Enzymes Flashcards
Thermodynamics doesn’t adress
Reaction speed
Table sugar breakdown
No reactions in the bag, it does in the cells because there are enzymes present
Chemical reaction occur when
Bonds are broken or established
Activation energy (Ea)
The initial energy investment required to start a reaction
Transition state
The necessary Ea was gained. Bonds are unstable and ready to be broken
What provides Ea
Particles natural movement or one reaction provides energy for another
Too much energy
Creates to much movement, leading to too much heat, which causes too many reaction and there is often burning (propane)
Why biology cannot use heat as Ea
Heat destroys the cell (specifically proteins) by destroying the structure
All reactions in the cell would start, killing the cell
Catalyst
Used in biology. A chemical agent that speeds up a reaction without taking part in it.
The most common catalyst
Enzymes
Importance of the transition state
A kinetic barrier as only some molecules have enough energy to react. Allows reactions to go one at a time
Enzymes job
Lower the transition state so more molecules can react. The do not alter thermodynamics or provide energy for a reaction
Substrates
The reactant an enzyme works on
Enzyme specificity
Each enzyme can only catalyze one of a couple similar molecules. This is why there are many enzymes per cell
Active site
The location on the enzyme where the catalysis takes place. A grove is formed when the protein folds, a very small section of the enzyme
Lock and key theory
Substates (keys) use the lock (Enzyme) to unlock the door (start a reaction) this is an old theory from the 1900’s
Induced fit hypothesis
Current view on enzyme function. Before a substrate bonds an enzyme goes though conformation so the active site is the most precise shape
Conformation
The process of an enzyme changing shape
Enzyme cycle
The process of grabbing substrates, catalyzing them, releasing them…
Cofactor
A non protein group that binds to an enzyme. Often a metal in which very little is required for catalysis
Cofactor metals
Fe, Cu, Zn, Mn
Coenzyme
A cofactor made of organic molecules, often derived by a vitamin
3 ways enzymes lower Ea
Bring reactant molecules together
Exposing the molecule to altered changed environments
Changing the shape of the substrate molecule
Bring reactant molecules together
Makes them collide in the right orientation so there is a reaction
Exposing the molecule to altered changed environments
Active sites may contain ionic group with positive or negative charges
Changing the shape of the substrate molecule
Strain the molecule into a conformation that mimics the transition state
Without enzymes
Reactions would still happen, just not frequently
Factors that effect enzyme activity
Substrate and molecule concentration, temperature, pH
Common way to study enzymes
Rate of reaction by the enzyme and how it changes in response to experimental parameters
Procedure
Purify the enzyme from the cell, incubate it in a buffered solution, five the reaction a substrate, look at the rate of the product being formed
Excess substrate
Rate of catalysis is proportional to the amount of enzyme. The amount of enzymes limits the reaction
Constant enzyme concentration- low to high concentration
Low- few collisions, few reactions
As it increases it is linear until the maximum amount of an enzyme can be catalysis is reached. Then concentration has no effect
Saturated with substrate
When the catalyic cycle is going as fast as possible
Competitive regulation (competitive inhibition)
When molecules that resemble substrates, and substrates fight for the same active sight
Strength of competitive regulators
Some are covalently bonded, strong and irreversible
Non covalent bonds are weaker and reversible, can be overcome by high substrate concentration
Cyanide
An inhibitor that prevents cellular respiration.
Drugs are..
both helpful and harmful inhibitors
Non competitive regulation
Competitors interact with the parts of the enzyme that are not the active site. Can increase of decrease enzyme function
Allosteric site
A irreversible bond on this site controls enzyme activity
Allosteric enzyme
An enzyme controlled by a allosteric site. Can have a high or low affinity state
High affinity state
Enzyme binds strongly to the substrate
Low affinity state
Enzyme binds weakly to the substrate
Allosteric inhibitor
Converts an enzyme from high to low affinity
Allosteric activator
Converts an enzyme from low to high affinity
How cell reactions are controlled
- Abundance of specific enzymes
- Allosteric control
- Covalent modification
Abundance of specific enzymes
The amount of enzymes is regulated by gene expression (only how many is needed is made). Can take up to 30 minutes
Allosteric inhibitors are…
A form of feedback inhibition
Feedback inhibition
If too much of a product is made, it becomes an inhibitor for its own reaction. When not enough is present the inhibitors leave and the reaction starts again
Multi step feedback inhibition
The product inhibits the production of the starting product to avoid wasting intermediate products
pH of enzymes
Each function in a specific pH and the farther from their optimum the less they work. Outside of the range the charge groups differ (H+ and OH- concentration)
Most enzymes pH
7 because that is what cells sit at
Pepsin
An enzyme with a ideal pH of 1.5 because it lives in the stomach
Trypsin
An enzyme with an ideal pH of 8 because it lives in the small intestine
Effects of temperature
- Reactions naturally increase as temp increases
2. With more, stronger collisions enzymes may become dismembered
Denaturation
The enzyme unfolding. Occurs when the amino acids start moving and more collisions in high heat.
0-40 c
Reaction rate doubles for every 10 increase
Above 40
Denaturation causes a level peak, then falls to 0.
Most enzymes peak temperature
40-50, and drop around 45-55
Corn enzymes
Peak at 30 and is harmed above that. Hot days are bad for corn
