proteins+enzymes

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What is an amino acid? 
The monomers from which proteins are made
What is a dipeptide? 
Formed by the condensation of two amino acids
What are polypeptides? 
Formed by the condensation of many amino acids
What is a peptide bond? 
Forms during a condensation reaction between the amine group of one amino acid and the carboxyl group of another amino acid
What is the primary structure of a protein? 
The sequence of amino acids in a polypeptide chain joined by peptide bonds
What is the secondary structure of a protein? 
The folding of the polypeptide chain into an alpha helix or beta pleated sheet because of hydrogen bonding between amine group of one amino acid and carboxyl group of another
What is the tertiary structure of a protein? 
The folding of the polypeptide chain into a specific complex 3D shape held together by hydrogen bonds, ionic bonds and disulphide bridges between R groups of different amino acids
Explain the quaternary structure of a protein? 
The arrangement of more than one polypeptide chain
Biochemical test for proteins
- Add biruet solution to a sample
- Colour change from blue to lilac
What elements are found in amino acids?
Carbon
Hydrogen
Oxygen
Nitrogen
(some contain sulphur)
How many types of amino acids are there and how do they differ?
20
Differ in their R groups
How does changing the primary structure affect the tertiary structure of a protein?
- Changing sequence of amino acids
- Changes the position of R groups
- Hydrogen/ ionic/ disulphide bonds form in different places
- Different tertiary structure so different 3D shape
What is the quaternary structure of a protein? 
- Function proteins may contain one or more polypeptide chains
- The arrangement of the different chains is called the quaternary structure
What does it mean if a protein has been denatured? 
- When the hydrogen bonds in a protein break, the tertiary structure of the protein is altered
- The protein can no long carry out its function
- Protein is denatured
The induced fit model 
-The substrate enters the enzymes active site
- The binding of the substrate molecule alters the 3D tertiary structure of the active site
- This stresses the bonds which cause them to break more easily
- this explains how how enzymes lower the activation energy
The effect of temperature on Enzyme action 
As temp increases, the rate of of enzyme action increases:
- enzymes and substrates have more kinetic energy
- there are more collisions per second between enzymes and substrates
- more enzyme-substrate complexes form

Beyond the optimum temperature, the rate of enzyme action decreases:
- enzyme denatures as hydrogen bonds holding the tertiary structure break
- this changes the specific 3D tertiary structure of the active site so it is no longer complementary to substrate
- fewer enzyme-substrate complexes form
Effect of pH on enzyme action
Below or above the optimum pH the rate of enzyme action decreases:
- the enzyme denatures as hydrogen bonds holding the tertiary structure break
- this changes the specific 3D tertiary structure of the active site so it is no longer complementary to substrate
- fewer enzyme-substrate complexes form
Effect of substrate concentration on enzyme action
- Rate of reaction increases as the Conc of substrate increases as there are more collisions per second
- more enzyme-substrate complexes form
- concentration of substrate is the limiting factor

- the rate of reaction platies as there is another limiting factor prohibiting the reaction (Conc of enzyme)

- at high substrate concentrations, there are no free active sites and the maximum number of enzyme-substrate complexes formed (enzyme is the limiting factor)
Effect of enzyme concentration on enzyme action
- adding more enzymes increases the rate of reaction as more enzyme-substrate complexes form

- concentration of enzyme is the limiting factor
What is a competitive inhibitor? 
- competitive inhibitors are similar in shape to the real substrate
- they enter into the enzymes active site and prevent the substrate from binding
- they are not permanently bound
Explain why the competitive inhibitor reduces the rate of reaction of the enzyme 
- The competitive inhibitor is similar in shape to the substrate
- it enters into the enzymes active site and prevents the substrate from binding
- so less enzyme-substrate complexes form
Explain why a maximum rate of reaction can be reached with a high concentration of substrate in the presence of a competitive inhibitor.
- at high concentrations of substrate, the chance of the inhibitor molecules entering the active site is low
- competitive inhibitors bind temporily
- higher conc of substrate means a higher chance of the substrate binding to the enzymes active site
- maximum number of enzyme-substrate complexes can still be reached
What is a noncompetitive inhibitor? 
- these bind to the enzyme away from the active site
- they change the tertiary structure and shape of the active site
- The substrate cannot bind
- enzyme-substrate complexes cannot form
Explain how a noncompetitive inhibitor reduces the rate of reaction of an enzyme.
- noncompetitive inhibitors bind to the enzyme away from the active site
- they change the tertiary structure and shape of the active site so the substrate cannot bind as it is no longer complementary
-enzyme-substrate complexes cannot form
Explain why by adding more substrate you cannot reduce the effect of the noncompetitive inhibitor.
- active site has been changed on some enzymes permanently reducing the concentration of functioning enzymes
- cannot reach the maximum number of enzyme-substrate complexes as without the inhibitor.
Large variety of proteins
- haemoglobin = transports oxygen
- antibodies = defend against infection.
- enzymes = biological catalysts
- actin + myosin = muscle contraction

- keratin = nails + hooves
- collagen = tendons