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)