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week 46 > Carbs, Proteins, Minerals and Vitamins > Flashcards

Carbs, Proteins, Minerals and Vitamins Flashcards

1
Q

Absorptive Cells

A
  • Transport nutrients and ions
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2
Q

Capillaries

A

Transport most Absorbed nutrients

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3
Q

Intestinal epithelium

A
  • intestinal epithelial cells
    • joined by tight junctions
    • microvilli on apical surface (lumen facing)
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4
Q

Carbohydrate Digestion

A
  • Involves:
    • salivary amylase
    • pancreatic amylase
    • enzymes on intestinal brush border:
      • disaccharides
        • sucrase
        • maltase
        • isomaltase
        • lactase
      • glucomylase
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5
Q

Amylose vs Amylopectin

A
  • Amylose
    • straight polygllucose chain
    • a-1,4 glycosidic linkages
  • Amylopectin
    • Branched polyglucose chain
    • a-1,4 & a-1,6
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6
Q

Cellulose

A

Insoluble to humans

B-1,4 Glycosidic linkage

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7
Q

What are the brushborder membrane bound enzymes

A
  • Disaccharides
    • maltose
    • sucrose
    • Lactose
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8
Q
A
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9
Q

Maltose, Sucrose, and Lactose are broken down into

A
  • Maltose–> 2 glucose
  • Sucrose–>1 glucose + 1 Fructose
  • Lactose–> 1 glucose + 1 galactose
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10
Q

What are examples of glucose polymers?

A
  • Starch
  • Glycogen
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11
Q

What are Glucose polymers are broken down into and by what enzyme?

A
  • Starch/Glycogen–>Disaccharides
    • Salivary/Pancreatic Amylase
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12
Q

Lactose Intolerance

A
  • Lactase decreases after childhood
    • except northern european decent
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13
Q

Artificial Sweetener

A
  • Splenda
  • Sugar substitute
  • Non-digestable derivative of sucrose
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14
Q

Absorption of Monosaccharides

A
  • Glucose, Fructose, Galactose, and amino acids are absorbed in the small intestine
    • duodenum and jejunum
  • SGLT1 symporter
    • transport Glucose/Galactose mainly w/Na+
      • and xylose=not digested
  • Fructose enters via GLUT5 and exits via GLUT2
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15
Q

Protein Digestion: Proteases and Peptidases in what parts of GI tract and what enzymes

A
  • Stomach/Gastric lumen
    • Pepsin
    • HCl
  • Intestinal Lumen
    • Trypsin
    • Chymotrypsin
    • Carboxypeptidases A & B
    • Elastase
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16
Q

Pancreatic Juice: Conversion from inactive proenzymes to active

A
  • Trypsinogen–> Trypsin
    • via enteropeptidase (aka enterokinase)
  • Trypsin activates all proenzymes
    • Chymotrypsinogen–>Chymotrypsin
    • Procarboxypeptidase–>Carboxypeptidase
    • Procolipase–> Colipase
    • Prophospholipase–> Phospholipase
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17
Q

Digestion of Proteins into amino acids and small peptides

A
  • Stomach:
    • Acid Hydrolysis
    • Gastric Pepsin (endopeptidase-digests internal peptide bond)
  • Pancreas
    • secrete peptidases
      • exopeptidase-digest terminal peptide bonds to release amino acids
      • Aminopeptidase
      • Carboxypeptidase
    • Trypsin
      • activated by enteropeptidase (enterokinase)
    • Trypsin (endopeptidase) activates pancreatic proteases
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18
Q

Amino Acid/peptide absorption

A
  • Amino Acids
    • Na+-coupled transport
      • Na+ and aa in
    • basolateral transport=facilitated diffusion
  • Di/Tripeptides
    • H+-coupled Transport
    • proton gradient created by NHE
  • Small Peptides
    • PepT1 symporter
      • H+-coupled transport
      • also absorbs antibiotics, chemotherapeutics, other peptidomimemetic drugs
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19
Q

What cells are CCK released from

A

I cells of duodenum

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20
Q

Mechanism for controling the release of CCK

A
  • During digestion, CCK-RP and pancreatic monitor peptide stimulates release of CCK
  • After absorbing amino acids: CCK-RP, monitor peptide, and luminal digestive enzymes are removed from lumen
    • reduces CCK release and pancreatic enzymes
21
Q

Regulate Enzyme release

A
  • Cephalic Phase
    • vagal release of HCL and digestive enzymes
  • Gastric phase
    • Food in stomach
    • Gastrin stimulates HCL
      • HCL converts pepsinogen to pepsin
  • Intestinal phase
    • Fats and proteins in duodenum
    • CCK, Secretin stimulate pancrease
22
Q

Regulate Enzyme Activity

A
  • Pepsin requires acidic pH
    • don’t have to remove pepsin
  • Pancreatic proteases
    • secreted as zymogens
    • Trypsin activated by enteropeptidase (enterokinase)
23
Q

Where is enteropeptidase is located?

A
  • ONLY duodenal epithelial cells
24
Q

Regulate enzyme degradation

A
  • Proteases autodigest when no proteins are present
  • Monitor peptide
    • Pancrease secreted in intestine lumen
    • stimulates CCK release until protein digestion is complete
    • last proteins to be digested
25
NaCl Reabsorption in the small intestine and colon
* Small intestine or Colon epithelial cells absorb Na+ using 3 membranep proteins: * apical Na+ channels * Na+-Cl- symporter * NHE Na+-H exchanger * Also in Small intestine=Na+-depedent trasnporters coupled to sugars and aminoa acids * Chloride uptake * apical side: * Cl-HCO3- exchanger * Basolateral side * Cl- channel * K+ uptake: * passive diffusion via paracellular pathway * Water absorption: * osmotic gradient
26
Where does most water absorption take place?
* Mainly in SI * Little in colon
27
Water and chloride absorption in colon are driven by:
* Cl- * Electrical gradient * H2O * osmotic gradient
28
Uptake of SCFA in colon
* uptake by SMCT1=Na+-monocarboxalate transporter-1 * Na+ SCFA cotransporter
29
Examples of SCFA
Acetate proprionate butyrate
30
Nucleic acids
digested into nitrogenous bases and monosaccharides
31
What does the intestine absorb?
* Vitamins and minerals * Fat-soluble vitamins absorbed with fats * but not in olestra diet * Water soluble-transport * Vit B12 + IF=ileum * Mineral by activae transport
32
What does Vitamin B12 deficiency lead to?
Pernicious anemia
33
Mechanisms of Vitamin Absorption in Intestine
* Simple Passive absorption * Vitamin C (ascorbic acid) * Biotin\*, pantothenic acid, pyridoxine (B6) * Fat solube (A,D,E) * Facilitated passive absorption * Fat soluble: K * Folic Acid\*, Niacin\* * Riboflavin (B2) * Active Absorption * Vit B12 * Folic acid\*, Thiamine\*(B1) \*=Vitamins absorbed by more than one mechanism Vit K and BIotin synthesized by gut microflora
34
Intrinsic Factor
* secreted from stomach * binds to Vit B12 and allows absorption in ileum into bloodstream
35
Vitamin B12
* Bound to dietary protein when enterin stomach * acid and pepsin digest and release B12 * B12 binds to **haptocorrin** (**R-Protein)**in stomach * Forms B12-R-protein complex * resistant to acid and pepsin digestion in the stomach * Duodenum * R-protein digested in duodenum, releases B12 and binds to IF * Ileum * B12 absorbed by endocytosis/pinocytosis
36
Ca2+ absorption
* Absorbed in small intestine via Calcium Binding protein * Active transport * pumped out by Ca2+-ATPase/Na+-Ca+ antiport
37
Iron Absorption
* Ferric (Fe+3) reduced to ferrous (Fe2+) in duodenum * by Ferrireductase * on brush border membrane * Fe2+ binds to ferrin binding protein (DMT1) * Inside cell, Fe2+ is bout to ferritin * Ferroportin * Fe2+ exits basolateral membrane * oxidized to Fe3+ via hephaestin * Fe3+ binds to transferrin and circulates
38
Trivalent ion absorption
* Trivalent ions--\> Divalent ions before absorption * via DMT1 * Copper, Zn * Phosphorus absored as Pi via Na+-coupled transporter
39
Colonic Microflora
* Microorganisms not flora * 700-1000 species * Make up 60% of the feces dry weight * Symbiotic relationship: * produces Vit K and B (Ex: biotin, B7) * Ferment starches into fatty acids * stimulate development of immune system
40
Intestinal Gas
* ~1L odorless gas/day * Produced by intestinal bacteria * fermentation of nutrient in colon * Polysaccharids (Benas, lentils) not digested in small intestine * Composition; * Nitrogen: * Co2: * Methane: * Hydrogen: * Butyric acid, hydrogen sulfide, carbonyl sulfide
41
Risks of Intestinal Gas
* Explosive * electrocautery * High altitude flatus expulsion * airplane depressurization * Social Stigma
42
What happens b/w meals in GI system after gastric/intestinal emptying?
* Salivary production-low rate * Secondary peristalsis in esophagus * slow wave * gastric-intensity diminishes * intestinal-do not reach threshold * Motilin stimulates MMC * Water and electrolytes absorbed in gallbladder and cecum
43
Diarrhea
* Secretory * enhanced secretion/impaired absorption of ions * Osmotic * maldigestion * magnesium ingestion * Motility: * inadequate time for water absorption * inflammatory * damage to mucosal lining
44
Vomoting
* Protective reflex * aka Emesis
45
Vomiting: stimuli
* CNS * chemical trigger zone * opiates * Labyrinthine receptors * motion * balance * Throat Touch receptors * Visceral Mechanoreceptors * Stomach/duodenal chemoreceptors * ipecac * Genitourinary pain receptors
46
Vomiting: Integration
* Medullary Vomiting Center * Medullary Retching Center * Retching before vomiting
47
Vomiting: Effectors
* Smooth Muscle-reverse peristalsis (upper GI) * intestinal smooth muscle * stomach * Sphincters (Backflow) * Pylorus * Esophageal sphincters * Abominal Muscles * Respiratory muscles
48
Vomiting: Sequence
* Sympathetic Activation * sweat * pale * Retching center activated * reverse peristalsis * small intestine & stomach * Inspiration against a closed glottis * negative thoracic pressure * LES open * Gastric contents forced into esophagus * Upper Esophageal sphincter= closed * Vomiting Center activated * Reverse Peristalsis (SI and stomach) * inspiration agsint closed glottis * negative thoracic pressure * LES opens * Gastric contents forced into esophagus * **abdominal muscles contract** * **diaphragm contracts** * UES opens *

week 46 (9 decks)

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