Biochem Final Flashcards
1
Q
The strongest non-covalent interactions are
A
ionic interactions
2
Q
Which of the following components is bonded to the backbone chain of DNA by phosphodiester bond?
A
deoxyribose sugar molecules
3
Q
If the following two reactions were coupled, what would be the ΔG° for the overall exergonic reaction?
Glucose + Pi —–> Glucose-6-Phosphate ΔG° = 21kj/mol
ATP + H20 ——> ADP + Pi ΔG° = -31kj/mol
A
-10 kj/mol
4
Q
Fatty acid anions with two tails assemble into ________ in aqueous solution.
A
lipid bilayers
5
Q
Which of the following biopolymers is correctly paired with the bond that forms between the monomers?
A
DNA; phosphodiester bond
6
Q
Which of the following would be the strongest acid?
A
oxalic acid, pK = 1.25
7
Q
The replication of DNA is made possible by the presence of ________ strands in the double helix of DNA.
A
complementary
8
Q
The DNA strand that serves as the template for the synthesis of RNA is often called the
A
noncoding strand
9
Q
What term is used to describe the exclusion of nonpolar substances from an aqueous solution?
A
hydrophobic effect
10
Q
Photosynthetic organiss use energy from the sun to reduce ______ to _______.
A
CO2; carbohydrates
11
Q
In aqueous solutions, globules of up to several thousand amphiphilic molecules arranged with the hydrophillic groups on the surface and the hydrophobic groups buried in the center are called
A
micelles
12
Q
Which DNA base pair is held ogether by two hydrogen bonds
A
adenine and thymine
13
Q
Which of the following statements concerning the double helix structure present in DNA molecules is correct?
A
Base pairings between strands always involve one pyrimidine base and one purine base
14
Q
Polynucleotides are cleaved within the strands by
A
endonucleases
15
Q
A phosphate buffer solution at a pH = 6.86 would have equal amounts of phosphate in the _________ form and the H2PO4- form.
A
HPO4^2-
16
Q
Which of the major types of biomolecules are never found in polymeric form?
A
lipids
17
Q
Which of the following non-covalent interactions is the most important in maintaining the structure of the double helix?
A
base stacking between adjacent bases
18
Q
Which of the biopolymers is correctly paired with its major function?
A
polysaccharide; energy storage
19
Q
The pH at the midpoint of an acid/base titration is
A
equal to the pK of the corresponding acid
20
Q
If a solution is buffered at a pH of 4.70, then the addition of a small amount of acid will cause the solution to have a pH of approximately
A
4.70
21
Q
Amphiphilic molecules
A
have both hydrophilic and hydrophobic groups
22
Q
Name the major pyrimidine bases found in DNA
A
cytosine and thymine
23
Q
The pK of [NH4+]/[NH3] buffer is 9.25. What is the optimum buffering range for this compound?
A
pH = 8.75 - 9.75
24
Q
Which of the following molecules would be prevented from readily crossing a lipid bilayer?
A
sodium ions
glucose
potassium ions
water
25
In an aqueous solution, if the [OH-] is 3.0x10^-5 M, what is the [H+]?
3.3 x 10^-10
26
At any given moment, a single water molecules participates in _________ strong hydrogen bond(s). The role played by the water molecule is best characterized as __________.
two; one as a H-bond donor, one as a H-bond acceptor
27
A thermodynamically unfavorable chemical reaction can occur in a cell because
the unfavorable reaction can be coupled to a favorable reaction
28
RNA molecules differ from DNA molecules in that they
are single stranded rather than double stranded
29
A spontaneous process always has
ΔG < 0
30
Which of the following shows the buffer that is found in the blood stream?
H2CO3 -------> HCO3- + H+
31
The melting point of DNA is always higher in DNA with
high GC content
32
A base found exclusively in DNA is __________ while ___________ is found only in RNA.
thymine; uracil
33
Which of the following is a physical property of water that results from hydrogen bonding?
ability to solubilize polar molecules
high surface tension
a solid state that is less dense than the liquid state
high boiling point relative to molecular weight
34
If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain?
75
35
Any given nucleotide in a nucleic acid contains
one sugar, one base, and one phosphate
36
Which of the following describes the difference between ribose and deoxyribose?
Deoxyribose has one less oxygen atom than ribose
37
Entropy is used to measure
randomness
38
Which of the following is the best explaination for the hydrophobic effect?
It is an entropic effect, caused by the desire of water molecules to increase their entropy by excluding hydrophobic groups, which they must otherwise surround with highly ordered structures
39
Bacteria and archaea typically have fewer than ___________ genes while plants and animals typically have greater than ___________ genes.
5,000; 10,000
40
Which of the following shows the intracellular buffer?
H2PO4- -------> HPO4^2- + H+
41
If the pK values for phosphoric acid are 2.15, 6.82, and 12.38, ___________ would predominate at pH 5 while __________ would predominate at pH 10.
H2PO4-; HPO4^2-
42
The blood buffering syste is based on:
the control of the bicarbonate content by the kidneys
the decrease of the blood pH due to the production of H+
the reaction of CO2 with H2O to form carbonic acid
the ionization of aqueous carbonic acid to H+ and the bicarbonate anion
43
What is the [H+] of an aqueous solution with a pH of 6.2?
6.3x10^-7
44
Protein folding in vivo is assisted by a
molecular chaperones
45
Quaternary structure is possible for a protein only when
two or more protein chains are present
46
Which of the following details the nucleotide-binding site when tubulin dimers assemble into microtubules?
the alpha site is bound to GTP; the beta site is bound to GDP
47
Lysine, a positively charge amino acid, can form a salt bridge by associating with a nearby ___________ residue.
glutamic acid
48
Which of the following correctly describes the sequence of events in the myosin-actin cycle?
ATP binds to myosin, myosin release from actin, myosin binds to another actin subunit, release of Pi and ADP, stretched myosin returns to original conformation
49
Myoglobin is ____________; hemoglobin is ____________.
monomeric; tetrameric
50
The central ion of the heme group of hemoglobin is
Fe^2+
51
If the following mixture of proteins was applied to a size-exclusion chromatography column, what would be the order of elution? Proteins with molecular weights: myoglobin (17.7 kDa), hemoglobin (64.5 kDa), lysozyme (14.3 kDa) and triose phosphate isomerase (57.4 kDa)
hemoglobin, triose phosphate isomerase, myoglobin, lysozyme
52
Proteins are made of ___________ which contains __________.
alpha-amino acids; a carboxylate group and a primary or secondary amine
53
Which of these characteristics is not true for the alpha helix?
The side chains of the amino acid residues extend inward from the helix
54
The heads of kinesin bind to ___________; the light chains of kinesin bind to __________.
collagen fibers; proteins in the cell membrane
55
The primary structure of protein represents
linear sequence of amino acids joined by peptide bonds
56
What level of protein structure is created by the binding of several peptides to produce a functional protein?
quaternary
57
The secondary structure of myoglobin is mainly made of eight
alpha-helices
58
When a cell moves along a surface, actin _________ occurs at the leading edge while __________ occurs at the trailing edge
polymerization; depolymerization
59
A plot of the binding of oxygen to myoglobin as a function of pO2 gives a ___________ shape; a similar plot for hemoglobin gives a ___________ shape.
hyperbolic; sigmoidal
60
At pH 3, how many charged groups are present in the pentapeptide Ala-Asp-His-Ser-Lys?
3
61
Using the figure below, determine what type of column chromatography is being used to separate the mixture of proteins into individual proteins?
size-exclusion chromatography
62
Which allosteric effector has the greatest ability to stabilize the deoxy state of hemoglobin?
2,3-Bisphosphoglycerate
63
The formation of a peptide bond is best described as
a dehydration reaction
64
For a globular protein that is found in the cytosol, _________ would most likely be found in the proteins interior while __________ would most likely be found on the surface (Use the Hydrophobicity Scale)
Leu; Ser
65
Bone and tendons contain _________ while hair and nails contain _________.
collagen; keratin
66
Which of the following explains the conversion of hemoglobin subunits from deoxy to oxy state?
all four subunits switch simultaneously
67
A fully functional hemoglobin molecule has ___________ structure.
quaternary
68
When oxygen is bound to the heme group of myoglobin, it is coordinated between ___________ and ____________.
E7 His; Fe^2+ of heme
69
Which of the following statements about the structure of myoglobin is FALSE?
Myoglobin contains both types of secondary structure
70
During the formation of microfilaments, which of the following occurs?
ATP hydrolysis is catalyzed by F-actin
71
The disulfide bond between two cysteine molecules:
is a covalent bond formed by oxidation
72
Which of these characteristics does not describe the beta sheet?
Parallel beta sheets are most common secondary structure
73
In the peptide Try-Ser-Tyr, Tyr is at the
C-terminus
74
What is the most prevalent secondary structure observed in the proteins of intermediate filament
beta-sheets
75
What type of attractive force is responsible for maintaining the secondary structure of a protein?
hydrogen bonds between carbonyl and amine groups of peptide bonds
76
In which of the following separation method where proteins are separated on the basis of their net charge?
ion exchange chromatography
77
Which of the following fibers is correctly paried with the protein that forms the fiber?
intermediate filaments: keratin
microfilaments: actin
microtubule: tubulin
78
Which of the following correctly describes the sequence of events on the kinesin reaction cycle? For simplicity, the two heads are referred to as head 1 and head 2. Head 1 starts as the leading head.
ATP binds to head 1, head 2 swings forward, head 2 binds to tubulin, ADP release from head 2, ATP hydrolysis in head 1, head 1 releases tubulin
79
The idea that binding of one molecule of oxygen to hemoglobin enhances further binding of oxygen to hemoglobin is called
cooperativity
80
What is the most common type of secondary structure in a protein
alpha helix
81
An uncatalyzed reaction has a rate of 4.2x10^-7 sec^-1. When an enzyme is added the rate is 3.2x10^4 sec^-1. Calculate the rate enhancement caused by the enzyme. (rate of enhancement = catalyzed/uncatalyzed)
7.6x10^10
82
What three amino acids are found in the catalytic triad of chymotrypsin?
Asp, His, Ser
83
Km is a measure of
binding efficiency of substrate by enzyme
84
What is the function of enzymes within living systems?
catalysts
85
Some irreversible inhibitors are called ____________ because they bind to the active site of the enzyme and begin the catalytic process, just like a normal substrate
suicide substrates
86
The oxidized form of NADH is
NAD+
87
A zymogen is
an inactive precursor of an enzyme
88
When an enzyme is saturated with substrate
the reaction velocity approaches a maximum
89
Which of the following is mobilized for energy use by a phosphorolysis reaction, not a hydrolysis?
glycogen
90
A lineweaver-burk plot is a
double reciprocal plot
91
Which of the following is a correct skeletal equation for a hydrolysis reaction involving adenosine triphosphate?
ATP -----> ADP + Pi
92
An enzyme active site is the location in an enzyme where substrate molecules
undergo change
93
The mechanism of action for most antihistamines, which are used to alleviate allergy symtoms, is based on ________ inhibition
competitive
94
Which of the following is used to move lipids around the bloodstream?
lipoproteins
95
Which of the following is true about enzymes?
enzyme activities can often be regulated
96
Degradation of proteins within a cell can occur within the ___________ or by use of ___________.
lysosome; a proteasome
97
The coenzyme ____________ is a hydride ion (H+) receptor in a metabolic pathway.
NAD+
98
Which of the following statements about metabolism is correct?
metabolsm is the sum total of all the biochemical reactions that take place in a living organism
99
The highest point ina reaction coordinate diagram represents
the transition state
100
Of the following ions, which would be most likely to participate in metal ion catalysis?
Zn^2+
101
An extremely efficient enzyme has a ___________ Km and a ___________ Kcat.
small; large
102
In a lineweaver-burk plot, the y-interceot indicates the value of
1/Vmax
103
In the degradative pathway major nutrients are ___________ broken down, resulting in the synthesis of ___________.
exergonically; ATP
104
The process by which nutrients are degraded in order to salvage their components and/or to generate energy is most specifically called:
catabolism
105
The __________ stores glucose as glycogen and converts excess glucose to __________.
liver; fatty acids
106
Generally speaking, ATP is produced by __________ reactions and used by ____________ reactions.
catabolic; anabolic
107
The number of substrate molecules acted upon per minute by one molecule of enzyme is alled the
turnover number
108
The correct notation for the reduced form of nicotinamide adenine dinucleotide is
NADH
109
Plants are considered
photoautotrophs
