proteins Flashcards
Describe each structure of a protein
primary- number and sequence of amino acids
secondary- folding of protein due to the hydrogen bonds betwen NH and C=O(alpha helix/beta pleated sheet)
tertiary- 3D folding of polypetide chain due to interactions BETWEEN amino acid R grps (disulfide, ionic, hydrogen)
quatertiary- one+ polypeptide formed by interactions of bonds.
Test for proteins and result
Biuret and blue to purple/lilac if positive, stays blue if negative
How do enzymes act as biological catalysts
- lower the activation energy
*speeds up the reaction
How is the activation energy lowered?
bonds in substate are altered which then lowers the activation energy
What is the induced fit model
*substrate binds to (not completely complementary) active site of enzyme
*active site changes shape (slightly) complementary to substrate
- enzyme-substrate complex forms
*causing bonds in substrate to bend / distort, lowering activation energy
Why do the bonds in the substrate distort in the induced fit model after the E-S complexes were formed
*weak interactions occur between substrate and AT
*conformational change in the At allows gthe substrate to bind
*BECAUSE of coformational cchange it causes stress on the substrate bonds
Explain how active sites are complementary
*specific tertiary structure determines the shape of the active site (dependemt on primary structure)
*active site is complementary to a specific substrate.
Describe and explain the effect of enzyme concentration on the rate of enzyme-controlled reactions
*as enzyme increases, rate of reaction increases
*E-S complexes formed
*rate of reaction levels off, as substrates are in use
Name 2 limiting factors in rate of reaction
*enzyme cause of excess substrate- inot enough active sites as they are occupied OR
*substrate as theyre all in use, so left of active sites are not being used
Define limiting factor
any condition or resource that limits the rate of a reaction.
Describe and explain the effect of temperature on the rate of enzyme-controlled reactions
*as temperature increases, more ES complexes due to more kinetic energy
*when temperature goes above optimum, enzymes denature- active site and tertiary structure change shape
*active site no longer complementary
*less ES complexes
What is a non-competitive inhibitor
*rate of reaction decreases
*inhibiror binds to allosteric site- causes a change in the tertiary structure
*active site no longer complementary shape to substrate
*less ES complexes formed
What is a competitive inhibitor
*decreases rate of reaction
*Similar shape to substrate
*binds to active site
* So substrates can’t bind and fewer E-S complexes form
*increasing substrate conc. reduces effect of inhibitors
Describe how temperature can be controlled.
*thermostatically controlled water bath
*monitor using a thermometer at regular intervals
*add hot / cold water if temperature fluctuates
Describe how pH can be controlled.
● Use a buffer solution
● Monitor using a pH meter at regular intervals
