Lecture 32

• Energy (NRG)
  
  • If we take a bomb calorimeter – can put food in and with O2 – put wire – ignite food stuff – food stuff burns into ashes – monitoring how much H20 increase in heat – counting calories of heat – amount of gross energy
    
  • 1calorie = the amount of heat it takes to raise 1g of H20 1 degree Celsius – kcal/calorie – on food really mean kcal
    
    • 1g of carbohydrates and burn them in bomb calorimeter get 4.1kcal - - 1gr of protein and burn it 4.35kcal - - Lipids = 9.3kcal
      
  • Not all the calories we eat are digested – subtract amount in feces as fecal energy
    
    • Gross energy – facal matter = digestive energy, digestive energy – urine energy = metabolic energy, metabolic energy – specific heat of digestion = net energy
      

      * Specific heat of digestion varies between foods
      

    • Net energy not used in NY state because heat is retained during cold months – in NY we feed by digestible energy levels
      
  • Smaller animal has larger surface area per kg of body weight
    
    • Kg^.66 – net body size of animal – adjests for body size and not metabolis, K^.75 (learn this one), adjusts for both body size and metabolism
      
  • Calories in vs. calories out
    
    • Diet – balance calories in compared to calories out
      
    • Couch potatoes – 2,000 cal per day – laborer/ athlete 6,000-7,000 kcal/day
      
    • No such thing as empty calories – in corn there is carotene which makes vitamin A - Fat not only higher in calories but also more concentrated – fat is not water soluble when carbs and protein are water soluble – potatoes are made more of water - fat very concentrated – carbs and proteins usually formed in watery matrix
      

   
   

  Fat
  

  • is higher in calories and is more concentrated form of food
    
  • much of what we eat is lipid
    
  • Lipids NOT water soluble, whereas proteins/CHOs are water soluble and tend to be in a matrix
    

   
   

  Phospholipids
  

  • are necessary for plasma membrane, cholesterol needed to maintain these membranes along with hormone production
    
    • three essential fatty acids:
      
      • Linoleic
        
      • Linolenic
        
      • Aracnidonic
        
  • all 29 carbon acids, your body cannot create 29 carbon acids so they have to be consumed, but these acids will end up being changed to prostaglandins (used as a signaling boat for other cells)
    

     
     

  Polyunsaturates
  

  • OK cold
    
    • Cook them, creates more free radicals
      
    • Use monosaturates instead
      

       
       

  Vitamins
  

  • hypovitaminosis can occur if fat soluble vitamins are overfed
    

   
   

  Elements:
  

  -Ca and Phosphate ratios must be balanced
  

  • are taken in at a ratio of 2:1 (Ca : Phosphate)
    
  • Can get dibasic phosphate which is a balanced calcium/phosphate level
    
  • 3:1 ratio: Greater Ca than phosphorous you will have an arthritic animal
    
  • 1:1 ratio: get an osteoporosis animal
    
  • NOT mutually exclusive - one doesn't reverse the other
    

     
     

   
   

  Liver Function
  

  • Sugar metabolism
    
    • Galactose and fructose converted to glucose in the liver
      
      • Drainage from GI tract is going right to liver first
        
    • the liver will create glucose from non-CHO sources or the breakdown products of proteins = gluconeogenesis
      
    • liver will synthesize glycogen
      
  • Protein metabolism
    
    • the liver produces many blood proteins
      
    • Interconversion of amino acids takes place in the liver
      
      • Take one in, and change it to essential a.a.
        
    • Deamination
      
      • Destroying a.a.
        
      • Amine group breaking off
        
      • Take bicarb and make urea and glutamine from it
        
        • only site of urea production in the human body
          
  • Fat metabolism
    
    • Liver burns fatty acid and supply energy for other body functions
      
    • Creates:
      
      • cholesterol
        
      • phospholipids
        
      • most lipoproteins
        
    • Stores:
      
      • Glycogen,
        
      • Vitamin B12, A, D, and E
        
      • Iron in the form of Ferrotin
        
      • 0.5 – 1L of blood when it is not needed elsewhere
        
    • Produces:
      
      • Bile (emulsifies fats)
        
        • Secretes into GI tract
          
    • Removes:
      
      • Hormones, drugs, toxins from circulation
        
        • By chemically changing them or excreting them in bile
          

           
           

  Endocrinology
  

  • Study of hormones
    

     
     

  • Hormones of the GI Tract:
    

     
     

    • Gastrin:
      
      • Produced by
        
        • The stomach and duodenum
          
      • Turned on by
        
        • Vagal activity (sympathetic activity)
          
        • Increase in the stomach contents (especially protein)
          
      • Turned off by (regulated by)
        
        • HCl in the stomach
          
        • Secretin
          
      • Actions of gastrin:
        
        • Increase the secretion of HCl and pepsinogen (changes to pepsin by HCl and is used to digests proteins)
          
        • Increase motility of the whole GI tract (peristalsis)
          

           
           

    • Secretion:
      
      • Produced by
        
        • Duodenum mucosa
          
      • Turned on by:
        
        • Acid in the duodenum (when the acid leaves the stomach and heads into the GI tract it causes secretin to be secreted)
          
      • Turned off by:
        
        • Neutralization of this acid
          
      • Actions:
        
        • Stimulates duck cells to make HCO3 rich solution from the pancreatic duct cells (neutralizes pH)
          
        • Closes the pyloric sphincter (holds the acid in the stomach)
          
      • 1902 Baylus and Starling discovered secretin, they proposed that there were other chemical signalers in the body and that they should be called hormones (secretin = first hormone discovered)
        

       
       

    • Cholecystokinin-Pancreozymin = CCK-Pz = CCK
      
      • Produced by
        
        • The duodenum mucosa
          
      • Turned on by
        
        • Fats and proteins in the duodenum mucosa
          
      • Turned off by:
        
        • Absence of fats and proteins in the duodenum mucosa
          
      • Actions:
        
        • CCK levels are monitored by the satiety center (hypothalamus) to keep track of the amount of fats/proteins in the GI tract
          
          • Contracts gallbladder
            
          • Causes pancreozymin (digestion enzyme) secretion by the pancreas
            
          • helps to close the pyloric sphincter (just like secretin)
            

       
       

    • Gastrin Inhibitory Peptide (GIP)
      
      • Produced by
        
        • Duodenum and jejunum
          
      • Turned on by:
        
        • fat or glucose in the duodenum
          
      • Turned off by:
        
        • absence of fats/glucose in the duodenum
          
      • Actions:
        
        • promotes insulin secretion
          
        • inhibits gastrin secretion
          

           
           

    • Vasoactive intestinal polypeptide (VIP)
      
      • Produced by
        
        • neurons of the GI tract
          
      • Turned on by
        
        • CNS
          
      • Turned off by
        
        • CNS
          
      • Actions:
        
        • Increases secretion of H2O and electrolytes into the GI tract
          
          • throws electrolytes into GI tract and water follows in via obligatory H2O flow
            
        • dilates peripheral blood vessels
          
        • inhibits gastrin
          

           
           

    • Enterogastrone:
      
      • Doesn't exist:
        
        • GIP and VIP account for anything that is attributed to enterogastrone
          

           
           

    • Motilin
      
      • Produced by
        
        • The duodenum mucosa
          
      • don't know what turns it ON/OFF
        
      • Causes gut motility between meals
        
        • When nothing is stimulating the gastrin to be secreted (have empty stomach) you still need to keep the motility going and this is done by motilin
          

           
           

    • Neurotensin
      
      • produced by
        
        • Ilial mucosa
          
      • Turned on by:
        
        • Free fatty acids in the small intestine
          
      • Turned off by:
        
        • lack of free fatty acids in the small intestine
          
      • Actions:
        
        • Reduces got motility
          
        • increases ilial blood flow
          

          We have some free fatty acids and the ilium doesn't want them to escape b/c the free fatty acids are good for energy, so we slow the motility of the gut and increase the ilial blood flow to pick up more of these free fatty acids
          

    • Substance P
      
      • Produced by
        
        • Intestinal mucosa
          
      • Actions
        
        • Increase motility of small intestine
          
      • Hormones are things that you put into the bloodstream, but Substance P is NEVER put into the bloodstream it is put into the lumen of the small intestine – is it really a hormone? – never appears in the blood
        

         
         

    • Somatostatin = Growth Hormone Inhibiting Hormone
      
      • Produced by
        
        • Stomach
          
        • Duodenum
          
        • Pancreas
          
      • Turned on by:
        
        • HCl in the intestine
          
        • Sympathetic stimulation
          
      • Turned off by
        
        • Lack of those things
          
      • Actions:
        
        • Inhibits:
          
          • Gastrin
            
          • VIP
            
          • GIP
            
          • Motilin
            
          • Secretin
            
          • CCK
            
        • decreases absorption of
          
          • Glucose
            
          • a.a.
            
          • Triglycerides
            
        • shuts the gut down (this is what the sympathetic system is using to turn the gut off)