Metabolism Flashcards
What element is central to energy intensive steps in metabolism?
Carbon.
What three reasons mean that decarboxylation has a very negative delta G?
- Very stable.
- Escapes the reaction site as a gas.
- Increases entropy.
Name one example of a decarboxylation reaction and the enzyme that catalyses it.
Pyruvate + CO2 – Oxaloacetate
Pyruvate carboxylase.
Does decarboxylation require energy?
Yes.
What are three sources of hydrogen?
H20, NH3, NH4+.
What are two sources of oxygen?
H20, CO2.
Name an example of a biosynthetic reaction that uses molecular oxygen.
Synthesis of tyrosine from phenylanaline. The oxidation part of the reaction is favourable while the addition of oxygen is unfavourable.
Oxygen is a stable gas. What does this mean in terms of energetics?
That the addition of oxygenic unfavourable and requires energy.
Do biosynthetic reactions use NADPH or NADH?
NADPH.
What ‘high energy bond’ does acetyl coA contain?
Thioester.
Name three occasions in nature where sulphur plays a key role.
- Iron sulphur clusters.
- Protein folding.
- An energy store in some microorganisms.
When will disulphide bonds not be stable?
In reducing conditions.
S-S are strong covalent bonds that can add a large amount of stability to structures. How do they differ from C-C bonds?
They allow some flexibility as they require less energy to make and break.
Why can sulphur coordinate iron?
Has extra orbitals to coordinate metals.
What is acetyl coA a carrier for?
C2.
Why can acetyl coA be a carrier for C2?
It has a thioester bond which are high energy and have less resonance stability than oxygen esters. When this bond is broken it provides enough energy for ne bonds to be made.
What do the evolution theories say H2S used to be and subsequently produce ?
An early reducing molecule producing pyrites (FeS2) on the surface of volcanic rocks.
Where is sulphur thought to have come from for it to be found in biological compounds such as enzymes?
Through the use of H2S as a reducing molecule.
In regards to sulphur why are higher organisms completely dependant on lower organisms?
As only lower organisms can fix sulphur.
How do higher organisms obtain sulphur?
Through their diet.
How can lower organisms turn sulphur into a organic metabolite?
Serine is activated by acetyl coA and captures S from H2S to produce cysteine.
What enzymes allows for the production of cysteine from serine via the use of H2S?
Cysteine synthase.
Where do biosynthetic precursors often come from?
Central catabolic pathways.
What compound in glycolysis produces serine ?
3PGA.