BIOMG 3350 Que &Answ | 2024 Review| With correct
answers
What is the most important thing change in Gibbs free energy tells us? What does a
negative value mean and what does a positive value mean? ** answer** how
spontaneous a reaction is
negative delta G = spontaneous, energy is released, exergonic
positive delta G = non-spontaneous, energy is consumed, endergonic
what does enthalpy represent? what does it mean when it's positive vs negative? **
answer** delta H is change in enthalpy, which is the heat content of the reacting
system.
It reflects the number and kinds of bonds in the reactants and products.
When delta H is negative, the reaction releases heat and is exothermic
When delta H is positive, the reaction absorbs heat and is endothermic
what is entropy? what does it mean when it's positive vs negative? ** answer** delta S
is change in entropy, which is a quantity describing the level of disorder of a system
When delta S is negative, the reactants are more disordered than the product (requires
input of energy)
When delta S is positive, the reactants are less disordered than the product (does not
require input of energy)
Based on the Gibbs free energy equation, what factors make it more likely for a reaction
to be spontaneous and what factors make it more likely for a reaction to be non-
spontaneous? ** answer** G = H - TS
Spontaneous (-G) = positive S
Non-spontaneous (+G) = negative S
,What type of information does the equilibrium constant K tell us? What is the
relationship between the equilibrium constant and Gibbs free energy? ** answer** the
ratio of products to reactant
If K > 1, there is more product than reactant, so this reaction seems to be spontaneous,
thus delta G is negative
If K < 1, there is more reactant than prouct, so this reaction does not seem to be
spontaneous, thus delta G is positive
What does it mean when change in G = 0? ** answer** equilibrium = death
What are the four components of amino acids? ** answer** carboxyl group, amino
group, hyrogen atom, R group
Which amino acid has a second H-atom instead of an R group? ** answer** glycine
In proteins, are amino acid residues D or L stereoisomers? ** answer** L stereoisomers
Zwitterion. when does it occur? ** answer** A molecule that contains charges, but is
neutral overall.
What are the five main classes of amino acids? ** answer** Nonpolar, aliphatic
Aromatic
Polar, uncharged
Positively charged
Negatively charged
Which nonpolar alipathic amino acid has a ring structure as an R group? ** answer**
proline
,The hydrophobic effect stabilizes amino acids containing what classes of R groups?
Describe this interaction ** answer** the hydrophopic effect stabilizes nonpolar alipathic
AND aromatic R group amino acids
the tendency of non-polar molecules in an aqueous solution to avoid the contact with
water molecules
nonpolar molecules clump together in aqueous solutions. This displaces/disorders the
water molecules around them, and causes the water molecules to surround the
nonpolar molecules.
this effect increases entropy by disordering the water molecules. increased entropy
means negative change in gibbs free energy, which means more stable
What type of interaction stabilizes amino acids that have polar, uncharged R groups?
Within this class of R groups, there is an amino acid that can form a much stronger
bond, which amino acid is it and what type of bond is it? ** answer** Hydrogen bonding
Cysteine can form disulfide bridges (covalent)
What are nucleophiles? What are electrophiles? ** answer** Electrophiles = "electron
lovers", they are electron deficient functional groups that seek electrons (they get
attacked by nucleophiles)
Nucleophiles = they are functional groups rich in and capable of donating electrons.
they give electrons to electrophiles
At pH = 7 (neutral pH), what is the charge of amino acids positively charged R groups?
negatively charged R groups? what charge is associated with acids and which with
bases? ** answer** at neutral pH,
positively charged amino acids have significant positive charge
negative charged amino acids have significant negative charge
, positive charge means rich in H+, so these amino acids donate H+, therefore they act
as acids
negative charge means poor in H+, so these amino acids accept H+, therefore they act
as bases.
what is the equilibrium expression for titration of amino acids? what does a titration
curve show? what is the isoelectric point? Is the distribution of H+ reversible or
irreversible? ** answer** cation ⇌zwitterion ⇌anion
at first, the solution is positively charged (acid), then the slow addition of a base makes
it neutral (zwitterion neutral), until finally the solution is mostly negatively charged
(basic)
a titration curve shows the change in pH of the solution in the conical flask as the
reagent is added from the burette. If a strong base is added to a strong acid, the
solution in the flask:
1) starts positive (acid)
2) become neutral (zwitterion)
3) ends basic (base)
At first the H+ are "on". At the end, the H+ are "off".
the pH at which the net electric charge is zero is the isoelectric point (pI)
The distribution of H+ is reversible. Related to protein binding, enzymatic reactions, and
equilibrium constants.
Do strong acids have high or low pka values? ** answer** Strong acids have low pKa
values. The lower the pKa value, the more powerful the acid and its capacity to transfer
protons.
Conversely, the pka of the conjugate acid of strong bases is high.
answers
What is the most important thing change in Gibbs free energy tells us? What does a
negative value mean and what does a positive value mean? ** answer** how
spontaneous a reaction is
negative delta G = spontaneous, energy is released, exergonic
positive delta G = non-spontaneous, energy is consumed, endergonic
what does enthalpy represent? what does it mean when it's positive vs negative? **
answer** delta H is change in enthalpy, which is the heat content of the reacting
system.
It reflects the number and kinds of bonds in the reactants and products.
When delta H is negative, the reaction releases heat and is exothermic
When delta H is positive, the reaction absorbs heat and is endothermic
what is entropy? what does it mean when it's positive vs negative? ** answer** delta S
is change in entropy, which is a quantity describing the level of disorder of a system
When delta S is negative, the reactants are more disordered than the product (requires
input of energy)
When delta S is positive, the reactants are less disordered than the product (does not
require input of energy)
Based on the Gibbs free energy equation, what factors make it more likely for a reaction
to be spontaneous and what factors make it more likely for a reaction to be non-
spontaneous? ** answer** G = H - TS
Spontaneous (-G) = positive S
Non-spontaneous (+G) = negative S
,What type of information does the equilibrium constant K tell us? What is the
relationship between the equilibrium constant and Gibbs free energy? ** answer** the
ratio of products to reactant
If K > 1, there is more product than reactant, so this reaction seems to be spontaneous,
thus delta G is negative
If K < 1, there is more reactant than prouct, so this reaction does not seem to be
spontaneous, thus delta G is positive
What does it mean when change in G = 0? ** answer** equilibrium = death
What are the four components of amino acids? ** answer** carboxyl group, amino
group, hyrogen atom, R group
Which amino acid has a second H-atom instead of an R group? ** answer** glycine
In proteins, are amino acid residues D or L stereoisomers? ** answer** L stereoisomers
Zwitterion. when does it occur? ** answer** A molecule that contains charges, but is
neutral overall.
What are the five main classes of amino acids? ** answer** Nonpolar, aliphatic
Aromatic
Polar, uncharged
Positively charged
Negatively charged
Which nonpolar alipathic amino acid has a ring structure as an R group? ** answer**
proline
,The hydrophobic effect stabilizes amino acids containing what classes of R groups?
Describe this interaction ** answer** the hydrophopic effect stabilizes nonpolar alipathic
AND aromatic R group amino acids
the tendency of non-polar molecules in an aqueous solution to avoid the contact with
water molecules
nonpolar molecules clump together in aqueous solutions. This displaces/disorders the
water molecules around them, and causes the water molecules to surround the
nonpolar molecules.
this effect increases entropy by disordering the water molecules. increased entropy
means negative change in gibbs free energy, which means more stable
What type of interaction stabilizes amino acids that have polar, uncharged R groups?
Within this class of R groups, there is an amino acid that can form a much stronger
bond, which amino acid is it and what type of bond is it? ** answer** Hydrogen bonding
Cysteine can form disulfide bridges (covalent)
What are nucleophiles? What are electrophiles? ** answer** Electrophiles = "electron
lovers", they are electron deficient functional groups that seek electrons (they get
attacked by nucleophiles)
Nucleophiles = they are functional groups rich in and capable of donating electrons.
they give electrons to electrophiles
At pH = 7 (neutral pH), what is the charge of amino acids positively charged R groups?
negatively charged R groups? what charge is associated with acids and which with
bases? ** answer** at neutral pH,
positively charged amino acids have significant positive charge
negative charged amino acids have significant negative charge
, positive charge means rich in H+, so these amino acids donate H+, therefore they act
as acids
negative charge means poor in H+, so these amino acids accept H+, therefore they act
as bases.
what is the equilibrium expression for titration of amino acids? what does a titration
curve show? what is the isoelectric point? Is the distribution of H+ reversible or
irreversible? ** answer** cation ⇌zwitterion ⇌anion
at first, the solution is positively charged (acid), then the slow addition of a base makes
it neutral (zwitterion neutral), until finally the solution is mostly negatively charged
(basic)
a titration curve shows the change in pH of the solution in the conical flask as the
reagent is added from the burette. If a strong base is added to a strong acid, the
solution in the flask:
1) starts positive (acid)
2) become neutral (zwitterion)
3) ends basic (base)
At first the H+ are "on". At the end, the H+ are "off".
the pH at which the net electric charge is zero is the isoelectric point (pI)
The distribution of H+ is reversible. Related to protein binding, enzymatic reactions, and
equilibrium constants.
Do strong acids have high or low pka values? ** answer** Strong acids have low pKa
values. The lower the pKa value, the more powerful the acid and its capacity to transfer
protons.
Conversely, the pka of the conjugate acid of strong bases is high.
