Unit 2 Flashcards
(215 cards)
1
Q
D-glucose and L-glucose are ____________.
A
enantiomers
2
Q
The furanose form of fructose is generated by a form of a hemiketal involving the attack of the hydroxyl group on on carbon __ with carbon __.
A
5; 2
3
Q
Formation of pyranose and furanose forms of sugar result in the generation of a new asymmetric carbon giving rise to alpha and beta forms of the sugars. The carbon at which this newly created asymmetric center is generated is referred to as ___________.
A
the anomeric carbon.
4
Q
Cellulose is a polymer of glucose joined via ______________ linkages.
A
Beta 1, 4 glycosidic linkages
5
Q
Fibrils of cellulose have high tensile strength, due to hydrogen bonds between _______________.
A
straight chains
6
Q
Once formed, the alpha and beta forms of D-glucose are what?
A
interconvertible only through a linear, noncyclic intermediate with which they are both in equilibrium
7
Q
What connects sugar molecules in both linear and branches of complex carbohydrates?
A
Glycosidic bonds
8
Q
Human blood groups are the result of _______________.
A
differing glycotransferases
9
Q
The amino acid R-groups that serve as sites for covalent attachment of glycoproteins to carbs include ____________.
A
hydroxyl-containing R-groups
10
Q
Which two sugars are joined via an O-glycosidic bond to make lactose?
A
Beta-D galactose and alpha-D glucose, joined via 1 –> 4 glycosidic bond
11
Q
Sorting which targets glycoproteins to their correct destination is done in what organelle?
A
Golgi apparatus
12
Q
Diisopropylphosphofluoridate (DIPF) inactivates chymotrypsin by covalently modifying serine-195. This occurs because of what?
A
serine-195 is in environment which gives it a higher than normal reactivity with respect to DIPF
13
Q
The observation of “burst” kinetic in rapid kinetic studies of the hydrolysis of N-acetyl-L-phenylalanine p-nitrophenyl ester by chymotrypsin is due to what?
A
The rate of the acylation reaction being faster than the deacylation reaction
14
Q
TPCK inactivates chymotrypsin but not trypsin because
A
TPCK looks like the substrate for chymotrypsin and thus can bind in its active site and modify His-57
15
Q
A competitive inhibitor often ____________ the substrate for the enzyme it inhibits.
A
resembles
16
Q
The effects of a ____________ inhibitor can be overcome by increasing the concentration of the substrate.
A
competitive
17
Q
Regarding the cleavage of peptide bonds by chymotrypsin being caused by a nucleophilic attack with an active-site residue, Serine is what?
A
Serine is a strong nucleophile because of the action of Asp and His in the active site.
18
Q
Which type of inhibitor causes Vmax to decrease while Km stays the same?
A
Noncompetitive
19
Q
Which type of inhibitor has no affect on Vmax while Km increases?
A
Competitive
20
Q
Which type of inhibitor causes Vmax to decrease while Km decreases?
A
Uncompetitive
21
Q
Which type of inhibitor binds at the active site?
A
Competitive
22
Q
Which type of inhibitor binds to the ES?
A
Uncompetitive
23
Q
Which type of inhibitor is allosteric?
A
Noncompetitive
24
Q
Which type of inhibitor can only bind after the enzyme substrate complex has formed?
A
Uncompetitive
25
Why is penicillin called a suicide inhibitor for the biosynthesis of bacterial cell walls?
Penicillin forms a covalent intermediate which is enzymatically inactive.
26
The binding of oxygen to myoglobin and hemoglobin has what effect on the heme iron?
It causes the iron to move into the plane of the porphyrin ring
27
How do we know that the binding of oxygen to hemoglobin is cooperative?
A binding plot of Y (fraction of sites occupied) against pO2 is sigmoidal rather than hyperbolic.
28
Oxygen and 2,3-bisphosphoglycerate (2,3- BPG) cannot bind to hemoglobin at the same time because of what?
The structure of hemoglobin is changed when oxygen binds such that 2,3-BPG can no longer bind.
29
Because readily metabolizing tissues generate large amounts of protons and carbon dioxide, the oxygen-binding curve of hemoglobin does what?
Y vs pO2 is shifted to higher pO2 levels.
30
How is hemoglobin used to transport CO2 from the tissues to the lungs?
CO2 reacts with the terminal amino groups on hemoglobin in a reversible manner.
31
What is the relationship of the R-state and the T-states in oxygen binding?
Oxygen binds to the T-state, converting it into the R-state.
32
The difference between the "concerted" and "sequential" models of oxygen binding to hemoglobin is what?
whether the transition between T and R states is "all-or-nothing" or has intermediate states
33
Replacing beta subunits of hemoglobin with gamma subunits results in a higher affinity for oxygen due to what?
decreased binding to 2,3-BPG
34
The mutation of hemoglobin's beta subunit to hemoglobin S as in sickle cell anemia results in the change of what?
a negatively charged amino acid R-group to a hydrophobic amino acid R-group
35
The molecular consequences of the hemoglobin S mutation are what?
hemoglobin S forms aggregates and fibrous precipitates when oxygen is released
36
Lipid molecules are said to be ___________.
amphipathic
37
Cis double bonds in fatty acids cause a ______ in the molecule.
bend
38
In phosphoglycerides, fatty acids are esterified at what?
glycerol carbons 1 and 2
39
Archaeal membrane lipids and those of other organisms both can have what?
a backbone other than glycerol
40
Archaeal membrane lipids' fatty acid esters are replaced with what?
long chain alcohol enter links to the glycerol
41
Archaeal membrane lipids' long hydrophobic tails are what?
branched rather than linear
42
Which major type of membrane lipid is not found in prokaryotes?
Cholesterol
43
What are the three major types of membrane lipids?
Phospholipids, glycolipids, and cholesterol
44
Decreasing the length of a fatty acid chain, does what to the Tm for a phospholipid bilayer?
lowers Tm
45
Unsaturating a carbon, does what to its Tm?
lowers Tm
46
Cis carbons have a _______ Tm compared to trans carbons.
lower
47
More carbon atoms in fatty acids, ___________ Tm
higher
48
________ van der Waals interactions lead to a higher Tm.
More
49
How many carbons do naturally occurring fatty acids have?
an even number, ranging from 14-24
50
Lipids are used by organisms for _________.
energy storage
51
Lipids can be attached to what and by what means?
Carbohydrates; covalent bonds
52
Riemann-Pick disease can result from lack of what?
sphingomyelinase
53
The HIV envelope protein is coated with what class of biomolecules?
Carbohydrates; sugars
54
These monosaccharides differ at a single asymmetric carbon
epimers
55
This is the most abundant organic molecule in the bioshphere
cellulose
56
What is the second most abundant molecule in the biosphere
chitin
57
The storage form of glucose in animals
glycogen
58
The storage form of glucose in plants
starch
59
Explain why cellulose and storage carbs have different structural properties.
The glucose polymers' alpha hollow helix is more compact and easily accessible for storage. Cellulose's beta formation is a rigid, strong structure because of the straight chains it creates.
60
These proteins bind to specific carb structures
lectins (selectin)
61
In n-linked glycoproteins, the carb portion is attached to this residue in the protein
asparagine
62
An o-linked glycoprotein is when the carb portion is attached to what?
serine or threonine
63
The influenza virus recognizes this acidic sugar molecule found on glycoproteins that are present on human cell surfaces. What functional group makes this sugar acidic?
Sialic acid; carboxylic acid
64
Mostly, the pentasaccharide core of N-linked glycoproteins is made of ________ and ________.
manose; N-acetyl glucosamine
65
What is the difference between proteoglycans and glycoproteins?
Proteoglycans are more sugar than protein and play a structural role. Glycoproteins are more protein than sugar and are used for communication.
66
A surface protein of influenza virus that binds to a sugar residue on the host cell membrane.
Hemagglutinnin
67
A surface protein of influenza virus that cleaves glycosidic bonds
neuraminidase
68
Draw the chair structure of beta-D-glucose.
(oxygen right corner, CH2OH equatorial, alternating OHs equatorially)
69
Most fatty acids have odd or even number of carbon atoms and why?
Even, C2 is required to make fatty acids, therefore, only in pairs
70
What are the 3 major types of membrane lipids?
Phospholipids, Glycolipids, Cholesterol
71
What features are common to other macromolecules but not lipids?
inability to form polymers; can bendefined by solubility
72
Lipids which contain carbs
glycolipids
73
Type of lipid with two acyl-chains, a glycerol backbone, and a phosphate head-group.
phosphoglyceride
74
Flat hydrophobic 4-ring molecule that is precursor to many steroidal hormones
Sterol ring or steroid nucleus
75
Name the enzyme reversible inhibitors
competitive, uncompetitive, and noncompetitive
76
What are the 4 categories of irreversible inhibitors?
Group-specific reagents, affinity labels, suicide inhibitors, and transition-state analogs
77
Lipid bilayers are formed how?
The bilayers are formed by phospholipids and glycolipids due to the hydrophobic effect.
78
How many amino acids does it take to span a lipid bilayer?
20
79
What is the melting temperature?
Temperature when a membrane transitions from highly ordered to very fluid
80
Longer chains of fatty acids have _________ Tm and therefore, _________ membrane fluidity.
higher; lower
81
Cis Tm __ Trans Tm and why?
Cis Tm
82
Cholesterol __________ Tm
broadens
83
An increase in temperature has what affect on chain length and unsaturation?
Longer; less
84
What must happen for beta strands with polar groups to pass through a membrane.
The polar groups must hydrogen bond with water
85
What is prostaglandin?
membrane protein that participates in inflammatory response
86
The prostaglandin active site within the membrane can be inhibited by _______________.
Salicylic acid
87
Enzyme that facilitates flip-flopping.
flipase
88
What is the ion gradient needed for?
nerve impulse
89
Digitalis inhibits what?
Na+ and K+
90
What is the ABC transporter?
ATP-binding cassette is an ion pump involved in drug efflux.
91
What is the explanation for bigger molecules passing through an ion channel when smaller molecules cannot?
The bigger molecules strip the K+ ions of water because of their hydrogen backbone.
92
Phospholipids spontaneously form _________.
bilayers
93
The driving force for the formation of membrane bilayers
hydrophobic effect
94
_______ has a high permeability through lipid bilayers.
Water
95
_________ proteins are only removed from a membrane with detergents
integral
96
This substance inhibits prostaglandin H2 synthase-1 by blocking the channel through which the substrate, arachidonate, travels
Aspirin
97
The type of amino acid found in the transmembrane helix of an integral protein
nonpolar
98
This is the process by which lipids and proteins move in the membrane layer.
lateral diffusion
99
These membrane components contain carbohydrates.
glycolipids
100
__________ are bilayer lipid vesicles with an aqueous compartment.
Liposomes
101
________ membrane proteins are bound primarily by electrostatic and hydrogen bond interactions with the head groups of lipids.
Peripheral
102
Some proteins are anchored to the membrane by being covalently attached to a ________ or ________ group by a thirster linkage to a specific cysteine residue.
farnicyl; palmytic
103
An increase in the amount of unsaturated fatty acid chains in a membrane ________ the fluidity of the membrane.
increases
104
Which 3 classes of lipids make up cell membranes
Phospholipids, glycolipids, and steroids
105
Triacylglycerol serves what purpose?
Storage of fatty acids that provides energy
106
Which class of lipid is a hormone precursor?
Free fatty acids
107
What are the beginnings and ends of fatty acid chains called?
alpha and omega
108
Type of fatty acid in vegetable oils
unsaturated, cis
109
Which fatty acid is naturally occurring in animals
Palmitate C16 saturated
110
What factors determine the melting point of fatty acids?
```
# of carbons
# of double bonds
```
111
Draw Glycerol
3 Cs w/ OH and H
112
Triacylglycerols pack 6 times more _______ than glycogen by weight
energy
113
Phosphoglyceride components
Glycerol backbone with 2 non polar fatty acids and polar phosphate attached to alcohol
114
What are carbohydrates?
Hydrated carbons
115
What functional classification does dihydroxyacetone have?
ketose
116
What functional classification does D-Glyceraldehyde have?
Aldose
117
What functional classification does L-Glyceraldehyde have?
aldose
118
D-Glucose and D-mannose are _________.
epimers differing at C2
119
What are anomers?
Isomers that differ at a new asymmetric carbon atom formed on ring closure
120
What is the difference between ribose and deoxyribose?
C2 in ribose is hydrated whereas C2 in deoxyribose has 2H's
121
Fructose and Galactose have how many carbons?
6
122
A ketone and an alcohol form what?
A hemiketal in which the hydrogen atom from the alcohol bonds with the ketone and the R group and oxygen from the alcohol form their own side chain.
123
An aldehyde and an alcohol form what?
A hemiacetal in which the alcohol hydrogen bonds to the aldehyde oxygen and the alcohol's oxygen and R group create their own side chain
124
How is the cyclic form of D-glucose created?
The glucose reacts with its own hydroxyl and can form anomer because the reaction can occur from top or bottom.
125
What is the sugar of fruits?
D-fructose: 6 carbon ketose
126
Draw D-glucose
O at corner with CH2OH next to it in equitorial and OHs alternating
127
The sugars that reduce Cu 2+ into Cu2O have what type of ends?
aldose
128
Carbohydrates form _______ linkages to phosphates.
ester
129
maltose is made of what?
two glucose molecules bound together by an alpha-1,4-glycosidic bond
130
Glycosyltransferases
make sugars
131
Humans don't have enzymes to break what?
Glycosidic bonds
132
Proteins, DNA, and RNA all have what in common?
They are unbranched
133
Starch and Glycogen cannot what?
Pack well due to their alpha-1,4 linkages
134
Cellulose packs to what degree?
It packs well because of its beta-1, 4 linkages and H bonding
135
Steroids are what class of carb?
Glycoprotein
136
Why did the aids vaccine fail?
N-linked Glycoproteins
137
Lance Armstrong
Erythropoietin
138
Glycoproteins function
cell-cell recognition and signaling
139
Which class of carbs function as shock absorbers for joints?
Proteoglycans
140
N-linked glycoprotein
Asn
141
O-linked glycoprotein
Ser, Thr, Tyr
142
Glycosylation of erythropoietin ______________ of the protein in the blood.
enhances the stability
143
Proteoglycans have what charge?
Negative
144
How do proteoglycans function as a shock absorber?
They absorb water and then release it upon compression
145
What is the difference between O, A, and B blood antigens?
O is missing and alpha-1,3 link. A has GalNAc at its alpha-1,3 link. B has Gal at its alpha-1,3 link.
146
Which amino acids are used for the attachment of carbohydrates to proteins?
Asparagine, Serine, Threonine, Tyrosine
147
Tay Sachs is the result of what?
Failure to degrade glycoproteins sugars that accumulate in the lysosomes.
148
What is the flu virus surface protein?
Hemagglutinin
149
What does the flu virus bind to?
Sialic acid
150
What does hemoglobin do?
O2 carrier for red blood cells
151
Does myoglobin or hemoglobin have a quaternary structure?
hemoglobin
152
What does myoglobin do?
O2 storage, exponential graph
153
What are some key characteristics of hemoglobin?
Tetra shape, exhibits cooperativity and is therefore sigmoidal
154
Max Perutz
molecular structure of hemoglobin
155
Addition of what to deoxyhemoglobin creates flat structured oxyhemoglobin?
O2 binding to Heme
156
Deoxyhemoglobin and oxyhemoglobin are associated with what states respectively?
T state; R state
157
What happens upon O2 binding to the T state?
A conformational change occurs forming the R state which includes a smaller space in the middle.
158
What are the differences between hemoglobin with and without BPG?
Hemoglobin with BPG has a lower affinity for O2 and hemoglobin without BPG has a higher affinity for O2.
159
What does the binding of BPG to hemoglobin do?
Stabilizes the T state
160
How does BPG bind to hemoglobin?
BPG is negatively charged and binds to the positively charged residues of the hemoglobin.
161
Why does fetal hemoglobin have a tighter affinity to O2?
The alpha chain is replaced with a gamma chain.
162
What happens in sickle cell?
Soluble fibrils deform cells so that they cannot flow through capillaries
163
More CO2 --> _________ pH
lower
164
What affect does CO2 have on hemoglobin?
Hemoglobin reacts with N-terminus to stabilize deoxy T-State.
165
What kind of bonds occur in reversible inhibitors?
non covalent
166
Sulfa drug is what type of inhibitor?
Competitive inhibitor
167
Which type of inhibitor binds at the active site?
Competitive
168
Which type of inhibitor binds at the ES?
Uncompetitive
169
Which type of inhibitor has allosteric binding?
Noncompetitive
170
Which type of inhibitor raises Km?
Competitive
171
Which type of inhibitor lowers Km?
Uncompetitive
172
Which type of inhibitor does Km remain steady in?
noncompetitive
173
Which type of inhibitor has no effect on Vmax?
competitive
174
Which type of inhibitor lowers Vmax?
Uncompetitive and noncompetitive
175
What is an example of a suicide inhibitor?
Penicillin
176
What is an example of a group specific reagent?
DIPF
177
What is an example of affinity labels?
TPCK
178
Bacterial cell walls have __________ cell walls.
D amino acid
179
How does penicillin work?
It forms covalent bonds to inhibit the enzyme that forms bacterial cell walls.
180
Chymotripsin will cleave what?
Amino acid after big amino acid
181
What is the catalytic triad?
Asp, His, Ser connected by peptide bonds
182
DIPF means _________.
serine is present
183
TPCK will only react with __________.
histidine forming keto group
184
Chymotripsin has a ______ pocket with ______ van der Waals forces.
large, weak
185
An enzyme that temporarily undergoes covalent catalysis as part of its mechanism.
chymotrypsin
186
The type of reaction catalyzed by proteases
hydrolysis
187
The inhibitor which binds only to the ES complex and lowers the Vmax and Km
uncompetitive
188
The enzyme inhibition that can be overcome by increasing concentration of substrate.
competitive
189
The shape of the kinetic plot of an enzyme that exhibits cooperative binding
sigmoidal
190
An enzyme catalyst mechanism that uses a molecule other than water to accept or donate a proton.
Acid-Base Catalysis
191
A catalytic mechanism that forces two substrates into proximity
Catalysis by approximation and orientation
192
The sulfa drug is an example of what kind of inhibitor?
Competitive
193
An uncompetitive inhibitor will have _________ lines on a double reciprocal plot.
parallel
194
A _________ inhibitor binds irreversibly to the active site of an enzyme
suicide
195
The ____________ stabilizes the intermediate of the hydrolysis of a peptide bond by chymotrypsin.
oxyanion hole
196
A __________ inhibitor has a structure similar to the substrate and reversibly binds to the active site of the enzyme.
competitive
197
Which three amino acids play the most important role at the active site in chymotrypsin?
```
Serine (-OH)
Histidine (pentagon with nitrogen bottom left and top and double bonds bottom right and top left)
Aspartic acid (Cooh-ch2)
```
198
The mechanism of chymotrypsin involves the formation of an unstable ________-shaped intermediate that is stabilized by the oxyanion hole
tetrahedral
199
This is the organic portion of the heme group in hemoglobin
porphyrin
200
This is the chemical form in which most of the CO2 is transported in the blood.
Bicarbonate
201
This type of hemoglobin is composed of two alpha chains and two gamma chains.
Fetal Hb
202
This is the molecule whose function is to store oxygen in muscle cells.
myoglobin
203
A type of covalent bond that attaches the heme in myoglobin and hemoglobin
metal coordination bond
204
This type of binding is indicated by a sigmoidal-shaped binding curve.
Cooperative
205
This condition is a result of a single point mutation in the beta chain of hemoglobin.
Sickle cell
206
Under normal conditions the heme iron in myoglobin and hemoglobin is in the ___ oxidation state
Fe 2+
207
The ability of myoglobin to bind oxygen depends on the presence of this bound prosthetic group
heme
208
In hemoglobin, the iron of the heme is bonded to the four nitrogens of porphyrin and to the proximal ____ residue of the global chain.
Histidine
209
The biding of 2-3-bisphosphogycerate to hemoglobin _________ its affinity of oxygen binding
decreases
210
The effect of pH on oxygen-binding of hemoglobin is referred to as the ________.
Bohr effect
211
Carbon dioxide reacts with the amino terminal groups of hemoglobin to form carbamate goups, which carry a _______ charge.
negative
212
The T-state of hemoglobin is stabilized by a salt bridge between Beta 1 Asp 94 and the C-terminal ________ of the Beta 1 chain
Histidine
213
In normal adult hemoglobin, HbA, the Beta6 position is a glutamate residue whereas in sickle cell anemia hemoglobin, HbS, it a _____ residue.
Val
214
As the presence of carbon increases, the affinity of oxygen binding to hemoglobin ___________.
decreases
215
2,3-Bisphosphoglycerate binds only to the ________ form of hemoglobin.
Deoxy or Tstae
