Proteins Macronutrients - PDF

Proteins Macronutrients Dr Kathy Check-in: Redfern Function GROWTH METABOLIS ENERGY M What are proteins?  Long chains of amino acids in a particular sequence.  The sequence and subsequent structure give proteins their function. Amino acid Di...

Proteins Macronutrients Dr Kathy Check-in: Redfern Function GROWTH METABOLIS ENERGY M What are proteins?  Long chains of amino acids in a particular sequence.  The sequence and subsequent structure give proteins their function. Amino acid Dipeptide (2) Tripeptide (3) Oligopeptide (4-10) Polypeptide (>10) Amino Acid Structure  Side chain varies to give rise to different AAs.  Interactions between side chains influences protein’s structure. AA Examples Amino Glucogenic Acids Glucogenic or Ketogenic Ketogenic Essential Essential Non-essential Conditionally precursor essential (semi essential) Histidine Alanine Arginine Isoleucine Aspartate Asparagine Leucine Glutamate Glutamine Lysine Glycine Methionine Cysteine Proline Phenylalanine Tyrosine Serine Threonine Tryptophan Valine Origin of non-essential AAs AA Origin Alanine Pyruvate Asparagine From citric acid cycle intermediates Arginine Glutamine Proline Serine From 3- phosphoglycerate Glycine From serine Cysteine From serine Tyrosine From phenylalanine Digestion  Amino group from one aa forms a link with the carboxylic acid group of another to form a peptide bond in a condensation reaction.  Dietary proteins are broken down by peptidases into aa.  Enter body pool  Transamination  Deamination - fuel Nitrogen Balance Difference between intake and output of nitrogen Dietary protein (80g) Enzymes Body protein ~ Intestinal cells 10kg Mucus (70g) Amino acids Amino acids Dipeptides Metabolites Urine Faecal loss excretion (10g) (70g)  Synthesis of proteins relies on the supply of all essential amino acids. Protein If there is inadequate supply of any eaa in the diet then the rate of protein synthesis Quality with be limited by the rate that that eaa is available. This eaa is the limiting aa. Foods that contain all eaas in adequate proportions are known as complete proteins. Generally proteins derived from animal sources are complete, as are many plant sources.  Biological value (BV) Net protein – proportion of utilisation (NPU) – absorbed protein that proportion of dietary remains in the body. protein that remains in Protein Protein with high BV is complete. the body. Digestibility is included. Quality Protein efficiency Chemical score – the Definitio amount of limiting aa in ratio (PER) – gain in test food compared to weight per gram of the amount of that aa protein eaten. ns in egg protein. Protein score – same as chemical score but compares to a reference pattern aa as standard.  Meat e.g. chicken, beef, lamb, pork, duck etc. Example Fish s of Dairy complet e.g. milk, cheese, butter, eggs Soy products e e.g. tofu, tempeh, soy yoghurts etc. proteins Mycoprotein i.e. Quorn Some grains and seeds e.g. quinoa, buckwheat, chia, hemp Limiting aa Protein source Limiting amino acid Wheat Lysine Rice Lysine Legumes Tryptophan Maize Lysine and tryptophan Pulses Methionine (+cysteine) Egg, chicken None – reference for absorbable protein Sources of Protein Meat, fish, beans, pulses and alternatives. Dairy and Meat also good source of alternatives Also sources of B vitamins Pulses and beans good vitamins and sources of fibre. minerals. Especially calcium. Protein Requirements:  0.75g/kg body weight/day  15% total/food energy  Red meat