c1.1 enzymes & metabolism Flashcards
what is metabolism?
metabolism is the sum of all chemical processes that occur within a living organism in order to maintain life. it is the web of all enzyme-catalysed reactions that occur within a cell or organism.
metabolic reactions serve two functions:
- they provide a source of energy or simple molecules for cellular processes
- they enable the synthesis and assimilation of new materials for use within the cell.
what is an enzyme?
enzymes are biological catalysts - they speed up metabolic reactions but aren’t used up.
why does all life depend on enzymes?
reactions such as oxidation do occur naturally, however living organisms need enzymes to help them happen quickly.
human cells contain around 1300 different enzymes. all enzymes are specific to their substrate. as such, every step of a metabolic pathway that generates a new intermediate compound needs a new enzyme.
each step along the pathway changes the energy level by a small amount. so reactions with large energy changes, such as respiration, need many steps.
what is catabolism?
catabolism is cellular reactions which break down molecules to release energy and/or simple molecules. examples include hydrolysis of macromolecules into monomers in digestion and oxidation of substrates in respiration.
what is anabolism?
anabolism is reactions that result in the formation of complex molecules, often storing energy in chemical bonds. examples include the formation of macromolecules from monomers by condensation reactions including protein synthesis, glycogen formation and photosynthesis.
what are the consequences of a mutation?
a mutation is a change in the sequence of bases in DNA. this results in different codon triplets and so we get a different sequence of amino acids, meaning we get a different shaped protein (or enzyme).
what is denaturation?
denaturation is a change in the shape of the active site so that the substrate does not fit and the reaction will stop.
the active sit is only one small part of a much larger globular protein structure containing thousands of amino acids, but the shape in this region is critical for the correct fit.
what is the induced fit model?
the induced fit model suggests that as the substrate enters the active site, it causes a conformational change in the protein structure. this movement either brings the reaction molecules together (anabolism) or stretches and weakens the bonds (catabolism).
what are immobilised enzymes?
enzymes are often used in industrial processes. they are expensive to buy as they can only be produced by living organisms.
by immobilising enzymes it prevents them from being lost. it also means that liquid products (such as lactose free milk) are not contaminated by the enzyme. immobilised enzymes are less likely to be denatured by heat and so processes can run hotter.
we can also immobilise substrates. this allows us to investigate enzyme action or use them in medical testing.
how are immobilised enzymes used in cells?
within cells, many of the enzymes involved in regulating metabolic processes are embedded in membranes such as the cristae of mitochondria or the thylakoids of chloroplasts.
the organelle can ensure the enzymes are located where internal processes that maximise the concentration gradients of the necessary substrates or supplies of ATP so that the reactions happen at their fastest rate.
explain the graph of enzyme activity against temperature
- as temperature increases, the particles have more KE. there are more successful collisions between enzyme and substrate. substrate binds more often with active site.
- optimum: temperature at which there is the fastest rate.
- denaturing of enzymes, substrate no longer complementary and reaction stops.
explain the graph of enzyme activity against pH
- denaturing at low pH, substrate no longer complementary and reaction stops.
- optimum: pH at which there is the fastest rate.
- denaturing at high pH, substrate no longer complementary and reaction stops.
explain the graph of enzyme activity against substrate concentration
- as concentration increases, there are more successful collisions between the substrate and active site.
- plateaus: all enzyme active sites are full and so any additional substrate has nowhere to bind. this is known as the saturation point.
