Biological Molecules : Proteins Flashcards
What is haemoglobin?
A protein. This means that haemoglobin is made up of amino acids like all proteins
What are amino acids and what is the polymer made from amino acids?
Monomers.
The polymer made from amino acids is a polypeptide chain and the folded polypeptide chain or chains makes the protein
What is the basic structure of every amino acid?
An amine group (left side) NH2
R group or side chain (this is variable function group ) MIDDLE
Carboxylic acid group COOH (right Hand side)
What protein are red blood cells packed with?
Haemoglobin
It’s important because it carries oxygen around the body where it is needed
What are some R groups like?
Some R groups carry a charge (some are positively charged and some are negatively charged
Some ARE POLAR (so have a slightly positive charge and others a slight negative charge
SOMe have NO CHARGE and are NON-POLAR
WHAT is the function group (R group) like?
It is variable
Whats a peptide bond?
The bond formed when amino acids are brought close together and bonded together
Condensation reaction
As a pep[tide bond is formed, one hydrogen atom and one oxygen atom from one amino acid and one hydrogen atom from the other join together to form a water molecule
Peptide bond (covalent) is formed
Water eliminated (released)
Hydrolysis reaction
Peptide bond (covalent) broken
Water used up
What do two amino acids joined together result in?
A dipeptide molecule
Whats a polypeptide ?
On ribosomes, a long chain of amino acids is formed all linked together by peptide bonds
What are the four levels of protein organisation?
- primary
- secondary
- tertiary
- quaternary
Many proteins are just a single polypeptide chain. However a haemoglobin molecule is made of…
Four polypeptide chains all wound around each other in a very precise pattern
What are the two of the polypeptide chains in haemoglobin molecules (and the two others)?
Two of the polypeptide chains are identical and called alpha chains (a chains)
Two are identical and are called beta chains
Each of the chains is made up of 141 amino acids
Why do a chains differ from b chains?
Although they are the same length, they have a different primary structure
(Same size and length, different sequences)
Explain primary structure
The primary structure of a protein is the exact sequence of amino acids in the polypeptide chain
(Different amino acids can be represented by one letter or three letter abbreviations)
Explain the secondary structure
The secondary structure of a protein describes the coiling and folding of the polypeptide chain into :
- an alpha helix(singular) or helices (plural)
- beta pleated sheets
What bonds occur in secondary structure?
Weak hydrogen bonds between the amine and carboxylic groups from between different parts of the chain to stabilise it
(Hydrogen bonding in the secondary structure does not involve the R groups
Explain tertiary structure
Further folding of the polypeptide chain which gives a specific 3 dimensional shape. (Makes more of a spherical shape)
Further folding of the polypeptide chan; the secondary structure alpha helix and beta pleated sheets are incorporated into the tertiary structure
What are the different types of bonds that the shape in the tertiary structure is stabilised by?
- weak hydrogen bonds: wherever slightly positive charged groups are found close to slightly negatively charged groups, hydrogen bonds form. This includes R groups
- DISULPHIDE BONDS: strong bonds between two cysteine molecules (amino acids with sulphur R groups)
- IONIC BONDS: (opposite charges) R groups sometimes carry a charge, either +ve or -ve. Where oppositely charged amino acids are found close to each other, an ionic bond forms
- HYDROPHOBIC AND HYDROPHILIC INTERACTIONS: (wants to be in the middle inside) In a water based environment, hydrophobic amino acids (with nonpolar R groups) will be most stable if they are held together with water excluded (hydrophobic amino acids and hydrophilic amino acids)
In general, when polypeptide chain is folded, the hydrophobic amino acids are on the inside therefore keeping them away from the water based solvent
Explain quaternary structure
Some proteins have more than one polypeptide chain; these have quaternary structure. This is the way the polypeptide chains fit together (these chains are held together by hydrogen or ionic bonds involving the R groups)
What are prosthetic groups in the quaternary structure?
Some proteins have non protein prosthetic groups attached. In the case of haemoglobin there are 4 haem groups associated with the quaternary structure