Proteins Flashcards
What is the general structure of an amino acid?
A carbon with an amine group, a hydrogen, a carboxyl group and an R-group attached to it
What differs between different amino acids?
The only thing that changes from amino acids is the R-group
What type of bond is formed between amino acids?
A peptide bond
What is it called when two amino acids are joined?
A dipeptide
How do amino acids join?
Via condensation reactions
What is it called when many amino acids are joined?
Polypeptide
What enzymes catalyse the breakdown of peptides?
Proteases
How are peptides broken down into individual amino acids?
Via hydrolysis reactions (water is used to break the bond, reforming the amine and carboxyl groups)
What is primary protein structure?
The sequence in which amino acids are joined, as directed by DNA
What bonds are involved in primary structure?
Only peptide bonds
What is secondary protein structure?
The oxygen, hydrogen and nitrogen atoms of the basic structure of the amino acids interact
What new bonds are involved in secondary protein structure?
Hydrogen bonds form within the amino acid chain, forming one of two secondary structures
What are the two possible secondary protein structures?
Alpha helix or beta pleated sheet. It varies between the two depending on the amino acid composition
What is tertiary protein structure?
The folding of a protein into its final shape
How does secondary structure allow tertiary structure to develop?
The coiling or folding of sections of proteins in secondary structures bring R-groups of different amino acids close enough to interact
What new bonds are involved in tertiary protein structure?
- Hydrophobic and hydrophillic interactions
- Ionic bonds
- Disulphide bridges
(hydrogen bonds continue to form)
What are hydrophobic and hydrophillic interactions?
Interactions between polar and non-polar R-groups
What are ionic bonds?
Strong forces that form between oppositely charged R-groups
What are disulphide bridges?
Strong covalent bonds that only form between R-groups that contain sulfur
What is quaternary protein structure?
The association of two or more individual proteins (called subunits)
What bonds are involved in quaternary protein structure?
Same as tertiary, except they are between different protein molecules (subunits) rather than within a single protein molecule
What is the structure of globular proteins?
They fold in such a way that their hydrophobic R-groups are kept away from the aqueous environment, and their hydrophillic R-groups are on the outside
What does the structure of globular proteins mean about its properties?
It means globular proteins are soluble
Why is the solubility of globular proteins important (example)?
Insulin is a globular protein, and it has to be soluble as it is transported in the blood
What are conjugated proteins?
Globular proteins that contain a non-protein component
What is the non-protein component of conjugated proteins called?
The prosthetic group
What is an example of enzyme which is a conjugated protein?
Catalase, which has a haem group (Fe2+) attached
What is another example of a common conjugated protein?
Haemoglobin
What is the structure of haemoglobin?
Haemoglobin is a quaternary protein, made from 4 subunits (2 beta, 2 alpha). Each subunit contains a prosthetic haem group (Fe2+)
What are the properties of fibrous proteins?
Strong
Long
Insoluble
Not folded into complex 3d shapes (like globular proteins)
What are 3 examples of fibrous proteins?
Keratin
Elastin
Collagen
What are the properties and function of keratin?
Strong, inflexible and insoluble.
Found in hair, skin and nails
What are the properties and function of elastin?
Adds flexibility and elasticity
Found in elastic fibres, which are present in the walls of blood vessels and aveoli
What are the properties and function of collagen?
Flexible and strong
Found in connective tissue
Why are fibrous protein not soluble in water?
They have a high proportion of hydrophobic R groups in their primary structures
