M2- Chapter 4 - Enzymes Flashcards
What is metabolism
The sum of all the different reactions and reaction pathways happening in a cell or an organism
What is Vmax
Enzymes can only increase the rates of reaction up to a point. This is called Vmax.
What is the specificity of an enzyme
Enzymes can only catalyse 1 reaction, and hence they only accept that one substrate.
What are enzymes
Biological catalysts
How do enzymes help molecules?
They lower the activation energy needed.
by:
- Lock and key hypothesis
- Induced Fit hypothesis
Lock and Key hypothesis
The active site is an area within the tertiary structure that has a shape that is complementary to the shape of the substrate. It creates an enzyme-substrate complex.
How does the lock and key hypothesis lower the activation energy
The substrate is held in such a way that atoms are close enough to react. The R-Groups create a temporary bonds between the substrate by the active site.
Induced Fit hypothesis
The idea that the active site actually changes shape slightly to fit the substrate.
The weak interactions between the substrate and the enzyme rapidly induces changes in the enzyme’s tertiary structure that strengthens the bonding and puts strain on the substrate molecule.
Hence, it weakens a particular bond in the substrate, lowering the activation energy.
What is an extracellular enzyme
They work outside the cells that make them.
How are nutrients usually found?
In the form of polymers (polymers and polysaccharides)
Examples of intracellular enzymes:
Catalase
Examples of intracellular enzymes:
Amylase and Trypsin
How does temperature affect enzymes
increase KE
increase particles moving faster
increase successful collisions
increase the rate of the reaction
What is the temperature coefficient (Q10)
How much the rate of a reaction increase with a 10 degrees rise in temperature. (Usually 2 for an enzyme-controlled reactions)
What happens when an enzyme denatures due to temperature
increase temperature increase vibration increase the bond strain and they break increase changing of tertiary structure active site changes
Enzymes in cold temperatures
they are more flexible structures, meaning they are less stable. This means small temperatures changes will denature them.
Enzymes in hot temperatures
They have more bonds (especially hydrogen and disulfide bonds). Hence, they are a lot more stable and resistant to changes in temperature.
A change in pH means
Change in H+ ion concentration
Increase H+ conc means
Low pH (acidic)
Decrease H+ conc means
High pH (alkaline)
Renaturation
Small changes with pH concentration can cause the active site to change, but if the pH is returned, the active site can go back to its original shape.
However, if the pH is significantly beyond the optimum temperature, the enzyme might denature permanently.
How does a change in pH affect the active site?
Hydrogen ions can interact with the polar and charged R-Groups, and hence change the tertiary structure of the enzymes.
Increasing Hydrogen ions means increase bonds breaking.
Increasing the substrate or enzyme concentration means what
The rate of the reaction will continue to increase till Vmax, and when one of the factors becomes a limiting factor.
What is an enzyme
A biological catalyst
They are proteins that speed up metabolic reactions
How to check the reliability of data
Repeat experiments
Find the mean or standard deviation
Identify any anomalous results
Compare results
How to measure the change in concentration as a reaction proceeds?
Take samples at a range of temperatures Remove samples Heat with Benedict’s solution Change to colour to brick red Remove precipitate and filter Calibrate using plain water Use a red filter Read the transmission Using a known concentration to transmission calibration curve Read off the concentration
Describe how an antibiotic- resistant population could develop
Mutation
Resistant ones survive
Alleles passed down to offspring
Carries over generations
Explain the induced-fit hypothesis of breaking molecules
What is the substrate? Substrate fits into active site Active site changes shape To fit the substrate better Gets more bonds Forms an ESC Puts strain on the molecule to break The activation energy is reduced Shape of active site changes again once the products have left
Explain how the an enzyme breaks down a substrate
The substrate is complimentary to the active site
Substrate enters the active site
The enzyme changes shape to fit the substrate
An ESC is formed
Straining of bonds
Substrate leaves the enzyme’s active site
cofactor
a non-protein substance that allows some enzymes to work
inorganic cofactors
they held the substrate bind to the enzymes, but they don’t directly participate
They aren’s used up at all.
Example of inorganic cofactors
Chlorine for amylase.
Coenzymes
Organic cofactors
They do participate in the reactions
They are constantly being changed and they act as carriers moving chemical groups that are continuously recycled.
What is a prosthetic group
A cofactor that is tightly bound to an enzyme
example of coenzymes
Vitamins
Example of a prosthetic group
Zn ions for carbonic anhydrous.
They are a permanent group of the enzyme’s active site.
Competitive inhibitors
They are very close and similar to the shape of the substrate but not identical.
No reaction occurs, the active site is only blocked.
Generally reversible
Non-competitive inhibitors
Completely different shape to the active site
But it joins the enzyme somewhere else (at an allosteric) and causes the active site to change.
So the reaction cannot go on.
Explain the graph for the types of inhibitors
Competitive ones reach the top of the plateau but they take more time.
Non-competitive ones don’t even reach the plateau, but they do reach their own plateau at the same rate.
Reversible reaction- inhibitors
Competitive inhibitors
There are weaker ions/ hydrogen bonds
Non-reversible reaction- inhibitors
Non-competitive inhibitors.
They have covalent bonding
Drugs
An antiviral drugs- reverse transcriptase inhibitor prevents viral DNA from replicating.
Penicillin inhibits transpeptidase, which forms the protein to synthesise bacterial cell walls.
Metabollic poisons
Cyanide- non-competitive inhibitors of cytochromec oxidase.
Arsenic- Non-competitive inhibitors of pyruvate dehydrogenase.
Malonate- competitve inhibitor of succinate dehydrogenase.
