Bio digestion 1.txt

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  1. Explain why digestion of large food molecules is essential
    • needed to break down large complex substances to allow absorbption + later arranged into useful building blocks for body processes
    • food made up o compounds made by other organ not suitable for human tissue
    • need to be broken down reassembled for body to use
    • small enough to be absorbed by villi in small intest through diffusion facilitated diffus, active transport
  2. Draw and label diagram of digestive system
    include mouth, esophagus, stomach, small intes, large intes, anus, liver, pancreas, gall bladder
  3. 4 stages food processing
    • ingestinon: taking food into mouth
    • digestion: see earlier
    • enzymes: speed up process
    • absorption: small molec absorbed by diffusion, facilitated diffusion, active transport
    • elimination: solid waste products egested
  4. Why need enzymes digestion?
    • digestion o starches, proteins, triglycerides happen naturally at body temp but process too slow to be useful
    • enzymes needed speed up process
    • need increase rate o digestion at body temp
    • biological catalysts
  5. Difference between absorption/assimilation?
    • after nutrients are absorbed they are assimilated and become part o body's tissue
    • absorption: passage of digested nutrients into the blood from the gastro-intestinal tract, into cells tissues
    • assimilation: integration of these absorbed molecules into the living processes of the organism that ingested them
  6. State type o amylase ,protease, lipase w/ example, source, substrate, products, optimum pH
    • amylase: salivary amylase, salivary glands, starch, maltose, 7
    • protease: pepsin, wall o stomach, proteins, small polypeptides, 1.5
    • lipase: pancreatic lipase, pancreas, triglycerides, fatty acids/glycerol, 7
  7. Outline path o digestion (3)
    • mouth
    • esophagus
    • stomach
  8. mouth
    • teeth used for ingestion + physical breakdown food by chewing
    • salivary glands prod digestive juice called saliva w/ 3 main comp
    • amylase (enzyme for starch breakdown i)
    • mucus (lubrication food for swallowing)
    • water (helps taste food/swallowing)
  9. esophagus
    • smooth mucles move bolus o food toward stomach by rhythmic muscular contractions called peristalsis
    • peristaltic contractions involun
  10. stomach
    • before food reaches stomach, glands in stom wall already begin secrete gastric juice by reflex(sight/smell)
    • entry food into stomach increase prod gastric juice b/c hormone gastrin
    • gastric juice contains pepsinogen, HCL + mucus
    • protein digestion begins w/ enzyme pepsin
    • pepsin initially synthesized and secreted as inactive precursor: pepsinogen, b/c active enzyme can harm exocrine gland cells (peptic cells) tt secrete it
    • HCL secreted by oxyntic cells in stomach activate pepsinogen -> pepsin
    • acid cond pH 2 also kills most bacteria
  11. small intestines
    • final stages digestion occur
    • contains villi to greatly increase s.a.
    • enzymes prod by wall o small intestine complete digestion; include disaccharaidases, maltase & sucrase
    • enzymes not secreted; immobilized in plasma memb o epithelial cells lining villi
    • enzyme active sites exposed to food in small intes; substrates digested and products absorbed immediately
    • even if epithelium cells rubbed off tips o villi, enzymes still work as cells mix w/ intestinal contents
  12. small intestine: after pancreatic juices secreted?
    • pancreatic juices secreted into small intestine, fr pancreas
    • pancreatic amylase: for starch breakdown int maltose
    • pancreatic lipase: for lipid breakdown into fatty acids + glycerol
    • phospholipase: phospholipid breakdown
    • trypsinogen: precursor active enzyme trypsin, could harm cells o pancreas if stored as active
    • activated into trypsin by enzyme enterokinase, secreted by small intestine
    • trypsin breaks down polypeptides into shorter chains
    • carboxy peptidase: removes one amino acid at a time fr polypeptide, beginning at end w/ free carboxyl group
    • aminopeptidase: removes amino acids at end w. free amino group
    • bicarbonate ions (HCO3): to raise pH o intestinal contents close to 8 (prevents harm) so enzyme function not altered
  13. large intestine
    • indigestible parts o food along w/ lrg vol water move into lrg intestine
    • water absorbed, solid feces egested
  14. list materials that are not absorbed and are egested
    • cellulose
    • lignin
    • bile pigments
    • bacteria
    • intestinal cells
  15. cellulose
    • humans dont prod enzyme cellulase, gene coding for production o enzyme lacking
    • cellulose cant be digested
    • carbohydrates tt we do prod cant hydrolyze linkages in cellulose molec
    • cellulose addes fibre to diet
    • fibre adds bulk to solid waste helps ensure regular bowel movements
    • may reduce time for toxins to be absorbed maybe link reduce colon cancer
  16. lignin
    another part o plant cell structure
  17. bile pigments
    bilirubin fr hemoglobin breakdown in liver transferred to bile -> converted yellow pigment egested in feces
  18. bacteria
    • many harmless species inc escherichia coli live in lrg intes
    • live on unabsorbed mat, prod gases as metabolic by-prod
    • some also prod vitamins, vitamin k
    • feces contain masses o bact; presence used to indicate water poll by untreated sewage
  19. intestinal cells
    scraped off as food moves along alimentary canal
  20. compare composition saliva, gastric juice, pancreatic juice
    • saliva: fr salivary glands, contains salivary amylase, mucus
    • gastric juice: fr glands in stomach wall, contains pepsinogen, hydrochloric acid, mucus
    • pancreatic juice: fr pancreas, contains pancreatic amylase, pancreatic lipase, phospholipase, trypsinogen, carboxypeptidase, HCO3
  21. Digestive juices are secreted into where by what? (4)
    • alimentary canal by glands including
    • salivary glands into oral cavity
    • gastric glands in stomach wall
    • ? epithelium o stomach wall (above?)
    • pancreas -> juices w/ bicarbonate ions
    • wall o small intestine, mucosa secretes mucin
  22. Outline control o digestive juice secretion by nerves and hormones using ex secretion o gastric juice
    • gastric juice: mucus, pepsinogen, HCL
    • sight smell thought o food stimulates nerves = reflex action
    • brain sends impulses to exocrine glands in stomach = release gastric juice
    • more secreted when food actually enters stom
    • food in stomac stimulates chemoreceptors and stretch receptors in stomach itsef
    • receptors send impulses to brain, release more gastric juice
    • impulses sent to endocrine glands in stom release hormone gastrin
    • gastrin stimulates exocrine glands in stom to increase secretion gastric juice, esp HCL and pepsinogen
    • sustained release o HCL reduces pH to about 3.0, condition needed for conversion pepsinogen to active enzyme pepsin
  23. When is this response appropriate?
    • respone appropriate when stomach contains protein-rich foods
    • caffeine & alcohol = same response even when no food
    • not needed acid irritates stomach and small intestine -> people w/ ulcers gastric hyperactivity (excess stomach acid) should avoid caffeine and alcohol
  24. label exocrine gland cells
    • one secretory cell: part o acinus
    • nucleus
    • nucleolus
    • mitochondrion: makes atp
    • rough e.r.: protein synthesis
    • secretory vesicles: granules storage proteins molc or other substances, transport to plasma membrane by exocytosis
    • golgi apparatus: modifying/processing o proteins)
    • duct
  25. explain structural featurs o exocrine gland cells
    • secretory cells: layer one cell thick, large surface area b/c folding + branching; grouped acini and ducts
    • acinus: one group secretory cells clustered around end o duct
    • secretory vesicles: store sub. being secrete + transport to plasma memb, release by exocytosis
    • duct: carries chem to surface o cavity
  26. What types of glands are there?
    endocrine and exocrine
  27. endocrine glands
    • secrete substances, hormones directly into blood, no ducts
    • e.g. pancreas, pituitary gland, kidney, ovary, testes
  28. exocrine glands
    • secrete substances such as digestive juices through ducts or tubes onto body surface or cavity, ducts
    • e.g. pancreas, musuc, sebacceous, sweat
  29. explain and label structural features o epithelial cell o villus (4)
    microvilli, mitochondria, pinocytotic vesicles, tight junctions
  30. tight junctions
    plasma membranes o adjacent epithelial cells firmly linked together by tight junctgions which prevent food molec fr leaking b/twn cells
  31. pinocytotic vesicles
    many small vesicles formed by endocytosis; each vesicle contains droplet fluid fr lumen o ileum
  32. mitochondria
    many scattered in cytoplasm to produce ATP needed for absorbption o sub by active transport
  33. microvilli
    • protrusions o plasma membrane greating increase s.a. exposed to digested food increase rate o absorption digested food
    • protein pumps in microvilli carry out active transport o glucose, amino a, mineral ions
  34. lipids are what?
    • hydrophobic molecules compoased o glycerol and fatty acids
    • triglyceride
  35. Explain the problem o lipid digestion in hydrophilic medium and role o bile
    • lipase is watersoluble w/ hydrophobic active site for binding lipid substrates
    • enzyme lipase hydrolyzes bonds b/twn glycerol and fatty acids
    • lipid molc coalesce in large globules
    • lipased only acts at lipid-water interface, cannot enter globules works only on surface
    • relatively small s.a. avail. for lipase to work
    • large globules wouldn't be fully digested compl when pass through alimentary canal
    • bile secreted by liver stored in gall bladder increases s.a. for lipase by process emulsification
    • physical breakdown o globule by bile to droplets o fat
    • bile molec have hydrophilic end and liophilic (hydophobic) end; attracted to both water + lipids
    • bile salts coat lipid mol prevent coalescing
    • smaller lipid droplets formed -> increase s.a. for lipase action, larger SA; volume ratio small droplets
    • speeds up process o lipid digestion so can be compled in sml intes
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Bio digestion 1.txt
bio number 1
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