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 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. ATPpowers 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 N- poor soils Adaptation: occasionally feed on animals CH 2 O Photosynthesis N+ minerals insects, etc. Pitcher plant Heliamphora nutans Flypaper trap Pinguicula gigantea Sundew Drosera capensis Venus fly trap Dionaea muscipula Insect traps Glands in trap secrete digestive enzymes Nutrients absorbed by leaves
Evolution of digestion Different types depending on diet and lifestyle All must accomplish 1. Ingestion 2. Digestion 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 Endocytosisof 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 Food is phagocytizedby choanocytes(collar cells) and amebocytes Waste eliminated into water in the sponge body SPONGES
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) Food gathered by cnidocytes and tentacles Food enters mouth Food circulated in gastrovascular cavity Cnidarians Hydra Waste materials are eliminated into the GVC, out mouth 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 Ingestion via mouth Enters branched GVC Secretion of digestive enzymes by intestinal cells Platyhelminthes Planariaand tapeworms Waste eliminated through mouth Digestion complete within food vacuole Food phagocytizedby 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: cropand gizzard Absorbed through long straight intestine Waste eliminated through anus
Feeding adaptations for ingestion Suspension- Deposit- Substrate feeders feeders feeders Fluid feeders Bulk feeders Vertebrate dentition
Comparison of vertebrate digestive systems
Mammalian digestion General plan Organs of the GI tract Accessory digestive organs
Comparison of mammalian digestive systems (Diet plays an important role in the length and structure)