2.1.4 Enzymes COMPLETE Flashcards
Active Site
The intended area on the enzyme surface which has a complimentary shape to the substrate
Catalyst
A Chemical that speeds up rate of reaction but remains unchanged
Metabolism
Chemical reactions that take place in the living organisms
Substrate
The molecule that is altered by an enzyme catalysed reaction
DEFINITION- Enzyme
A globular protein with a specific shape that can act as a biological catalyst, speeding up metabolic reactions in living organisms
Turnover Number
The number of reactions that an enzyme molecule can catalyse per second
Intracellular Vs Extracellular
Intracellular work inside the cell catalysing reactions such as photosynthesis.
Example: Catalase
Extracellular work outside cells catalysing hydrolysis reactions that breakdown macromolecules
Example: Amylase & Trypsin
How enzymes work
They speed up metabolic reactions by acting like a catalyst. Make substrates into products when they randomly collide
Catabolic Reactions
Where substrates are broken down, strain is applied after the enzyme attaches so the molecule breaks apart.
Anabolic Reactions
Where substrates are joined to make a larger product, When the enzyme attaches repulsion is reduced so they bond more easily
Why enzymes are specific
The active site is specific for a reaction and the shape is maintained by the tertiary structure, therefore the enzyme only works with one molecule.
Activation Energy
The energy that is required to begin a chemical reaction
Enzymes decrease the Ea so reactions take place more easily
Lock and Key
The complimentary active site and substrate fit together like a lock and key
Induced Fit
The enzymes active site changes slightly upon collision making the active site fit closer to the substrate.
May also be changes to the amino acids in the active site that contributes to holding the substrate in place.
Temperature on rate of reaction
When heated kinetic energy increases so random collisions are more frequent, these also occur with more energy and greater force.
Therefore ROR increases
Optimum Temperature
The temperature that gives the enzymes the maximum rate of reaction. Its a balance between increasing kinetic energy of the molecules and not denaturing it
Temperature and Denaturation
When the tertiary structure I changed to the point where it no longer works, irreversible.
Molecules vibrate putting strain on the bonds, when the hydrogen and ionic bonds break the tertiary structure changes and ROR decreases
ROR calculation
=1/ Time taken to reach end point
Refers to temp increasing by 10 degrees
pH on Enzyme Reactions
H+ ions attach to negative charges and alter the active site. This is because they attach to the R groups in the amino chains and interfere with bonding.
Optimum pH
Where the concentration of H+ gives the tertiary structure the best complimentary shape
A very narrow range is expected as small changes make big differences
pH and Denaturation
Minor changes in pH do not denature enzymes as disrupted bonds reform. Denaturation only occurs with extreme pH away from the optimum
Affect of Substrate Conc.
More substrate increases the rate of successful collision
When it reaches max value all the active sites are full so no more affect
V Max is the maximum initial velocity of rate of the enzyme catalysed reaction
Affect of Enzyme Conc.
Increased enzyme conc. increases the ROR until all the substrates are full.
If both increased ROR consistently increases
Enzyme Synthesis
Depending on the cells needs, genes for synthesising particular enzymes can be switched on or off
Enzyme Degradation
In cells the proteins are broke down into constituent amino acids to be used to make new ones.
Initial Reaction rates
Reaction rate will be highest when the substrate and enzymes initially mix
As the reaction processes it slows
Use a tangent to calculate
Limiting Factors
Causes it to plateau as no more reaction can take place
Cofactors
Some enzymes only work is there’s a non protein substance bound to them.
Two types including inorganic and organic
Inorganic Cofactors
Ions
Do not permanently bind, and are not used up as don’t take part in the reaction.
Will either change the charge distribution or shape of the complex which makes the binding easier
Organic Cofactors
Non protein molecules containing O, C and H
Bind temporarily to the active site, they take part in the reaction and are changed in some way however will be recycled.
Often act as carriers
Prosthetic Groups
Coenzymes that permanently bind covalently
Enzyme Inhibitors
A substance or molecule that slows down the rate of enzyme controlled reactions.
They can affect one or many enzymes.
Reversible and Non reversible inhibitors
Don’t permanently bind to the enzyme or permanently bind.
Depends on the strength of the bonds, If covalently bonded then they can’t easily be removed
If Hydrogen or ionic bonds the inhibitor can be removed
Competitive Inhibition
Molecules with a similar shape to the substrate will bind to the active site with no reaction. They block the active site, level of inhibition depends on relative concentration.
Non competitive Inhibition
They bind to the Allosteric site and cause change to the tertiary structure so the active site changes and the substrate can no longer fit. Increasing conc. of substrate won’t make a difference.
Metabolic Poisons
Interfere with metabolic reactions causing damage, illness or death.
E.g. Cyanide
Venom
A mixture of toxins and different enzymes including ATPases, Phosphodiesterase’s and acetylcholinesterase inhibitors
Control of metabolic Sequences
Many metabolic processes require a series of enzyme controlled reactions, these are called metabolic pathways.
End product Inhibition
The end product binds to an earlier enzyme to change its active site reducing the ROR, this causes less product to be made. This is reversible and non competitive
Enzyme Activation
Some enzymes are synthesised but are missing some amino acids. This means they are an inactive precursor. Many digestive enzymes are produced in this way. i.e. trypsin and pepsin
