Bioenergetics

and Digestion

We’ll be discussing

1. Trends and Various

Strategies Used by

Organisms to Process

FoodFood

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

• essential nutrient

• extracellular digestion

• filter feeders

• gallbladder

• gastrovascular cavity

• gizzard

• heterotroph

� minerals

� nutrition

� obesity

� pancreas

� peptic ulcers

� peristalsis

� phagocytosis

� pharynx

salivary glands• bulimia

• cecum

• chyme

• complete digestive tract

• crop

• digestion

• duodenum

• elimination

• endocytosis

• enzyme

• esophagus

•• ileum

• incomplete digestive tract

• ingestion

• intracellular digestion

• jejunum

• large intestine

• liver

• malnutrition

• microvilli

� 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 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 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-

Pitcher plant –Heliamphora nutans

Sundew–Drosera capensis

Venus fly trap–Dionaea muscipula

Insect traps� Habitats with N-poor soils

� Adaptation: occasionally feed on animals

CH2O � Photosynthesis

N+ minerals � insects, etc.

Flypaper trap –Pinguicula gigantea

Insect traps

Glands in trap secrete digestive

enzymes

Nutrients absorbed by

leaves

Evolution of digestion

� Different types depending on diet and lifestyle

� All must accomplish1. Ingestion

2. Digestion2. 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)

ProtistsParamecium

Endocytosis of food particle

Fusion with lysosomeFusion with lysosome

Digestion by enzymes

Elimination of waste by exocytosis

Intracellular digestion ( 2 ) (evolved in single-celled protists, retained in simplest animals)

SPONGES

Food obtained by filtering microorganisms

from water

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 • No internal cavity � release

digestive enzymes

Image from http://www.aber.ac.uk/fungi/graffeg/decomp/digestion-by-hypha.jpg

Food outside the body

Enzymatic hydrolysis outside the body

Absorption by cells across the body surface

Extracellular and intracellular digestion1. In animals with incomplete

digestive systems (1)

CnidariansHydra

Food gathered by cnidocytes

and tentacles

Food enters mouth

Food circulated in gastrovascu-

lar cavity

Hydrolytic enzymes

break down food in GVC

Small food particles

endocytizedinto food vacuoles

Waste materials are

eliminated into the GVC,

out mouth

Image from http://www.anselm.edu/homepage/jpitocch/genbio/digesthydra.jpg

Extracellular and intracellular digestion 1. In animals with incomplete digestive systems (2)

PlatyhelminthesPlanaria and tapeworms

Food enters pharynx

Ingestion via mouth

Enters branched GVC

Secretion of digestive enzymes by intestinal cells

Food phagocytized by intestinal cells

Digestion complete within

food vacuole

Waste eliminated through mouthtapeworms intestinal cellsfood vacuolethrough mouth

Extracellular digestion 2. In animals with complete digestive systems

Nematoda to Vertebrates

Earthworms• 20 cm long with ~ 100 segments

– 1st – 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

Feeding adaptations for ingestion

Suspension-feeders

Deposit-feeders

Substrate feedersfeeders feeders feeders

Fluid feeders Bulk feedersVertebrate dentition

Comparison of vertebrate digestive systems

Mammalian digestion General plan

Accessory

digestive organs

Organs of the GI tract

digestive organs

Comparison of mammalian digestive systems(Diet plays an important role in the length and structure)