Chapter 3 + 4 Flashcards
Cofactors
non-protein additional component that is essential for the normal functioning of some enzymes
Examples of cofactors
calcium, zinc, potassium, magnesium.
Coenzyme
organic compound that acts with an enzyme to alter the rate of a reaction.
Important thing to remember about cofactors
if it is organic e.g. vitamin, then it is a coenzyme
Antioxidant
molecule that prevents the oxidation of other molecules that is synthesised in our body
What do antioxidants prevent
tissue damage due to oxidative reactions
Coenzyme Q10
needed for antioxidant (lipid soluble), used aerobic respiration in mitochondria
Role of Coenzyme Q10
improves energy production, enhances muscle function, reduced lipid oxidation
Enzymes
biological catalyst that increase the rate of a reaction by lowering the activation energy
How enzymes work
reduce the activation energy required through weakening bonds in substrates, which happens when the enzyme puts stress on the chemical bonds
Activation energy
the minimum amount of energy required for a reaction to take place
A chemical reaction can only occur if
there is sufficient energy to begin the reaction
In the absence of enzymes the activation energy is…
high
Enzymes only bind to
substrates with a complementary shape to active site
Term when substrate binds in correct way to enzyme
it binds in the correct orientation
What are enzymes made up of
protein and RNA
Enzymes can be either….
intracellular or extracellular
Enzymes are highly….
specific in their action
Most enzymes have the suffix…
“ase”
Exceptions examples
pepsin, trypsin
Enzymes act best at their…
optimal conditions e.g. temp, pH
What is it called when enzymes combine with substrates
enzyme-substrate complex
Are enzymes used up in the reaction
no, they are available for reuse
Substrate
compound upon which an enzyme acts
Products
the compounds obtained as a result of enzyme action.
Lock and key theory
Lock and key model - the specific shape of the active site fits exactly the shape of the substrate it will act on, hence will only act on that substrate.
Induced fit theory
the specific shape of the active site of the enzyme varies slightly from that of the substrate and the two fit only after contact when the substrate induces a complementary shape at the active site of the enzyme.
Factors that affect rates of enzyme reactions (5)
temperature, pH, enzyme concentration, substrate concentration, inhibition
If temperature is too hot
is (permanently) denatured, active sites are destroyed, enzyme-substrate complexes can no longer form, therefore reaction rates fall
How does temperature denature enzyme
hydrogen bonds break
Denatured
the shape of the active site being changed meaning that the enzyme can no longer bind to its complementary substrate hence the function of the enzyme is lost.
If temperature is too cold
enzymes and substrate molecules lose kinetic energy, so collisions between these molecules occur less often, enzyme-substrate complexes are less likely to form, therefore reaction rates fall. The effects are fully reversible with the addition of heat.
Can some enzymes survive in extremely hot temperatures
yes, an example is thermophilic bacteria in the hot springs
If pH is not optimal
changes the shape of active site so is denatured, enzyme-substrate complexes can no longer form, therefore reaction rates fall
Enzyme concentration
if solution has enough enzymes and enzymes are added then no affect, if not enough enzymes and more are added then rate rapidly increases, if enzymes are taken from too many then no effect, if taken from normal then rate decreases
Substrate concentration
if there is more enzymes than needed and substrate is added then rate increases, if there is not enough enzymes and substrate is added then rate decreases.
Two types of inhibition
competitive, non-competitive
Competitive inhibition
an enzyme inhibitor which binds with the active site of an enzyme and hence prevents normal action of the enzyme. An example of the use if competitive inhibition is alcohol treatment of a person suffering from poisoning by ethylene glycol.
Non-competitive inhibitor
an enzyme inhibitor which binds to a site on an enzyme other than the active site. In so doing, it alters the shape of the active site, preventing the binding by the normal substrate. For example, the action of heavy metals, such as arsenic, mercury and lead, on several enzymes.
Heterotrophic organisms
organisms that cannot make their own food and must ingest or absorb organic material from their environment.
Heterotrophs are also known as
consumers
Autotrophic organisms
organisms that, given a source of energy, can produce its own food from simple inorganic substances. Are generally photosynthetic or chemosynthetic.
Autotrophs are also known as
producers
Why do we need energy in cells
to drive metabolic reactions
E.g. of how energy is used
protein synthesis, protein carriers involved in active transport, contraction of muscle cells
