Digestion

Question 1

Digestion

Answer 1

• nutrient procurement
• food sources, diversity of food sources - humans are omnivores
• human GI tract is geared toward specialization - which is possible due to one way flow for food
• commonality about digestion is biochemistry
• nutrient requirements are almost universal - humans don’t make vit C

Question 2

Identify Lumen, mucosal side of membrane, serosal side of membrane, circular and longitudinal smooth muscle

Answer 2

• Serosal side is outer side bounded by connective tissue
• then longitudinal smooth muscle which contract lengthwise
• then circular smooth msucles toward mucosal side which contracts inward
• then mucosal side - membrane side and then inside that is lumen

Question 3

How does food move in GI?

Answer 3

• Peristalsis - result of contraction of 2 special smooth muscle layers - coordinated mvmt moves food through GI
• don’t depend on gravity for mvmt
• GI tract also has lots of mucus -(water based substance w/glycoproteins) produced by goblet cells esp. in stomach
  
  • mucus works as lubricant and provides physical protection and resistant to digestive enzymes
  • helps form fecal mass
  • amphoteric - can act as acid or base so it a buffer

Question 4

Acid Secretion Rxn

Answer 4

H₂O + CO₂ equilibrium H⁺ + HCO3^-

H+ to stomach

HCO3^- to blood

uses carbonic anhydrase as enzyme

Question 5

Metabolism of Food Stuffs

Answer 5

• 3 major macronutrients w/energy yield/gram and then per liter O2
• direct to indirect calorimetry
• generalized calorie equivalent : 4.825 kcal/lO2
• RQ = CO2/O2
• CO2 blow off vs O2 you take in - tells us what primarily metabolizing; use mask if 1:1 ratio then metabolizing carbs
• diabetic only metabolizing fats so RQ of about 0.7 to confirm

Question 6

Exercise and MR vs. Time

Answer 6

• 90% of NRG budget is aerobic - will give us 90% of what expend if measure O2
• VO2 max is max O2 used per body wt per period of time - how much can elevate
• O2 debt - MR stays elevated beyond period of activity
• O2 debt - lactic acid contributes since need to metabolize from skeletal muscle
• Well trained - higher MR, less O2 debt and can repay it better

Question 7

Average MR in humans

Answer 7

• average MR in humans as function of age and sex
• MR goes down as age –> if keep kcal consistent as age will gain wt
• males have higher MR than women due to testosterone which > MR

Question 8

Effects of Exercise/Limits of Metabolic Scope

“central limit” and “peripheral limit”

Answer 8

1. limits O2 delivery to tissue - amount of O2 we can deliver to tissue per unit time “cental limit”
   
   • limiting factors - cardiovascular, respiratory changes, capillaries to get O2 deep into tissues
2. O2 utilization to the tissues
   
   • how much O2 can be metabolized? w/training we can > number of mitochondria and then > activity of mitochondrial enzymes “peripheral limit”

*training > utilization and delivery

3. GI tract gets better at extracting and get better at eating more food

Question 9

Diet

Answer 9

• thermal effect of food/dietary induced thermogenesis
• starvation - drop MR to protect energy levels
• regular diet
• caloric restriction and aging

Question 10

Thermal Effect of Food/Dietary Induced Thermogenesis

TEF/DIT

Answer 10

• carbohydrate 5% meaning that percent of energy in carbs is used to make it available for metabolism
• fat 12%
• protein 30%, so can starve self on diet of only protein since 30% of nergy in protein used to make protein available for metabolism

Question 11

Starvation

Answer 11

• drop MR to protect energy levels
• Ance Keys - minnesota starvation study w/pop in WWII that is starving - recruited volunteers for study
  
  • 3 months fed 3200 Cal/day, walk 27 mi/week
  • then for 6 months folloing drop to 1800 Cal/day, same exercise
  • effected psychological profile - trouble doing work, getting along
  • USA gov’t realized for democracy to survive need to feed people

Question 12

Regular Diet

Answer 12

• decrease calories
• goal to lose 10% body wt
  
  • body decrease energy expendeture (per kg BW)
  • decrease sympathetic tone (autonomic nervous system) activity of fight or flight
  • increase parasympathetic tone (for rest and digest)
  • decrease thyroid hormone, which decreases MR (thyroid hormone increases MR rate)
  • skeletal muscle - contractions are 20% more efficient - spend less energy to do same amount of work
    
    • decrease fraction of energy (ATP) from glycolysis - less anaerobic metabolism and more aerobic metab.
  • we protect fat as energy reserve for environmental challenges and reproduction in women need 15% fat

Question 13

Caloric Restriction and Aging (rebirth in pharmaceauticals)

Answer 13

• in rodents look at effects but only live 2 yrs
• companies realize if < calories by 25-50% and all proper nutrients then extend life of rodent 50% to 3 yrs
• why?
  
  • > protein turnover, so use some body protein for energy (less protein w/macromolecular damage)
    
    • proteins go through nonenzymatic glycosylation to form sugar-protein complex (proteins less function)
      
      • ex. hemoglobin E1C - glycosylated hemoglobin
    • proteins subject to oxidative damage (ROS - reactive oxygen species like peroxide) - DNA damage too
    • but if proteins turn over at higher rates then less damamge like above
  • sintuins produced - proteins expressed w/CR (caloric restrictions)
    
    • sintuins expressed - nucleus, mito, cytosol
    • some act as histones and increase DNA stability
    • resveretrol in red wine can induce sintuins

Question 14

Other Caloric Restriction Effects

Answer 14

• effects fundamental to metabolism
• influence IGF-1 Insulin-like growth factor 1, it < with CR
• effects AMP kinase which adds Pi to ADP to form ATP
• effects mtor (mammalian target of rapamyicin) - kinase phophorylates for cell growth and metabolism

Question 15

Does CR work in primates?

Answer 15

• U of Wisconsin - CR primates and increase survival, healthier and live longer
  
  • controls fed more food and > sugar content
• NIH - CR primates were healthier but not > survival
  
  • controls fed less and food naturally sourced - less dif w/CR diet
• CR can work in mammals

Question 16

CR in rodents

Answer 16

• direct relationship, more you restrict calories, longer they live to about 60% CR

Question 17

CR Rodents when to start CR

Answer 17

• porportion of life elapse when start CR
• if start CR young you get full effect, later in life you start it, less of effect on life span
• in primates needt o start as an adult

Question 18

Longevity Curves w/Diff Diets

Answer 18

• percent survival vs. Age of various cohorts
• each curve is diff cohort
• more cuve to R w/less of slope then vegetarian or medeterranian diet

Question 19

Obesity - heterologous condition

Answer 19

• heterologous condition - w/many contributing factors to obesity
• calories in vs. calories out and many other factors
• leptin - hormone from fat issue w/this leads to obesity
• microbiome - guts role
• epigenetics - environ stressors can alter expression of genes - infants born to malnourished mother, likely to be obese