C1.1 Enzymes and Metabolism Flashcards
What are enzymes?
Catalysts and Proteins. They speed up reactions.
Where are enzymes made?
In the ribosomes of a cell
What do enzymes do?
Lower the activation energy for a reaction to take place.
What is metabolism?
The web of all the enzyme catalysed reactions in a cell or organism.
What group of reactions are enzymes always a part of?
ALL Cell metabolic reactions
What is a metabolic pathway?
The series of chemical reactions within a cell
What do anabolic reactions do?
Synthesize complex molecules from simple molecules
Example of an anabolic reaction
The formation of macromolecules from monomers via condensation reactions.
What do anabolic steroids build?
Protein and muscle
What do catabolic reactions do?
Break down complex molecules into simpler molecules
Anabolic reactions summary
- Build macromolecules from monomers by condensation reactions
- Release water
- Require energy
Catabolic Reactions summary
- Break macromolecules into monomers by hydrolysis
- Require water
- Release energy
What does the active site do?
It brings the reactive part of molecules together (binds the reactants) and catalyses the reaction
What type of bonds are responsible for the structure of enzymes?
Intramolecular
Enzyme-substrate complex
Formed temporarily when enzymes and their substrates bind.
Induced fit
The changes in the 3d shape of enzymes and their substrates after the enzyme-substrate complex is formed
How does an enzyme catalyse the reaction?
- Bond angles and lengths change in the enzyme and bound substrate
- This make the chemical bonds i the substrate strained
- They break and form new bonds
- The new product is now formed and can detach from the active site
What is the role of enzymes in living cells?
To catalyse (speed up) reactions that would otherwise be too slow to sustain life.
Collision Theory
- Particles must collide
- Must have the correct orientation
- Must collide with sufficient energy- (activation energy)
What will increase the rate of reaction?
Any factor that increases the number of collisions or the energy they collide with. Eg inc conc of enzyme or reactants, inc surface area, inc temp.
Additional considerations of collision theory in the context of enzymes.
- Generally substrates move to enzymes as they are smaller, but when the substrates are too large the enzymes will move to the substrates
- Many enzyme reactions occur in the cytoplasm (liquid environment) the enzymes and substrates are dissolved in the water and can move freely
- Some enzymes are immobilized as they are embedded in membranes, so substates must move to them
Enzyme action summary equation
E+S<–>ES<–>E+P
S- substrate
E- Enzyme
P- Product
What does “enzymes are specific” mean?
They can usually only catalyse one reaction
How do specific enzymes and substrates know to bind to each other?
They are chemically attracted to each other
What happens when an enzyme is denatured?
Its active site changes shape and can no longer bind to substrates or catalyse reactions
What factors will affect enzyme activity?
Temp, pH and substrate concentration
Effect of temp on enzymatic activity
- Low temp- enzyme rxns are slow due to few collisions
- As temp rises action speeds up until it reaches an optimum (diff for each enzyme)
- After the optimum the enzyme is denatured and speed drops off quickly
Effect of pH on enzymatic activity
- The optimum ph is specific for each enzyme but for most enzymes is 5-9
- Changes in pH affect the charged amino acids in the active site which interact with the charged areas on substrates
- If the charges are changed the enzyme and substrate cannot bind effectively- rate of rxn dec
What happens to the charges on amino acids when pH is decreased?
H+ ions (protons) are added making the charge more positive
What happens to the charges on amino acids when pH is increased?
OH- ions are added making the charge more negative
Effect of substrate conc on enzymatic activity
As substrate conc is increased the rate of reaction increases. This is bc more and more substrate molecules are able to collide with the active site of the enzyme.
Why can the rate of reaction reach a maximum when the substrate conc is increased?
The enzymes are working as fast as possible, every enzymes active site is occupied with a substrate and there is still a surplus of substrate molecules
How is rate of reaction measured?
By measuring either the loss of reactants (substrates) or the gain in products over time.
What is the enzyme that breaks down hydrogen peroxide?
Catalase
Activation energy
The minimum energy needed to break down the bonds in the reactants so the reaction can proceed. (energy required to initiate a chemical rxn)
How do enzymes lower the activation energy?
By holding the substrate in a way that chemical bond breaking and bond forming take place more readily.
Extracellularly
The spaces around cells
How much food (in%) does an organism convert to ATP?
35%, the remaining is transformed to heat energy
Endotherms
Organisms that maintain a constant internal body temp. Eg mamals and birds
What are the two types of metabolic pathways
Linear and Cyclical
What is formed in linear metabolic pathways?
a final product
What is formed in cyclical metabolic pathways?
The same substrate that you started with. (make things along the way)
Where do non-competitive inhibitors bond?
The allosteric site
Where do competitive inhibitors bind?
The active site
What happens when a non-competitive inhibitor binds to the allosteric site?
The shape of the active site changes and can no longer catalyse the reaction (or do so at a slower rate), even if the substrate is still able to bind
Is non-competitive inhibiting reversible?
Yes
What is end product inhibition?
- A form of negative feedback in metabolic pathways.
- The final product of a reaction sequence inhibits an enzyme involved earlier in the process.
- This prevents overproduction and conserves energy by stopping the pathway when enough product is made.
What role does penicillin play in bacterial metabolism?
Penicillin acts as a competitive inhibitor of growth factors required for bacterial metabolism.
How does penicillin inhibit bacterial reproduction?
Penicillin binds irreversibly to the active site of transpeptidases, which are enzymes that catalyze the last step in bacterial cell wall biosynthesis. This prevents bacteria from reproducing.
What enzyme is targeted by penicillin in bacteria?
Penicillin targets transpeptidases, the enzymes responsible for the final step of bacterial cell wall biosynthesis.
What happens when transpeptidases are inhibited by penicillin?
Inhibition of transpeptidases prevents the synthesis of bacterial cell walls, leading to an inability of the bacteria to reproduce.
Why have some bacteria become resistant to penicillin?
Bacterial mutations in the transpeptidase enzymes can change the active site, preventing penicillin from binding and making the bacteria resistant.
What is the relationship between bacterial mutations and penicillin resistance?
Mutations in the transpeptidase enzyme can alter its active site, rendering penicillin ineffective in binding, which leads to antibiotic resistance.
