Chapter 43 1 Nutritional Requirements a Animals get chem energy and carbon containing bldg blocks from carbohydrates and fats b nutrient substance that an organism needs to remain alive food is any material that contains nutrients 2 Meeting Basic Needs in Humans a Essential Nutrients must be obtained in the diet b Proteins provide amino acids used to synthesize polypeptides body makes only 12 20 req amino acids c vitamins are organic compounds vital for health several function as coenzymes in critical reactions d inorganic substances are imp components of enzyme cofactors or structural materials Example of Inorgan Subst calcium and phosphorous 3 Capturing Food The Structure and Function of Mouthparts a suspension feeders filter small organisms and organic debris from water sponges and tubeworms use this method b Deposit Feeders swallow organic rich sediments and other deposited materials earthworms and sea cucumbers use this method c Fluid Feeders suck or lap up fluids such as blood nectar or sap d Mass Feeders manipulate chunks of food using jaws teeth and organs 4 Mouthparts as Adaptations a Mammals are the only animals that chew their food and swallow distinct packets b Diversification in tooth shape has allowed mammals to exploit a wide range of foods c snakes jawbone and skull structure allow them to swallow large prey whole d Evolutions is not perfect mouths do not get better or become more complex e Adaptation is not perfect wisdom teeth in humans lowers fitness on average 5 The Cichlid Jaw a Adaptive Radiation diversification of a single ancestral lineage into many species each of whom lives in a diff habitat or employs a distinct feeding method b Endemic Species species that live nowhere else c many fish species have pharyngeal jaw located behind normal jaws d Pharyngeal jaw provides 2nd set of biting jaws and an extra set of teeth e mouthparts diversified in response to natural selection for exploiting a diversity of food sources 1 How Are Nutrients Digested and Absorbed a Ingestion followed by digestion absorption excretion b digestion breakdown of food into small enough pieces for absorption c absorption uptake of specific ions and molecules that act as nutrients d nutrients are extracted from digested food and waste materials are eliminated 2 Introduction to the Digestive Tract a 3 Advantages of tube like digestive tract 1 It allows animals to feed on large pieces of food 2 Diff chem and physical processes are separate within the canal so they occur independently of each other in a certain seq 3 material can be ingested continuously instead of in batches unlike in incomplete digestive tract where it happens in batches 3 Overview of Digestive Processes a Chemical changes occur as food is digested b Chem breakdown of carbohydrates beings in mouth through enzymes and saliva c protein digestion begins in acidic environment of the stomach d Chem processing of carbohydrates lipids and proteins is completed in small intestine small molecules resulting are absorbed in the small intestine e In large intestine or colon more water is absorbed result is feces 4 The Mouth and Esophagus a Enzyme in saliva hydrolyzes the starch molecules of a cracker into maltose b Maltose is a disaccharide that is split in small intestine to form two glucose monomers 5 Digestion Starts in the Mouth a Amylase enzyme responsible for starch digestion in the mouth initiates the digestion of carbohydrates b cells in the tongue synthesize and excrete lipase beings digestion of lipids c Salivary glands in the mouth also release water and glycoproteins called mucins combination of water and mucus makes food soft and slippery enough to swallow d Some snakes release venom initiating digestion before eating the organism 6 Peristalsis Moves Material Down the Esophagus a Peristalsis a wave of muscular contractions that propels food down esophagus b Upper third of esophagus consists of skeletal muscle lower third is composed of smooth muscle middle third contains a mix of both muscle types c In response to nerve signals the muscle contracts or relaxes in a coordinated fashion this is a reflex stimulated by act of swallowing 7 A Modified Esophagus The Bird Crop a Some bird species have a widened segment of esophagus called the crop where food can be stored and sometimes processed b Often the crop is a simple sac that holds food and regulates its flow into the stomach c In Hoatzin and Kakapo species the crop is capable of digestion bacteria inside break down cellulose found in leaves 8 The Stomach a Stomach is bracketed on both sides by sphincters which control movement of material through the gut b When a meal fills the stomach muscular contractions result in churning that mixes the contents and reduces food to a uniform consistency and solute concentration or osmolarity c the lumen of the stomach is highly acidic d the predominant acid in the stomach is hydrochloric acid 9 The Stomach as a Site of Protein Digestion a gastric juice digests food particularly meat b pepsin enzyme responsible for digesting proteins in the stomach c pepsin is synthesized and stored in cells so that it doesnt kill cells that make it d granules occur in specialized stomach cells called chief cells precursor compound in chief cells pepsinogen is converted to active pepsin by contact w the acidic environment of the stomach e secretion of protein digesting enzyme in inactive form is imp so that proteins in cells where enzyme is synthesized are not destroed 10 Which Cells Produce Stomach Acid a Parietal cells are located in pits that communicate w the lumen of the stomach they are the source of HCl in gastric juice b Mucous cell secretes mucus found in gastric juice mucus protects stomach from damage by HCl 11 How Parietal Cells Secrete HCl Draw 43 9 and 43 10 a Carbonic anhydrase catalyzes formation of carbonic aid from CO2 and water b parietal cells are packed w mitochondria which produce ATP so the parietal cells also function in active transport c protons formed by the dissociation of carbonic acid are actively pumped into the lumen of the stomach 12 Ulcers As An Infectious Disease a Ulcer a hole in an epithelium that damages the underlying basement membrane and tissues b Ulcers are associated w infections from a bacterium called Helicobacter pylori 13 The Ruminant Stomach a Ruminants refers to species w stomach specialized for digesting cellulose not proteins mammals lack enzyme cellulase req to digest cellulose b When symbiosis
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