Proteins Flashcards
Describe how the amino acids are joined together to form a dipeptide
-Condensation reaction
-Water is removed
-Peptide bond forms between OH of carboxyl and H on amine group
What is a protein
-Proteins are polymers,made up of the monomer amino acids
What is the primary structure
-The order of the amino acids in a polypeptide chain-this is a polymer
What is the secondary structure
-The sequence of amino acids causes parts of a protein molecule to bend into a helix shapes or fold into B
pleated sheets
-Hydrogen bonds hold the secondary structure
In secondary structure, where do h bonds form
-Hydrogen bonds form between the
C=O groups of the carboxyl group of one amino acid and the H in the amine group of another amino acid
What is the tertiary structure
-The further folding of the secondary structure
-To form a unique 3D shape.
-Held in place by ionic, hydrogen and disulphide bonds.
Where are the ionic,disulfide bonds formed in tertiary structures
-The ionic and disulfide bonds form between the R groups of different amino acids.
-Disulphide bonds occur sometimes , as there must be a sulfur in the R groups for this bond to occur (S—S)
What is a quaternary structure
-A protein made up of more than one polypeptide chain
-For example, haemoglobin is made of 4 polypeptide chains
What does it mean if a protein is denatured
-If a protein is denatured, this means that bonds which hold the tertiary and secondary structure in shape break, and therefore the unique 3D shape is lost. (e.g. enzymes lose their unique active site shape)
What is the induced fit model
-Induced fit is when the enzyme active site is induced, or slightly changes shape, to mould around the substrate.
When the enzyme-substrate complex occurs, due to the enzyme moulding around the substrate it puts strain on the bonds and therefore lowers the activation energy
What are the factors affecting enzymes
-Temperature
-pH
-Substrate and enzymes concentration
-Enzyme inhibitors
How does temperature affect enzymes
• If the temperature is too low there is not enough kinetic energy for successful collisions between the enzyme and substrate.
•If the temperature is too high enzymes denature, the active site changes shape and enzyme-substrate complexes cannot form.
How does pH affect enzymes
•Too high or too low a pH will interfere with the charges in the amino acids in the active site. This can break the bonds holding the tertiary structure in place and therefore the active site changes shape.
How does substrate and enzymes concentration affect enzymes
-If there is insufficient substrate, then the reaction will be slower as there will be fewer collisions between the enzyme and substrate.
-If there is insufficient enzymes, then the enzyme active sites will become saturated with substrate and unable to work any faster.
How does enzyme inhibitors affect enzymes
Competitive inhibitor
• Same shape as the substrate
• Bind to the active site.
• Prevents enzyme-substrate complexes.
If you add more substrate it will flood/out-compete the inhibitor, knocking them out of the active site.
Non-competitive inhibitors
•Bind to the allosteric site.
•Causes the active site to change shape
• No enzyme-substrate complexes
The substrate can no longer bind, regardless of how much substrate is added.
