food and Health School of Agriculture and Food Science 1 Carbohydrate Digestion and Absorption • • • • Introduction Nutrient transport Carbohydrate digestion Carbohydrate absorption 2...

HNUT10010 HNUT10020 Human Nutrition 1: Understanding Nutrients Aifric O’Sullivan BSc, MSc, PhD UCD Institute of Food and Health School of Agriculture and Food Science 1 Carbohydrate Digestion and Absorption • • • • Introduction Nutrient transport Carbohydrate digestion Carbohydrate absorption 2 Absorption and Circulation 3 Passive Transport Down its concentration gradient Down its concentration gradient facilitated by a membrane bound transport protein Movement of water 4 Active Transport cell membrane surrounds the substance forming a vesicle 5 Carbohydrate Digestion Glycaemic Non-glycaemic Starch Fibre Salivary amylase Mechanical action crushes and tears Stomach acid inactivates amylase Not digested, delays gastric emptying Pancreatic amylase Small glucose polymers and disaccharides Not digested in small intestine Enzymes on surface of intestinal cells Maltose, sucrose, lactose Bacterial enzymes digest fibre in the large 6 intestine Carbohydrate Digestion 7 Carbohydrate Absorption • Sodium monosaccharide transporter (SGLT1) • Fructose transporter (GLUT5) • Monosaccharide transporter on the basolateral membrane accepts all 3 monosaccharides (GLUT2) 8 Using different mechanisms to our advantage? 9 What impacts the rate of absorption? • Lipid (fat) content of food • Structure of food • Ratio of amylose-amylopectin • Amount of chewing • Rate of gastric emptying • Small intestine transit time 10 Quiz • On a scale of 1 to 5, how difficult was this lecture? • What slides were most difficult? 11 Reading • Lanham-New S, Macdonald IA, Roche Hm, eds. Nutrition and Metabolism. 2nd ed: Wiley-Blackwell, 2011. Chapter 10 • Gibney M, Lanham-New S, Cassidy A, Vorster H, eds. Introduction to Human Nutrition. 2nd ed: WileyBlackwell, 2009. Chapter 5 • Gropper SS, Smith JL. Advanced Nutrition and Human Metabolism, International Edition 6th ed: Wadsworth Cenage Learning, 2013. Chapter 3 & 4 12