Exam 3: Energy of Phosphorylation and Redox Reactions Flashcards
The actual free-energy change in a reaction depends on standard free energy and which other factor?
The actual concentrations of the products and reactants.
What is the standard free-energy change for the hydrolysis of ATP?
-30.5 kJ/mol.
The free-energy change is _____ favorable if the [ATP]_reactants:[ATP]_products exceeds that of the standard [ATP] ratio.
a. more
b. less
a. more
What makes the free-energy change less favorable when [ATP] is low?
There are fewer molecules to drive the reaction and ΔG also becomes less negative.
Cellular ATP is typically kept ______ than equilibrium concentration.
a. higher
b. lower
a. higher
The hydrolysis of a phosphate generates more or less free energy than phosphorylating a molecule?
The hydrolysis of a phosphate generates more free energy.
What are the two steps of the activation process?
1st. A phosphate is bound to a substrate or enzyme.
2nd. The phosphate is displaced.
_TP and _TP can be hydrolyzed directly to provide energy for movement.
ATP and GTP.
True or false, proteins can undergo conformational changes when they are phosphorylated.
True.
True or false, proteins can undergo a change in activity when they are phosphorylated.
True.
What is required in order for two ADP to react to produce an ATP and AMP ?
[ATP] must be low.
Why will the cell react two ADP to create an ATP and AMP?
Because in order for ATP reactions to move forward with a complimentary free-energy change, [ATP] must be kept high.
What are the four main types of Redox Reactions?
- Where a single electron is transferred with or without stimulus from proton transfer.
- Where there is a transfer of a hydride ion (H^2-).
- Where electrons transfer to a molecular oxygen.
- Where both molecular oxygens from an O_2 are incorporated into a substrate.
In the transferring of a single electron, name 4 cofactors that are often required for the redox reaction to occur.
- Hemes
- Iron-sulfur proteins
- Copper ions
- Flavin nucleotides (FMN or FAD)
In reactions with a transfer of a hydride ion, which two positively charged molecules are usually involved? What do they become with the donation of the electron from the hydride ion?
NAD+ and NADP+ become NADH and NADPH.
In reactions that transfer electrons to a molecular oxygen, the reactions are catalyzed by enzymes called ________.
oxidases.
In reactions where both molecular oxygen atoms of an O_2 are incorporated into a substrate, the reactions are catalyzed by enzymes called ________.
oxygenases.
_______ organic molecules serve as fuels.
a. Reduced
b. Oxidized
a. Reduced
This is because the stripping of their electrons can be used to continue or initiate a reaction.
True or false, the exchange of electrons or pairs of electron are typically partnered with the exchanging of protons. Why or why not?
True, as this helps maintain a balance of charge.
In reactions with dehydrogenases, the reactions proceed with the transfer of a ______ and then a ______.
…a proton and then a hydride.
The combination of the oxidized and reduced forms of a molecule is called a __________________.
…conjugate redox pair.
Define the standard reduction potential of a chemical species and which units it is defined in.
The standard reduction potential is the tendency for the chemical species to be reduced at standard conditions and is measured in volts.
Does a more positive value or a more negative value in a reduction potential indicate that a chemical species is more likely to be reduced?
A more positive reduction potential indicates that a species is more likely to be reduced.
What does the variable E represent?
What conditions does ∆E*’ assume?
E represents the reduction potential of a chemical species.
∆E*’ assume a pH of 7 and concentrations of 1M.
True or false: coenzymes can dissociate from the enzyme after the reaction and react somewhere else.
True.
NADPH is usually used to ______ other molecules.
a. reduce
b. oxidize
a. reduce
True or false: flavin cofactors (FAD+) only allows for single electron transfers.
False, flavin cofactors allow for both single and double electron transfers.
