Proteins and enzymes Flashcards
What is an amino acid?
An amino acid is the monomer that forms protein polymers and there are 20 naturally occurring amino acids
What is the structure of an amino acid?
It contains A variable group and an a mean group and a carboxyl group
What happens when two amino acids undergo a condensation reaction?
When two amino acids undergo condensation, it forms a peptide bond And formed a dipeptide molecule
What are the four structural forms of a protein and explain what happens in each stage
The primary structure consists of a sequence of amino acids and a polypeptide chain joined by peptide bonds
The secondary structure is when the primary structure folds or twists the folds are called beta pleated sheets and the twist are called Alpha Heli’s. These are held in place by hydrogen bonds between the NH of one amino acid and the CO of another.
The tertiary structure is when the secondary structure folds even further into a specific 3-D shape. The shape is held in place by bonds between the our group. The bonds are hydrogen ionic and disulphide bridges.
The Cortana structure forms more than one polypeptide chain joined together and these contain the same bonds as in the territory structure for example haemoglobin has four chains and insulin has two chains
What are the two types of proteins?
Globular proteins are soluble proteins with biochemical functions such as enzymes and hormones and fibrous proteins are insoluble and have structural functions example keratin and nails
What is the test for proteins?
BR solution is used to test for the presence of proteins and it is added to the sample and if the solution changes from a blue to a lilac purple then protein is present
What is an enzyme?
An enzyme is a biological catalyst and it lowers the activation energy of the reaction at catalyses
How do enzymes work?
They bind to substrate and the substrate binds to a specifically shaped part of the enzyme known as the active site and the active site is complementary to the substrate and once the substrate has bound to the enzyme and enzyme substrate complex is formed
How do you enzymes lower activation energy?
They bend the bonds in the substrate put strain on the bonds, making them more likely to break
They bring two molecules close together, overcoming the natural repulsion between the two molecules making a bond between the two molecules more likely
What does the lock and key theory state?
The active site is a perfect complementary fit to the substrate
What does the induced fit model say about the enzyme?
The active site is a complementary shape to the substrate, but not perfectly when the substrate binds it induces a slight change in the active site. This change in shape bends the bonds in the substrate putting strain on the bonds and causing them to break more readily.
How is the active site shape maintained?
By the bonds in the enzymes territory structure if these bonds change, then the Active site could change shape resulting in it no longer be in complementary to the substrate therefore no enzymes substrate complexes could form
How can enzymes be activated?
By a non-protein molecule this molecule binds to the enzyme and causes a confirmational change. The active site is now complementary to the substrate and the substrate can bind
What are the factors that affect enzyme activity?
As temperature increases the kinetic energy of the enzyme and substrate increases they are more likely to collide and form enzyme substrate complexes. This increases the rate of reaction however above the optimum temperature the hydrogen bonds in the territory structure break the active site change the shape and there is no longer complementary to the substrate and enzyme substrate complexes cannot form.
PH also affects enzymes as deviation away from the optimum pH causes changes in the ionic bonds between our groups the active site changes shape and is no longer complimentary to the substrate and enzyme substrate complexes cannot form
Also enzymes are substrate concentration as the concentration increases the rate of reaction also increases this is due to more collisions and an increase in enzyme substrate complex is formed at high concentrations the rate levels off as there is another limiting factor
What does a competitive inhibitor do?
They are molecules which have a similar shape to the substrate. This means that they can fit and bind to the active site blocking the substrate from binding. This reduces the number of enzyme substrate complexes that form and reduces the rate of reaction. However, at high substrate concentrations the substrate is more likely to bind to the active site than the inhibitor and the effect of the inhibitor can be overcome. The reaction can reach its maximum rate.
What does a non-competitive inhibitor do?
It binds to an area away from the active site which is known as the allosteric site binding to this inhibitor causes a change in the shape of the active site so it is no longer complementary to the substrate. This reduces the formation of enzyme substrate complexes and reduces the rate of reaction. Even at high substrate concentrations substrates are unable to form enzyme substrate complexes therefore maximum rate is never reached.
