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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
gastric glands
respond to signals from brain, activated by sight, taste, and smell 3 types of cells: mucous, chief, and parietal cells
26
3 types of cells in gastric glands
mucous, chief, and parietal cells
27
mucous cells
produce mucus that protects muscular wall from harshly acidic (pH 2) and proteolytic environment of stomach
28
gastric juice
combo of secretions from chief and parietal cells
29
chief cells
in gastric juice, secrete (zymogen form of proteolytic enzymes pepsin)
30
pepsin
zymogen form of proteolytic enzyme is zymogen digests proteins by cleaving peptide bonds near aromatic AAs => short polypeptide fragment
31
parietal cells
secrete HCl 1. zymogens activated and HCl does this for pepsin => active of pH 2 2. kills harmful bacteria
32
pyloric gland
secrete gastrin
33
gastrin (hormone)
secrete by pyloric gland induce stomach secrete more HCl and mix content => chyme
34
chyme
acidic, semifluid mixture resulting from gastrin induce stomach secrete more HCl and mix content in duodenum => release disac, peptidases, enterokinase, secretin, CCK
35
small intestine
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
36
p3 sections of small intestine
duodenum, jejunum and ileum (dow jones ind.)
37
villi
surface of inner wall of small intestine cover in these projections
38
microvilli
each villi covered in its own set of this
39
small intestine: digestive functions
digestion in duodenum chyme in duodenum => release of hormones leading to secretino from small intestine and accessory organs
40
pancreatic juince
complex mix of several enzymes in bicarbonate (basic) => neutralize acidic chyme + ideal working environment for digestive enzymes pH 8.5
41
pancreatic juice enzymes digest
carbs, fats, and proteins
42
pancreatic amylase
large poly to small disac carb digestion
43
list of pancreatic peptidases
trypsinogen, chymotrypsinogen, elastinogen, and carboxypeptidase
44
pancreatic peptidase
released in zymogen form once activated => protein digestion
45
enterokinase
produced by small intestine activates trypsinogen to trypsin => activate other zymogen
46
lipase
pancreas secretes this breaking down fats to free fatty acids
47
bile
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
intestinal and pancreatic enzymes
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
bile salts
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
maltase, lactase and sucrase (disac)
digest disacc
51
peptidase
break down protein
52
small intestine release these enzymes
in duodenum => release disac, peptidases (also di), enterokinase, secretin, CCK enzymes called brush border enzymes
53
dipeptidases
cleave pep bond of dipep to release monopep (free AA)
54
secretin
hormone cuasing pancreatic juice to be exuded from pancreas
55
CCK
hormone stimulating release of both pnacreatic juice and bile
56
small intestine
capable of digesting carbs and proteins
57
mech control of digestive system
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
Small Intestine: Absorptive Functions
most occur in jejunum and ileum
59
Carbs and AA in Absorptive Functions
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
hepatic portal circulation
absorbed molecules go to liver from cap via
61
Fats in Absorptive Functions
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
chylomicron
tri and esterified cholesterol package into this => lymphatic circulation through lacteal processed directly in bloodstream into low-density lipoprotein (LDL) ("bad cholesterol)
63
LDL ( low-density lipoprotein)
in excess => atheroscloerosis taken up by liver => repackaged into high density lipoprotein (HDL, good), VLDL or more LDL
64
types of vitamins
fat and water soluble
65
fat solubles vitamins (4)
failure to digest => inhibit proper absorption => deficiency of vitamins (absorbed alongside fats)
66
water soluble
absorbed w/ water, AA, and carbs across endothelial cells => pass directly into plasma of blood
67
large intestine
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
three majors sections of large intestine
cecum, colon, and rectum
69
cecum
pocket w/o outlet that connects small and large intestine and contains appendix
70
appendix
cecum contains this tiny structure once thought be to vestigal
71
vestigal
organ or limb no apparent function now but func some time in evo past
72
colon
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
rectum
storage site for feces
74
feces
stored in rectum indigestible material, water, bac, and certain digestive secretion that aren't reabsorbed (enzymes and bile)
75
anus
opening where wastes are eliminated two sphincters: internal and external
76
internal sphincter
part of anus involuntary control (autonomic)
77
external sphincter
under voluntary control (somatic) part of anus
78
epi of skin
origin is ectoderm
79
epi of blood vessels
origin is mesoderm
80
epi of GI tract
origin is endoderm
81
salivary and pancreatic amylase
have same function
82
chemi digestion of carbs
initiated in mouth, but completed in small intestine
83
stomach secretes
H+ (kills microbes, denatures proteins, converts pepsinogen into pepsin)
84
stomach secretes
pepsinogen (pepsin partially digests proteins)
85
stomach secretes
mucus (protects mucosa)
86
stomach secretes
bicarbonate (protects mucosa)
87
stomach secretes
water (dissolves and dilutes ingested material)
88
stomach secretes
instrinctic factor (required for normal absorption of vitamin b12)
89
stomach secretes acronym
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