| what is metabolism | the term used to describe the large number of integrated and complex biochemical reactions that occur in an organism |
| what are metabolic pathways? | integrated and controlled pathways of enzyme-catalysed reactions within a cell |
| what kind of steps/routes can metabolic pathways have? | reversible steps, irreversible steps and alternative routes |
| what can the reactions within metabolic pathways be? | anabolic
catabolic |
| what is an anabolic reaction | build up large molecules from small molecules and require energy |
| what is a catabolic reaction | break down large molecules into smaller molecules and release energy |
| what are the three types of protein molecules the membranes of cells or organelles contain? | protein pores
pumps
enzymes (they are embedded in membranes) |
| what do metabolic pathways rely on | molecules such as glucose getting into cells/organelles |
| what type of molecules do protein pore molecules transport | larger molecules/ions
they depend on protein pore molecules to allow them to diffuse across the membrane |
| what is the function of protein pump molecules | they transport molecules across membranes and often require energy provided by atp |
| label this diagram | 1 - pump
2 - protein pores
3 - enzyme |
| what are metabolic pathways controlled by | presence or absence of particular enzyme
regulation of the rate of reaction of key enzyme |
| what is induced fit | it occurs when the active site changes shape to better fit the substrate after the substrate binds
this change in shape of the enzymes active site facilitates the reaction by correctly orienting the reactants |
| what happens at the end of an induced fit reaction | the products have a low affinity for the active site and are released
the active site then resumes its normal shape and the enzyme is free to attach to more substrate molecules |
| what is the name given to the initial input of energy reactions need in order to take place | Ea - Activation energy |
| how does an enzyme lower the activation energy | by forming an enzyme-substrate complex that accelerates the rate of reaction.
They provide an alternative path for reactions allowing a smaller activation energy, which means reactions can take place at a lower temperature. |
| what must be done in order to ensure metabolic efficiency | number of enzyme molecules must be tightly controlled, as the number of enzyme catalysed reactions in a cell is enormous |
| name three ways in which regulation of enzyme activity can be achieved | control number of enzyme molecules actually present in the cell (usually achieved at the level of gene expression)
increase substrate concentration
inhibition (change of enzyme shape) |
| how does increasing substrate concentration affect enzyme activity | In general the activity of an enzyme shows a limiting factors curve when substrate concentration is altered |
| what is an inhibitor | a substance which slows down or prevents a particular reaction
(it reduces the activity of an enzyme) |
| what are the two types of inhibitors | competitive inhibitors
non competitive inhibitors |
| describe how a competitive inhibitor works | very similar shape to substrate
binds directly to the active site, preventing a substrate molecule from binding
causes a temporary blockage, meaning a proportion of active sites are temporarily unavailable
competitive inhibition can be reversed by increasing substrate concentration |
| describe how a non competitive inhibitor works | does not bind to the active site, binds to an area of the enzyme away form the active site
shape of the active site therefore changes, preventing the substrate from binding
more permanent inhibition of the active site, meaning substrates cant bind
non competitive inhibition cannot be reversed by increasing substrate concentration |
| what is feedback inhibition/ end product inhibition | occurs when the ed product in the metabolic pathway reaches a critical condition. The end product then inhibits an earlier enzyme, blocking the pathway, and so prevents further synthesis of the end product. |
