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 animal1. Food
• Fuel• C-skeletons• essential
nutrients2. ATP
• resting metabolism• activity• temperature
regulation3. Excess for
biosynthesis4. 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
with primitive digestive systems
Habitats with N-poor soils
Adaptation: occasionally feed on animals
Pitcher plant – Heliamphora nutans
Flypaper trap – Pinguicula gigantea
Sundew– Drosera capensis
Venus fly trap– Dionaea muscipula
Evolution of digestionDifferent types depending
on diet and lifestyleAll must accomplish
1. Ingestion2. Digestion
Mechanical breakdown Chemical breakdown
3. Absorption4. Elimination
Digestion occurs in specialized compartments
Intracellular digestion
(evolved in single-celled protists, retained in simplest animals)PROTISTSParamecium
Intracellular digestion (Protists, Porifera)
SPONGES
Extracellular digestion FUNGI• Sedentary heterotrophs
living in or on food supply• Saprotroph/parasites• No internal cavity
release digestive enzymes
Image from http://www.aber.ac.uk/fungi/graffeg/decomp/digestion-by-hypha.jpg
Image from http://www.anselm.edu/homepage/jpitocch/genbio/digesthydra.jpg
Extracellular and intracellular digestionIncomplete digestive systemCNIDARIANSHydra
Extracellular and intracellular digestion Incomplete digestive system
PLATYHELMINTHESPlanaria
Extracellular digestion Animals with complete digestive systems
NEMATODA to VERTEBRATESEarthworms• 20 cm long with ~ 100 segments
– 1st – mouth– Last – anus
• Eats its way through soil
Feeding adaptations for ingestion
Comparison of vertebrate digestive systems
Mammalian digestion General plan
ACCESSORY DIGESTIVE ORGANS
Organs of the GI tract
Comparison of mammalian digestive systems(Diet plays an important role in the length and structure)