Bioenergetics and Digestion Well be discussing 1 Trends

Bioenergetics and Digestion

We’ll be discussing 1. Trends and Various Strategies Used by Organisms to Process Food 2. Process of Digestion in Man 3. Disorders of the Human Digestive System

Core Concepts • • Nutritional requirements – Animals are heterotrophs that require food for fuel, carbon skeletons, and essential nutrients. – Metabolic rate provides clues to an animal’s bioenergetic strategy. Evolutionary adaptations of feeding mechanisms and digestive systems – Diverse feeding adaptations have evolved among animals. – Structural adaptations of digestive systems are often associated with diet. – Symbiotic microorganisms help nourish many vertebrates. Overview of food processing – The four main stages of food processing are ingestion, digestion, absorption, and elimination. – Digestion occurs in specialized compartments. – The oral cavity, pharynx, and esophagus initiate food processing. – The stomach stores food and performs preliminary digestion. – The small intestine is the major organ of digestion and absorption. – Reclaiming water is a major function of the large intestine. – Hormones regulate digestion. – Reclaiming water is a major function of the large intestine. Nutrition and disorders of the human digestive system – A healthful diet provides both fuel and building materials. – Nutritional disorders damage health.

Keywords • • • • • absorption alimentary canal amebocytes anorexia bile bolus brush border bulimia cecum chyme complete digestive tract crop digestion duodenum elimination endocytosis enzyme esophagus • • • • essential nutrient extracellular digestion filter feeders gallbladder gastrovascular cavity gizzard heterotroph ileum incomplete digestive tract ingestion intracellular digestion jejunum large intestine liver malnutrition microvilli minerals nutrition obesity pancreas peristalsis peptic ulcers peristalsis phagocytosis pharynx salivary glands small intestine sphincters stomach undernutrition vesicles villus vitamins

Bioenergetics of an animal 1. Food • Fuel • C-skeletons • essential nutrients 2. ATP powers resting metabolism, activity, and temperature regulation 3. Excess calories can be used for biosynthesis 4. 85 -90% of energy from food is lost as heat

Metabolic rates • Metabolism – Anabolism – Catabolism • Resting/ Basal Metabolic Rate (BMR) – energy/unit mass/hr • Size and relative metabolic rate are inversely proportional

Do plants have digestive systems? Carnivorous plants in marshlands have primitive digestive systems Habitats with Npoor soils Adaptation: occasionally feed on animals CH 2 O Photosynthesis N+ minerals insects, etc. Pitcher plant – Heliamphora nutans Sundew– Drosera capensis Venus fly trap – Dionaea muscipula Insect traps Glands in trap secrete digestive enzymes Flypaper trap – Pinguicula gigantea Nutrients absorbed by leaves

Evolution of digestion Different types depending on diet and lifestyle All must accomplish 1. Ingestion 2. Digestion v v Mechanical breakdown Chemical breakdown 3. Absorption 4. Elimination Digestion occurs in specialized compartments

Intracellular digestion ( 1 ) (evolved in single-celled protists, retained in simplest animals) Protists Paramecium Endocytosis of food particle Fusion with lysosome Digestion by enzymes Elimination of waste by exocytosis

Intracellular digestion ( 2 ) (evolved in single-celled protists, retained in simplest animals) Food obtained by filtering microorganisms from water SPONGES Food is phagocytized by choanocytes (collar cells) and amebocytes Waste eliminated into water in the sponge body

Extracellular digestion ( by fungi ) Fungi • Sedentary heterotrophs living in or on food supply • Saprotroph/parasites • No internal cavity release digestive enzymes Food outside the body Enzymatic hydrolysis outside the body Absorption by cells across the body surface Image from http: //www. aber. ac. uk/fungi/graffeg/decomp/digestion-by-hypha. jpg

Extracellular and intracellular digestion 1. In animals with incomplete digestive systems (1) Cnidarians Hydra Food gathered by cnidocytes and tentacles Waste materials are eliminated into the GVC, out mouth Food enters mouth Food circulated in gastrovascular cavity Small food particles endocytized into food vacuoles Hydrolytic enzymes break down food in GVC Image from http: //www. anselm. edu/homepage/jpitocch/genbio/digesthydra. jpg

Extracellular and intracellular digestion 1. In animals with incomplete digestive systems (2) Food enters pharynx Platyhelminthes Planaria and tapeworms Ingestion via mouth Enters branched GVC Secretion of digestive enzymes by intestinal cells Waste eliminated through mouth Digestion complete within food vacuole Food phagocytized by intestinal cells

Extracellular digestion 2. In animals with complete digestive systems Nematoda to Vertebrates Earthworms • 20 cm long with ~ 100 segments – 1 st – mouth – Last – anus • Eats its way through soil Food from mouth to muscular pharynx Travels through esophagus Digested in stomach: crop and gizzard Absorbed through long straight intestine Waste eliminated through anus