Chapter 431. Nutritional Requirementsa. Animals get chem. energy and carbon-containing bldg blocks -from carbohydrates and fatsb. nutrient: substance that an organism needs to remain alive-food is any material that contains nutrients2. Meeting Basic Needs in Humansa. Essential Nutrients-must be obtained in the dietb. Proteins provide amino acids used to synthesize polypeptides-body makes only 12/20 req. amino acidsc. vitamins are organic compounds vital for health-several function as coenzymes in critical reactionsd. inorganic substances are imp. components of enzyme cofactors-or structural materials. Example of Inorgan. Subst.-calcium and phosphorous3. Capturing Food: The Structure and Function of Mouthpartsa. suspension feeders: filter small organisms and organic debris from water-sponges and tubeworms use this methodb. Deposit Feeders: swallow organic-rich sediments and other deposited materials-earthworms and sea cucumbers use this methodc. Fluid Feeders: suck or lap up fluids such as blood, nectar, or sapd. Mass Feeders: manipulate chunks of food using jaws, teeth, and organs4. Mouthparts as Adaptationsa. Mammals are the only animals that chew their food-and swallow distinct packetsb. Diversification in tooth shape has allowed mammals to exploit a wide range of foodsc. snakes' jawbone and skull structure allow them to swallow large prey wholed. Evolutions is not perfect: mouths do not get better or become more complexe. Adaptation is not perfect: wisdom teeth in humans lowers fitness on average5. The Cichlid Jawa. Adaptive Radiation: diversification of a single ancestral lineage into many species-each of whom lives in a diff. habitat or employs a distinct feeding methodb. Endemic Species: species that live nowhere elsec. many fish species have pharyngeal jaw-located behind normal jawsd. Pharyngeal jaw provides 2nd set of biting jaws and an extra set of teethe. mouthparts diversified in response to natural selection-for exploiting a diversity of food sources1. How Are Nutrients Digested and Absorbeda. Ingestion followed by digestion, absorption, excretionb. digestion: breakdown of food into small enough pieces for absorptionc. absorption: uptake of specific ions and molecules that act as nutrientsd. nutrients are extracted from digested food and waste materials are eliminated2. Introduction to the Digestive Tracta. 3 Advantages of tube-like digestive tract1. It allows animals to feed on large pieces of food2. 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 batches3. Overview of Digestive Processesa. Chemical changes occur as food is digestedb. Chem. breakdown of carbohydrates beings in mouth through enzymes and salivac. protein digestion begins in acidic environment of the stomachd. Chem. processing of carbohydrates, lipids, and proteins is completed in small intestine-small molecules resulting are absorbed in the small intestinee. In large intestine or colon, more water is absorbed-result is feces4. The Mouth and Esophagusa. Enzyme in saliva hydrolyzes the starch molecules of a cracker into maltoseb. Maltose is a disaccharide that is split in small intestine-to form two glucose monomers5. Digestion Starts in the Moutha. Amylase-enzyme responsible for starch digestion in the mouth-initiates the digestion of carbohydratesb. cells in the tongue synthesize and excrete lipase-beings digestion of lipidsc. Salivary glands in the mouth also release water and glycoproteins called mucins-combination of water and mucus makes food soft and slippery enough to swallowd. Some snakes release venom, initiating digestion before eating the organism6. Peristalsis Moves Material Down the Esophagusa. Peristalsis-a wave of muscular contractions that propels food down esophagusb. Upper third of esophagus-consists of skeletal muscle-lower third is composed of smooth muscle-middle third contains a mix of both muscle typesc. In response to nerve signals the muscle contracts or relaxes in a coordinated fashion-this is a reflex stimulated by act of swallowing7. A Modified Esophagus: The Bird Cropa. Some bird species have a widened segment of esophagus called the crop-where food can be stored and sometimes processedb. Often the crop is a simple sac that holds food and regulates its flow into the stomachc. In Hoatzin and Kakapo species, the crop is capable of digestion-bacteria inside break down cellulose found in leaves8. The Stomacha. Stomach is bracketed on both sides by sphincters-which control movement of material through the gutb. 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 osmolarityc. the lumen of the stomach is highly acidicd. the predominant acid in the stomach is hydrochloric acid9. The Stomach as a Site of Protein Digestiona. gastric juice digests food, particularly meatb. pepsin-enzyme responsible for digesting proteins in the stomachc. pepsin is synthesized and stored in cells-so that it doesnt kill cells that make itd. 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 stomache. secretion of protein-digesting enzyme in inactive form is imp. so that-proteins in cells where enzyme is synthesized are not destroed10. Which Cells Produce Stomach Acida. Parietal cells are located in pits that communicate w. the lumen of the stomach-they are the source of HCl in gastric juiceb. Mucous cell secretes mucus found in gastric juice-mucus protects stomach from damage by HCl11. How Parietal Cells Secrete HCl Draw 43.9 and 43.10a. Carbonic anhydrase catalyzes formation of carbonic aid from CO2 and waterb. parietal cells are packed w. mitochondria which produce ATP-so the parietal cells also function in active transportc. protons formed by the dissociation of carbonic acid -are actively pumped into the lumen of the stomach12. Ulcers As An Infectious Diseasea. Ulcer: a hole in an epithelium that damages the underlying basement membrane and tissuesb. Ulcers are associated w. infections from a bacterium called Helicobacter pylori13. The Ruminant Stomacha. Ruminants-refers to species w. stomach specialized for digesting cellulose not proteins-mammals lack enzyme
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