Chem/phys day 1

what equation would you use for this question:

What is the magnitude of the electric field used in the MALDI-MS imaging device described in the passage?

E = V/d; voltage/distance

In MALDI, a plate containing the sample is coated with 2,5-dihydroxybenzoic acid (DHB) (structure shown).

Which reaction leads to the formation of DHB whose structure is shown in the passage?

carboxylation of hydroquinone

when trying to find organic chemistry questions always do what first

look at the functional groups

What property must be different between ions in order for them to separate? (MALDI-MS)

their mass-to-charge ratios

what am i solving for in this scenario:

what is one of the values of the electromagnetic energy delivered during one pulse by the ionizing radiation?

work

original equation: power = w/t

work = PT

proteolytic cleavage is what type of reaction

a hydrolysis

photon energy is directly proportional to

frequency. + bond energy (ΔH) = + frequency

Based on the ray diagram and distances shown in Figure 1, the focal length of the lens is:

1/f = 1/do + 1/d1

what is this?

a tertiary alcohol

what is this?

a primary alcohol

what is this?

a secondary alcohol

what is this?

a primary alcohol

d

d

what is this -

a phospholipid specifically a phosphatide

can be difficult to detect since they do not absorb visible light

liposomes

The inside of a liposome is most similar to what type of environment?

aqueous

what does this situation imply:

Compound 2 formed new liposomes with an average size

Compound 2 is under thermodynamic control

what does this imply:

Compound 1 were stable to mixing

Compound 1 is under kinetic control

Kinetic control

product forms fastest, may get “stuck”

Thermodynamic control =

system can rearrange to the most stable, lowest-energy state

Assume the hydrolysis of ATP proceeds with ΔG′° = –30 kJ/mol.

ATP + H₂O → ADP + P_i

Which expression gives the ratio of ADP to ATP at equilibrium, if the [P_i] = 1.0 M? (Note: Use RT = 2.5 kJ/mol.)

what equation would you use for this

ΔG∘= - RTlnK

What is the electronic configuration of the Co(II) center found in vitamin B12?

[Ar] 3d⁷

Which cation is most likely to be found in place of Fe(II) in the square planar binding domain of hemoglobin?

Co²⁺

The ATP-dependent phosphorylation of a protein target is catalyzed by which class of enzyme?

transferase

Colored molecules usually have:

more conjugation (many connected double bonds)

K_M is

when the kinetics experiment reaches half the maximum velocity

kcat ​ →

how fast the enzyme catalyzes the reaction (turnover rate)

Tm​ →

thermal stability (higher = more stable)

the bond that links monosaccharides together in an oligosaccharide is a special type of acetal linkage known as a

glycoside bond

what kind of curve is Michaelis–Menten

hyperbolic

relating voltage, current, and resistance

ohms law. V = IR

Which amino acids CAN hydrogen bond?

Polar / charged: Ser, Thr, Asn, Gln, Asp, Glu, Lys, Arg, His

What does kcat measure?

Catalytic turnover (rate) → how fast enzyme converts substrate → product

What does Tm measure?

Protein stability (folding) → temperature where protein unfolds

If mutations ↓ kcat MUCH more than Km → what’s affected?

Catalysis > binding

Hybridization change in nucleophilic attack on carbonyl?

Why?

sp2→sp3→sp2

• carbonyl (sp²)

• nucleophile attacks → tetrahedral (sp³)

• collapse → carbonyl reforms (sp²)

What does base (NaOH) do in extraction?

Deprotonates acids → charged → aqueous layer

Where do neutral molecules go?

organic layer (ether)

Why does amide stay in organic layer?

it is neutral and not easily protonated/deprotonated

What type of ions replace Fe²⁺ best?

Transition metals with similar charge/size

What makes a compound colored?

Extended conjugation (delocalized electrons)

More conjugation → what happens?

absorbs visible light → appears colored

To measure kcat, substrate concentration should be:

saturating to ensure enzyme is always working at max rate

1 mM × 1 mL =

μmol

0.1 mM × 1 mL =

0.1 μmol = 100 nmol

μM/s → what does it mean?

μmol/L/s

2 μM/s for 60 s → concentration change?

2×60=120μM

Then multiply by volume (1 mL = 10⁻³ L):

120μM×10^-3 = 1.2 μM×10^-7

1 μmol =

10⁻⁶ mol

1 nmol =

10⁻⁹ mol

0.1 μmol = ? nmol

100 nmol

1 × 10⁻⁷ mol = ? nmol

100 nmol

1 mL = ? L

10−3L