Lecture 4 9-12-10

Lecture 4 9-12-10 - Chapter 5: Nutrition, Feeding, and...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chapter 5: Nutrition, Feeding, and Digestion 13 September 2010 A More Explicit Energy Budget C R C=P+R+U+F Inclusion or exclusion of more detailed information does not change balance F U P Reproduction Growth Allocation Trade-Offs: How much energy will be allocated to Production versus Respiration? How much energy will be allocated to Growth versus Reproduction? Feeding Diverse processes for obtaining and ingesting food Morphology Physiology Behavior Trophic relationships provide insight into the diversity of feeding mechanisms. Aquatic Habitats Suspension feeding is common in aquatic animals. Aquatic Habitats Suspension feeding is common in aquatic animals. Aquatic Habitats Feeding apparatus of baleen whale is specialized for filter feeding Symbiotic Relationships with Microorganisms • Photosynthetic autotrophs – Algal symbionts • Reef corals • Chemosynthetic autotrophs – Hydrothermal vent communities • Dr. Richard Lutz, IMCS, Rutgers • Sulfur-oxidizing bacteria Hydrothermal Vent Communities • Sulfur-oxidizing bacteria oxidize inorganic sulfide – Use released energy for biosynthesis • Section of periodic table Hydrothermal Vent Communities • Sulfur acts as an “energy shuttle” Symbiotic Relationships with Microorganisms • Heterotrophic microorganisms – Foregut fermentation – Ruminants – Hindgut fermentation – Rabbits – Horses Symbiotic Relationships with Microorganisms: Sheep vs. Pony Ruminant vs. Non-ruminant Pregastric vs. Postgastric fermentation Symbiotic Relationships with Microorganisms • Ruminants – Anaerobic fermentation in the foregut – Biosynthesis – Recycling of nitrogen • Urea diffuses into rumen • NH3 • Protein synthesis Symbiotic Relationships with Microorganisms • Hindgut fermenters – Anaerobic fermentation in the hindgut – Ingestion of defecated material Terrestrial Habitats Lots of energy in structural carbohydrate (i.e., cellulose) is inaccessible to animals. The use of microorganisms for digestion of plants was the most important nutritional adaptation to terrestrial life. Lots of energy in structural carbohydrate (i.e., cellulose) is inaccessible to animals. Terrestrial Habitats Plants are hard to eat. They are tough, hard to penetrate, and hard to digest. They hold a lot of energy in their structural carbohydrates, but this energy is inaccessible to animals. Plants are nutritionally poor: they hold lots of carbohydrate energy, but they are low in nitrogen, they have the wrong balance of amino acids, insufficient sodium, and none of the necessary steroids. And plants are well defended – physically and chemically – against herbivores. Characteristics of Terrestrial Herbivores 1) Hardened mouth parts. 2) Elongated guts. 3) Unusual gut structures to enhance “processing” relative to “absorbing” regions. 4) Cellulase-providing symbionts. 5) Mechanisms to achieve pH homeostasis. 6) Supplemental salt intake. 7) Good detoxification systems. Gut Capacity • Rate of food intake, v = g/s • Retention time = td – ∴ weight of materials in digestive chambers ≈ v • td – Net rate of obtaining energy = v • kd(td) • Food yield kd units of energy after td • Where kd(td) ≡ quantity kd that is a function of td – Substituting: net rate of obtaining energy = (weight carried) • kd(td) / td • For a given weight carried, kd(td)/td should be maximized – If nutritional requirements are equal, animals eating poorer quality food should have larger digestive chambers because kd(td)/td is lower for poorer quality food Four Basic Functions of the Four (Human) Digestive System Overall: Big particles →Small particles Small particles Molecules Molecules →Small water-soluble molecules Small particles → Large particles Four Generalized Regions of the Vertebrate Digestive Tract Vertebrate Headgut Foregut Headgut: capture and capture preparation of food for digestion for Foregut: move, store, Foregut: grind, solubilize, solubilize digest food digest Midgut Midgut: majority of majority digestion and absorption absorption Hindgut: storage and Hindgut: elimination of waste; reabsorption of water reabsorption of and minerals and Hindgut Generalized Mammalian Digestive Tract Generalized Generalized Structural Organization Generalized Mammalian Digestive Tract Fundus Specializations of structure and function in the wall of the stomach. (Note: the word “gastric” refers to stomach.) Smooth muscle is highly developed in the stomach, and gastric mucosa is characterized by highly involuted secretory “pits”. Rate of chemical digestion depends on the surface area of food Rate surface particles accessible to digestive enzymes. Rate of absorption depends on the surface area of the small intestine. surface Generalized Mammalian Digestive Tract Villi and microvilli increase surface area. Digestion and Absorption of Maltose Digestion Maltose is formed when the polysaccharides starch and glycogen are digested by salivary and pancreatic amylases. Absorption of Fructose, Glucose, & Galactose Galactose Protein Digestion Begins in the Stomach Protein Similar to gastric pepsinogen, Similar pepsinogen pancreatic proteolytic enzymes proteolytic enzymes are stored in zymogen granules zymogen granules and released as inactive proand enzymes, which are activated in enzymes, the small intestine by proteolytic proteolytic cleavage of some amino acids cleavage after secretion. after Amino acids are absorbed by Nalinked secondary active transport linked across the apical membrane and by facilitated diffusion across the basal membrane of small intestinal absorptive cells. intestinal Activation of Proteases Figure 20.15 Lipid (fat) digestion is facilitated by bile salts, which emulsify fats and Lipid thus increase the surface area of fat droplets accessible to lipases. Bile salts are amphipathic, having amphipathic hydrophobic and hydrophilic sides. Pancreatic lipase and the formation of micelles Pancreatic Formation and Absorption of Chylomicrons Chylomicrons About 95% of bile salts are recovered through enterohepatic circulation. enterohepatic Hormones and Endocrine Functions of the Digestive Tract Remarkable Remodeling of Structural and Remarkable Functional Capacities of the Digestive Tract of an Episodic Feeder (Burmese python) See Secor and Diamond, 1998 Remarkable Remodeling of Structural and Remarkable Functional Capacities of the Digestive Tract of an Episodic Feeder (Burmese python) Secor and Diamond, 1998 Remarkable Remodeling of Structural and Functional Capacities of the Digestive Tract of an Episodic Feeder (Burmese python) Episodic Remarkable Remodeling of Structural and Functional Capacities of the Digestive Tract of an Episodic Feeder (Burmese python) Episodic See Feder, 2005 ...
View Full Document

This note was uploaded on 04/03/2011 for the course BIO 704:360 taught by Professor John-alder during the Fall '11 term at Rutgers.

Ask a homework question - tutors are online