BI0004 - Lecture 4 - Digestion

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BI0004 - Lecture 4 - Digestion
2014-02-18 07:26:25
BI0004 Lecture
BI0004 - Lecture 4
BI0004 - Lecture 4
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  1. What are essential amino acids?
    "Essential amino acids" must be obtained from food in preassembled form.
  2. How many essential amino acids are there for adults?
  3. What can happen during malnutrition when essential amino acids aren't gained through diet?
    Some animals (including humans) can use their own muscle protein as a supplement.
  4. What is an example of an essential fatty acid?
    • Linoleic Acid.
    • This is important in cell signalling - signals cell damage, cell repair, wound healing, platelet formation.
  5. Most animals are essentially a "tube". What is this tube called?
    The "alimentary canal".
  6. What are the different sections of the alimentary canal?
    • Mouth
    • Esophagus
    • Stomach - secretions from the gastric glands of the stomach.
    • Small intestine - Secretions from the pancreas and the liver enter. Lipids exit to the lymphatic system and then bloodstream.
    • Large intestine - Absorbed food and absorbed water enters the bloodstream.
    • Rectum
    • Anus
  7. What's the difference between herbivore and carnivore cecum?
    • Herbivores have a relatively large cecum, hosting a large number of bacteria, which aid in the enzymatic breakdown of plant materials such as cellulose.
    • Carnivores, whose diets contain little or no plant material, have a reduced cecum.
  8. What are the 4 stages of processing food?
    • Ingestion
    • Digestion
    • Absorption
    • Excretion
  9. Briefly, what is ingestion?
    • Taking in food.
    • Crushing or chopping.
    • Swallowing food.
  10. Briefly, what is digestion?
    • Breaking-down food into constituent parts.
    • Breaking-down protective/resilient components.
  11. Briefly, what is absorption?
    • Taking nutrients into cells.
    • May occur via a circulatory system.
  12. Briefly what is excretion?
    • Removal of undigested food.
    • Removal of waste products.
    • Removal of cellular debris from organism.
  13. How do carnivores tend to ingest food?
    • Tend to tear meat, cut meat into smaller sections and swallow whole with no chewing.
    • Vertical chewing motion.
  14. How do herbivores tend to ingest food?
    • Tend to tear plant material and then chew for long periods.
    • Rotary motion chewing
  15. How do omnivores tend to ingest food?
    • Use both approaches - tearing and chewing.
    • Tend to chew most material before swallowing.
  16. How does saliva help ingestion?
    • Moistens/lubricates food - ease of swallowing.
    • Dissolves components of food to allow taste - required for taste buds to work properly.
    • Digestion of starch and sugars - contains amylase. breaks starch down into sugars.
    • Antibiotic properties - healthy teeth and gums.
  17. What 3 physical adaptations have developed for ingestion?
    • The Pharynx
    • The Crop
    • The Gizzard
  18. What is the Pharynx (throat)?
    • The opening of the oesophagus.
    • The division of the oesophagus and the trachea.
    • The Glottis
    • The Epiglottis
  19. What is the oesophagus?
    The esophagus (commonly known as the gullet) is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach.
  20. What is the trachea?
    The trachea, or windpipe, is a tube that connects the pharynx and larynx to the lungs, allowing the passage of air.
  21. What is the epiglottis?
    The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx.
  22. What is the process of the swallowing mechanism?
    • Bolus formation by saliva and chewing.
    • The swallowing response - Glottis up, Epiglottis down.
    • The oesophageal sphincter relaxes
    • The oesophageal sphincter closes
    • Wave of contraction (peristalsis) down the oesophagus.
  23. Birds can't chew, so they have...
    ...a crop and a gizzard.
  24. What is a crop?
    • Most birds have them, also some reptiles and invertebrates.
    • It is a muscular sac; an extension of the oesophagus.
    • For storage of food (short term).
    • For softening food, early digestion.
  25. What is a gizzard?
    • A muscular second region of the stomach.
    • A strong, rough inner lining.
    • Contains sand or tiny stones for grinding food.
  26. What is external digestion?
    • It is digestion outside of the organism or in an open cavity.
    • Digestion before ingestion.
  27. What is internal digestion?
    • Digestion within the cell.
    • Digestion within enclosed alimentary canal.
    • Ingestion before digestion.
  28. Example of external digestion?
    • Housefly
    • Regurgitation of enzyme solution in saliva.
    • Digests food source in situ.
    • Ingestion of liquid food source.

    • Saprophytic fungus
    • Excretion of enzyme solution from hyphae.
    • Digests food source in situ.
    • Diffusion of nutrients into hyphal cell.
  29. What is an example of constitutive external digestion.
    • Pitcher plants
    • Have an enticing smell
    • Slippery lip and sides for capture.
    • Aqueous solution of enzyme in base
    • Direct diffusion of dissolved nutrients
  30. What is the example of induced external digestion?
    • Venus fly trap / honeydew
    • Enticing smell
    • Adhesive or trap
    • Holds prey immobile.
    • Secretion of enzymes
    • Direct diffusion of dissolved nutrients
  31. What are intracellular compartments?
    Discrete "compartments" in which digestion takes place.
  32. What are three types of intracellular digestion?
    • Endocytosis
    • Phagocytosis
    • Autophagy
  33. What is endocytosis?
    Endocytosis is an energy-using process by which cells absorb molecules (such as proteins) by engulfing them.
  34. What is phagocytosis?
    In cell biology, phagocytosis is the process by which a cell —often a phagocyte or a protist—engulfs a solid particle to form an internal vesicle known as a phagosome.
  35. What is Autophagy?
    Autophagy, is the basic catabolic mechanism that involves cell degradation of unnecessary or dysfunctional cellular components through the actions of lysosomes. The breakdown of cellular components can ensure cellular survival during starvation by maintaining cellular energy levels.
  36. In digestion "compartments", each compartment ... and ...
    ...performs a specific function... and... each digest a key component of the food. e.g starch, protein.
  37. Generally, the stomach and small intestine digest...
    ...animal material.
  38. Generally, the caecum and the large intestine digest...
    ...plant material.
  39. What does digestion require?
    • Sufficient Space.
    • Large surface area.
    • Ability to secrete enzymes.
    • Defence vs. Enzymes for host cells.
    • Link with absorption methods and structures.
  40. Briefly describe cnidarian digestion?
    • Cnidarian - hydra
    • Single enclosed tube.
    • Large interior surface area
    • Body cavity 1 cell thick.
    • Structures to aid movement of food (cilia)
  41. Briefly describe annelid (worm) digestion?
    • Open-ended enclosed tube.
    • Large interior surface area.
    • Folded inner structure to increase surface area.
    • Defined regions of gut (crop, gizzard, etc).
    • Structures to aid movement of food (cilia).
  42. Briefly describe arthropod digestion?
    • Open-ended enclosed tube
    • Large interior surface area
    • Structures to aid movement of food
    • Defined section with differential enzyme activities.
    • Regions to process chewed leaf tissue.
  43. Briefly describe bird vertebrate digestion.
    • Open-ended enclosed tube
    • Large interior surface area
    • Intestines very long for efficient processing of food
    • Structures to aid movement of food
    • Defined secretions with differential enzyme activities
    • Regions to process chewed plant tissue.
  44. Briefly describe the stomach.
    • It has deep folds and elastic walls allowing expansion.
    • Secretes gastric juices (acid pH).
    • Mixes every 20s.
    • It disrupts the extra cellular membrane of meat.
    • It is antibacterial.
    • Gastric pits produce pepsinogen which mixes with HCL to form pepsin (digests proteins)
    • There is mucal defence against self-digestion.
  45. What is the small intestine?
    • The small intestine (or small bowel) is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place.
    • The small intestine is composed of a duodenum, jejunum, and ileum. It receives bile juice and pancreatic juice through the hepatopancreatic duct.
  46. What is the duodenum?
    The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds.
  47. What is the ileum?
    • The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds.
    • Contains Villi, microvilli, blood capillaries
  48. What is the liver?
    • The liver is a vital organ present in vertebrates and some other animals.
    • It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion. e.g secretes bile.
  49. What is the pancreas?
    • The pancreas is a glandular organ in the digestive system and endocrine system of vertebrates.
    • It is an endocrine gland producing several important hormones, including insulin, glucagon, which circulate in the blood.
    • The pancreas is also a digestive organ, secreting pancreatic juice containing digestive enzymes (hydrolytic enzymes) that assist digestion and absorption of nutrients in the small intestine. e.g. proteases
    • These enzymes help to further break down the carbohydrates, proteins, and lipids in the chyme.
  50. Briefly describe carbohydrate digestion.
    • Begins in the mouth with salivary amylase.
    • Then pancreatic amylases.
    • Absorbed in the Ileum.
  51. Briefly describe protein digestion.
    • Broken down by pepsin in the stomach.
    • Then by pancreatic trypsin and chymotrypsin in the small intestine.
    • Absorbed by the ileum
  52. Breifly describe nucleic acid digestion.
    • Digested by pancreatic nucleases in the small intestine.
    • Absorbed by the Ileum as bases, sugars and phosphates.
  53. Briefly describe fat digestion
    • Emulsification of fats by bile salts
    • Breakdown by pancreatic lipase
    • Breaks down into small droplets (mycelles)
    • Absorbed in Ileum into lymph as fatty acids.
  54. Plant material is difficult to digest so it requires different physical structures. What are they?
    • Difficult to digest plant cellulose, hemicellulose, and lignin.
    • Need enlarged large intestine.
    • Expanded Caecum
    • Increased bacterial flora
    • Ability to regurgitate (ruminants)
  55. Describe the role of symbiotic relationships in digestion.
    • Most intestines contain a flora of bacteria. e.g. E. Coli
    • Bacteria gain nutrients; hosts breakdown cellulose etc.
  56. Methane is...
    ...a bi-product of E. coli.
  57. What are passive and active absorption?
    • Passive - Water, water-soluble (e.g. glucose), lipid soluble (e.g. fats)
    • Active - requires ATP-dependent pumps, insoluble or hydrophobic matter.
  58. How are nutrients absorbed into the blood stream?
    • Through the ilium.
    • Through the epithelial sheet
    • To the capillaries
    • To the hepatic portal vessel.
  59. What is lymph?
    • Lymph is the fluid that circulates throughout the lymphatic system. The lymph is formed when the interstitial fluid (the fluid which lies in the interstices of all body tissues) is collected through lymph capillaries.
    • It is then transported throughlymph vessels to lymph nodes before emptying ultimately into the right or the leftsubclavian vein, where it mixes back with blood.
    • Since the lymph is derived from the interstitial fluid, its composition continually changes as the blood and the surrounding cells continually exchange substances with the interstitial fluid.
  60. What does the large intestine do?
    • Concentrates waste
    • Removes water
    • Stores waste until removal as faeces.

    • Varies in size between organisms
    • Larger for herbivores
    • bacterial residents
  61. Excretion removes what?
    Excretion includes what?
    Water, undigested waste, toxins/bile, cellular debris.

    Urine, sweat, faeces, pellets.
  62. What are two specific excretion adaptations.
    • Creating pellets - regurgitated bones and fur.
    • Recycling faeces - e.g. rabbits - passed through large intestine/anus, partially digested, re-ingested.