Presentation on theme: "Lecture 3. Learning outline Composition Functions of protein Classifications of proteins Amino Acids Classes of AA Biological Value protein."— Presentation transcript:
Proteins are made up of chains of amino acids. For each protein, there are specific amino acids in a specific amount, and they are joined in a unique order. This is what makes a chicken different from cheese or a fingernail different from a strand of hair. There are 22 amino acids. Eight of these are called the essential amino acids because they cannot be made by the body and must be provided by the diet. Amino acids
Uses of amino acids Amino acids are used in three ways in the body : protein synthesis The synthesis of new proteins is very important during growth. In adults new protein synthesis is directed towards replacement of proteins as they are constantly turned over. synthesis of a variety of other compounds Examples of compounds synthesized from amino acids include purines and pyrimidines (components of nucleotides) neurotransmitters (serotonin) histamine porphyrins (the central oxygen binding component of haemoglobin) as a biological fuel About 10% of energy production in humans is from amino acids. The percentage is much higher in carnivores, whose diet is almost entirely protein.
Functions of Protein Protein has a range of essential functions in the body, including the following: Required for building and repair of body tissues (including muscle) Enzymes, hormones, and many immune molecules are proteins Regulation of the body process : Glucagon(action opposite those of insulin ). Essential body processes such as water balancing, nutrient transport, and muscle contractions require protein to function. Protein is a source of energy if adequate of carbohydrate and fat are lacking. Protein helps keep skin, hair, and nails healthy. Protein, like most other essential nutrients, is absolutely crucial for overall good health.
Proteins as Enzymes: The function of proteins as enzymes is perhaps their best-known function. Enzymes are catalysts—they initiate a reaction between themselves and another protein, working on the molecule to change it in some way. The enzyme, however, is itself unchanged at the end of the reaction. Enzymes are responsible for catalyzing reactions in processes such as metabolism, DNA replication, and digestion.
Protein Sources Animal proteins Meat, milk and milk products, egg, poultry, and fish, Plant proteins legumes (soybean and soybean products, peas, beans etc.), cereals and nuts,.
Biological Value : The Biological Value (BV) is a scale of measurement used to determine what percentage of a given nutrient source is utilized by the body. The scale is most frequently applied to protein sources, particularly whey protein. Biological Value is derived from providing a measure intake of protein, then determining the nitrogen uptake versus nitrogen excretion. The theoretical highest BV of any food source is 100%. In short - BV refers to how well and how quickly your body can actually use the protein you consume.
Protein foods are classified in two ways: Complete proteins : which come from animal sources such as chicken, fish, dairy and soybeans, contain all the essential amino acids that help build your muscle and body tissue. Incomplete proteins : found in plant foods, such as grains, seeds, nuts, beans and vegetables, provide a varying but limited array of amino acids. A greater variety and amount of incomplete proteins must be consumed to cover all the amino acids needed for protein building. We can compensate for the amino acid deficiencies in an incomplete protein by combining it with another protein, thus providing all the building blocks for protein creation. This is the concept of complementary proteins, in which proteins with opposite strengths and weaknesses complement each other. Classification of protein
For example: many cereals are low in an amino acid called lysine, but high in methionine and cystine. legumes beans, soybeans and kidney beans are high in lysine but low in methionine and cystine. Many cultures, have limited animal protein sources but eat combinations of incomplete foods. Examples of appropriate combinations include: rice and beans cereal and milk beans and corn bread and cheese. Recent research indicates that such combinations need not be eaten at the same meal. If they are consumed over the period of a day, the necessary building of muscle and body tissue will occur. Vegetarians thrive on non-animal protein diets because of our body's ability to do this. Use the following chart to help select foods that are good sources of protein.
Examples of amounts of protein in food: 1 cup of milk has 8 grams of protein (85 g) of piece of meat has about 21 grams of protein 1 cup of dry beans has about 16 grams of protein An 8-ounce container of yogurt has about 11 grams of protein
protein needs are determined by : age, sex, weight and pregnant, lactating or in sports training. 10% to 15% from total calorie : Adults : 0.8 g proteins /1 Kg body weight Children: 1.0- 2.2 g proteins /1 Kg body weight Adolescence : 0.9 – 1.0 g proteins /1 Kg body weight Recommended:
it's recommended that 10–15 % of your daily calories come from protein. Below are the Recommended Dietary Allowances (RDA) for different age groups. Grams of protein needed each day Children ages 1 – 313 Children ages 4 – 819 Children ages 9 – 1334 Girls ages 14 – 1846 Boys ages 14 – 1852 Women ages 19 – 70+46 Men ages 19 – 70+56
Tissue protein Catabolism due to in adequate dietary energy or to in adequate dietary carbohydrate Tissue protein catabolism of worn-out cells Dietary proteins Amino Acid pool Catabolism of protein
Tissue protein Anabolism Remainder of molecule processed to glucose or stored as fat or burned as energy Nitrogen removed from amino acid by liver Amino Acid pool Anabolism of protein Nitrogen Excreted in urine as Urea
Is there any harm in getting more protein than we need? Most people eat more protein than they need without harmful effects However, protein contributes to calorie intake, so if you eat more protein than you need, your overall calorie intake could be greater than your calorie needs and contribute to weight gain. Besides that, animal sources of protein can be sources of saturated fat which has been linked to elevated low-density lipoprotein (LDL) cholesterol, a risk factor for heart disease. In addition, for people with certain kidney diseases, a lower- protein diet may be recommended to help prevent an impairment in kidney function.
Phenylketonuria Phenylketonuria or (PKU) is an inherited metabolic disorder. In PKU, the body cannot completely break down the protein phenylalanine because a necessary enzyme, phenylalanine hydroxylase, is deficient. Because of this, phenylalanine builds up in the body’s cells and causes nervous system and brain damage. Phenylketonuria is a treatable disease that can easily be detected by a simple blood test. newborn babies be tested for PKU. Phenylketonuria occurs in both males and females of all ethnic backgrounds. If an infant is tested at less than 24 hours old, it is recommended that the test be repeated when the infant is one week old.
Symptoms An infant born with phenylketonuria will develop normally for the first few months. If left untreated, symptoms begin to develop by three to six months of age and may include: delayed development mental retardation seizures very dry skin (eczema) and rashes distinctive “mousy” or “musty” odor of the urine, breath, and sweat light complexion, light or blonde hair irritability, restlessness, hyperactivity
Kwashiorkor Kwashiorkor is a condition resulting from inadequate protein intake. Early symptoms include fatigue, irritability, and lethargy. As protein deprivation continues, one sees growth failure, loss of muscle mass, generalized swelling (edema), and decreased immunity. A large, protuberant belly is common.