Unit 3 - Proteins Flashcards
Importance of Protein In The Body
Proteins are major structural materials of animal tissue.
Proteins are also involved in the maintenance and regulation of life processes.
* Hormones e.g insulin which regulates carbohydrate metabolism
* Immunoglobins secreted to protect against bacteria and viruses
* Haemoglobin iron containing molecule found in blood that transports oxygen to cells
* Enymes for controlling chemical reactions
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 biological catalysts and all contain protein. Each enzyme catalyses a specific reaction.
starch -> (amylase) maltose -> (maltase) glucose** -> (zymase**) ethanol
Amino Acids
Proteins are ploymers made from monomers called amino acids. Amino acids contain a baci amino group (-NH2)
Essential amino acids are ones required by the body for protein synthesis but must be acquired through the diet.
Protein Formation
During protein formation, 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 s[irals, folded into sheets or wound around to form other complex shapes. The chains are held in theseforms 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 during cooking, the intermolecular bonds (generally H bonds) are broken so the proteins denature (changes shape). Denaturing of proteins in foods causes the texture to change when it’s cooked. Proteins can also be denatured by extremes of pH and mechanical action.
