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Bio — 6.1
digestion
| Question | Answer |
|---|---|
| Alimentary Canal | organs through which foods actually passes (esophagus, stomach, small intestine, large intestine) |
| Accessory Organs | aids in digestion but do not actually transfer food (salivary glands, pancreas, liver, gall bladder) |
| Mouth | - mechanical digestion of food by chewing and mixing with saliva - saliva contains lubricants and enzymes such as salivary amylase that starts starch digestion |
| Esophagus | - hollow tube connecting oral cavity to stomach (separated from trachea by epiglottis) - food is mixed with saliva and then is moved in bolus via action of peristalsis - secretes mucus - sphincters to prevent acid from coming up |
| Stomach | - temporary storage tank where food is mixed by churning and protein digestion begins - lined by gastric pits that release digestive juices, which create acidic environment (pH~2) |
| Small Intestine | - long, highly folded tube where usable food substances (nutrients --> lipids, carbs, proteins, nucleic acids) are absorbed - three sections --> duodenum, jejunum, ileum - neutralizes stomach acids |
| Large Intestine | - final section of alimentary canal, where water and dissolved minerals (i.e. ions) are absorbed - further digestion --> carbs by symbiotic bacteria - formation and storage of feces |
| Salivary Glands | release saliva to moisten food and contains enzyme (e.g. amylase) to initiate starch breakdown |
| Pancreas | - production and secretion of lipase, endopeptidase, amylase - released into small intestine via duodenum - secretes certain hormones (insulin, glucagon) to regulate blood sugar concentrations |
| Liver | - takes raw materials absorbed by small intestine and uses them to make key chemicals - role includes secretion of surfactants in bile to break up liquid droplets |
| Gall Bladder | - storages bile produced by liver (bile salts are used to emulsify fats) - bile stored in gall bladder is released into small intestine via common bile duct |
| Mechanical Digestion | food is physically broken down into smaller fragments via acts of chewing (mouth), churning (stomach), and segmentation (small intestine) |
| Mechanical Digestion — Mouth (Chewing) | - food is broken down by grinding action of teeth (chewing or mastication) - tongue pushes food towards back of throat, where it travels down esophagus as bolus - epiglottis prevents bolus from entering trachea; uvula prevents it from nasal cavity |
| Mechanical Digestion — Churning (Stomach) | - stomach lining has muscles which physically squeeze and mix food with strong digestive juices - digested for several hours and turned into creamy paste called chyme - chyme enters duodenum where absorption will occur |
| Movement of Food — Peristalsis | - principal mechanism of movement in esophagus (in stomach and gut as well) - continuous segments of longitudinal smooth muscle rhythmically contract and relax - moved unidirectionally along alimentary canal in caudal direction (mouth to anus) |
| Movement of Food — Segmentation | - contraction and relaxation of non-adjacent segments of circular smooth muscle in intestines - move chyme in both directions, allowing for greater mixing of food with digestive juices - bidirectional propulsion can slow overall movement |
| Chemical Digestion | food is broken down by action of chemical agents (such as enzymes, acids, and bile) |
| Chemical Digestion — Stomach Acids | - contains gastric glands which release digestive acids to create pH 2 - denature proteins and other macromolecules - stomach epithelium has mucous membrane which prevents acids from damaging gastric lining |
| Chemical Digestion — Bile | - liver produces bile and is stored within gall bladder prior to release in small intestine - bile salts interact with fat globules to divide them into smaller droplets (emulsification) - increase total SA for lipase |
| Chemical Digestion — Enzymes | - biological catalysts speed up chem reaction by lowering activation energy - occur at body temps at sufficient speeds for survival requirements - substrate specific and can allow digestion of certain molecules to occur in distinct locations |
| Digestive Enzymes — Proteases/Endopeptidases | - digest proteins/polypeptides - proteins --> peptides --> amino acids |
| Digestive Enzymes — Amylase | - digest sugars - starch --> maltose |
| Digestive Enzymes — Nuclease | - digest DNA/RNA - nucleic acid --> nucleosides |
| Digestive Enzymes — Lipase (+ Bile Salts from Liver) | - lipase (digest fats) and bile salts (emulsify fats) - dietary fat/triglycerides --> monoglycerides/fatty acids |
| Carbohydrate Digestion | - mouth with release of amylase from salivary glands (amylase = starch digestion) - amylase is also secreted by pancreas in order to continue carb digestion within small intestine - enzymes for hydrolysis are on small intestine's epithelium |
| Protein Digestion | - stomach with release of proteases that function in acidic pH - smaller polypeptide chains enter small intestine where they are broken down by endopeptidases by pancreas - work in neutral environments (pH~7) as pancreas neutralizes acids in intestine |
| Lipid Digestion | - intestines with emulsification of fat globules by bile released from gall bladder - smaller fat droplets are then digested by lipases released from pancreas |
| Nucleic Acid Digestion | pancreas also releases nucleases which digest acids (DNA, RNA) into smaller nucleosides |
| Ingestion | food is taken into body via act of eating |
| Absorption | digested food products are absorbed into bloodstream |
| Assimilation | digested food products are moved from bloodstream into cells |
| Elimination | undigested food residues are egested from body as semi-solid feces |
| Structure of Small Intestine — Serosa | protective outer covering composed of layer of cells reinforced by fibrous connective tissue |
| Structure of Small Intestine — Muscle layer | outer layer of longitudinal muscle (peristalsis) and inner layer of circular muscle (segmentation) |
| Structure of Small Intestine — Submucosa | composed of connective tissue separating muscle layer from innermost mucosa |
| Structure of Small Intestine — Mucosa | highly folded inner layer which absorbs material through its surface epithelium from internal lumen |
| Structure of Small Intestine — Epithelial Cells | absorbs digested materials in small intestine |
| Structure of Small Intestine — Villi | - increase SA for absorption - highly folded into finger-like projections - protrude into intestinal lumen |
| Features of Villi — Microvilli | ruffling of epithelial membrane further increases SA |
| Features of Villi — Rich blood supply | dense capillary network rapidly transports absorbed products |
| Features of Villi — Single layer epithelium | minimizes diffusion distance between lumen and blood |
| Features of Villi — Lacteals | absorbs lipids from intestine into lymphatic system |
| Features of Villi — Intestinal glands | exocrine pits release digestive juices |
| features of Villi — Membrane proteins | facilitates transport of digested materials into epithelial cells |
| Starch Digestion — Process | - digestion of starch is initiated by salivary amylase in mouth and continued by pancreatic amylase in intestines - maltose and dextrin are digested by maltase and dextrinase which is fixed into epithelial lining of small intestine --> forms glucose |
| Starch Digestion — Formats of Starch | - can exist in one of two forms — linear chains (amylose) or branched chains (amylopectin) - amylase digests amylose into maltose - amylase digests amylopectin into branched chains called dextrins |
| Modelling Digestion | - core function of digestive system is to break down large molecules into smaller subunits that can absorbed by cells - cell membranes are impermeable to large molecules (polypeptides, polysaccharides) unless transport is facilitated by proteins |
| Dialysis Tubing (size-specific permeability of cell membranes) | - contains pores typically ranging from 1-10 nm in diameter and is semi-permeable according to molecular size - large molecules such as starch cannot pass through tubing, however smaller molecules (such as maltose) can cross |
| Dialysis Tubing (permeability) | unlike membranes of living cells, dialysis tubing is not selectively permeable based on charge (ions can freely cross) |
| Dialysis Tubing to Model Digestive Processes (Starch Breakdown and Maltose Absorption) — Prediciton | - water will enter via osmosis - amylase will digest starch into maltose - maltose will leave via diffusion - meniscus level will drop (less solute = less osmosis) |
| Dialysis Tubing to Model Digestive Processes (Starch Breakdown and Maltose Absorption) — Control and Experiment | - control: dialysis tube with starch solution only - experiment: dialysis tube with starch and amylase |
| Dialysis Tubing to Model Digestive Processes (Starch Breakdown and Maltose Absorption) — Expected Results | - amylase will digest starch into maltose - maltose will leave tubing via diffusion - benedict's reagent will detect maltose in beaker (leading to color change) |
Created by:
soguzman
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