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Fundamentals
of Nutrition

What is a
Food Portion?

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Physiology
of Nutrition
Lecture Series
Lecture 1
Lecture 2

Lecture 3
Lecture 4
Lecture 5
Lecture 6
Lecture 7
Lecture 8

 

Lecture 3 page 1 2 3 4 5

Protein

Made up of 20 amino acids
Adult Requirements: 0.8 g protein/kg/d

Essential Amino Acids (not synthesized in the body)
Methionine Threonine
Valine Isoleucine
Phenylalanine Leucine
Tryptophan Lysine
Histidine  
Sources of protein
Diet  
Digestive Juices (35g)  
Desquamated intestinal cells (30g)  
Excretion: 6-12 g/d in feces

Digestion
-Intraluminal hydrolysis by proteases secreted by stomach and pancreas

-Peptidases in brush border membrane of small intestine digest protein to amino acids and di- and tripeptides that are taken up by the enterocyte

Stomach (Pepsin)
-Proteolytic enzymes contained in gastric juice
-Requires acid environment of stomach to hydrolyze protein
-Denatured by alkaline fluid (small intestine)
-Synthesized in the gastric chief cells as inactive pre-proenzymes (pepsinogen)

Pancreas

-Secretes proteases as proenzymes

-Enterokinase - an intestinal brush border enzyme that activates pancreatic proteases. Stimulated by trypsinogen contained in pancreatic juice.

Figure 3
Protein digestion and absorption in the small intestine

1. brush-border membrane peptidases
2. brush-border membrane amino acid transporters
3. brush-border membrane di- and tripeptide transporters
4. intracellular peptidases
5.basolateral-membrane amino acid carriers
6. basolateral membrane di- and tripeptide carriers

 

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Lecture 1
:Introduction to Nutrition in Western Civilization
Lecture 2:
Dietary Macronutrients, Body Fat, and Blood Lipids
Lecture 3:
Digestion and Absorption of Macronutrients
Lecture 4:
Basic Principles of Nutrient Metabolism
Lecture 5:
Obesity
Lecture 6:
Fuel Utilization During Exercise
  Lecture 7:Biochemistry of Oxidant Stress in Health and Disease Antioxidants
Lecture 8:Nutrition for the 21st Century

 

 

 

 

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