Nutrition and Metabolism

Metabolism All of the chemical reactions that occur in cells – Reactants – Products Metabolic pathways – A series of reactions Begins with a specific reactant and through multiple steps, produces an end product Each step is catalyzed by a specific enzyme

Metabolism cont’d Enzymes – Protein molecule which functions as a catalyst to speed up rate of chemical reaction

Digestive Enzymes - Overview Hydrolytic Reactions – Substrate interacts with water and results in the decomposition of that substrate. Must have optimum pH for activity

Major Digestive enzymes Salivary amylase – Catalyzes the reaction starch + H 2 O  maltose Pepsin – Catalyzes the reaction protein + H 2 O  peptides

Major Digestive enzymes cont’d. Pancreatic amylase – Catalyzes the reaction starch + H 2 O  maltose Occurs in duodenum Completes digestion of starches to dissaccharides

Major Digestive enzymes cont’d. Trypsin – Catalyzes the reaction protein + H 2 O  peptides Occurs in duodenum Lipase – Catalyzes the reaction fats + H 2 O  glycerol + 3 fatty acids – Emulsification by bile salts occurs first – Occurs in duodenum

Major Digestive enzymes cont’d. Peptidases – Catalyze reaction peptides + H 2 O  amino acids Maltase – Catalyzes reaction maltose + H 2 O  2 Glucose Occurs in small intestine

Major Digestive enzymes cont’d. Table 14.3

Digestive Enzymes – Conditions Required Environmental conditions must be optimum Warm temperature Correct pH – Each enzyme has its own optimal pH

Digestion experiment Fig

Nutrition Science of foods and nutrients All body functions depend on proper nutrition Food Guide

Nutrition - Food guide

Nutrition - Guidelines Its just chemistry! – Balance energy input with energy output to maintain weight Eat a variety of foods – Our bodies require ALL the different types of nutrients for different things! – Drink lots of water!

Nutrition - Guidelines A healthy diet – You still need fat! – Protein!!! – Choose whole foods – Avoid Processed foods

Nutrients: Carbohydrates Primary energy source Glucose – Most readily available energy source Complex carbohydrates – Gradually broken down to glucose – Contain fiber

Nutrients: Carbohydrates cont’d Simple sugars – High glycemic index-elevate blood sugar rapidly – Pancreas releases overload of insulin

Nutrients: Carbohydrates cont’d Sugars – Monosaccharide: Simple sugars – Disaccharide: A molecule of sugar made of two simple sugars – Polysaccharide: A molecule of sugar made of more than two simple sugars

Reducing high glycemic index carbohydrates Table 14.4

Nutrients: Proteins Functions – Growth and development Used to make structural proteins

Nutrients: Proteins cont’d Synthesis of other proteins Synthesis of body proteins – 8 must be supplied in diet-essential amino acids

Nutrients: Proteins cont’d. Complete proteins – Contain all 20 amino acids Incomplete proteins – Proteins of plant origin – Each lacks at least essential amino acids – Vegetarians must combine plant protein sources

Nutrients: Proteins cont’d. Amino acids are not stored Too high intake of protein can be harmful – Deamination of amino acids produces urea – Urea excretion requires water Some protein foods also are high in saturated fats

Nutrients: Lipids Energy storage Saturated fats – Solids at room temperature – Associated with cardiovascular disease – Trans fatty acids are worst

Nutrition: Lipids cont’d Unsaturated fats – Oils have percentage of mono- and polyunsaturated fats Omega-3 fatty acids – Double bond in third position

Nutrition: Lipids cont’d. Fats that cause disease – Plaques- form in arteries – Cholesterol Carried in blood by low density lipoprotein (LDL) and high density lipoprotein (HDL) – Trans-fats In commercially packaged foods

Nutrition: Vitamins Coenzymes – organic molecules that are required by certain enzymes to carry out catalysis Cofactors – inorganic substances that are required for, or increase the rate of, catalysis 13 vitamins

Nutrition: Vitamins cont’d Antioxidants – Vitamins C,E, and A – Defend against free radicals – Cell metabolism generates free radicals

Nutrition: Vitamins cont’d – Vitamin D Converted in skin to active form by UV light Further modification in kidneys and liver

Nutrition: Minerals Major minerals – Body contains more than 5 grams Trace minerals – Body contains less than 5 grams – Components of larger molecules 14-30

Nutrition: Minerals cont’d. Calcium – Deficiency causes osteoporosis Osteoclasts more active than osteoblasts – Calcium intake can slow bone loss – Requirements – Vitamin D is essential companion to calcium

Nutrition: Minerals cont’d. Sodium – Requirement is 500 mg/day – Average intake in US is mg/day – Only is naturally occurring in diet

Nutrition: Eating Disorders Obesity – Body weight 20% above normal, or BMI of higher than 30.0 – Over weight = a BMI higher than 25.0, in Canada 40% of men, 27 % of women – 17% women and 20% men in Canada are obese – Hormonal, metabolic, and social factors

Nutrition: Eating Disorders cont’d Bulimia Nervosa – Can coexist with obesity or anorexia – Binging and purging-damage from vomiting – Psychotherapy and medication are treatments

Nutrition: Eating Disorders cont’d Anorexia Nervosa – Morbid fear of gaining weight – All symptoms of starvation – Can result in death – Force-feeding and psychotherapy are critical