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BIOL 103
Daniel Lefebvre

BIO 103 EXAM NOTESDigestionAbsorptionAutotrophs are organisms that harvest light or chemical energy convert it to carbon compounds and store themThey are called primary producersSuch as a plantHeterotrophs are organisms that get nutrients from the environment by eating other organismsThey are found at higher trophic levelsThey have evolved to have many strategies of obtaining foodFungi are also heterotrophic they consume dead organics matter bread mold or from living organic matter as parasites athletes foot by extending hyphae into cells and absorbing the nutrientsIntracellular digestion occurs in very simple organisms phagocytosis lets food into the vacuoles of the cell and hydrolytic enzymes digest the food into simple monomersIt is a very slow process and you cannot store food for long periods of time White blood cells use phagocytosis to kill microbes but some bacteria have evolved to make it more difficultFor example pneumonia bacteria have a slippery coating on the outsideExtracellular digestion is when an organism traps food consumes it through an oral cavity which transports it to the gastrointestinal system where digestive enzymes break it down into nutrients which are absorbed into the cells that line the cavityThey can be further digested intracellularlyUndigested products are then excreted through the mouthMore complex organisms have more complex systems ie humansHumans cannot produce enzymes to break down celluloseHowever in our guts there are bacteria which can break down cellulose which helps us to absorb more nutrients from plants Some animals have different adaptations that help themRabbits eat once during the day then at night eat their feces to absorb more nutrients that they missed the first time aroundRuminants a type of herbivore have complex stomachsThey have a forestomach which contains microbes to break down celluloseIt will also absorb the water and salt released from the partially digested foodsSometimes the cud is regurgitatedswallowed again to get more nutrients from itThen it passes on to the true stomach and digestion finishes in the intestinesThe human digestive tractOral cavity Contains saliva which is used to moistenAmylase is found in saliva it begins breaking food kills microbes down starch moleculesStomach Gastric juice is secreted when there isPepsin is found in gastric juice it breaks down food in the stomachprotein molecules The stomach lining is lined with a thickInitially released in the inactive form mucous with a pH of 6pepsinogen but when it reacts w HCl it becomes pepsin protects stomach lining from digesting itselfSmallStomach contents chyme passes on toMaltase and protease enterokinase Intestinethe S I to continue digestionaminopeptidase and dipeptidase are produced
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