Chemical and Physical Foundations of Biological Systems Flashcards
How does the primary structure of a protein form?
The amino-terminus of one amino acid attacks the carboxy-terminus of another.
Why might polarized light be used to determine whether a sample is composed entirely of Glycine?
Because glycine is not optically active (no chirality).
How would you go about making a nitrile group more reactive?
Attach an electron withdrawing group to the carbon of the nitrile group (becomes -C=N+).
What type of lens would be appropriate for correcting hyperopia (farsightedness)?
Convex. Light is being focused behind the retina, need it to converge more quickly.
Which type of lens will make light converge? Which will make light diverge?
Convex lenses converge light while concave lenses diverge light.
For a converging lens, at what distance from the lens will the image be real?
At any distance outside the focal length.
Will real images formed by a converging lens be inverted or right-way-up?
Inverted.
What is the simplest way to differentiate α-D-glucose and β-D-glucose?
Recognize that the OH on the anomeric carbon (hemiacetal carbon) will have opposite conformations.
How would we determine the mass percent composition of an element in the product of a reaction?
Starting moles are irrelevant. Figure out the reaction and then divide the atomic mass of the desired element by the total mass of product.
When an acyl halide reacts with a primary alcohol, what functional group is formed?
An ester. Try to draw it out if you’re confused!
What is an acyl halide?
Basically a carboxylic acid but replace the OH with a halogen (ex. Cl-).
How many neutrons and protons are in ¹⁴C? What about ³⁴P?
¹⁴C: 8 neutrons, 6 protons
³⁴P: 19 neutrons, 15 protons
How many reactant molecules are involved if a reaction follows second order kinetics?
- # of reactant molecules is = order the reaction follows.
How many reactant molecules are involved if a reaction follows third order kinetics?
- # of reactant molecules is = order the reaction follows.
if ΔG > 0, the reaction is _______.
Nonspontaneous.
If the potential energy of the products is greater than the potential energy of the reactants, we say that the reaction is ________.
Endothermic.
If a reaction proceeds spontaneously to the right, Kᴇǫ must be ______.
Greater than 1.
What is meant by an element’s “oxidation number”?
Oxidation numbers must be balanced in a neutral molecule (ex: O = -2, H = +1, Cl = -1, N = -3, etc.)
For use in titration, a triprotic acid with multiple acidic protons can _________.
Act as a buffer over several pH ranges.
If a lever with varied weights on each side is in static equilibrium, what must be true?
The torque on either side is equal, therefore the weights can not be positioned at equal distances from the fulcrum.
Which amino acids have hydrophobic side chains? Which ones are amphipathic? Which have hydrophilic side chains?
HPhobic: Gly, Ala, Val, Leu, Ile, Pro, Phe (GAVLIPF)
APathic: Met, Trp, Tyr, Lys (MWYK)
HPhilic: Ser, Thr, Cys, Asn, Gln, His, Arg, Asp, Glue (STCNQHRDE)
Are charged molecules more, or less soluble in water than neutral molecules?
Charged molecules are more soluble in water than neutral molecules.
What factors contribute to a molecule having a high melting point?
Larger size (increased dispersion forces) and capability for dipole-dipole interactions.
In thin-layer chromatography, is a molecule more or less likely to have a high Rғ (greater relative movement) if it is more polar?
More polar molecules tend to be stationary, having a relatively lower Rғ than molecules which are less polar.
How is the equivalence point of a titration determined?
Depends on the relative pH of the acid and the base (ex: stomach acid and NaOH have equivalence ~pH 7)
Which nucleotides are purines? Which are pyrimidines?
Purines: AG
Pyrimidines: C(U)T
(U replaces T in RNA)
The loss of which bonds is most likely to cause loss of quaternary/tertiary/secondary structure?
Hydrogen bond disruption will cause higher structures to be lost.
True or False: enantiomers (L/D-etc) will rotate polarized light in opposite directions and also have different physical properties?
False. Enantiomers have the same physical properties with the exception of polarized light rotation.
What must we know ahead of time to use bomb calorimetry to determine bond energies?
A lot (it’s inefficient). Reactant mass, reactant heat of formation, temperature of products and reactants, mass of calorimeter, specific heat of calorimeter, mass and specific heat of water in calorimeter, heat of formation of products, etc…
How would we calculate the solubility product constant Kₛₚ of a molecule? (think dissolution)
Figure out how many moles of each product are produced per mole of reactant. Describe this as Kₛₚ=(p₁x)ᵖ¹(p₂x)ᵖ² where pₙ is the number of moles of product produced per mole of reactant
In Sanger sequencing, lack of dideoxynucleotides would cause what erroneous result on gel electrophoresis?
A single dark band, because without dideoxynucleotides the entire template is replicated and all copies are the same length.
If we maintain the volume of air in a container at 3.8L as we increase the pressure from 1 atm to 2 atm, how many moles of air would we need to add to maintain the volume of air in the container?
When pressure doubles, the volume of air in the container will shrink to 1.9L. We must add back the 1.9L of air, but at double the pressure this means we add back double the moles of air, 3.8/22.4.
If we have a circuit containing 3 resistors in series and we know the current through the last resistor, how can we determine the current through the first resistor?
In series, the current through each resistor is the same.
What is the equation for Ohm’s Law?
I = V/(R₁ + R₂)
If the applied current is positive into a cell, what is the charge of the cell?
Negative.
If a cell has a negative resting potential but is constantly letting positive ions leak in, what must also be occurring?
Positive ions must be getting pumped out.
What must we know during a titration if we wanted to assess the concentration of an acid that we would not need if we just wanted to assess the number of moles of acid?
Initial volume of solution is only necessary if we want to get a concentration. Otherwise we can use our titrating base to determine the number of moles of acid.
What kind of bonding makes a molecule less soluble in water? What other effect does this have?
Increased intRAmolecular hydrogen bonding makes a molecule less soluble, and also lowers the melting point.
What is being lost when proteins lose their secondary, tertiary, or quaternary structure?
Hydrogen bonding.
If carbon dioxide is being produced in excess, the pH of blood is _____.
Decreasing. (becoming more acidic)
What is required for two molecules to form a hydrogen bond?
- A hydrogen bond donor ex: N-H or O-H
- A hydrogen bond acceptor
ex: =O: or N:
(w/ free electrons)
What would the pH be of a pool of 0.01M HCL(aq)? How do you determine this?
For strong acids, pH is the exponent of the concentration. So 0.01M = 10^-2M = pH of 2.
An element which can act as an electron acceptor should have ______.
High electron affinity.
How is the polarity of a molecule associated with its boiling point?
More polar molecules have higher boiling points than less polar molecules.
Why might it be necessary to break the surface tension of a liquid during heating?
To prevent superheating of the liquid and allow boiling to occur.
What must be true of two identical molecules, on in the (+) configuration and the other in the (-) configuration?
They differ in orientation around a chirality centre. (At least one carbon must be chiral and a stereocentre).
The boiling point of a liquid is the temperature at which the vapour pressure equals _____.
The surface pressure.
What is Avogadro’s number?
6.02*10^23 ions/mol.
How would you calculate the number of ions in a sample, given the mass?
Determine the number of moles (mass/molar mass), then multiply by Avogadro’s number (6.02*10^23 ions/mol).
When exposed to a base, what does red litmus paper do?
Turns blue.
When exposed to an acid, what does red litmus paper do?
Stays red.
How can electrons in partially filled d orbitals cause a solution to be coloured?
The electrons in lower energy orbitals absorb visible light to move to the higher energy orbitals.
Between (CH₃CH₂)₂NH and (CH₃CH₂)₂CH₂, which is more soluble in water? Why?
(CH₃CH₂)₂NH, because it can form H-bonds with water (because of N-H), while (CH₃CH₂)₂CH₂ cannot.
Which is more polar, =O or -OH?
-OH
What is the Henderson-Hasselbach equation?
pH = pKa + log([conj. base]/[conj. acid])
More hydrogen bonding ______ the boiling point of a liquid.
Increases.
