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Human Nutrition


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substance obtained from food that promotes proper function

essential nutrients have at least one of more:

- provide energy
- provide structural material
- participate in regulating body processes
list the nutrient categories
- energy yielding:
* carbohydrates
* fats and oils
* proteins
- vitamins
- minerals
- water
the property of a living organism to regulate its internal environment to maintain a stable, constant condition by means of multiple dynamic equilibrium adjustments controlled by interrelated regulation mechanisms
the capacity to do work

- potential vs. kinetic
- measure energy in nutrition
* kcal - measure of heat energy
* bomb calorimetry - how we measure the potential energy in food
potential energy
chemical energy is a form of potential energy related to the breaking and forming of chemical bonds
measuring energy
- kcal - measure of heat energy
- 1 calorie is the amount of heat needed to warm 1g of water 1 degree celcius
- food calories as expressed by Kcals or 1000 calories
what does energy do?
- maintains homeostasis - 60% of energy
* heat
* pumping fluids
* maintaining structure
* ionic gradients
* respiration
- locomotion and voluntary movement
* exercise
- dietary induced thermogenesis
exergonic vs. endergoic reactions
exergonic - AB -> A+B (energy released)

endergonic - A+B -> AB (energy required)
ATP -> ADP + Pi + energy (7.3 kcal/mol)

macronutrients provide energy for ATP synthesis:

ADP + Pi + energy from CHO, protein + fat -> ATP
6CO2 + 6H2O -> C6H12O6 + 6O2
radient energy from the sun
cellular respiration
C6H12O6 + 6O2 -> 6CO2 + 6H2O

+ energy = ATP -> ADP + Pi

energy for biologic work:
- mechanical
- chemical
- transport
are not changed into ATP molecules; rather energy stored in the chemical bonds is released from CHO, fat and proteins and the liberated energy is used to synthesize ATP from ADP and Pi

only small amounts are stored in the body tissue
chemical breakdown of foods to basic chemical constituents
- mechanical alteration
- mixing
- chemical alteration
oral cavity and salivary glands
- saliva contains amylase
- secretions contain lingual (pharyngeal) lipase
- swallowing inhibits respiratory center
- lubrication
- immunoglobulin (small amount)
- 20-25 cm tube
- lower esophageal sphincter (LES) - relaxes during swallowing; constricts at other times to prevent gastro-esophageal reflex
- leads to stomach
GERD treatment
- gastro-esophageal reflux disorder

- treatment:
* smaller meals
* medications
* gravity
* avoidance of alcohol, fatty foods, caffeine, chocolate, heavy spices
- can lead to cancer
- 3 layers of involuntary smooth muscle
- volume
- lined by mucosal cells
- 3 distinct glands
- gastric juice
* pH < 2.0
* digestion of all 3 macronutrients, primarly protein
3 distinct glands of the stomach
- cardiac - pacemaker section
- oxyntic (body of stomach)
* neck cells - mucus, bicarbonate
* parietal cells - gastric digestive enzymes including pepsinogen, gastrin and secretin
- pyloric - hormone gastrin - increased HCl and pepsinogen
reglation of gastric emptying
important for protection of duodenum which has no thinck mucus barier:
- peristalsis of antrum
- enterogastric reflex
- acidic chyme in duodenum
- influence type and amount of food
- fats markedly decrease the rate of gastric emptying
small intestine
- microscopic anatomy
* surface folding
* villi
* microvilli
* epithelial cells - contain digestive enzymes
- mucosa
- peptides
- segmentation - mixing
- peristalsis
= adsorption (fats, water, Na+)
intestinal regulatory peptides
- secretin - secretion of bicarbonate rich pancreatic fluid, decreases gastric mobility
- cholecystokinin - contraction of gall bladder, pancreatic secretions including digestive enzymes and bicarbonate
* secretes bile to immulsify fats
- gastric inhibitory peptide - decreases gastric HCl secretion, reduced gastric motility
main regions of the gastrointestinal tract

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