Chem/Phys

Question 1

What functional group is formed from the formation of a peptide bond?

Answer 1

Amide group: (O=C-N-H) have a general structure in which a nitrogen atom is bonded to a carbonyl carbon atom

Question 2

What is the difference between an amide and amine group? Can an amide group be formed from an amine group?

Answer 2

Amide: nitrogen attached to carbonyl carbon
Amine: nitrogen with lone pairs and alkyl groups
Amines and carboxylic acids can combine in a condensation reaction to form amides.

Question 3

In a gas-liquid chromatograph, the first peak observed in the gc trace is attributable to which compound?

Answer 3

The compound with lowest molecular weight and also the weakest intermolecular forces of attraction. This substance will therefore migrate the fastest and be the first peak in the gas chromatograph (gc) trace.

Question 4

Which statement correctly describes how enzymes affect chemical reactions? Stabilization of:

A.the substrate changes the free energy of the reaction.
B.the transition state changes the free energy of the reaction.
C.the substrate changes the activation energy of the reaction.
D.the transition state changes the activation energy of the reaction.

Answer 4

D

The enzyme’s ability to make the reaction faster depends on the fact that it stabilizes the transition state. The transition state’s energy or, in terms of a reaction, the activation energy is the minimum energy that is needed to break certain bonds of the reactants so as to turn them into products.

Question 5

The index of refraction of a medium is equal to the ratio of the speed of light in ____ to the speed of light in the _____.

Answer 5

1. VACCUME

2. MEDIUM

Question 6

The intensity of the radiation is directly proportional to the:

Answer 6

Number of photons emitted.

The intensity of electromagnetic radiation is defined as energy emitted per unit time. Thus, intensity is directly proportional to the number of photons emitted

Question 7

15 O has a half-life T 1/2 of 2 minutes. What fraction of a 15O sample decays in 10 min?

Answer 7

31/32

The half-life of 15 O is 2 minutes; thus, 10 minutes = 5 half-lives. Therefore, only (1/2)^5 = 1/32 of the sample will be left after 10 minutes, while 31/32 of the sample will decay.

Question 8

Why is the velocity of blood flow slower in capillaries than in arteries?

A.Capillary walls are more elastic than arterial walls.
B.Capillaries have less resistance to blood flow than arteries.
C.The total cross-sectional area of capillaries exceeds that of arteries.
D.Blood pressure is higher in the capillaries than in arteries.

Answer 8

C.

The answer to this question is C because the high number of capillaries in the body means that the total cross-sectional area of these vessels is larger than any other vessel type in the circulatory system. This causes the velocity of the blood to decrease.

Question 9

The environment of the retinal binding site is most likely:

A.hydrophilic.
B.positively charged.
C.negatively charged.
D.hydrophobic.

Answer 9

The answer to this question is D because retinal is composed of mainly carbon and hydrogen, making it largely hydrophobic.

Question 10

The source of the phosphate groups that are added to rhodopsin is:

A.arrestin.
B.rhodopsin kinase.
C.ATP.
D.all-trans-retinol.

Answer 10

The answer is C because the requirement of ATP for kinase activity implies the phosphate groups come from ATP.

Question 11

Which reaction is catalyzed by lysosomal lipase (LipA)?

A.ATP hydrolysis
B.Peptide bond cleavage
C.Hydrolysis of triacylglycerides
D.Transfer of carboxyl groups

Answer 11

The answer is C because of the fact that LipA is a lipase, which means it must hydrolyze fatty acids.

Question 12

Glycogen synthase adds on the glucose to glycogen through _____ whereas branching enzyme will create different branches of glucose via ____.

Answer 12

1. alpha-1,4 bonds

2. alpha-1,6 bonds

Question 13

Bonds formed through glycogen synthase (alpha/beta + numbers): Maltose, Lactose, Sucrose, Glycogen, Starch, Cellulose

Answer 13

Maltose: alpha 1, 4 
Lactose: beta 1, 4 
Sucrose: alpha 1,2 
Glycogen: alpha 1,4 with alpha 1,6 branch 
Starch: alpha 1, 4 
Cellulose: beta 1, 4

Question 14

Each of the following equations shows the dissociation of an acid in water. Which of the reactions occurs to the LEAST extent?

A.HCl + H2O → H3O+ + Cl−
B.HPO42− + H2O → H3O+ + PO43−
C.H2SO4 + H2O → H3O+ + HSO4−
D.H3PO4 + H2O → H3O+ + H2PO4−

Answer 14

The answer to this question is B. HPO42− has a high negative charge and so dissociation of it will occur to the least extent.

Question 15

Gamma decay occurs when a nucleus emits:

A.a photon.
B.a proton.
C.a neutron.
D.an electron.

Answer 15

A

The answer to this question is A because, by definition, gamma decay means the emission of photons by the nucleus.

Question 16

pH < pkA it will be protonated

pH > pkA it will be deprotonated

Answer 16

• higher pkA=higher affinity
• lower pkA=lower affinity, more likely to give up protons, and deprotonate

pH below the pKa of the group means the group is protonated, (low pH means acidic conditions, and acids give protons) any pH above the pKa is deprotonated (high pH means basic conditions, and bases steal protons)

Question 17

Know these

Answer 17

Alpha emission is the release of a helium nucleus (two protons and two neutrons). Each alpha emission reduces the atomic mass and atomic number of the atom by 4 and 2, respectively.

Beta minus emission is the release of an electron from the nucleus and turns a neutron into a proton; it increases the atomic number by 1. The mass of an electron is negligible compared to the nucleus, so beta emission does not alter the atomic mass.

Gamma emission is the release of a high energy photon that occurs when the protons and neutrons in a nucleus change configuration. It does not alter the atomic mass or atomic number of an atom.