Protein

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Lecture 4
Protein
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Amino Acid structure

• H
• central carbon atom
• H C H
• H H H O
• H C C C C C OH
• organic acid group
• H H H N Carboxyl group
• side group H H
• amino group

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Protein

• Basic unit AMINO ACID
• Protein POLYPEPTIDE of 50-300
• amino acids
• eg. human Insulin has 51 amino acids (very small)
• more complex larger molecules than CHO
• due to side group

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Amino Acids

• 22 common amino acids in food
• each has a different side group
• constituent amino acids characterize a PROTEIN
• eg. protein of BEEF muscle different to protein
  of PORK muscle
• Appendix C, Whitney Rolfes
• amino acid structures

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Amino Acids structural functional roles

• cell membrane
• connective tissue
• (collagen elastin)
• inert protein
• (hair nails)
• enzymes

• blood proteins
• (albumin haemoglobin)
• antibodies
• skeletal smooth muscle
• 20 energy source

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Protein

• AAs continually synthesised catabolised in the
  body
• daily turnover ?3 - 4g/kg body weight/day
• dietary intake ? ¼ - ½ this amount

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• MOST Protein made from recycling amino acids
• synthesise
• new proteins essential, from food or
  already in body

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Essential (indispensable) amino acids

• new protein synthesis requires full complement of
  amino acids
• cannot make part proteins
• other AAs are wasted (deaminated)
• most amino acids synthesised in the body
• need Nitrogen for amine group
• C-fragments H atoms from CHO or Fat molecules
  AND/OR from degraded AAs in the body

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Essential (indispensable) amino acids

• 8 (9 in children) cannot be synthesised in the
  body
• ? MUST BE SUPPLIED FROM FOOD

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Essential (indispensable) amino acids

• Histidine (in children)
• Isoleucine
• Leucine
• Lysine
• Methionine

• Phenylalanine
• Threonine
• Tryptophan
• Valine
• branched chain
• amino acids

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Protein Quality

• Definition
• the amount of protein in a particular food its
  supply of essential amino acids
• ANIMAL protein BEST QUALITY
• supplies ALL 8(9) essential amino acids
• usually the HIGHEST concentration

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Protein Quality

• PLANT protein LESSER quality
• doesnt supply ALL essential amino acids
• LOWER concentration
• exception SOY PROTEIN

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Plant protein cont...

• combining LEGUME CEREAL protein will ensure ALL
  essential amino acids
• each food contributes the essential AAs missing
  in the other food
• COMPLEMENTARY PROTEINS

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Complementary proteins
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Protein Quality

• eg. Complementary proteins
• baked beans and rice
• peanut butter on bread (wheat)
• refried beans Tacos (corn)
• stir-fried vegetables rice

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Protein requirements

• 1 gram protein supplies 17kj
• sedentary individuals
• balanced diet 10-15 of Etotal from protein
• athletes
• balanced diet 12-17 of Etotal from protein

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Protein requirements

• Sedentary individuals
• or 0.8g - 1.0g protein/kg body weight/day
• if weight 70kg
• protein requirement will be
• between 70 x 0.8 56g protein/day
• and 70 x 1.0 70g protein/day

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Protein

• Athletes
• elite endurance athletes
• 1.2 - 1.4g protein/kg body mass/day
• oxidisable fuel when CHO stores depleted
• strength power athletes
• 1.2 - 1.7g protein/kg body mass/day
• maintains ve Nitrogen balance
• AAs can be synthesised incorporated into
  required protein

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Protein from food

• Food Protein g/100g
• HIGH CONTENT
• Beef lamb 28
• Cheese 26
• Chicken 25
• Fish 18
• Eggs 12
• Beans 7
• Peas 5
• Milk 3.3

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Protein from food

• Food Protein g/100g
• MEDIUM CONTENT
• Cornflakes 8.6
• Bread (white) 7.8
• Spaghetti 4.2
• Sweetcorn 4.1
• Rice 2.2
• Cauliflower 1.6
• Potatoes 1.6
• Cabbage 1.3

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Protein from food

• Food Protein g/100g
• LOW CONTENT
• Apples 0.3
• Honey 0.5
• Butter margarine lt0.4
• Wine 0.1
• Soft drink 0

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HOMEWORK

• Sedentary individual (70kg body mass)
• 56 - 70g protein/day FOOD
• Endurance athlete (75kg body mass)
• 90 - 105g protein/day FOOD
• Strength Power athlete (100 kg body mass)
• 120 - 170g protein/day FOOD

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Recommended Reading

• Whitney Rolfes
• Understanding Nutrition
• Chapter 6 Protein Amino Acids
• Wahlqvist
• Food Nutrition in Australia
• Chapter 19 Protein