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