8.1 : Metabolism Flashcards
what are metabolites/intermediates?
the molecules involved in metabolism
what is anabolism & example?
the synthesis of complex molecules from simpler ones with the storage of energy. (energy-requiring = endergonic)
- -> e.g. photosynthesis is an anabolic process ( simple to complex)
- -> e.g. polysaccharides, proteins, lipids, hormones, etc.
what is catabolism & example?
the breakdown of larger molecules to simpler ones, releasing energy. (exergonic)
- ->e.g. cellular respiration is a catabolic process (complex to simple)
- ->e.g. inorganic molecules (CO2, H20, ions, etc)
what is ATP?
the energy currency linking endergonic & exergonic reactions.
what type of reaction is ATP to ADP + Pi?
a hydrolysis reaction = catabolic reaction –> breaking it down to a simpler molecule.
what type of reaction is ADP + Pi to ATP?
a condensation reaction = anabolic reaction –> building it up to a more complex molecule.
what is metabolism?
a series of continuous reactions in which the product of one reaction is an intermediate of the next.
(intermediate - used to make the product)
what are the two types of metabolic pathways?
- straight chains (linear sequences)
- cyclic processes.
- branched.
what determines the way in which a branched metabolic pathway splits?
the amount of enzymes present in each direction –> chain will split in direction that has the most enzymes.
an example of a branched metabolic reaction/pathway?
glucose –> activated by enzyme –> enters blood stream used for energy in respiration…
–>takes part in glycolysis
OR
–> is stored in the form of glycogen in the liver –> activated by insulin.
how is the enzyme-substrate complex formed?
substrate binds to enzyme at active site –> enzyme-substrate complex (short lived & unstable) formed at transition state.
–> after it is formed –> the product is formed (energy released when substrate becomes product) & enzyme is not used up –> substrate & enzyme (unchanged) are released –> substrate will have a different shape due to chemical reactions that have occurred in active site.
what is the transition state?
a short period in which the potential energy is at its highest where the molecule is no longer only a substrate but not yet a product & when the enzyme-substrate complex is formed.
what is the active site?
part of enzyme where a substrate fits and binds –> site of catalytic activity.
what occurs when the substrate becomes the product?
(small amount of energy needed to bring about this reaction)
–> bonds break / weaken in the substrate –> brining about the transitional state –> enzyme-substrate complex formed –> then substrate turns into product –> energy that is put in for this to occur = activation energy.
what is activation energy & how do enzymes influence this?
a small but significant energy barrier that has to be overcome before the reaction can occur = exergonic (energy released when reaction takes place).
- enzymes lower the amount of activation energy –> reaction occurs faster.
what happens to the activation energy once the substrate is in contact with an enzyme?
it decreases –> less energy is required for the reaction to begin –> more chance of reaction going faster & continuing
what do enzyme inhibitors do?
inhibitors lower the rate of a reaction & enzyme inhibitors disable the work and function of enzymes (doesn’t function properly) –> large amount of activation energy needs to be overcome for the reaction to begin (lower reaction rate)
what is competitive inhibition? Is it reversible? How?
- molecules that sufficiently resemble the substrate in shape and compete with a substrate molecule to occupy the active site –> binds to active site
- reversible –> add enough substrate (more than inhibitor) –> most enzymes present will be occupied by substrate molecule.
what is the enzyme that catalyses the reaction between CO2 and NADP in photosynthesis? What is its competitive inhibitor?
- RuBisCo (Ribulose Biphosphate Carboxylase)
- competitively inhibited by oxygen in chloroplasts;
what is non-competitive inhibition? Is it reversible? Why?
- molecule that binds to the enzyme in another location besides the active site, but partly blocks access for the substrate to attach or changes the shape of the active site.
- irreversible if the active shape changes site as the enzyme will never go back to its original shape –> substrate will never bind.
explain why the shape of globular proteins that are enzymes is important in enzyme action.
globular proteins acting as enzymes –> must be folded such that their active sites are in the correct direction (orientation) and conformation to interact with substrates.
what are allosteric activators?
substances that activate the reaction a bit more
–> binding to them –> temporarily stabilises the enzyme
what are allosteric inhibitors?
substance that inhibit a reaction a bit –> ‘fine-tuning’-doesn’t completely inhibit –> only a little to find balance = homeostasis
–> binding to them –> changes enzyme shape to an inactive form.
what is negative feedback? what is an example of this?
- an opposite response to a stimulus (creating the opposite reaction).
- end product inhibition
