Proteins Flashcards
biological molecules - AQA - topic 1
Elements in protein
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
- Sometimes sulfur
What are proteins made of
Amino acids
What are proteins
Proteins are polymers made up of the monomer amino acids
Describe how amino acids are joined together to make a dipeptide
- 2 amino acids join in a condensation reaction
- Water is removed
- peptide bonds are formed between OH of carboxyl and H of amine group
2 ways in which protein can be hydrolysed
- heat w an acid
- use enzyme protease at optimum temperature
Primary structure
SEQUENCE of amino acids in a polypeptide chain
Secondary structure
- Sequence of amino acids that can be coiled to form alpha helix or folded into beta pleated sheets
- Held by hydrogen bonds
Tertiary structure
- Further folding and coiling of the secondary structure
- form a unique and specific 3D structure
- held in place by hydrogen, ionic and disulfide bonds
Location of ionic and disulfide bonds in the tertiary structure
Between the R groups
Globular proteins
- Soluble
- Highly folded and coiled polypeptide chains
- produce a complex and compact tertiary structure
- Globular structure include enzymes and antibodies
Quaternary structure
- More than 1 polypeptide chain
- held together by ionic, hydrogen bonds and SOMETIMES disulfide.
- E.g. haemoglobin is made up of 4 polypeptide chains
What is the denaturation of proteins
- Alteration in the tertiary structure of the proteins
- Irreversible
- No longer functional
Conditions of a denaturation of a protein
- Caused by breaking of hydrogen and ionic bonds (not disulfide bonds because they remain unbroken at 70’)
- Caused by high temperature above room temperature
- Extreme changed in pH’s
- Heavy metals (lead,copper,zinc)
What might cause a change in an amino acid sequence
Mutations - change in DNA sequence might code for different amino acids therefore primary structure changes
Explain how a change in the primary structure of a globular protein may result in a different 3D shape
- Changes in the sequence of the amino acids
- Bonds formed in different place
- Changes in the tertiary structure which given protein its function
