Note

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Note Final Exam-please check final schedule
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Lecture 24 - 4 March 2011 Proteins
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Proteins Comes from the Greek word protos
meaning of prime importance
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What are they?   -chains of amino
acids   -an amino acid is an organic acid with
a side group and an NH2 group attached
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Functions of proteins in the
body -structure -hair, nails,
cells   -mechanical functions motor
proteins -eg contractile proteins in
muscle
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Functions of proteins in the body
-enzymes -aid in reactions- make the reactions
go faster   -hormones -signals to
cells -eg insulin   -antibodies -help
fight infection
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Functions of proteins in the body
-fluid balance -osmotic influence   -acid
base balance -charge on certain proteins
affects pH   -channels e.g.-move ions into
and out of cells
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• Functions of proteins in the body
• pumps
• -move substances across cell wall by use of
  energy
• -transport
• -eg -lipoproteins transport fat in bloodstream
• -carry fat soluble vitamins
• -source of energy and glucose
• -when protein is broken down it gives energy
•  

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Functions of proteins in the body -used to
make neurotransmitters
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Digestion of protein -stomach acid -denatures-s
traightens out proteins readies them for
small intestine digestion of proteins   -small
intestine- enzymes attack proteins and make
them into amino acids
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Absorption of protein Amino acids moved across
intestinal wall into blood   Transport of
protein No special needed-the amino acids are
water soluble
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Excretion Proteins are broken down into amino
acids and then amino acids are further broken
down- urea is one product of amino acid
breakdown, urea and other components of protein
breakdown are put in the urine and excreted  
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How are proteins made in the body? -remember
protein in is not protein out   -proteins are
made from copies of DNA
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Nitrogen balance -positive nitrogen balance-
more protein being made than broken down
pregnant female -zero nitrogen balance- protein
is being made as fast as it is being broken
down-healthy person -negative nitrogen balance-
protein is being broken down faster than it is
being made eg illness    
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Recommended intake of protein Infants 0-6
months 2.2 g/kg body weight/day Children
1-1.6 g/kg body weight/day Adults
0.8 g/kg body weight/day Seniors
0.8 g/kg body weight/day   -For all about 15-20
of daily energy intake -Must be high quality
(complete) protein  
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Protein quality Complete proteins correct
balance of essential amino acids Definitions of
two types of amino acids -essential and
non-essential   Most animal proteins are
complete   Many plant proteins are incomplete-
exception soybean protein  
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Complementarity Beans and rice Beans and
corn Rice and lentils Pasta and
beans Peanut butter on bread
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Estimating protein intake Food labels will allow
you to do this Following Canadas food guide
will allow you to estimate this  
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Vegetarianism Types of diets
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Health risks Vegans-low in iron, calcium, zinc,
vitamin D and B6 and B12 -higher intakes of
oxalates   Fruitarian-limited in many essential
nutrients Supplements of deficient nutrients
frequently required for vegans and fruitarians
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Protein deficiencies Protein energy malnutrition
(PEM) Marasmus Wasting- skin and bones
look Not enough energy or protein Kwashiokor
Evil spirit that affects first child
when the second one is born Enough energy
not enough protein Swollen belly appearance
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Excess protein intake Risk of cancer, heart
disease and osteoporosis and renal failure