proteins Flashcards
What part on an amino acid is variable?
The R group
How many amino acids occur in life?
20 amno acids , 9 are essential ( have to be found in the diet) and 11 are non essential, we can produce them ourselves.
What are the different types of amino acids?
- hydrophobic (non polar) R groups- hydrocarbon
- polar R groups - can form H bonds
- positively charged ( basic)
- negatively charged ( acidic)
How many possible dipeptides are there?
400 different dipeptides
define polypeptide bond
A peptide bond is a covalent bond formed between two amino acids.
define protein
A molecule composed of polymers of amino acids joined together by peptide bonds.
What is the primary structure of a protein?
the primary structure of a protein is the sequence of amino acids in the polypeptide chain.
What is the secondary structure of a protein?
the alpha helices- an extended spiral maintained by weak H bonds formed between CO and NH group molecules with only these form long fibrous proteins ( collagen, helices in tendons and bones..)
Beta pleated sheets- polypeptide chains run parallel or non parallel to each other held by H bonds.
What is the tertiary structure of a protein?
compact 3D shape of a protein.
It is controlled by the primary structure of the protein as it’s the R group that holds the structure in it’s place by:
H bonds - slightly + R groups
disulphide bonds - R group contains sulphur
ionic bonds - oppositely charged R groups
hydrophobic interactions - R group is in the centre of the molecule.
What is the Quaternary structure of a protein?
the joining of two or more polypeptide chains to form a functioning protein is held in its’s place by the same bonds of the tertiary structure.
what is meant by a zwitterion?
when the amino acid is simultaneously a cation and anion ( carboxyll group lost H+ and amine group gained) but the overall charge is zero. An amino acid can only exist as a zwitterion at a certain pH
what is meant by amphoteric?
Amino acids are both basic and acidic so they can act as buffers to resist change to pH and maintain the conditions important for e.g homeostasis.
what is a gobular protein?
when the irregular folding is roughly spherical and are soluble in water ( have a hydrophillic R group)
What is a fibrous protein?
Form long fibres and are insoluble in water.
What is a prosthetic group?
a non protein group forming part of the protein required for the function of the protein.
