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BU BIOL 118 - Nutritional Requirements
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Biol 118 1st Edition Lecture 26Outline of Last Lecture I. IntroductionII. Osmoregulation & ExcretionIII. KidneyOutline of Current Lecture I. Nutritional RequirementsII. Structure & Function of MouthpartsIII. How Are Nutrients Digested & Absorbed IV. Nutritional Homeostasis- Glucose as a Case StudyCurrent LectureNutritional Requirements- Nutrient: a substance that an organism needs to remain aliveo Carbohydrate, protein & fato Essential nutrients: cannot be synthesized and must be consumed through diet Essential amino acids Vitamins: organic compounds that are vital for health, but only in minute quantities Minerals: inorganic substances used as components of enzyme cofactors or structural materials Electrolytes: mineral ions that influence osmotic balance & are required for normal membrane function- Food: any material that contains nutrientso Energy provided by food is measured in kilocalories- Fats have more C-H bonds than do carbohydrates & proteinso Have 9 kcal/go Proteins/carbs: 4 kcal/gStructure & Function of MouthpartsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Suspension feeders: filter small organisms or bits of organic debris from water by meansof cilia, mucus-lined “nets” etc.; sponges & tubeworms- Deposit feeders: swallow sediments & other types of deposited material rich in organic matter; earthworms & sea cucumbers- Fluid feeders: Suck or lap up fluids, like blood or nectar- Mass feeders: majority of animals. Seize and manipulate chunks of food by using mouthparts such as jaws & teeth, beaks or special toxin-injecting organs- Close correlation between structure & function of mouthparts is because of natural selection- Adaptive radiation: diversification of a single ancestral lineage into many species, each of which lives in a different habitat or employs a distinct feeding methodo In response to natural selection, mouthparts have diversified to exploit a diversity of food sources How Are Nutrients Digested & Absorbed?- Ingestion: process of bringing food into the digestive tract- Alimentary tract (digestive/GI tract): chamber or tube where digestion occurs- Digestion: breakdown of food - Absorption: uptake of specific ions and molecules across the membrane of the digestive tract- Incomplete digestive tract: single opening that doubles as the location where food is ingested & wastes are eliminated. The mouth opens into a chamber, called a gastro-vascular cavity, where digestion takes place- Complete digestive tract: 2 openings- they start at the mouth & end at the anus. The interior of this tube communicates directly with the external environment via these openings- Advantages of tube-like digestive system:o Allows animals to feed on large pieces, which expands the range of food sources that can be ingestedo Different chemical and physical processes can be confined to different compartments within the canal, so that they occur independently of each other & in a prescribed sequence.o Because there is a one-way flow of food & wastes, material can be ingested & digested without interruption- In the mouth, enzymes in the saliva begin chemical breakdown of carbohydrateso Salivary amylase: enzyme responsible for starch digestion- cleaves bonds to release maltose from starch & glycogeno Lingual lipase: synthesized & secreted by cells in the tongue; breaks down triglycerides into diglycerides & fatty acidso Salivary glands: produce amylase & release water and glycoproteins (mucins) When mucins contact water they form mucus which makes food soft and slippery enough to be swallowed- Peristalsis moves material down the esophagus o When food is swallowed it enters the esophagus Connects the mouth & stomacho Peristalsis: wave of muscular contractions that propels food down the esophagus Allows food to be swallowed even when mouth is lower than the stomach- The stomacho Stomach: tough, muscular pouch in the digestive tract, bracketed on both side bysphincters, which control the passage of materialo Muscular contractions churn & mix contents to a uniform consistency & solute concentrationo Stomach is highly acidic, mostly due to hydrochloric acido Secretion of a protein-digesting enzyme in inactive form is important; it prevents the destruction of proteins in the cells where the enzyme is synthesizedo Parietal cell: produces the hydrochloric acid found in the stomach Carbonic anhydrase: catalyzes the formation of carbonic acid from carbon dioxide in water o Mucous cell: secretes additional mucus found in gastric juiceo Ulcer: an eroded area in an epithelium; exposes underlying tissue to damage- caused by bacterial infectionso Ruminants: Collective name for species whose stomachs digest cellulose, not protein Have 4 chambered stomachs:- Rumen: largest chamber that serves as fermentation vat. Filled with symbiotic bacteria & protists. Contains cellulose, which yieldsglucose. Produces ATP- Reticulum: Adjacent to rumen & similar in function. Helps form cud that is regurgitated, rechewed & then swallowed once more- Omasum: where water & some minerals are absorbed- Abomasum: contains digestive enzymes & is most like a true stomacho Gizzard: modified stomach in birds; birds swallow sand & small stones that pulverize food as the gizzard contracts- Small intestineo Small intestine: long tube that is folded into a compact space within the abdomeno Villi: fingerlike, folded projections of the small intestine’s epitheliumo Microvilli: tiny projections of the apical surface of the villi- project into lumen of digestive tracto Enormous surface area increases the efficiency of nutrient absorptiono Proteases: protein-digesting enzymes o Pancreas: connected to small intestine by pancreatic duct Trypsin: active enzyme that triggers the activation of other protein-digesting enzymeso Secretin: hormone produced by small intestine in response to the arrival of food in the stomach- induces flow of bicarbonate ions (neutralizes stomach acid)o Cholecystokinin: stimulates secretion of digestive enzymes from the pancreas and the secretion of molecules from the gallbladder that aid in processing lipidso Gastrin: Hormone that signals parietal cells to begin secreting HClo Nucleases: digest the RNA & DNA in foodo Pancreatic amylase: continues the digestion of carbs that began in the moutho Two principles of carb & protein absorption: Highly selective-


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