©2002 Learning Zone Express Protein Structure - large, complex molecules made up of amino acids Found as essential components of all living cells Made of carbon, oxygen, hydrogen and nitrogen Structure is determined by DNA ©2002 Learning Zone Express

©2002 Learning Zone Express Amino acids Proteins are made of amino acids (AA) bonded together in specific sequences (each can be hundreds of AAs long) But there is only 20 different amino acids that are used in different combinations to make the hundreds of thousands of different proteins we use 9 of the 20 are ESSENTIAL amino acids (our body can not produce them, therefore we MUST get them from your diet) ©2002 Learning Zone Express

THE 20 AMINO ACIDS 9 essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

©2002 Learning Zone Express Amino Acid Structure ©2002 Learning Zone Express

©2002 Learning Zone Express 2 Aas = dipeptide Peptide bond ©2002 Learning Zone Express

©2002 Learning Zone Express After peptides are made they fold up because the AAs are attracted to each other and form weak intermolecular bonds Sequence of AAs determines the 3D shape it will form The 3D shape of a protein is what determines its function in the body ©2002 Learning Zone Express

©2002 Learning Zone Express HEMOGLOBIN - Protein found in red blood cells that carries oxygen molecules to the cells and carbon dioxide away from the cells ©2002 Learning Zone Express

Denaturation of Protein Loss of shape of protein This is caused by excess heat, pH changes, heavy metals, alcohol etc Denatured proteins can’t work properly due to loss of 3D structure Deficient AAs can limit protein synthesis ©2002 Learning Zone Express

Dietary Protein sources Food Sources: Meat, fish,eggs, poultry, dairy products, legumes, nuts and seeds. (Breads, cereals and vegetables also contain small amounts of protein.) “high quality” proteins – contain all the essential amino acids Mutual supplementation – foods can be combined to provide a complete source of protein (e.g. beans and rice), but should be during the same day, so protein synthesis is not limited The incomplete proteins that are combined are called “complementary proteins” ©2002 Learning Zone Express

©2002 Learning Zone Express A complete protein An incomplete protein source is one that provides all of the essential amino acids. You may also hear these sources called high quality proteins. Animal-based foods; for example, meat, poultry, fish, milk, eggs, and cheese are considered complete protein sources. source is one that is low in one or more of the essential amino acids.Complementary proteins are two or more incomplete protein sources that together provide adequate amounts of all the essential amino acids. ©2002 Learning Zone Express

©2002 Learning Zone Express Stomach pH is low (1-3) denature proteins Pepsin polypeptides amino acids + smaller polypeptides 2. Duodenum neutral pH (because of sodium bicarbonate from the pancreas) stops the action of pepsin proteases Peptide amino acid peptidases Proteases – from the pancreas Peptidases – from the intestinal cells 3. Jejunum – AAs are absorbed into the blood stream and travel to the liver ©2002 Learning Zone Express

©2002 Learning Zone Express Function of Proteins Function in the Body: Provides energy, but not the preferred energy source, but will be used if there is not enough carbs or fats Cell growth, repair and maintenance. Help to build, maintain, and repair body tissues. Enzymes, antibodies, neutrotransmitters, haemoglobin, and some hormones (e.g. insulin) are made of protein Maintain fluid and electrolyte levels Proteins help to maintain acid-base balance in the blood ©2002 Learning Zone Express

Problems with excess dietary proteins High cholesterol (high protein diets) Bone loss (high protein diets – sulphur amino acids – pull Calcium from bones) Kidney disease (diabetics) – too much urea production in the kidney ©2002 Learning Zone Express