2. Amino Acids.pdf

HNUT10010 HNUT10020 Human Nutrition 1: Understanding Nutrients Aifric O’Sullivan BSc, MSc, PhD UCD Institute of Food and Health School of Agriculture and Food Science Amino Acids • • • • Nutrition classification of amino acids Indispensable Conditionally indispensable Dispensable What Are Prot...

HNUT10010 HNUT10020 Human Nutrition 1: Understanding Nutrients Aifric O’Sullivan BSc, MSc, PhD UCD Institute of Food and Health School of Agriculture and Food Science Amino Acids • • • • Nutrition classification of amino acids Indispensable Conditionally indispensable Dispensable What Are Proteins? • Complex molecules made up of amino acids joined together by peptide bonds • Contain nitrogen unlike other macronutrients • Can be 2 amino acids (dipeptide) • > 12 amino acids is a polypeptide Insulin Polypeptide Chain B 30 AA Chain A 21 AA disulfide cross bridge Nutritional Classification of Amino Acids • 20 different amino acids • Nutritional classification: – Do you need to consume them in your diet? Or – Are you capable of making them from other compounds? Nutritional Classification • Dispensable AA: can be synthesized de novo from a non-amino acid source of nitrogen • Conditionally indispensable AA: measurable limitations to the rate of synthesis e.g. provision of other AAs, synthesised in a limited number of tissues • Indispensable AA: cannot be synthesized de novo and therefore must be supplied in the diet Nutritional Classification Indispensable Valine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Histidine Conditionally indispensable Glycine Arginine Glutamine Proline Cysteine Tyrosine Dispensable Glutamic acid Alanine Serine Aspartic acid Asparagine Conditionally Indispensible 1. Synthesis requires another amino acid 2. Only synthesised in a limited number of tissues 3. Quantities that can be synthesised are limited Conditionally Indispensable • • • • • • Glycine Arginine Glutamine Proline Cysteine Tyrosine Precursors Serine Glutamine or glutamate Glutamate, ammonia Glutamate Methionine, serine Phenylalanine Amino Acids Choose the correct statement: Answer: a a) Conditionally indispensable amino acids may become essential under certain conditions. b) All amino acids are indispensable c) Indispensable amino acids are made in the body. d) The terms “indispensable” and “conditionally indispensable” are interchangeable. Explanation: “Dispensable” amino acids are made in the body. “Indispensable” amino acids are those the body cannot make in significant quantities to meet needs. “Conditionally indispensable” amino acids are those that are usually nonessential but, under certain conditions, must be supplied by the diet. Quiz • On a scale of 1 to 5, how difficult was this lecture? • What slides were most difficult? 11 Reading • Gibney M, Lanham-New S, Cassidy A, Vorster H, eds. Introduction to Human Nutrition. 2nd ed: WileyBlackwell, 2009. Chapter 4 • Campbell MK, Farrell SO. Biochemistry, International Edition, 7th Edition. Singapore: CENGAGE Learning, 2012. Chapters 3 & 4 • McGuire M, Beerman KA: Nutritional Sciences: From Fundamentals to Food. 3rd ed. Belmont, CA: Wadsworth; 2013. Chapter 5