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Protein Synthesis
- DNA contains
- coded instructions
- Copies of codes
- o Transferred to the cytoplasm (via mRNA)
- Amino acids added one at a time
- o With aid of transfer RNA (tRNA)
- Requires energy
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Essential amino acid
- o Cannot be synthesized by the body in sufficient amounts
- o Also called “indispensable”
- o Required in the diet
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Protein Synthesis
Will stop without Essential Amino Acids
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Digestion of Protein in the Stomach
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Over intake of Protein
Body doesnt have room to store it, so it is form into fat or carbs (glycogen)
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Nitrogen balance
Proteins have nitrogen, Which is important in growth.
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The concept of complementary proteins
To incomplete (complementary) proteins can be combined to make a complete protein.
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protein digestion
Digestion of Protein in the Stomach
Digestion of Protein in the Small Intestine
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Digestion of Protein in the Small Intestine
· Release of CCK · Pancreatic enzymes: o Trypsin, among others, into the duodenum · Peptones à - peptides à
- amino acids
· Small peptides and amino acids o Ready for absorption
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Protein absorption
· Final site of digestion is- microvilli surface and within absorptive cells
o Breaks down di- and tri-peptides into single amino acids · Many different amino acid transport- mechanisms
· Active absorption · Amino acids are sent to the liver o Via portal (vein) circulation
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What are the sources of amino
acids entering the pool
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What are the destinations of
amino acids leaving the pool
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What is the by-product of
amino acid catabolism and how is it processed
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How do circulating proteins
(primarily albumin) contribute to fluid balance
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RDA for Protein
- Promotes equilibrium
- AMDR for protein is 10-35 percent
- of energy for adults
- 0.8 gm/kg of healthy body weight
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High-Protein Diet
· Low in plant foods (fiber),- vitamins, phytochemicals
· High in saturated fat and cholesterol · Excessive intake of processed red- meat is linked with colon cancer
· Burden on the kidney · May increase calcium loss in the- urine
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Excessive intake of processed red
- meat is linked with colon cancer
- Burden on the kidney
- May increase calcium loss in the
- urine
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How does the RDA
change in pregnancy, endurance exercise training, resistance exercise training
- Increased by ~10-15 gm /day for pregnancy
- Endurance athletes
- o May need 1.2-1.7 gm/kg healthy weight
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