Unit 1- Enzymes + factors effecting enzymes Flashcards
What are enzymes?
Proteins which speed up the rate of chemical reactions
How do enzymes speed up chemical reactions?
By acting as a biological catalyst
What type of reactions do they catalyse?
-Metabolic
Both:
-cellular level (eg. respiration)
-the organism as a whole (eg. digestion in mammals)
What do ezymes effect ?
-Function and structure
Where can enzyme action take place?
-Intracellular (inside the cell)
-Extracellular (outside the cell)
What is the active site?
The part of the enzyme where the substrate molecules bind to
What are substrate molecules?
The substance that the enzyme interacts with
Why are enzymes highly specific?
Due to their tertiary structure
Define activation energy
The minimum amount of energy needed to be supplied to the chemicals before a reaction can start
How is activation energy usually supplied?
As heat
How do enzymes speed up the rate of reaction?
-They lower the amount of activation energy needed
-Often make reactions happen at a lower temperature than they would without an enzyme
Why do enzyme-substrate complexes lower activation energy?
-If two substrate molecules need to be joined, being attached to the enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily
-If the enzyme is catalysing a breakdown reaction, fitting into the active site puts strain on the bonds in the substrate so the substrate molecule breaks up more aesily
Define catalyst
A substance which speeds up a chemical reaction without being used up itself
Describe the lock and key theory
-The substrate fits into the active site the same way a key fits in a lock
-The active site and substrate are complementary to each other
-Enzyme-substrate complex is formed
-Enzyme is unchanged after reaction
Describe the induced fit model
-The substrate needs to be the right shape for the active site and needs to make the active site change into the right shape
-After the products are released the active site returns to its original shape and binds to the next substrate molecule
Explain how enzymes can catalyse synthesis reactions
-Two substrate molecules go into the active site
-Bind to form enzyme-substrate compex
-One product produced
Explain how enzymes can break down substrates
-One substrate molecule goes into the active site
-Enzyme substrate complex formed ]
-2 products produced
What are enzyme properties such as active sites related to?
-Their tertiary structure
Why may a reaction not be catalysed?
-If the active site and substrate do not have complementary shape
-The substrate can not fit into the active site
-As the enzyme’s active site is determined by the tertiary structure
What happens if the tertiary structure of a protein is altered in any way?
-The shape of the active site will change
-The substrate will not be complementary to the active site
-No enzyme-substrate complex formed
-Enzyme no longer able to carry out its function
Why may the tertiary structure of an enzyme change?
-Ph
-Temprature
Why else may the tertiary structure be altered?
-The primary structure (amino acid sequence) is determined by a gene
-A mutation can occur in that gene
How can we measure enzyme activity?
How fast the product is made- different molecules are present at the end of a chemical reaction than there are at the beginning, by measuring the amount of end product at different points in the experiment the rate of reaction can be calculated
How fast the substrate is broken down- to produce end products, substrate molecules have to be used up, by measuring the amount of substrate molecules left at different times in a reaction rate of reaction can be calculated
Rate of reaction 1.___ when tempraturate increases
- Increases
How does temperature increase the rate of reaction?
-More heat= more kinetic energy
-More kinetic energy molecules moving faster
-Substrate molecules more likely to collide with active sites
-Energy of collisions increase
-Higher energy collisions = more chance for successful collisions
Why does the reaction stop if the temperature is too high?
-Rise in temperature makes molecules vibrate more
-If the temp is too high then the vibration can make bonds that hold the enzymes’ shape break
-The active site changes shape and the enzyme substrate no longer fits together
-Enzyme denatures
-No longer functions as a catalyst
Is denaturation usually permanent?
Yes
What is the optimum temprature for human enzymes?
37c
What pH do most human enzymes work best at?
7 (neutral)
What happens if the Ph is below/above optimum?
-The H+ and OH- ions found in acids and alkalis can disrupt the ionic/hydrogen bonds that hold the enzyme tertiary structure in place
-Enzyme becomes denatured, active site changes shape
-
The higher the 1.____ _____ the faster the reaction
- Substrate concentration
How does substrate concentrationj effect rate of reaction?
-More substrate molecules= more collisions between substrate and enzyme, more likely active sites will be occupied
What happens after the saturation point?
There are too many substrate molecules and the enzymes have enough to cope with as all the active sites are full so adding more will not make a difference
The more 1_____ _______ there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme-substrate complex
- Enzyme molecules
What happens when the amount of substrate is limited?
More than enough enzyme molecules for the number of substrates so adding more enzymes has no effect
How do competitive inhibitors prevent enzyme activity?
-They have a similar shape to the substrate
-They compete with the substrate molecules to bind with the active site
-They block the active site so no substrate molecules can fit in
What does the enzyme inhibition depend on?
-The relative concentrations of the inhibitor or substrate
-If there is a high concentration of the inhibitor the inhibtor will take up most of the active sites
-If there is a higher concentration of the substrate they will take up most of the active sites
Increasing the concentration of 1____ will increase the rate of reaction (up to a point)
- Substrate
Where do non-competitive inhibitors bind to? What does this cause?
-The enzyme away from its active site
-The active site changes shape so the substrate molecules can no longer bind to it
Increasing the concentration of substrate 1____ make a difference
- Will not
