Kinesiology 3339A/B Lecture Notes - Lecture 20: Peptide Bond, Pancreatic Juice, Carboxylic Acid
19 Oct 2016
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Lecture 20!
Kinesiology 3339: Exercise Nutrition !
Protein Part 1
Protein Introduction
•Made up of amino acids (20; different combinations make up different proteins) that give proteins their
appearance and characteristics
•Order of AA determined by the genetic information in DNA which directs synthesis of that particular
protein – DNA directs body to combine AA into sequences
•Each AA contains carbon, oxygen, hydrogen & nitrogen
•Protein is as important as CHO, not as an exercise fuel but important for building muscle
•Peptide bond: condensation of amine group of 1 AA with the carboxyl group of another AA
-Bond is very strong
•Can have 2 amino acids (dipeptide), 3 AA (tripeptide), about 50-100 AA (polypeptide), or >100 AA
(protein – long grouping of AA joined together by peptide bonds) - Not linear but globular structure
•Interactions of side chains causes folding and resultant 3D structure determines function
Functions of Protein
•1. Structure (by muscle proteins)
-Almost half of body (40%) is muscle
-Look after protein requirements to gain muscle
-Health is proportional to amount of muscle mass you have
-Older people have less muscle mass, can minimize if stay active, do weights
-Loss is linear beginning at age 30-65, then increases a lot
-If not enough structural protein, can become life threatening stress for older person
•2. Regulators of metabolism
-Regulation of enzymes/hormones - allow you to break down food more quickly
•3. Energy
-ATP formed from AA oxidation less important unless involved in starvation situation
-If eat meal with a lot of protein, ~20% energy from AA
-When exercise contribution of protein to energy decreases ~5% or less
-Prolonged exercise, deplete CHO stores, and lean athlete, might use protein ~10% , 90%
comes from CHO or fat
Pathway of Dietary Protein
•Dietary protein breakdown into AA during digestion enter into free pool of AA in blood and body fluids
-Synthesis can synthesize body tissues, hormone, enzymes, antibodies
-Degradation can recycle body tissue, hormones, enzymes, antibodies into AA pool again
-If degradation > synthesis: will lose muscle tissue, hormones, enzymes and antibodies
-Normally as an adult the two processes are equal (as get older, degradation exceeds synthesis)
•If you do not have all of indispensable AA, synthesis stops
•Degradation can give buffer in pool, give indispensable AA you do not get from diet due to breakdown
•Can take AA from the pool that have formed during digestion, if not producing a lot of functional/
structural protein, you can deaminate (remove N) them in liver and end up with carbon hydrogen
oxygen chain much like carbs and fat
•Can also convert nitrogen into urea which is excreted into urine when using a lot of AA
Digestion
•Proteases (enzymes that attack peptide bonds) in stomach are activated by acid – low pH — (stomach
pH=1.5) and break down protein into polypeptides and finally into AA
•The acid is neutralized (pH=7) by bicarbonate in pancreatic juice released into small intestine and
remaining protein pieces are broken down into AA and absorbed into blood
•Amino acids absorbed via carriers; similar amino acids use same carrier
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Document Summary
Almost half of body (40%) is muscle. Look after protein requirements to gain muscle. Health is proportional to amount of muscle mass you have. Older people have less muscle mass, can minimize if stay active, do weights. Loss is linear beginning at age 30-65, then increases a lot. If not enough structural protein, can become life threatening stress for older person: 2. Regulation of enzymes/hormones - allow you to break down food more quickly: 3. Atp formed from aa oxidation less important unless involved in starvation situation. If eat meal with a lot of protein, ~20% energy from aa. When exercise contribution of protein to energy decreases ~5% or less. Prolonged exercise, deplete cho stores, and lean athlete, might use protein ~10% , 90% comes from cho or fat. Pathway of dietary protein: dietary protein breakdown into aa during digestion enter into free pool of aa in blood and body fluids. Synthesis can synthesize body tissues, hormone, enzymes, antibodies.
