Biosynthesis Flashcards
The energy released from energetically favourable reactions must be temporarily stored -> ho do cells do that?
- energy is stored as chemical bond energy in Activated carriers = small organic molecules that contain one or more energy-rich covalent bonds e.g. ATP, NADH, NADPH
- readily transferable chemical group OR readily transferable electrons => source of energy OR chemical group addition
How (in general terms) is the energy “transmitted to activated carriers?
Via the use of Coupled reaction = a process in which energetically favorable reaction is used to drove energetically unfavourable productions of activated carriers
- additionally the amount of heat released is reduced by the amount of transmitted energy
What does ATP stand for? How does it work?
ATP = adenosine 5-triphosphate
- synthesized in energetically unfavourable Phosphorylation reaction = addition of phosphate group to ADP (adenosine 5-diphosphate)
- when required -> ATP gives up the phosphate group Pi via energetically favourable hydrolysis to ADP
=> regenerated ADP is available for the new cycle
How in general does ATP help the cell (no details)? What could it, for instance, power?
By the means of hydrolysis it looses one phosphate group -> this can be attached to a different molecule = phosphorilation -> will drive the next reactions
- e.g. intracellular signaling pathways, activating substrates, exchange of chemical energy, pumps for transport , power of molecular motors
How is ATP involved in biosynthesis of 2 molecules?
We want this: A-H + B-OH => A-B + H2O (aka condensation reaction), however that is energetically unfavourable
BUT we may add hydrolysis of ATP and addition of the phosphate group which will force the reaction to happen (in 2 steps):
What are the most common electron carriers? What exactly do they carry? What happens to them after?
NADH = nicotinamide adenine dinucleotide
NADPH = nicotinamide adenine dinucleuotide phosphate
- both carry 2 high-energy electrons and proton H+ => which together forms H-
=> when hydryde ion is donated they become NAD+ and NADP+
How is NADH and NADPH used in chemical reactions?
- during catalytic reactions a hydryde ion is removed from a substrate and added to NADP+ to form NADPH ->substrate is oxidized and NADP+ reduced
-> hydride ion is the given up by NADPH in the next oxidation-reduction reaction (because the ring is more stable without it) -> NADPH is oxydized and substrate reduced -> NADP+
=> cycle can begin yet again
What is the difference between NADPH and NADH? Why would there be 2 similar carriers?
Both function as electron carriers BUT have different conformation -> can affect different sets of enzymes
- NADPH acts on enzymes catalyzing anabolic reactions (i.e. synthesizing biological molecules)
- NADH provides intermediate step in catabolic sequence of reactions producing ATP (by the means of oxidation of food molecules)
Additionally, their genesis from NAD+ and NADP+ occurs by different pathways -> cell can control their supply separately
=> NAD+ is kept high, while NADP+ low
Can you think of other groups carried by activated carriers?
Apart from phosphates, electrons and hydrogens -> acetyl g., carboxyl g., methyl g. glucose
- in these, the carried group is only a small portion of the entire molecule
How are polymers formed and destroyed? Which is energetically favourable?
Polymers are made from smaller subunits (monomers)
- linked by bonds facilitated through enzyme-catalyzed condensation reaction =>UNfavourable
- broken down by enzyme-catalyzed hydrolysis reactions => favourable
Nucleic acids, proteins, polysaccharides are formed by stepwise condensations that depend on ATP -> how come there isn’t a phosphate group added?
There are actually many intermediate steps involved in this formation
e.g. ATP via hydrolysis initially produces AMP and pyrophosphate (PPi) instead of ADP and Pi
What is enzyme-catalyzed reaction limited by?
The reaction rates might be limited by (1) the concentration of the substrate, e.g. how often a molecule of CO2 collides with the active site on the enzyme; (2) how many of these collisions are energetic enough to lead to a reaction; and (3) how fast the enzyme can release the products of the reaction and therefore be free to bind more CO2
What is the difference in mechanism of competitive and non-competitive inhibitor?
Competitive inhibitor acts on the same binding site of the substrate while non-competitive has a different binding site
How do competitive and non-competitive inhibitors impact the Lineweaver-Burke plot and the Michaelis menten curve?
Competitive I does NOT change Vmax because the substrates can still bind to other binding sites BUT it will take longer to achieve it - Kmax is increased (we’re increasing the concentration of the substrate)
Non-competitive I does NOT change the binding concentration of the substrate - Kmax the same, BUT does change their overall impact - Vmax decreased
