Protiens And Enzymes Flashcards
Structure of amino acid
What can R groups be
Charged
Hydrophobic
Hydrophilic
How is a dipeptide formed
Condensation reaction which the removal of H2O bond between the amine group on of molecule and carboxyl group of another amino acid forming a peptide bond
What is the primary structure
Number and sequence of amino acids in a polypeptide chain forming peptide binds joined by condensation reaction
What is the secondary structure
Polypeptide chain folds into alpha helix or beta pleated sheets with many weak hydrogen bonds only
What is the tertiary structure
Further folding of a polypeptide chain forming a steric 3D complex. Number of amino acids in the R groups the polypeptide chain determines how the polypeptide folds. 3D shape held by binds which are hydrogen, ionic and disulphide bonds between different amino acids. All proteins have a specific tertiary structure which gives them a specific shape
3 different bonds between R groups
Ionic , hydrogen, disulphide
3 different bonds between R group of 2 different amino acids
Ionic
Hydrogen
Disulphide
Do proteins have active sites or binding sites
Binding sites
What is Quaternary structure
2 or more polypeptide Chains joined together
how can proteins denature
High temperatures and change in PH
Effect of increasing temperature of proteins
Increase Kinetic energy so more vibration which breaks many weak hydrogen bonds in secondary and tertiary structure
Effect of changing PH of proteins
Breaks ionic bonds as change in charge so they repel each other
Biuret test
Add equal volumes of biurets solution
Colour change from, blue to lilac if protein present
What are enzymes
They are globular proteins that act as biological catalysts which increases rate of reaction by lowering activation energy by distress and distort of bonds but don’t get used up
How do active sites form enzyme substrate complexes
Active site is specifically complementary to substrate and forms enzyme substrates complex by distress and distortion of bonds which is weakling them
How many amino acid R groups are active sites made from
Less than 10
2 models of enzyme action
- Lock and key
- Induced for model
Differences between lock and key and induced fit model
LK = active site is rigid whereas in IF active site is not rigid
LK= active site is perfectly complex try to substrate whereas in IF not exactly complementary
LK = cannot change tertiary structure IF = slight change in active site
Both form enzyme substrate complexes
LK= forms products IF = produces products by distress and distort
Describe lock and key
The active site is rigid
Substrate binds to active site which is specifically complementary
Products are formed and enzyme free to take part in another reaction
Describe induced fit model
Active site is not rigid
Substrate binds to active site and active site slightly changes shape to induce itself around the substrate as not perfectly complementary using distress of bonds. When substrate leaves, active site returns to original shape
Effect of increasing substrate concentration
As rate of reaction increases , substrate concentration increases as number of enzyme substrate complexes formed increases but then plateaus as all active sites of enzymes full so enzyme active sites becomes a limiting factor
Effect of enzyme concentration
As enzyme concentration increases, rate of reaction increases as number of substrate complexes formed per second increases.
Then graph plateaus as not enough substate to bind to active site so substrate concentration becomes a limiting factor
Effect of PH
Enzymes have an optimum PH
As PH decreases or increases, the hydrogen/ ionic bonds in the tertiary structure are altered means substrate is no longer specifically complementary to the active site so no more enzyme substrate complexes formed
Effect of temperature
As temperature increases , number of enzyme substrate complexes increases as more Kinetic energy so more frequent successful collisions , however above optimum temperature the rate of reaction decreases as too much kinetic energy which breaks many weak hydrogen binds between R groups of different amino acids, which means change in tertiary structure so active site no longer specifically complementary to substrate
Describe a competitive inhibitor
They have a similar shape to substance and bind to active site temporarily which prevent enzyme substrate complexes from forming however can be overcome by increasing substrate concentration.
Describe non-competitive inhibitions
Inhibitor binds to the allosteric site and causes permanent change to the shape of the active site which means substrate is no longer specifically complementary to active site so no more enzymes substrate complexes
