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MCAT - Biology > MCAT Biology Ch7: Digestion Kap > Flashcards

MCAT Biology Ch7: Digestion Kap Flashcards

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1
Q

digestion

A

absorb from gut => to tissue by circulatory system => energy, growth, development, maintenance, and activities of cells

foodstuff broken down to single sugar, AA, and fatty acids

in human => w/in lumen of alimentary canal
between mouth and anus is long cont. tube, sectioned off by sphincters

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2
Q

extracellular digestion

A

digestion occurs outside the cells’ borders

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3
Q

human digestive tract

A

specialized sections w/ diff. func. roles => digestion and absorption

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4
Q

digestion (human digestive tract)

A

breakdown of food => organic molecules

  1. lipids –> free fatty acids
  2. starches (carbs) -> mono
  3. protein -> AA

subdivded into mech and chem

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5
Q

mechanical digestion (human digestive tract)

A

phys. break of large food into small

doesn’t involve breakage of chem bonds

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6
Q

chemical digestion (human digestive tract)

A

enzymatic cleave of chem bonds

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7
Q

absorption

A

prod. of digestion from digestive tract => circulatory system => tissue and cell’s

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8
Q

digestive tract pathway

A

oral cavity => pharynx => esophagus => stomach => small intestine => large intestine

in addition, salivary glands and accessory organs:

  • pancreas
  • liver
  • gall bladder
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9
Q

oral cavity

A

chem digestion of carbs and fat in mouth

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10
Q

two types of digestion in oral cavity

A

mech and chem

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11
Q

mech digestion (oral)

A

process of mastication

salivary glands (response to nervous system signals) secrete saliva, aids mech. => moisten and lubricate food

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12
Q

mastication

A

break large into small using teeth tongue, and lips

inc. SA => more efficient chem digrestion

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13
Q

chem digestion in oral cavity

A

enzyme activity brea chem bonds that store actual food energy (ATP)

saliva contains salivary amylase => chem digestion is min. => tongue forms bolus => pharynx => swallow

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14
Q

two types of salivary amylase

A

ptyalin and lipase…

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15
Q

ptyalin

A

hydrolyzing starch into smaller sugars (maltose and dextrin)

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16
Q

lipase

A

catalyze hydrolysis of lipids

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17
Q

tongue

A

muscle that forms food into bolus

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18
Q

bolus

A

tongue helps food turn into this

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19
Q

pharnyx

A

from mouth and nose to esophagus

has connection to larynx

epiglottis prevents food from getting into respiratory tract

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20
Q

epiglottis

A

folds down and covers the trachea during swallowing, prevents food from getting into respiratory tract

failure = choking

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21
Q

esophagus

A

mouth to stomach

muscular tube

starts w/ striated muscle => smooth muscle in thorax

majority of esophagus (and most rest of GI tract) is involuntary through ANS; upper 1/3, w/ striated skeletal muscle under voluntary motor control ]]

contraction in form of peristalsis is involuntary

no mech and chem in esophagus

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22
Q

pathway through esophagus

A

swallow initiated in muscles oropharynx => smooth muscle of esophagus w/ peristalsis => waves through GI => push food actively through tube => lower esophageal sphincter (cardiac sphincter) => bolus in stomach

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23
Q

stomach

A

capacity of 2 liters

muscular

acid and enzymes digest food in farily harsh environment

mucosa is thick, to protect stomach from autodigestion

combo mech and chem => inc. SA => chyme reach intestine => absorption MAX

site of digestion, not absorption

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24
Q

two glands of stomach mucosa

A

gastric and pyloric glands

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25
Q

gastric glands

A

respond to signals from brain, activated by sight, taste, and smell

3 types of cells: mucous, chief, and parietal cells

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26
Q

3 types of cells in gastric glands

A

mucous, chief, and parietal cells

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27
Q

mucous cells

A

produce mucus that protects muscular wall from harshly acidic (pH 2) and proteolytic environment of stomach

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28
Q

gastric juice

A

combo of secretions from chief and parietal cells

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29
Q

chief cells

A

in gastric juice, secrete (zymogen form of proteolytic enzymes pepsin)

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30
Q

pepsin

A

zymogen form of proteolytic enzyme is zymogen

digests proteins by cleaving peptide bonds near aromatic AAs => short polypeptide fragment

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31
Q

parietal cells

A

secrete HCl

  1. zymogens activated and HCl does this for pepsin => active of pH 2
  2. kills harmful bacteria
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32
Q

pyloric gland

A

secrete gastrin

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33
Q

gastrin (hormone)

A

secrete by pyloric gland

induce stomach secrete more HCl and mix content => chyme

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34
Q

chyme

A

acidic, semifluid mixture resulting from gastrin induce stomach secrete more HCl and mix content

in duodenum => release disac, peptidases, enterokinase, secretin, CCK

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35
Q

small intestine

A

food leaves stomach through pyloric sphincter => duodenum

bulk of chem digestion and MOST absorption (bacteria reside)

6 meters + villi => inc. relative SA over 300 square meters

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36
Q

p3 sections of small intestine

A

duodenum, jejunum and ileum (dow jones ind.)

37
Q

villi

A

surface of inner wall of small intestine cover in these projections

38
Q

microvilli

A

each villi covered in its own set of this

39
Q

small intestine: digestive functions

A

digestion in duodenum

chyme in duodenum => release of hormones leading to secretino from small intestine and accessory organs

40
Q

pancreatic juince

A

complex mix of several enzymes in bicarbonate (basic) => neutralize acidic chyme + ideal working environment for digestive enzymes

pH 8.5

41
Q

pancreatic juice enzymes digest

A

carbs, fats, and proteins

42
Q

pancreatic amylase

A

large poly to small disac

carb digestion

43
Q

list of pancreatic peptidases

A

trypsinogen, chymotrypsinogen, elastinogen, and carboxypeptidase

44
Q

pancreatic peptidase

A

released in zymogen form

once activated => protein digestion

45
Q

enterokinase

A

produced by small intestine

activates trypsinogen to trypsin => activate other zymogen

46
Q

lipase

A

pancreas secretes this

breaking down fats to free fatty acids

47
Q

bile

A

complex fluid made of bile salts, bile pigments and cholesterol

produced by liver, stored in gall bladder => hormone CCK released by small intestin in response to moving chyme out stomach and into intestines => bile release into duodenum from gall bladder

pH between 7.5 and 8.8

alkaline to help neutralize acidity

gets fats into solution => inc. SA by placing in micelles (mech) => lipase hydrolyze ester bonds (chem dig)

48
Q

intestinal and pancreatic enzymes

A

proper digestion and absorption

only monomeric form of organic compound absorbed by gut

w/o => would pass large intestine => digested by bac flora or expelled by body in feces

49
Q

bile salts

A

made from cholesterol

not enzymes

not directly in chem digestion, but role in mech of fats => chem digestion of lipids

hydrophobiic and hydrophilic region => bridge between aq. and lipid environment

small intestine => fat emulsified (mix of two immiscible liquids)

w/o emulsify dietary fats and cholesterol into micelles => unable to keep in solution (water soluble pancreatic lipase found)

micelle expose surface to lipase

50
Q

maltase, lactase and sucrase (disac)

A

digest disacc

51
Q

peptidase

A

break down protein

52
Q

small intestine release these enzymes

A

in duodenum => release disac, peptidases (also di), enterokinase, secretin, CCK

enzymes called brush border enzymes

53
Q

dipeptidases

A

cleave pep bond of dipep to release monopep (free AA)

54
Q

secretin

A

hormone cuasing pancreatic juice to be exuded from pancreas

55
Q

CCK

A

hormone stimulating release of both pnacreatic juice and bile

56
Q

small intestine

A

capable of digesting carbs and proteins

57
Q

mech control of digestive system

A

bile released coor. w/ amount of fat ingested
-fatty meal => duodenum release entergasterone to slow momvement of chyme => greater time to digest fat

ANS:

  1. parasymp. division = stimulation (rest and digest)
  2. symp. division = inhibition (fight or flight)
58
Q

Small Intestine: Absorptive Functions

A

most occur in jejunum and ileum

59
Q

Carbs and AA in Absorptive Functions

A

simple sugars and AA absorbed by active transport and facilitated diffusion into epithelial cells lining of gut => intestinal capillaries

cap blood passing by epi cells in capillaries => carb and AA away from them => cap blood lower conc. => simple carb and AA diffuse from epi cell into cap => into liver via hepatic portal circulation

60
Q

hepatic portal circulation

A

absorbed molecules go to liver from cap via

61
Q

Fats in Absorptive Functions

A

fatty acids diffuse directly into intestinal capillaries

nonpolar => easily cell membrane

larger fats, glycerol, and cholesterol separately into intestinal cells => reform triglycerides => tri and esterified cholesterol package into chylomicrons => lymphatic circulation through lacteal => lacteal converge => lymphatic duct in neck region (thoracic duct) through venous circulation

62
Q

chylomicron

A

tri and esterified cholesterol package into this => lymphatic circulation through lacteal

processed directly in bloodstream into low-density lipoprotein (LDL) (“bad cholesterol)

63
Q

LDL ( low-density lipoprotein)

A

in excess => atheroscloerosis

taken up by liver => repackaged into high density lipoprotein (HDL, good), VLDL or more LDL

64
Q

types of vitamins

A

fat and water soluble

65
Q

fat solubles vitamins (4)

A

failure to digest => inhibit proper absorption => deficiency of vitamins (absorbed alongside fats)

66
Q

water soluble

A

absorbed w/ water, AA, and carbs across endothelial cells => pass directly into plasma of blood

67
Q

large intestine

A

final part of GI tract

primarily involved in water absorption (although overall water balance in body is controlled by kidneys) => feces are semisolid when reach rectum

larger than SI in diameter, however only 1.5 meters long (shorter)

68
Q

three majors sections of large intestine

A

cecum, colon, and rectum

69
Q

cecum

A

pocket w/o outlet that connects small and large intestine and contains appendix

70
Q

appendix

A

cecum contains this

tiny structure once thought be to vestigal

71
Q

vestigal

A

organ or limb no apparent function now but func some time in evo past

72
Q

colon

A

absorb water and salts in undigested material small intestine

recycling system, pulling last bits of nutrients out of remaining waste products

too much or little water absorption => diarrhea or constipation

73
Q

rectum

A

storage site for feces

74
Q

feces

A

stored in rectum

indigestible material, water, bac, and certain digestive secretion that aren’t reabsorbed (enzymes and bile)

75
Q

anus

A

opening where wastes are eliminated

two sphincters: internal and external

76
Q

internal sphincter

A

part of anus

involuntary control (autonomic)

77
Q

external sphincter

A

under voluntary control (somatic)

part of anus

78
Q

epi of skin

A

origin is ectoderm

79
Q

epi of blood vessels

A

origin is mesoderm

80
Q

epi of GI tract

A

origin is endoderm

81
Q

salivary and pancreatic amylase

A

have same function

82
Q

chemi digestion of carbs

A

initiated in mouth, but completed in small intestine

83
Q

stomach secretes

A

H+ (kills microbes, denatures proteins, converts pepsinogen into pepsin)

84
Q

stomach secretes

A

pepsinogen (pepsin partially digests proteins)

85
Q

stomach secretes

A

mucus (protects mucosa)

86
Q

stomach secretes

A

bicarbonate (protects mucosa)

87
Q

stomach secretes

A

water (dissolves and dilutes ingested material)

88
Q

stomach secretes

A

instrinctic factor (required for normal absorption of vitamin b12)

89
Q

stomach secretes acronym

A

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