NUTR 8030 Exam Studying

• Layers of GI Tract:

  • Lumen
  • Mucosa: epithelium, lamina propria, muscularis mucosa
  • Submucosa: Meissners plexus
  • Muscularis externa: circular muscle, Auerbachs plexus, longitudinal muscle
  • Serosa
• Efferent signaling: Brain to intestine

  Afferent signaling: Gut to brain
• Branches of Nervous System:

  • CNS & ENS
  • ENS → somatic & autonomic
  • Autonomic → sympathetic & parasympathetic
• Cell types in gastric glands:

  • Parietal: HCl and intrinsic factor
  • Chief: pepsinogen and gastric lipase
  • G cells: gastrin
  • Mucous cells: mucous
  • ECL cells: release histamine
  • EEC cells: found all over GI, express lots of receptors, secrete hormones locally
• Function of gastric gland secretions:

  • HCl: higher stomach pH
  • Mucous: barrier/lines stomach
  • Intrinsic factor: B12 absorption
  • Pepsinogen: precursor to pepsin
  • Gastric lipase: fat breakdown
  • Gastrin: promotes gastric emptying
• Process of Gastrin → HCl production:

  • G cells release gastrin
  • Gastrin acts on ECL cells
  • ECL cells release histamine
  • Histamine binds to H2 receptors on parietal cells
  • Parietal cells release HCl into stomach
• Process of Negative Feedback → stopping HCl:

  • pH gets too low
  • D cells release somatostatin
  • Somatostatin stops HCl, histamine, and gastrin
• What does HCl do?

  • Denature proteins
  • Pepsinogen → pepsin
  • Kills pathogens
• What is the purpose of CCK?

  • To prevent gastric emptying
  • Regulates contents from stomach to SI
  • Released by SI
• What hormones are released in SI?

  • CCK: triggers bile release, triggers digestive enzymes from pancreas
  • Secretin: stimulates pancreas to release sodium bicarbonate, inhibits gastric emptying
  • GLP-1: stimulates insulin release, slows GI emptying
• What hormones act as neuropeptides to induce satiety/decrease food intake?

  • GLP-1 and CCK
• What cells in the pancreas use ducts to secrete hormones?

  • Exocrine
• What is the endocrine portion of the pancreas known as?

  • Islets of Langerhans
• What two types of endocrine cells are located in islets of Langerhans?

  • Alpha: glucagon
  • Beta: insulin and amylin
  • D cells: somatostatin
• What type of exocrine cells are located in the pancreas?

  • Acinar cells: secrete digestive enzymes
• What secretions enter the duodenum via the common bile duct?

  • Amylase, lipase, peptidase, and bile
• What is bile?

  • Contains bile acids to help emulsify fats
• Functions of the large intestine:

  • Remaining water/electrolytes
  • Microbial fermentation
  • Formation of feces
• Cell types in the LI:

  • Colonocytes: epithelial cells lining the colon
  • Goblet cells: secrete mucin
  • EECs: secrete serotonin, somatostatin, GLP-1, and PYY
• Types of polysaccharides:

  • Starch: amylose/amylopectin
  • Cellulose
  • Glycogen
• Other types of carbs:

  • Sugar alcohols
  • Sugar acids
  • Glycoproteins
• Recap of recommendations vs. actual intakes:

  • CHO RDA: 130g
  • CHO AMDR: 45-65%
  • Sugars: <10%
  • Dietary fiber AI: 25-38g
• Starch digestion:

  • Reducing end and non-reducing end(s)
  • Maltase works at non-reducing end(s)
• Monosaccharide uptake:

  • SGLT1: glucose/galactose
  • GLUT5: fructose
  • GLUT2: all monosaccharides
• Nonstarch polysaccharide (dietary fiber):

  • Cellulose, hemicellulosis, pectins
  • Ferment → SCFAs in colon
• Nondigestable oligosaccharides:

  • Raffinose
  • Oligofructose
• Glucose uptake into different types of cells:

  • GLUT 1 & 3: brain, RBCs, beta cells
  • GLUT2: intestinal, liver, beta, kidney
  • GLUT4: skeletal muscle
  • GLUT5: intestinal
• GLUT4 pathway:

  • Insulin binds to a-subunit of receptor
  • Receptor autophosphorylation of tyrosine residue
  • Full activation of Akt requires PDPK1 and mTORC2
• Hexokinase:

  • Muscle
  • Can be inhibited
• Glucokinase:

  • Liver/beta cells
  • Not inhibited
• Pancreatic beta cells as glucose sensors:

  • ATP inhibits activity of ATP sensitive K+ channel
  • Increased insulin secretion
• Glycolysis:

  • Hexokinase/glucokinase: converts glucose → glucose-6-phosphate
  • Phosphofructokinase 1 (PFK1): converts F6P → F1,6BP
  • Pyruvate Kinase (PK): converts PEP → pyruvate
• Regulation of glycolysis: PFK1:

  • + regulators: AMP, Pi, insulin
  • - regulators: ATP, citrate, glucagon, epinephrine
• Regulation of Glycolysis: Pyruvate Kinase:

  • Upregulated: F1,6BP
  • Downregulated: ATP and Alanine
• Glycolysis breakdown:

  • Occurs in all cell types
  • MOST cells metabolize pyruvate by mitochondrial oxidative decarboxylation of pyruvate
• What conditions is PFK1 most active under?

  • High AMP
  • High fructose 6 phosphate
• Fate of pyruvate in each cell type:

  • RBC: PPP & lactate
  • Brain: acetyl CoA oxidation
  • Adipocyte: acetyl CoA oxidation & G3P
  • Skeletal muscle: acetyl CoA oxidation, lactate, and glycogen
  • Liver: PPP, lactate, acetyl CoA oxidation, glycogen, FA synthesis
• Regulation of glycogen synthesis (glycogensis):

  • Glycogen synthase: increased by dephosphosphorylation, activated by G6P/insulin, inhibited by glycogen/cAMP
• Glycogen synthase is allosterically activated by G6P and inhibited by glycogen
• Glycogen synthase is active in its dephosphorylated state