Carbs, Proteins, Minerals and Vitamins Flashcards Preview

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

Flashcards in Carbs, Proteins, Minerals and Vitamins Deck (48)
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1

Absorptive Cells

  • Transport nutrients and ions

2

Capillaries

Transport most Absorbed nutrients

3

Intestinal epithelium

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

4

Carbohydrate Digestion

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

5

Amylose vs Amylopectin

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

6

Cellulose

Insoluble to humans

B-1,4 Glycosidic linkage

7

What are the brushborder membrane bound enzymes

  • Disaccharides
    • maltose
    • sucrose
    • Lactose

8

9

Maltose, Sucrose, and Lactose are broken down into

  • Maltose--> 2 glucose
  • Sucrose-->1 glucose + 1 Fructose
  • Lactose--> 1 glucose + 1 galactose

10

What are examples of glucose polymers?

  • Starch 
  • Glycogen

11

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

  • Starch/Glycogen-->Disaccharides 
    • Salivary/Pancreatic Amylase

12

Lactose Intolerance

  • Lactase decreases after childhood
    • except northern european decent

13

Artificial Sweetener

  • Splenda
  • Sugar substitute
  • Non-digestable derivative of sucrose

14

Absorption of Monosaccharides

  • 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

15

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

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

16

Pancreatic Juice: Conversion from inactive proenzymes to active

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

17

Digestion of Proteins into amino acids and small peptides

  • 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

18

Amino Acid/peptide absorption

  • 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

19

What cells are CCK released from

I cells of duodenum

20

Mechanism for controling the release of CCK

  • 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

Regulate Enzyme release

  • 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

Regulate Enzyme Activity

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

23

Where is enteropeptidase is located?

  • ONLY duodenal epithelial cells

24

Regulate enzyme degradation

  • 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