PROTEIN

What is protein…

ü  Protein is a macronutrient that is essential to building muscle mass. It is commonly found in animal products, though is also present in other sources, such as nuts and legumes.

ü  protein is composed of amino acids, which are organic compounds made of carbon, hydrogen, nitrogen, oxygen or sulfur.

How much protein needed…

ü  The Institute of Medicine recommends that 10 to 35 percent of daily calories come from protein.

ü  depends on the caloric needs of the individual.

ü  the amount of protein foods a person should eat depends on age, sex, and level of physical activity

The important of protein…

®    When protein is broken down in the body it helps to fuel muscle mass, which helps metabolism.

®   It also helps the immune system stay strong

:Monomer for protein amino acid

Amino Acid

  v organic compounds containing amine (-NH2) and carboxyl (-COOH) functional groups

  

  v having both the amine and the carboxylic acid groups attached to the first (alpha-) carbon atom have particular importance.

v R is an organic substituent known as a "side chain"

v 20 different "R" groups

 

Peptide bond

o -  is an amide type of covalent chemical bond linking two consecutive alpha-amino acids

o  - a covalent bond between the carboxyl group of one amino acid and the amino group of  amino acid

     Nitrogen cycle

Ø  Nitrogen = a component of proteins and nucleic acids, is essential to life on Earth.

Ø  78 percent by volume of the atmosphere is nitrogen gas.

Essential Amino Acids

ü  Essential amino acids cannot be made by the body. As a result, they must come from food.

ü  The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Nonessential Amino Acid

ü  Essential amino acids cannot be made by the body. As a result, they must come from food.

ü  The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

§  All amino acids are grouped into 6 families based on their biosynthetic pathways

:

1. Glutamate family

 2. Aspartate family

3. Serine family

 4. Pyruvate

5. Aromatic family

 6. Histidine family

§  Amino acids can be synthesized from available metabolites in the body, such as:

1. ketoglutarate

 2. Oxaloacetate (OAA)

 3. Pyruvate

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: Overview of amino acid biosynthesis. Precursors from glycolysis (red), the citric acid cycle (blue), and the pentose phosphate pathway (purple) are shaded, and the amino acids derived from them are boxed in the corresponding colors.

§  Reductive amination of -ketoglutarate forms Glutamate.

§  The amino acids glutamate and glutamine are the principal donors of amino groups in transamination reactions.

§  Carriers of one-carbon groups include biotin and derivatives of folic acid

®    In human body, excess amino acids (a.a) are not stored (as amino acids) or excreted (as amino acids), but rather excess amino acids are degraded to produce energy and ammonia.