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proteins
Lecture 3
Learning outline Composition Functions of protein Classifications of proteins Amino Acids Classes of AA Biological Value protein metabolism sources Related disease
Composition of protein
Classification of Proteins
Derived Proteins
Compound Proteins
Derived Proteins
Produced during
hydrolysis+ heat
Protein + (Carbs or Lipids or Phosphate or Zinc)
Produced during hydrolysis giving
completely analyzed Amino Acids
1 – Albumins: Eggs, Serum2 – Globulins:Serum, Actine, myosine (meat)3 – Gluteins: wheat 4 – Protamines: fish5 – Prolaminates: Ots , corn 6 - Sclero Proteins: Collagen
1 – Glycoproteins:
HydrolysisHexosamine + Uric
AcidIn the skin, bones, connective tissues,
blood, urine
Primary: Casin
Secondary:ProteosesPeptonesPeptides
Derived Proteins
Compound Proteins
Derived Proteins
1 - Albumins:Eggs AlbuminsSerum Albumin
Leucosin SerialsLegumin Legumes
2 - Globulins:Serum globulinActine Meat
Myosine MeatGlycinin Soy
2 – Lipoproteins: HDL,LDL , VLDL3 - Nucleo Proteins: (Lipds + Proteins)4 - Phospho Proteins: (casin)5 - Metallo Proteins: (Chromoproteins)
Classification of Proteins
Derived Proteins
Compound Proteins
Derived Proteins
3 - Gluteins: Glutenin wheatOrzsenin Rise
4 - Protamines:Clapein Ringa
Scombrin Macreal
5 - Prolaminates:Oats, Wheat, Corn
6 - Sclero Proteins: Collagen, Gelatin,
Criatenin
Classification of Proteins
Amino Acids
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 proteinneeded each day
Children ages 1 – 3 13
Children ages 4 – 8 19
Children ages 9 – 13 34
Girls ages 14 – 18 46
Boys ages 14 – 18 52
Women ages 19 – 70+ 46
Men ages 19 – 70+ 56
Metabolism of protein:
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.
Dr. Mona El-shafie