What are some functions of proteins?
- Enzymes
- Membrane proteins
- Antibodies
- Structure (keratin and collagen)
- Haemoglobin
What elements can proteins contain?
Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur
What monomer makes up proteins?
Amino acids
What do all amino acids contain?
- Central carbon atom
- Amine group (NH₂)
- Carboxyl group (COOH)
- Hydrogen (H)
- R-group (different for all amino acids)
How many amino acids are there?
20
How do amino acids join together and what do they form?
- Condensation reaction
- Polypeptide polymers
What are polypeptides broken down into and by what reaction?
- Monomers (amino acids)
- Hydrolysis reaction
What two amino acids contain sulfur?
Methionine and Cysteine
What are the four protein structures?
- Primary structure
- Secondary Structure
- Tertiary structure
- Quaternary structure
What is primary structure?
The sequence of amino acids in a polypeptide chain
What type of bond is formed when amino acid monomers are joined together?
Peptide bond
What two types of secondary structure are there?
- Alpha helix
- Beta pleated sheet
What type of bond forms between the amine and carboxy group of amino acids?
Hydrogen bonds
What is tertiary structure?
When a polypeptide chain forms a 3D structure (further coiling of the helix or pleated sheet)
What types of bonds are there in tertiary structures?
- Hydrogen (weakest)
- Ionic -> formed between R-groups and easily broken by pH change
- Disulphide (strongest -> S=S)
What structure allows the formation of active sites and gives functionality to proteins?
Tertiary structure
What is quaternary structure?
- Multiple polypeptide chains working together (this forms complex proteins e.g collagen & haemoglobin)
- Often contain non-protein (PROSTHETIC) groups (e.g haem in haemoglobin)
What structure do globular proteins have?
Complex tertiary and sometimes quaternary structure
Describe the structure (shape) of gkobular proteins
Roughly spherical
Are globular proteins usually soluble or insoluble?
Soluble (hydrophobic side chains in centre of structure)
What is a role of globular proteins?
Metabolic reactions
What structure do fibrous proteins have?
Little/no tertiary structure
Describe the structure (shape) of fibrous proteins?
- Long parallel polypeptide chains
- Cross linkages at intervals forming long fibres or sheets
