biochem part 1 laaa

What is thermodynamics?

The study of energy.

What information can thermodynamics provide about a reaction?

It can explain how and why a reaction can occur and the conditions required for the reaction to occur.

What is the First Law of Thermodynamics?

Energy is conserved.

What does the First Law of Thermodynamics state about energy?

Energy cannot be created or destroyed; it can only be converted from one form to another.

What are the forms of energy mentioned in the lecture?

Kinetic energy, potential energy, heat, and chemical energy.

What is kinetic energy?

Energy associated with motion.

What is potential energy?

Stored energy.

What is the Second Law of Thermodynamics?

The entropy of the universe is always increasing.

What is entropy?

A measure of disorder or randomness.

What happens to the entropy of a system when disorder increases?

The entropy of the system increases.

What is the Third Law of Thermodynamics?

The entropy of a perfect crystalline system at 0 K is zero.

What is Gibbs free energy?

The energy available to do useful work during a reaction.

What is the equation for Gibbs free energy?

ΔG = ΔH − TΔS.

What does ΔG represent?

The change in Gibbs free energy.

What does ΔH represent in the Gibbs free-energy equation?

The change in enthalpy.

What does T represent in the Gibbs free-energy equation?

Temperature in kelvin.

What does ΔS represent in the Gibbs free-energy equation?

The change in entropy.

What does a negative ΔG indicate?

The forward reaction is favorable or spontaneous.

What does a positive ΔG indicate?

The forward reaction is unfavorable or nonspontaneous under the given conditions.

Does ΔG predict the rate of a reaction?

No. ΔG does not predict reaction rate.

What happens when ΔH is negative and ΔS is positive?

ΔG is always negative, so the reaction is always spontaneous.

What happens when ΔH is positive and ΔS is positive?

The reaction may be spontaneous at high temperatures.

What happens when ΔH is negative and ΔS is negative?

The reaction may be spontaneous at low temperatures.

What happens when ΔH is positive and ΔS is negative?

ΔG is positive, so the reaction is never spontaneous.

What is the standard free-energy change, ΔG°?

The free-energy change under standard-state conditions.

What temperature is used for standard-state conditions?

298 K.

What pressure is used for standard-state conditions?

1 atm.

What solute concentration is used for standard-state conditions?

1 M.

What pH is used for the biochemical standard state in the lecture?

pH 7.0.

What is the equation relating actual free energy to standard free energy?

ΔG = ΔG° + RT ln([C]ᶜ[D]ᵈ/[A]ᵃ[B]ᵇ).

What is ATP hydrolysis?

The breakdown of ATP through the addition of water.

What is significant about ATP hydrolysis?

ATP hydrolysis has a large ΔG.

How can ATP hydrolysis be used in cells?

It can be used to drive other reactions forward.

What is reaction coupling?

A process in which an unfavorable reaction is made energetically possible by linking it to a favorable reaction.

Why are reactions coupled?

The favorable reaction helps provide the energy needed to drive the unfavorable reaction.

What is chemical equilibrium?

The chemical state in which the rates of the forward and reverse reactions are equal.

At equilibrium, must reactant and product concentrations be equal?

No. Their concentrations do not need to be the same.

What does Le Châtelier’s principle state?

A reaction system responds to a change by moving toward equilibrium.

What is the equilibrium constant, Keq?

A value that describes the relative concentrations of products and reactants at equilibrium.

What is the general equation for Keq?

Keq = [C]ᶜ[D]ᵈ/[A]ᵃ[B]ᵇ.

What is the value of ΔG at equilibrium?

ΔG = 0.

What is the relationship between standard free energy and the equilibrium constant?

ΔG° = −RT ln Keq.

What is another equation relating Keq and ΔG°?

Keq = e^(−ΔG°/RT).

What is kinetics?

The field of study that analyzes the rates of chemical reactions.

What can chemical kinetics involve?

Single or multiple reactants forming single or multiple products.

What factors can affect reaction rate?

Reactant and product concentrations, temperature, and factors specific to the individual reaction.

What is a rate law?

A mathematical expression that describes the rate of a chemical reaction.

What is the general reaction used to introduce rate laws?

A + B → C.

What is the rate-law equation shown in the lecture?

Rate = d[C]/dt = k[A][B].

What does k represent in a rate law?

The rate constant.

What is a catalyst?

A biological enzyme that speeds up a reaction by lowering the activation energy.

How does a catalyst affect activation energy?

It lowers the activation energy required for the reaction.

How does a catalyst affect the time needed to reach equilibrium?

It helps the system reach equilibrium more quickly.

Does a catalyst affect ΔG?

No. A catalyst does not affect ΔG.

Does a catalyst change the equilibrium concentrations of reactants or products?

No. A catalyst does not change the equilibrium concentrations.

What is the main learning objective of the organic chemistry section?

Describe biological molecules and processes using the tools of organic chemistry.

What are functional groups?

Fragments of a molecule, such as a hydroxyl or carbonyl group.

Why are functional groups important?

They influence the chemical properties and reactions of molecules.

What is polarity?

An unequal distribution of electrical charge within a molecule.

Why is polarity important in biochemistry?

Biochemistry occurs mainly in aqueous systems, and molecular polarity affects interactions with water.

What is the relationship between polarity and water solubility?

Adding more polar groups can make a molecule more water soluble.

Which groups mentioned in the lecture are polar and can form hydrogen bonds?

OH and NH2 groups.

What is a hydrophobic molecule?

A nonpolar molecule or region that does not interact favorably with water.

What is a reaction mechanism?

An explanation of how bonds are made and broken at the molecular level.

What do reaction arrows indicate?

The direction of the reaction or electron flow.

What is a polymer?

A macromolecular assembly made from smaller building blocks called monomers.

What is a monomer?

A smaller building block that can be linked to form a polymer.

How can monomers be connected in polymers?

They can be connected in linear or branched arrangements.

What examples of biological polymers or macromolecular assemblies are mentioned?

DNA, RNA, proteins, enzymes, glycogen, starch, and cellulose.

What is the main learning objective of the water chemistry section?

Perform basic calculations pertaining to the chemistry of water and aqueous systems.

Why is water a polar molecule?

Water has an unequal distribution of electrical charge.

What causes water to have partial charges?

The difference in electronegativity between oxygen and hydrogen.

Which atom in water is more electronegative?

Oxygen.

What partial charge does oxygen have in water?

A partial negative charge.

What partial charges do the hydrogen atoms have in water?

Partial positive charges.

What is a hydrogen bond?

A weak attraction involving a partially positive hydrogen and an electronegative atom.

How strong is a hydrogen bond compared with a covalent bond?

A hydrogen bond is weaker than a covalent bond.

What biological structure is specifically mentioned as being formed through hydrogen bonding?

The double helix of DNA.

What is electronegativity?

The tendency of an atom to attract electrons toward itself.

Why does oxygen form polar bonds with hydrogen?

Oxygen is more electronegative than hydrogen and attracts the shared electrons more strongly.

What is the dielectric constant?

A measure used to categorize the polarity of a solvent.

What does a high dielectric constant mean?

The solvent can readily solubilize many ionic solids and significantly decrease ionic interactions.

How does water’s high dielectric constant affect ionic interactions?

It decreases ionic interactions and helps solubilize many ionic solids.

What are the two acid-base definitions discussed in the lecture?

Arrhenius and Brønsted-Lowry.

According to Arrhenius, what is an acid?

An H+ donor.

According to Arrhenius, what is a base?

A substance that generates OH−.

According to Brønsted-Lowry, what is an acid?

An H+ donor.

According to Brønsted-Lowry, what is a base?

An H+ acceptor.

What is Ka?

The acid ionization constant.

What does Ka measure?

The acidity of a proton.

What is the equation for Ka?

Ka = [H+][A−]/[HA].

What does [H+] represent in the Ka equation?

The proton concentration.

What does [A−] represent in the Ka equation?

The concentration of the conjugate base of the acid.

What does [HA] represent in the Ka equation?

The concentration of the acid at equilibrium in M.

What does a high Ka value indicate?

A stronger acid because it dissociates more completely in water.

Why do strong acids have high Ka values?

They fully dissociate in water.

What is pKa?

A measure of acid strength.

What is the equation for pKa?

pKa = −log Ka.

What does a higher pKa indicate?

The proton is less acidic.

What does a lower pKa indicate?

The proton is more acidic.