General Properties Of Proteins Flashcards
What are amino acids?
- the monomers from which proteins are made
What are the groups in a protein?
- amine group (NH2)
- carboxyl group (COOH)
- R group (side chain)
How many amino acids does an organism have?
- 20
How are peptide groups formed?
- condensation reaction between two amino acids
How are dipeptides formed?
- the condensation of two amino acids
How are polypeptides formed?
- condensation of many amino acids
Primary structure
- order and sequence of the amino acids in the polypeptide chain bonded by a peptide bond to form a polymer
Secondary structure
- the sequence of amino acids causes parts of a protein molecules to bend into alpha helix shapes or fold into beta pleated sheets
- hydrogen bonds hold the secondary structure
Tertiary structure
- the further folding of the secondary structure
- to form a unique 3D shape
- held in place by ionic, hydrogen and disulphide bonds
What are globular proteins?
- soluble eg. Enzymes, haemoglobin
What are fibrous proteins?
- insoluble eg. Collagen
Quaternary structure
- a protein made up of more than one polypeptide chain
What bonds are in tertiary structure?
- hydrogen
- disulphide
- ionic bonds
- hydrophobic interactions
Describe the test for proteins
- put food sample in test tube
- put biuret solution in test tube and shake
- if proteins are present, will turn lilac from blue
Draw the general structure of an amino acid
Draw how a peptide bond is formed
Describe how the amino acids join to form dipeptide
- through condensation reaction
- water is removed
- peptide bond forms between OH of carboxyl and H or amine group
What are proteins?
- polymers made up of the monomer amino acids
Where is the hydrogen bond in secondary structure?
- form between the C=O groups of the carboxyl group of one amino acid and the H in the amine group of another amino acid
Where do the ionic and disulphide bonds form in tertiary structure?
- between the R groups of different amino acids
- disulphide bonds only sometimes occur as there must be a sulphur in the R groups for this bond to occur
What is an example of a quaternary structure?
- haemoglobin
What does is mean if a protein is denatured?
- bonds which hold the tertiary and secondary structure in shape break and therefore, unique 3D shape is lost
Eg. Enzymes lose their unique active site shape
Which conditions denature a protein?
- too high temperature (too much kinetic energy)
- too high/low pH (too many H+ or OH-)
Why is primary structure important?
- if even one amino acid in the sequence is different, will cause the ionic, hydrogen or disulphide bonds to form in a. Different location
- results in a different 3D shape
What is the impact of an amino acid in a sequence being different?
- enzymes will have a different shaped active site (non functioning)
- carrier proteins will have a different shaped binding site (molecules no longer complementary and cannot be transported across membranes)
What might cause a change to the amino acid sequence?
- mutations (change in DNA)
