3.1.4.2 many proteins are enzymes Flashcards
3.1.4.2 many proteins are enzymes
what is the definition of :
metabolism
All of the enzyme controlled reactions (anabolic and catabolic) that take place in an organism
what is the definition of :
Anabolic reaction
One that build up molecules
what is the definition of :
Catabolic reaction
One that breaks down molecules
what is the definition of :
Catalyst:
A substance that modifies and increases the rate of reaction without being used up or changed
what is the definition of :
Activation energy:
The energy required to start a reaction - to break existing bonds so new ones can be formed
what is the definition of :
Enzyme
A biological catalyst that controls metabolism. Highly specific. Cannot make reactions happen that would not otherwise occur. Cannot change the amount of product. Can be re used
what is the definition of :
Substrate:
The reactant(s) that fit into the active site of the enzyme
what is the definition of :
Active site:
The region of the enzyme (a group of amino acids) into which the substrate fits and binds
what is the definition of :
Intra/extra cellular:
Enzymes can act inside or outside of cells
what is the definition of :
Metabolic pathway:
A Sequence of enzyme controlled reactions
what is the definition of :
Denatured
The point at which an enzyme no longer functions
as a catalyst
how are enzyme substrate complexes held together
Enzyme substrate complex held together by weak non covalent interactions (H, ionic, hydrophobic).
waht are the three conditions for a chemical reaction to take place
- The reactant molecules must collide with sufficient energy to alter the arrangement of their atoms to form products.
2.The energy of the products must be lower than that of the reactants
3.Activation energy must be supplied, often in the form of heat.
how do enzymes lower activation energy
By putting stress on the bonds within a molecule
Or by holding molecules closer together
.
This increases the chances of a reaction, and so lowers the energy required to begin it.
Alternatively the enzyme can make the local conditions inside the active site quite different from those outside (pH, water concentration, charge for example) so that the reaction is more likely to happen.
what are the two main assumed moddels for enzymes
the lock and key moddel
The Induced-fit hypothesis
describe what the lock and key model hypothesesis
Lock-and-key hypothesis assumes the active site of an enzyme is rigid in its shape
describe what The Induced-fit hypothesis
The Induced-fit hypothesis suggests the active site is flexible and only assumes its catalytic conformation after the substrate molecules bind to the site. In other words the enzyme has a certain general shape that alters slightly to accommodate the substrate placing strain on the substrate molecule.
The induced fit model helps to explain why enzymes are so specific and only bond to one particular substrate. The substrate doesn’t only have to fit the active site, it has to make the active site change in the right way as well.
what factors effect enzyme activity
Temperature
pH
Substrate Concentration
Enzyme Concentration
how does tempreature effect enzymes
Generally the rate doubles for each 10 degrees C rise until the optimum is reached, usually 40 degrees C in humans.
Low temps can inactivate the enzymes due to zero KE of molecules (reversible)
But most are denatured between 50 and 70 degrees C (irreversible)
Exposure time is important
how does pH effect enzymes
Extremes of pH denature enzymes by breaking ionic bonds and hydrogen bonds that stabilise tertiary structure (non reversible)
Less extreme changes can inactivate enzyme (reversible)
pH fluctuations inside organisms are usually small, this means that they are far more likely to reduce an enzyme’s activity than to denature it.
why do bonds break and how does the active site change
The arrangement of the active site is partly determined by the hydrogen and ionic bonds between -NH2 and -COOH groups that make up the enzyme. The change in H+ ions affects this bonding, causing the active site to change shape.
At low pH (<7) the NH3+ group will not be affected but the COO- will pick up a H ion. Ionic bonds can no longer form between enzyme and substrate.
pH > 7, there are insufficient H ions so that
NH2 cannot become NH3+
why is it essential to use buffers in experiments involving proteins
In enzyme experiments it is essential to use buffers and controls.]
Buffers maintain a constant pH. If acid is added, the buffer ‘soaks up’ the hydrogen ions.
Controls are duplicate experiments, identical in every aspect to the experiment, except that the enzyme is boiled and cooled to denature it and thus cannot affect the DV.
what are competative and non-competative inhibitors
Competitive inhibitors that bind to the active site of the enzyme., they compeate with subtrates for the active site
Non competitive inhibitors that bind to the enzyme at a position other than the active site (alloteric site) they change the shape of the active site , preventing the subtrate from binding
competitive inhibitor vs non-competative inhibitor :
shape of molecule
comp :
similar to substrate
non-comp
different to substrate
competitive inhibitor vs non-competative inhibitor :
site on enzyme
comp
active site
non-comp
allosteric site
competitive inhibitor vs non-competative inhibitor :
effect of increasing inhibitor conc.
comp
may outcompete substrate and lower rate of reaction
non-comp
decreases the reaction as more enzyme molecules are made inactive
competitive inhibitor vs non-competative inhibitor :
effect of increasing substrate conc.
comp
may out compete the competitive inhibitor and the rate can increase
non-comp
no effect on rate as the active site will have been changed by non competitive Inhibitor
what are metabolic pathways
A metabolic pathway is a series of reactions in which each step is catalysed by an enzyme. Cells have evolved to use the products of their own reactions for feedback inhibition of enzyme activity. Feedback inhibition involves the use of a reaction product to regulate its own further production
info card (summarise after reading this info)
Pharmaceutical Drugs:
Understanding how enzymes work and how they can be regulated is a key principle behind the development of many of the pharmaceutical drugs.
Statins are a group of medicines used to control blood cholesterol.
The end product of a metabolic pathway known as the mevalonate pathway, produces cholesterol.
How do statins work to reduce cholesterol?
