Protein Lecture PDF

MACRONUTRIENTS 2. Protein  Learning outcomes  Describe the composition and nature of protein  List the difference classification of proteins.  Explain the balance of protein through (protein balance & nitrogen balance).  Clarify the functions of protein in human body.  Describe...

MACRONUTRIENTS 2. Protein  Learning outcomes  Describe the composition and nature of protein  List the difference classification of proteins.  Explain the balance of protein through (protein balance & nitrogen balance).  Clarify the functions of protein in human body.  Describe the process of protein digestion & absorption in GIT (mouth- stomach & intestine)  List the recommendation of protein in human diet. Calculate recommended protein intake and Develop a meal plan high in protein  Describe the nutritional challenge of vegan and vegetarian diets and develop an eating pattern that delivers nutritional adequacy 2  Introduction Protein is derived from the Greek word “proteos” meaning “holding first place” or “the most important” or “primary”. Proteins are large molecules, made up of a series of amino acids. Amino acids are the building blocks of proteins. There are about 20 different amino acids commonly found in plant and animal proteins. Proteins differ molecularly from CHO and fat in that they have nitrogens, also they differ from CHO that their amino acid in a strand of protein is different from one another unlike glucose molecules are identical. The sequence and number of amino acids contained in proteins determines its nature 3  Levels of protein structure  Primary structure: peptide bond formed between amino acids resulting in a linear chain of amino acids  Secondary structure: attraction between R groups of amino acids create helices and pleated sheet structure  Tertiary structure: helices and pleated sheets are folded into compact domain  Quaternary structure: individual polypeptides can serve as subunits in the formation of larger protein structure 4 Levels of protein structure 5 Building block of amino acids  All amino acids have the same basic structure:  An amino group (-NH2)  An acid group (-COOH)  A hydrogen group (-H)  A fourth group differ between amino acids –R “root” (the nature of the side chain will determine some of the properties of the amino acid)  In some cases sulfur group “S” (Cystine & Methionine)  The link between amino acids is called peptide link/bond 6 Building block of amino acids 7 Examples of Amino Acids 8  Amino acids  Plants combine nitrogen from the soil and air with carbon and other substances to produce amino acids then built to produce proteins by plants  Humans get their proteins from plants or animals which have consumed the plants  Amino acids are bound together 9  Classes of Amino Acids  Twenty (20) common amino acids have been identified, all of which are vital to life & health.  These amino acids are classified as:  Indispensable Dispensable Conditionally indispensable OR  Essential Nonessential Conditionally essential 10  Classes of Amino Acids  Indispensable (Essential) Amino Acids  Nine (9) amino acids are classified as essential or indispensable (why?) The body cannot manufacture them in sufficient quantity or at all.  The protein we eat are broken down to amino acid and rebuilt (essential amino acids) must be supplied by diet 11  Classes of Amino Acids  Dispensable (Nonessential) Amino Acids (11)  Five (5) amino acids are needed by the body for a healthy life, but not necessary in the diet.  These amino acids can be synthesized from other amino acids in the body.  It have essential tissue-building & metabolic functions in the body. Alanine Aspartic acid Asparagine Glutamic acid Serine Arginine Cysteine Glutamine Glycine Proline Tyrosine 12  Classes of Amino Acids  Semi-essential amino acids  Histidine and Arginine are semi-indispensable amino acids. Growing children require them in food.  But they are not essential for the adult individuals.. 13  Classes of Amino Acids  Conditionally Indispensable Amino Acids The remaining six (6) amino acids are classified as conditionally indispensable. Under certain physical logic conditions, these amino acids which are normally synthesized in the body must be consumed in the diet. These amino acids are indispensable when endogenous sources cannot meet the metabolic demands. When human body cannot make cysteine from methionine (diet is deficient), cysteine must be consumed from the diet. Read about phenylketonuria (PKU) 14 Classes of Amino Acids http://chemistry.tutorvista.com/biochemistry/amino-acids.html 15 pediaa.com/difference-between-essential-and-nonessential-amino-acids/ 16  Balance This concept of balance can be applied to life-sustaining protein & the nitrogen that it supplies. 17  Balance  Protein Balance:  The body’s tissue proteins are constantly goes into turnover, which comes through catabolism and anabolism, to maintain nitrogen balance.  When nitrogen have been removed from amino acids by process called deamination, converted into ammonia & excreted as urea in the urine.  The remaining non-nitrogen residue will be used to make CHO or fat or may be reattached to make another amino acid.  Tissue turnover is a continuous process of reshaping, building & adjusting to maintain overall protein balance within the body.  The body maintains a delicate balance among tissue protein, plasma protein & dietary protein. 18  Balance  Nitrogen Balance:  This balance indicates how well its tissues are being maintained.  The intake & use of dietary protein are measured by the amount of nitrogen intake in food protein & the amount of nitrogen excreted in the urine.  e.g. 1 g of urinary nitrogen results from the digestion & metabolism of 6.25 g of protein.  In state of malnutrition or illness the balance may shift or be either positive or negative. 19  Balance  Nitrogen Balance:  Positive nitrogen balance: exists when the body holds on to more nitrogen than it excretes, thus storing more nitrogen than it is losing.  Rapid growth period such as infancy, childhood, adolescence, pregnancy & lactation, also in ill or malnourished who are being “built back up”.  Negative nitrogen balance: occurs when the body holds on to less nitrogen than it excretes. This means that the body has an inadequate protein intake & is losing nitrogen by breaking down more tissue than it is building up.  Malnutrition and illness such as Kwashiorkor. 20 21  Digestion & absorption of proteins  Whole proteins are rarely absorbed  Proteins are digested into amino acids, dipeptides, tripeptides, polypeptides  99% of ingested protein is absorbed as amino acids in the small intestine  Amino acids are water soluble; they are absorbed directly to the blood stream through active transport  The cells put the amino acids together in the necessary order to produce the needed protein  The cell will make the nonessential amino acids, if an essential amino acid is missing the need for the production of a particular protein will not be met 22 Protein Digestion: Part 1 23 Protein Digestion: Part 2 24 Protein Digestion: Part 3 25 Protein Digestion: Part 4 26 Digestion & absorption of proteins 27  Functions of Proteins 1. Growth and maintenance:  No living tissue can be built without protein, it is part of every cell  Approximately 20% of human total weight is protein  building tissues ( children, blood, scars, hair, nails, worn out cells, skin) 28  Functions of proteins 2. Protein as energy  When amino acids are degraded, they can be used as energy source or glucose production (amine group incorporated by the liver into urea, then sent to the kidney for excretion) the remaining is used for energy  When there is sufficient CHO and fat, amino acids are used for their most important function which is making proteins  In starving state amino acids are used as a source of energy, resulting in protein deficiencies  When amino acids are oversupplied, the body has no place to store them. It removes the amine and convert remaining fragments to glucose, glycogen and fat for storage 29  Functions of proteins: 3. regulatory role  Proteins facilitate chemical reactions in the body; all enzymes are proteins  Some proteins act as chemical messengers, regulation of body processes example; glucagon, insulin and thyroid hormones (not all hormones are proteins)  Antibodies: Proteins help body resist disease by acting against antigens  Fluid balance; regulate quantity of fluid in body compartments  protein act as buffer to maintain normal acid base concentration in body fluids  Proteins act as a transporter by moving nutrients in and out of cell 30  Proteins food sources  The main source of protein in diet meat, fish, dairy products and eggs  Plant foods that are good sources of protein are: cereals and their products, legumes, nuts and seeds 31 Best Sources of Protein 32  Proteins food sources  Food proteins are classified as complete or incomplete proteins, depending on their amino acid composition.  Complete proteins:  Protein foods that contain all nine indispensable amino acids in sufficient quantity & ratio to meet the body’s needs.  Food sources such as: egg, milk, cheese, meat, poultry, fish)  Soy products are the only plant sources of complete proteins.  These proteins are generally of animal origin  Incomplete proteins:  Protein foods that are deficient in one or more of the nine indispensable amino acids.  These proteins are generally of plant origin  e.g. grains, legumes, nuts, seeds. 33  Protein complementation  Different proteins can complement one another in their amino acid pattern.  When two foods providing vegetable protein are eaten at a meal, such as a cereal (e.g. bread) and pulses (e.g. baked beans), the amino acids of one protein may compensate for the limitations of the other, resulting in a combination of higher biological value.  This is known as protein complementation. 34  Protein complementation  If vegetarians and vegans eat a variety of vegetable proteins in combination, there is no reason why the quality of protein cannot be as good as in a diet consuming animal proteins.  Can you think some of some examples of protein complementation? rice and peas; beans on toast; hummus and pitta bread; bean chilli served with rice 35  Protein complementation Combining plant-protein foods that have different but complementary amino acid patterns. This strategy yields complementary proteins that together contain all the essential amino acids in quantities sufficient to support health. 36 37 Recommendation for Dietary Protein  During growth period & illness (e.g. burns) the recommendation of protein would be higher in this stage of human life cycle.  The nature of protein influence its dietary quality.  Recommended Dietary Allowances (RDA) for both genders is set at 0.8 g/kg/day.  Or on average 56g/day for men and 46g/day for women + 25g for pregnancy and lactation  The UL is not established for proteins, however there are safety concerns if RDA exceeds double the requirements 38  Acceptable Macronutrient Distribution Range (AMDR)  The AMDR for proteins is 10% - 35% of total calories  In general, proteins needs are meet if 10% of energy intake is supplied from proteins  If total energy intake is low? 39 Factors influencing protein requirements:  Tissue growth (rapid growth > protein)  Protein quality (amino acid pattern) Vegan diet  Protein digestibility (food preparation, heat, time interval between meals and competition)  Energy content of the diet  Health status 40 Clinical implications of low protein diets  Low protein diets is associated with sever protein energy malnutrition (PEM) in famine-ravaged countries  Low protein intake during pregnancy increase risk of low birth weight  Disease such as Parkinson's disease, chronic kidney disease  Vegan diets 41 Clinical implications of high protein diets  High protein diets: diets in which provide 30% or more of calories from proteins to promote weight loss, add satiety and restore effective energy regulation  High protein intake from animal sources contains saturated fats  Low fiber intake  Could aggravate kidney problems 42  Activity Chose the correct answer: Nine (9) of the twenty (20) amino acids are indispensable, which means that: a) The body cannot make them & must obtain them from the diet. b) They are required for the body processes & the rest are not c) The body makes them because they are essential to life d) After making them, the body uses them for growth. A state of negative nitrogen balance may occur during periods of: a) Pregnancy b) Adolescence c) Injury, surgery, burns d) infancy 43  Activity Calculate the calories from proteins you need for an adult that weigh 67kg and height is 160cm – Calculate BMI – Use the short cut method to calculate to calorie requirements, (25kcal/kg/day for non-obese and 22-23 kcal/kg/day for obese) – How many calories from the total calories you will need for proteins – What percentage did you use? 44