1b. ENZYMES Flashcards
Define what an enzyme is
A biological catalyst
How do all enzymes speed up chemical reactions?
By lowering the activation energy
Why must enzymes be water soluble?
Because most enzyme controlled reactions occur in the cytoplasm or tissue fluid, which are aqueous
Give an example of an extracellular enzyme controlled reaction
Digestion
Give an example of an intracellular enzyme controlled reaction
Respiration, photosynthesis, protein synthesis
What is the functional part of an enzyme?
Active site
What is the 3D shape of an enzyme’s active site determined by?
The type and position of the hydrogen, covalent, ionic and disulphide bonds in its tertiary shape
Compare the shape of the substrate and the shape of the active site
They are complimentary
When an ESC is formed, what two things are interacting?
The substrate and the enzyme
Recall the two theories that describe how enzymes lower activation energy
Lock & key and induced fit
In the lock and key model, is the active site always complimentary to the substrate?
Yes
In the induced fit model, when is the active site not totally complimentary to the substrate?
Before the ESC is formed
Describe how thebinding of the substrate lowers activation energy in the induced fit model
As the active site changes shape, it distorts the bondswithin thesubstrate, lowering the activation energy.
Recall the two equations used to calculate rate of reaction
Product formed ÷ time & reactant formed ÷ time
Define what Vmax is, and how it’s reached
The maximum rate of an enzyme-controlled reaction. It is reached when all the enzyme’s active sites are full.
Explain why enzyme-controlled reactions have a high initial rate
Because the most ESC are formed at the beginning of a reaction
Describe how to calculate the rate of reaction at a specific point on a graph, if the line is a curve
Calculate the tangent of the curve
Explain why increasing temperature increases the rate of enzyme-controlled reactions
It increases the KE of the particles, which increases the frequency of collisions
Explain how changing temperature may affect the rate of an enzyme controlled reaction
As temperature increases, rate increases
Explain why changing temperature above the optimum may reduce the rate of reaction
Because the enzymes may denature
Recall the equation to calculate pH
pH = -log10 [H+]
Explain how changing pH may reduce the number of ESCs formed
As pH changes, more H+ causes the charges on the R groups of the amino acids in the active site to change, and the substrate will not be able to bind as easily. Less ESCs formed.
Explain why changing pH causes the shape of an enzyme’s active site to change
The change in [H+] causes theionic and hydrogen bonds to break, which changes tertiary structure of active site. No ESCs can be formed.
Explain why changing substrate concentration changes the rate of an enzyme-controlled reaction
It would change the frequency of collisions, changing the rate of ESCs formed
