Unit 3 - Proteins Flashcards
Importance of Protein In The Body
Proteins are the major structural materials of animal tissue and are also involved in the
maintenance and regulation of life processes
Testing for Protein
Proteins contain the elements carbon, hydrogen, oxygen and nitrogen. Some also contain sulfur.
All proteins produce ammonia when heated with soda lime (sodium hydroxide).
The test for ammonia gas is that it turns most pH paper blue.
Enzymes
Enzymes are proteins which act as
biological catalysts.
Amino Acids
Amino acids are small molecules which are the building blocks which join together to form proteins.
Amino acids contain the following:
* a carboxyl group (-COOH)
* an amino group (-NH2)
Essential Amino Acids
The body cannot make all of the amino acids required for protein synthesis and certain
amino acids, known as essential amino acids, must be acquired from the diet.
Protein Formation
Proteins are made from many amino acids joining together by a condensation reaction. The amino group on one amino acid and the carboxyl group on a nearby amino acid join together, with the elimination of water.
Amide Link
The link formed between two amino acids is called an amide link. (In proteins (ONLY protiens) this link can also be called a peptide link)
-CONH-
C=O
Protein Digestion (Enzyme Hydrolysis)
Protein molecules are too large to be absorbed into the bloodstream from the digestive system.
Enzymes hydrolyse dietary proteins to produce amino acids.
This chemical reaction can be described as hydrolysis because the protein molecule is split up by the chemical action of water.
Partial Hydrolysis
Partial hydrolysis:
* broken in 2
* broken in groups
Partial hydrolysis has to be in order, can’t rejoin amino acids.
Protein Structure
The long-chain molecules in proteins can be twisted to form spirals, folded into sheets or wound around to form other complex shapes. The chains are held in these forms by intermolecular bonding between the side chains of the constituent amino acids.
Primary Protein Structure
A chain of amino acids
Secondary Protein Structure
Occurs when the sequence of amino acids are linked by hydrogen bonds
Tertiary Protein Structure
Occurs when certain forces of attraction are present between alpha helices and pleated sheets
Quaternary Protein Structure
A protein consisting of more than one amino acid chain
Protein Denaturation
When proteins are heated, the intermolecular bonds (generally H bonds) are broken, allowing the proteins to change shape (denature). The denaturing of proteins in foods causes the texture to change when it is cooked.
