Bio 1080 Final Notes

• GI Tract


  • 28 ft long tube through body
  • Vomit and diarrhea of noxious substances
• T cells


  • Localized to intestinal mucosa
• Peyer's patches


  • First line of defense
• Sphincters and valves


  • Amplify surface area to absorb food
• Gut microbiome


  • Protects from pathogenic microbes that enter the tract
• Intrinsic nervous system


  • Controls the function, opening and closing of valves, etc.
• Processes of GI tract

  • Motility
  • Secretion
  • Digestion
  • Absorption
• Cephalic digestion


  1. Starts in mouth

  2. Chemical and mechanical chewing

  3. Sensory stimuli (sight, smell, taste)

  4. Saliva under autonomic control softens food, provides enzymes
• Gastric digestion


  1. Occurs when food is relaxed in stomach

  2. Relaxes sphincter

  3. Digestion of protein and fat, not carbohydrate
• Small intestine digestion


  1. Pancreas is main contributor

  2. Inactive enzyme trypsinogen becomes active enzyme trypsin

  3. Bile stored in gallbladder

  4. Villi increase surface area

  5. Bicarbonate from epithelial cells

  6. Digestive enzymes from pancreas
• Celiac disease


  Caused by flattened villi
• Carbohydrates


  • Simple vs complex based on amount of sugar molecules
  • Monosaccharides are building blocks (glucose, fructose, galactose)
  • Monosaccharides form disaccharides (sucrose, maltose, lactose)
  • Complex polysaccharides include starches, fibers, glycogen
• Enzymes


  Secreted through brush border into bloodstream
• Celiac disease


  Deficiency in lactase enzyme causes lactose intolerance
• Protein


  Peptides and amino acids transported through bloodstream for energy
• Lipid digestion


  1. Emulsified in mouth, stomach, small intestine

  2. Lipases can only act on lipids when broken down

  3. Bile produced in liver, stored in gallbladder, aids digestion of lipids

  4. Lipids absorbed as fatty acids and monoglycerides, then reassembled into triglycerides and chylomicrons
• Large intestine


  • Colonic epithelium absorbs water and simple ions
  • Resident microbes digest chemicals through fermentation, produce vitamins and gas
• ATP


  Medium of energy exchange, energy currency of cell
• Glucose and fatty acid metabolism

  1. Create most ATP

  2. Little ATP from amino acids

  3. Some by glycolysis and Krebs cycle, produce reducing equivalents NADH and FADH2

  4. Supply H+ to ETC where most ATP is made
• Anaerobic ATP


  Produced without oxygen, during high levels of exercise and sprints
• Energy storage


  • Fat stored as triglycerides in adipocytes
  • Carbohydrates stored as glycogen in liver and muscle
  • Protein is a large potential energy source
• Fuel


  • Carbohydrates generate ATP faster aerobically and anaerobically
  • Carbohydrates hold a lot of water, fat cannot hold water
  • Fat is the most abundant energy reserve but needs oxygen
• Absorptive state


  1. 4 hours after meal, energy is stored, macronutrients in anabolic state
• Postabsorptive state


  Fasting, stored macronutrients are mobilized for energy, glucose spared for nervous system
• Fasting hyperglycemia


  Blood glucose too high, over 7 mmol/L
• Fasting hypoglycemia


  Blood glucose too low, less than 3.5 mmol/L
• Insulin


  Released when blood glucose rises after a meal
• Glucagon


  Released when glucose is low during fasting
• Genetic variation


  May influence longevity
• SNPs


  Single nucleotide polymorphisms, a single difference in a DNA nucleotide, frequent source of polymorphic changes
• Increase in inflammatory cytokines

  Leads to aging and contributes to age-related disorders like Alzheimer's
• Interleukin 6


  Increased death rate, released from immune cells
• Mitochondrial damage


  Contains components of ETC genes, damage occurs frequently due to reactive oxygen species, DNA polymerase gamma replicates and proofreads but more errors occur with age
• Mutations in mitochondrial DNA cause aging, which can be modeled in mice
• Intense food restriction extends healthy lifespan in rats, not proven in humans