Biol 118 1st Edition Lecture 26 Outline of Last Lecture I Introduction II Osmoregulation Excretion III Kidney Outline of Current Lecture I Nutritional Requirements II Structure Function of Mouthparts III How Are Nutrients Digested Absorbed IV Nutritional Homeostasis Glucose as a Case Study Current Lecture Nutritional Requirements Nutrient a substance that an organism needs to remain alive o Carbohydrate protein fat o 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 nutrients o Energy provided by food is measured in kilocalories Fats have more C H bonds than do carbohydrates proteins o Have 9 kcal g o Proteins carbs 4 kcal g Structure Function of Mouthparts These 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 means of 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 method o 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 gastrovascular 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 ingested o 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 carbohydrates o Salivary amylase enzyme responsible for starch digestion cleaves bonds to release maltose from starch glycogen o Lingual lipase synthesized secreted by cells in the tongue breaks down triglycerides into diglycerides fatty acids o 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 stomach o 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 stomach o Stomach tough muscular pouch in the digestive tract bracketed on both side by sphincters which control the passage of material o Muscular contractions churn mix contents to a uniform consistency solute concentration o Stomach is highly acidic mostly due to hydrochloric acid o Secretion of a protein digesting enzyme in inactive form is important it prevents the destruction of proteins in the cells where the enzyme is synthesized o 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 juice o Ulcer an eroded area in an epithelium exposes underlying tissue to damagecaused by bacterial infections o 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 yields glucose 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 stomach o Gizzard modified stomach in birds birds swallow sand small stones that pulverize food as the gizzard contracts Small intestine o Small intestine long tube that is folded into a compact space within the abdomen o Villi fingerlike folded projections of the small intestine s epithelium o Microvilli tiny projections of the apical surface of the villi project into lumen of digestive tract o Enormous surface area increases the efficiency of nutrient absorption o Proteases protein digesting enzymes o Pancreas connected to small intestine by pancreatic duct Trypsin active enzyme that triggers the activation of other proteindigesting enzymes o 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 lipids o Gastrin Hormone that signals parietal cells to begin secreting HCl o Nucleases digest the RNA DNA in food o Pancreatic amylase continues the digestion of carbs that began in the mouth o Two principles of carb protein absorption Highly selective plasma membranes of microvilli are responsible for bringing specific nutrients into cell It is active ATP is expended o Pancreatic secretions include enzymes that act on fats proteins carbohydrates o
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