N 207 - Protein(1)

• maintenance and regulation of bodily functions
• growth
• repair and response to injury

• energy
• converted to glucose and other AA
• converted to fat and stored as fat in adipose tissue
• burned as fuel

      WE DO NOT STORE PROTEIN!!!

we store carbs as glycogen and fat in adipose tissue

precursors of : transmitters, nucleotides, melanin, thyroid hormone, histamine

peptides = glutathione, peptide regulators

proteins

• Plasma proteins
• nutrient transport proteins = albumin (binds FAs and bile acids) and transferrin (binds Fe)
• albumin is the most abundant protein
• acute phase proteins = protection, blood clotting
• pH buffering
• regulation of fluid balance

• Red Blood Cells
• transport oxygen (hemoglobin)

• White Blood Cells
• antibodies and immune effectors

• Tissue proteins
• enzymes
• structural proteins
• membrane receptor proteins carriers

• Secretory proteins
• digestive enzymes
• human milk proteins
• hormone an growth factors
• apolipoproteins

• 9 essential = indispensable in the diet
• 11 non essential = dispensable in the diet

• conditionally indispensable concept : needed in the diet under special circumstances (prematurity, rapid growth, liver disease, trauma)
• ex. arginine and histidine

secondary structure = folding helices

• tertiary structure = bonds between regions
• ex. insulin

• Stomach
• food arrives in the stomach
• acid denatures the protein strands
• an enzyme (pepsin) cleaves aa into polypeptides, tripeptides, dipeptides and a few aa

• Small intestine
• enzymes from the pancreas (proteases) and the intestine split peptides chains into tripeptide, dipeptides and bathe intestinal cells absorb and transfer amino acids to the bloodstream so that they can go to the rest of the body

• all aa must be present
• single gene disorders = inborn errors of metabolism 
• ex. PKU, CF, sickle cell anemia 
• non poorly functioning protein is made
• nutrition treatment important in some

• biotechnology = production of proteins for food industry 
• ex. rennet

• protein is 16% nitrogen 
• 6.25g protein contains 1g nitrogen

Nitrogen Balance = N intake - Fecal N (5%) - Urinary N (95%)

• ex. 100g of protein
• = 16g of N - 1G - 15g
• = 0 = healthy adult

0 balance : intake = output (healthy adult)

• +ive = intake > output
• growing children, pregnancy
• depositing protein (recovering from an illness)

• -ive = intake < output
• low protein diet - low intake
• GI problem - low absorption
• injury - high catabolism
• losing lean muscle mass
• muscle wasting

if energy requirements are not met, then amino acids will be catabolized to provide energy

• adults (e.g. 70kg)
• RDA = 0.8g/kg/d = 56g/d

• Usual intake
• 100g/d = 1.8 x RDA

no UL established but recommended max is 2 x RDA

AMDR = 10-35% energy intake

• infants and children
• add growth component
• AI for infants = 1.5g/kg/d

YES = more than the RDA

NO = just more than a normal diet

• USE IT OR LOSE IT
• must be able to catabolism AAs and excrete urea
• nitrogen excreted as urea (liver an dkidney function)
• problem for infants esp. premes and elderly
• carbon skeleton converted to glucose or fat and then stored or burn for energy
• calcium and osteoporosis - probably not critical
• some AAs are toxic

• its the AA present in the lowest amount for the body to need it
• all other must be present in excess and must be degraded

• combine sources
• ex. beans and rice

• Legumes = have Ile and Lys
• Grains = have Met and Trp

 important for vegans and if protein requirement is low and needed