Module 3 Flashcards
(585 cards)
1
Q
How do cells obtain energy from food?
A
From the chemical bonds in food molecules.
2
Q
What are the primary fuel molecules for cells?
A
Sugars.
3
Q
What are the products of sugar catabolism?
A
ATP, NADH, and other activated carrier molecules.
4
Q
What are the three main stages of cellular catabolism?
A
Digestion, Glycolysis, Citric Acid Cycle and Oxidative Phosphorylation.
5
Q
Where does digestion of food molecules occur?
A
Outside cells (intestine) or inside cells (lysosomes).
6
Q
What are proteins broken down into during digestion?
A
Amino acids.
7
Q
What are polysaccharides broken down into during digestion?
A
Sugars.
8
Q
What are fats broken down into during digestion?
A
Fatty acids and glycerol.
9
Q
Where does glycolysis occur?
A
Cytosol.
10
Q
What is the product of glycolysis?
A
Two molecules of pyruvate.
11
Q
What is the net gain of ATP from glycolysis?
A
Two ATP molecules.
12
Q
What high-energy electron carrier is produced during glycolysis?
A
NADH.
13
Q
Where does pyruvate go after glycolysis?
A
Mitochondria.
14
Q
What molecule is pyruvate converted into in the mitochondria?
A
Acetyl CoA.
15
Q
What is the main purpose of the citric acid cycle?
A
Oxidize acetyl CoA to CO2 and generate NADH.
16
Q
Where does the citric acid cycle occur?
A
Mitochondria.
17
Q
What molecule combines with acetyl CoA at the start of the citric acid cycle?
A
Oxaloacetate.
18
Q
What is the main source of ATP production in cells?
A
Oxidative phosphorylation.
19
Q
What drives oxidative phosphorylation?
A
High-energy electrons from NADH and FADH2.
20
Q
What molecule is required for oxidative phosphorylation?
A
Oxygen (O2).
21
Q
What enzyme synthesizes ATP during oxidative phosphorylation?
A
ATP synthase.
22
Q
How many ATP molecules are produced from the complete oxidation of one glucose molecule?
A
About 30 ATP molecules.
23
Q
What is the main storage form of energy in animals?
A
Fat.
24
Q
What molecule stores energy for short-term use in animals?
A
Glycogen.
25
Why is fat a more efficient energy store than glycogen?
Fat releases twice as much energy per gram as glycogen.
26
How long can stored glycogen sustain an average adult human?
About one day.
27
How long can stored fat sustain an average adult human?
Nearly a month.
28
What is the main source of acetyl CoA after an overnight fast?
Fatty acids.
29
What is the main source of acetyl CoA after a meal?
Glucose.
30
What are the products of pyruvate oxidation by the pyruvate dehydrogenase complex?
CO2, NADH, and acetyl CoA.
31
What molecules carry electrons to the electron-transport chain?
NADH and FADH2.
32
What process generates ATP using the proton gradient created by the electron-transport chain?
Chemiosmosis.
33
What molecule is produced at the end of the electron-transport chain?
Water (H2O).
34
What process produces ATP without oxygen?
Glycolysis.
35
What process regenerates NAD+ under anaerobic conditions?
Fermentation.
36
What are the two main types of fermentation?
Alcoholic and lactic acid fermentation.
37
What are the products of alcohol fermentation?
Ethanol and CO2.
38
What are the products of lactic acid fermentation?
Lactate.
39
What enzyme catalyzes the oxidation of glyceraldehyde 3-phosphate in glycolysis?
Glyceraldehyde 3-phosphate dehydrogenase.
40
What is the final product of the citric acid cycle?
Oxaloacetate (regenerated).
41
What is the main source of electrons for oxidative phosphorylation?
NADH and FADH2.
42
What are the main activated carrier molecules produced in the citric acid cycle?
NADH, FADH2, and GTP.
43
What molecule does FADH2 transfer electrons to?
Electron-transport chain.
44
How do plants produce NADPH and ATP?
Photosynthesis.
45
Where are sugars and fats stored in plant cells?
Chloroplasts.
46
What is the main storage form of energy in plant seeds?
Fats and starch.
47
What macromolecule provides nitrogen to vertebrates?
Proteins and nucleic acids.
48
What is nitrogen fixation?
The incorporation of atmospheric nitrogen into organic molecules.
49
What molecule carries nitrogen into biosynthetic reactions?
Glutamine.
50
What are the end products of amino acid oxidation?
CO2, H2O, and urea.
51
What are the main products of nucleotide metabolism?
RNA and DNA.
52
What are the precursors for nucleotide synthesis?
Glutamine, aspartic acid, and glycine.
53
What molecule is the primary source of nitrogen for nucleotide synthesis?
Glutamine.
54
What organ in mammals regulates glucose levels in the bloodstream?
Liver.
55
What molecule is recycled from lactic acid in muscle cells?
Glucose.
56
What molecule is the primary fuel source for nerve cells?
Glucose.
57
What is the purpose of metabolic regulation?
Maintain cellular balance and homeostasis.
58
What molecule signals a high-energy state in the cell?
ATP.
59
What molecule signals a low-energy state in the cell?
AMP.
60
What enzyme couples unfavorable reactions to favorable ones in glycolysis?
Glyceraldehyde 3-phosphate dehydrogenase.
61
What enzyme transfers a high-energy phosphate to ADP in glycolysis?
Phosphoglycerate kinase.
62
What are the two major end products of the citric acid cycle?
CO2 and NADH.
63
What molecule allows NADH to regenerate NAD+ under anaerobic conditions?
Pyruvate.
64
What molecule is regenerated at the end of the citric acid cycle?
Oxaloacetate.
65
What molecule serves as a direct phosphate donor for ATP synthesis in the citric acid cycle?
GTP.
66
What molecule is required for the electron transport chain to function?
Oxygen (O2).
67
What is oxidation in terms of electron transfer?
Loss of electrons.
68
What is reduction in terms of electron transfer?
Gain of electrons.
69
What type of reactions always pair oxidation and reduction?
Redox reactions.
70
What form of electron transfer is common in organic redox reactions?
Hydride ion (proton + two electrons).
71
What are hydrogenation and dehydrogenation?
Gain and loss of hydrogen, respectively.
72
What should hydrogenation and dehydrogenation not be confused with?
Hydration and dehydration.
73
What happens to a carbon atom during oxidation in organic chemistry?
Loses a bond to hydrogen and gains a bond to a heteroatom.
74
What happens to a carbon atom during reduction in organic chemistry?
Gains a bond to hydrogen and loses a bond to a heteroatom.
75
What types of reactions involve the gain or loss of oxygen atoms?
Oxygenase and reductase reactions.
76
What is the most reduced single-carbon compound?
Methane.
77
What is the most oxidized single-carbon compound?
Carbon dioxide.
78
What is the oxidation state series for single-carbon compounds from reduced to oxidized?
Methane → Methanol → Formaldehyde → Formate → Carbon dioxide.
79
What type of organic molecules are highly reduced?
Alkanes.
80
What oxidation state do alcohols and alkenes share?
Same oxidation state.
81
What happens during the dehydration of an alcohol to an alkene?
One carbon is oxidized, and the other is reduced.
82
What is an example of oxidation in organic chemistry?
Conversion of an alcohol to a ketone.
83
What is an example of double reduction?
Carboxylic acid derivative → Aldehyde → Alcohol.
84
Why are acyl transfer reactions not redox reactions?
No change in oxidation state of the organic molecule.
85
What indicates the involvement of a redox agent in an organic reaction?
Change in oxidation state.
86
What must occur when an organic molecule is oxidized?
A corresponding molecule is reduced.
87
What are the oxidation states of organic molecules with two or more carbons from reduced to oxidized?
Alkanes → Alcohols → Alkenes → Ethers → Amines → Sulfides → Phosphate esters → Aldehydes/Ketones/Imines/Epoxides → Carboxylic acid derivatives.
88
Why does oxidation result in a loss of electron density on carbon?
Loss of a bond to hydrogen and gain of a bond to a heteroatom.
89
Why does reduction result in a gain of electron density on carbon?
Gain of a bond to hydrogen and loss of a bond to a heteroatom.
90
What functional group forms when an alcohol is oxidized?
Ketone or aldehyde.
91
What functional group forms when a ketone or aldehyde is reduced?
Alcohol.
92
What type of reaction is the conversion of an acyl phosphate to an amide?
Acyl transfer reaction (not a redox reaction).
93
What is the redox state of an alkane?
Highly reduced.
94
What type of reaction is the oxidation of a primary alcohol to a carboxylic acid?
Double oxidation (via aldehyde intermediate).
95
What type of reaction is the reduction of a ketone to an alcohol?
Single reduction.
96
What type of functional groups are at the highest oxidation state?
Carboxylic acid derivatives.
97
What is the oxidation state of a molecule with more C–H bonds?
More reduced.
98
What is the oxidation state of a molecule with more C–O bonds?
More oxidized.
99
What happens when a carboxylic acid derivative is reduced?
Forms an aldehyde and then an alcohol.
100
Why is the ability to recognize redox reactions important?
Indicates the involvement of redox agents.
101
What change in hydrogen content indicates reduction of an organic compound?
Increase in hydrogen content.
102
What change in oxygen content indicates reduction of an organic compound?
Decrease in oxygen content.
103
What change in hydrogen content indicates oxidation of an organic compound?
Decrease in hydrogen content.
104
What change in oxygen content indicates oxidation of an organic compound?
Increase in oxygen content.
105
How are redox reactions best defined?
Electron transfer.
106
What happens when an atom loses electrons?
Oxidation.
107
What happens when an atom gains electrons?
Reduction.
108
What is the oxidation state of elemental carbon?
Zero.
109
What is the oxidation state of a carbon bonded to a more electropositive atom?
1
110
What is the oxidation state of a carbon bonded to a more electronegative atom?
-1
111
What is the oxidation state of a carbon bonded to another carbon?
0
112
What are examples of electropositive atoms in oxidation state assignment?
Mg, Li, Na, B, H.
113
What are examples of electronegative atoms in oxidation state assignment?
S, N, O, halogens.
114
How is the oxidation state affected by a double or triple bond to a heteroatom?
Count the attached heteroatom twice for a double bond, three times for a triple bond.
115
How does a formal positive charge on carbon affect oxidation state?
Decreases oxidation state by 1.
116
How does a formal negative charge on carbon affect oxidation state?
Increases oxidation state by 1.
117
How does an odd electron on carbon affect oxidation state?
No change.
118
What does an increase in the degree of oxidation of carbon correspond to?
Loss of electrons (oxidation).
119
What does a decrease in the degree of oxidation of carbon correspond to?
Gain of electrons (reduction).
120
Why is the oxidation state scale useful?
Helps balance redox equations.
121
Why should redox terminology not be confused with reaction mechanism?
No connection between them.
122
Why can most reactions theoretically be considered redox reactions?
Reacting atoms experience changes in their electronic environments.
123
When is a reaction described as a redox reaction of carbon?
When there is a net change in the oxidation state of carbon.
124
What is the oxidation state of a methyl group (-CH3)?
-3
125
What is the oxidation state of a methylene group (-CH2-)?
-2
126
What is the oxidation state of a methine group (-CH-)?
-1
127
What is the oxidation state of a carbonyl carbon (C=O)?
2
128
What is the oxidation state of a carboxyl group (COOH)?
3
129
What happens to the oxidation state when an alcohol is oxidized to an aldehyde?
Increases by 2.
130
What happens to the oxidation state when a ketone is reduced to an alcohol?
Decreases by 2.
131
What is the oxidation state change when a carboxyl group is reduced to an alcohol?
+3 to -1 (decrease by 4).
132
What is the oxidation state change when a primary alcohol is oxidized to a carboxyl group?
-1 to +3 (increase by 4).
133
What is the oxidation state change when an aldehyde is reduced to an alcohol?
+1 to -1 (decrease by 2).
134
Where does glycolysis take place?
Cytoplasm.
135
What are the end products of glycolysis?
Two pyruvate molecules.
136
Where is pyruvate converted into acetyl-CoA?
Mitochondrial matrix.
137
What enzyme converts pyruvate into acetyl-CoA?
Pyruvate dehydrogenase.
138
What is released during the conversion of pyruvate to acetyl-CoA?
CO2 and NADH.
139
What is the key metabolic intermediate linking glycolysis and the citric acid cycle?
Acetyl-CoA.
140
What does NAD+ become when reduced?
NADH.
141
How many steps are in the citric acid cycle?
Eight.
142
What is the starting molecule for the citric acid cycle?
Acetyl-CoA.
143
What enzyme catalyzes the formation of citrate from acetyl-CoA and oxaloacetate?
Citrate synthase.
144
What is the first product of the citric acid cycle?
Citrate (citric acid).
145
What enzyme converts citrate to isocitrate?
Aconitase.
146
What type of reaction converts citrate to isocitrate?
Isomerization.
147
What enzyme oxidizes isocitrate to alpha-ketoglutarate?
Isocitrate dehydrogenase.
148
What is released during the conversion of isocitrate to alpha-ketoglutarate?
CO2 and NADH.
149
What enzyme converts alpha-ketoglutarate to succinyl-CoA?
Alpha-ketoglutarate dehydrogenase.
150
What molecules are produced during the conversion of alpha-ketoglutarate to succinyl-CoA?
CO2 and NADH.
151
What enzyme converts succinyl-CoA to succinate?
Succinyl-CoA synthetase.
152
What high-energy molecule is produced during succinyl-CoA to succinate conversion?
GTP.
153
What is the function of GTP in the citric acid cycle?
Can transfer a phosphate to ADP to form ATP.
154
What enzyme converts succinate to fumarate?
Succinate dehydrogenase.
155
Where is succinate dehydrogenase located?
Inner mitochondrial membrane.
156
What coenzyme does succinate dehydrogenase use instead of NAD+?
FAD.
157
What does FAD become when reduced?
FADH2.
158
What component of the electron transport chain is succinate dehydrogenase also known as?
Complex II.
159
What is the electron carrier that accepts electrons from Complex II?
Coenzyme Q (ubiquinone).
160
What enzyme converts fumarate to malate?
Fumarase.
161
What type of reaction converts fumarate to malate?
Hydration (addition of water).
162
What enzyme converts malate to oxaloacetate?
Malate dehydrogenase.
163
What molecule is produced during the conversion of malate to oxaloacetate?
NADH.
164
What molecule combines with acetyl-CoA to restart the citric acid cycle?
Oxaloacetate.
165
How many NADH molecules are produced per acetyl-CoA in the citric acid cycle?
Three.
166
How many FADH2 molecules are produced per acetyl-CoA in the citric acid cycle?
One.
167
How many GTP molecules are produced per acetyl-CoA in the citric acid cycle?
One.
168
How many CO2 molecules are produced per acetyl-CoA in the citric acid cycle?
Two.
169
Where do the electrons from NADH and FADH2 go after the citric acid cycle?
Electron transport chain.
170
Why does the citric acid cycle require oxygen indirectly?
Oxygen is the final electron acceptor in the electron transport chain.
171
What happens if NAD+ and FAD are not regenerated by the electron transport chain?
The citric acid cycle stops.
172
What type of reaction is decarboxylation?
Loss of a carboxyl group (-COOH) as CO2.
173
What is the main function of the citric acid cycle?
Harvest energy from acetyl-CoA.
174
What is the main energy source for living cells?
Glucose.
175
Where does glucose come from?
Food.
176
What is glycolysis?
A sequence of enzyme reactions that breaks down glucose.
177
What are the end products of glycolysis?
Two pyruvate molecules.
178
What molecule provides the initial energy for glycolysis?
ATP.
179
What is ATP?
Adenosine triphosphate, the primary energy source in cells.
180
Where is most ATP produced in the cell?
Mitochondria.
181
What process generates large amounts of ATP in mitochondria?
Aerobic respiration.
182
What molecule is consumed during aerobic respiration?
Oxygen (O2).
183
What is the first enzyme in glycolysis responsible for?
Phosphorylation of glucose using ATP.
184
What is the product of glucose phosphorylation?
Glucose 6-phosphate.
185
What type of reaction forms glucose 6-phosphate?
Phosphorylation.
186
What enzyme converts glucose 6-phosphate into fructose 6-phosphate?
An isomerase.
187
What is the difference between glucose 6-phosphate and fructose 6-phosphate?
They are isomers (same formula, different structure).
188
What enzyme adds a second phosphate group to fructose 6-phosphate?
A kinase.
189
What is the product of phosphorylation of fructose 6-phosphate?
Fructose 1,6-bisphosphate.
190
What does the prefix "bis-" in fructose 1,6-bisphosphate indicate?
Two phosphate groups at different positions.
191
What enzyme splits fructose 1,6-bisphosphate?
Aldolase.
192
What are the two products of fructose 1,6-bisphosphate cleavage?
Glyceraldehyde 3-phosphate and dihydroxyacetone phosphate.
193
Which product of aldolase cleavage continues directly through glycolysis?
Glyceraldehyde 3-phosphate.
194
What happens to dihydroxyacetone phosphate in glycolysis?
It is converted into glyceraldehyde 3-phosphate.
195
What enzyme converts dihydroxyacetone phosphate to glyceraldehyde 3-phosphate?
An isomerase.
196
What enzyme catalyzes the addition of a second phosphate group to glyceraldehyde 3-phosphate?
A kinase.
197
What is the product of phosphorylation of glyceraldehyde 3-phosphate?
1,3-bisphosphoglycerate.
198
What molecule is reduced when glyceraldehyde 3-phosphate is phosphorylated?
NAD+.
199
What does NAD+ become when reduced?
NADH.
200
What type of reaction reduces NAD+ to NADH?
Redox reaction (reduction).
201
How many ATP molecules are consumed during the initial phase of glycolysis?
Two.
202
What enzyme transfers a phosphate group from 1,3-bisphosphoglycerate to ADP?
A kinase.
203
What is the product of the first ATP-producing step of glycolysis?
ATP and 3-phosphoglycerate.
204
How many ATP molecules are generated directly in glycolysis?
Four.
205
What is the net gain of ATP from glycolysis?
Two ATP (4 produced - 2 consumed).
206
What enzyme rearranges the phosphate group within 3-phosphoglycerate?
A mutase.
207
What is the purpose of phosphate group rearrangement in glycolysis?
To prepare for ATP production.
208
What enzyme catalyzes the removal of a water molecule in glycolysis?
A dehydratase.
209
What is the product of the dehydration reaction in glycolysis?
Phosphoenolpyruvate (PEP).
210
What is the final enzyme in glycolysis?
Pyruvate kinase.
211
What is produced in the final step of glycolysis?
Pyruvate and ATP.
212
What is the net production of NADH from glycolysis?
Two NADH.
213
How many molecules of pyruvate are produced from one glucose molecule?
Two.
214
What is the overall purpose of glycolysis?
To break down glucose and produce ATP and NADH.
215
What happens to pyruvate after glycolysis under aerobic conditions?
It is converted to acetyl-CoA and enters the citric acid cycle.
216
What happens to pyruvate after glycolysis under anaerobic conditions?
It is converted to lactate or ethanol.
217
Why is metabolic regulation important?
To balance metabolite flux and conserve energy.
218
What is the risk of unregulated metabolic pathways?
Energy waste and metabolic imbalances.
219
What are the two main regulatory mechanisms of metabolic pathways?
Enzyme activity modulation and enzyme concentration changes.
220
What is Km (Michaelis constant)?
A kinetic parameter representing substrate binding affinity (in molarity).
221
What happens when substrate concentration is much less than Km?
Low enzyme activity.
222
What happens when substrate concentration is much greater than Km?
Enzyme is saturated and maximally active.
223
How does product inhibition work?
The product binds to the enzyme and inhibits further reaction.
224
Why is product inhibition beneficial?
Prevents overproduction and conserves energy.
225
What is feedback inhibition?
End product inhibits an enzyme early in the pathway.
226
What type of enzyme is often targeted in feedback inhibition?
The first committed step enzyme.
227
What is allosteric regulation?
Binding of molecules at sites other than the active site to regulate enzyme activity.
228
What effect can allosteric binding have on an enzyme?
Activation or inhibition.
229
How does allosteric regulation allow interconnected pathway control?
Conformational changes influence activity of other pathways.
230
How can pH changes affect enzyme activity?
By altering protonation states of amino acid residues.
231
How can pH changes disrupt catalysis?
If the protonation state of key residues in the active site is altered.
232
What is covalent modification of enzymes?
Post-translational changes that alter enzyme activity.
233
What are common types of covalent modification?
Phosphorylation, acetylation, methylation, glycosylation, sulfation.
234
What enzyme adds phosphate groups to proteins?
Kinase.
235
What enzyme removes phosphate groups from proteins?
Phosphatase.
236
What is a key example of regulation by phosphorylation?
ERK2 (MAPK2) activation by phosphorylation at Thr183 and Tyr185.
237
What are enzyme condensates?
Supramolecular enzyme complexes formed by phase separation.
238
How do enzyme condensates affect metabolism?
Coordinate enzyme activity and increase metabolic flux.
239
What are examples of metabolism-related enzymes that form condensates?
P-Fructo-Kinase, cytidine triphosphate synthase, acetyl-CoA carboxylase.
240
How does changing enzyme concentration regulate metabolism?
By altering transcription, translation, and degradation rates.
241
How do extracellular signals regulate enzyme gene expression?
By activating or inhibiting transcription factors.
242
How does mRNA degradation regulate enzyme levels?
Less mRNA = less protein synthesis.
243
What enzyme cleaves small RNA-mRNA complexes?
Dicer.
244
What post-translational changes can activate enzymes?
Proteolytic cleavage, cofactor binding, structural changes.
245
How are enzymes degraded to regulate metabolism?
By proteasomes or lysosomes.
246
What characteristics make enzymes ideal for regulation?
Catalysis of irreversible steps and early committed steps.
247
What type of reaction is often far from equilibrium in metabolic pathways?
Hydrolysis or transfer of anhydride groups.
248
What type of energy change makes reactions thermodynamically favorable?
Negative ΔG and ΔG°'.
249
What analogy explains the regulation of flux in metabolic pathways?
Water flow through a valve.
250
What types of molecules have highly exergonic hydrolysis reactions?
ATP, thioesters (like acetyl-CoA), phosphoenol.
251
Why is thioester hydrolysis exergonic?
Weak C-S bond compared to esters.
252
What determines the direction of reversible redox reactions?
Concentrations of reactants and products.
253
What is the equation for the standard free energy change of a redox reaction?
ΔG°' = -nFE°'.
254
What is a committed step in a metabolic pathway?
The first essentially irreversible step in a pathway.
255
Why are committed steps good regulatory points?
They define the pathway’s direction and prevent waste.
256
What are key branch point intermediates in metabolism?
Glucose-6-phosphate and acetyl-CoA.
257
What pathways involve glucose-6-phosphate?
Glycolysis, pentose phosphate pathway, glycogen metabolism.
258
What pathways involve acetyl-CoA?
Citric acid cycle and fatty acid synthesis.
259
What is metabolic control analysis?
A mathematical analysis of pathway regulation.
260
What is metabolism?
The sum of all biochemical reactions in living organisms.
261
What are the two main types of metabolism?
Catabolism and anabolism.
262
What is catabolism?
Breakdown of molecules to release energy (exergonic).
263
What is anabolism?
Synthesis of complex molecules from simpler ones (endergonic).
264
What are the four stages of catabolism?
Digestion, acetyl CoA production, citric acid cycle, electron transport chain.
265
What is the primary role of acetyl CoA in metabolism?
Central molecule linking glycolysis, fatty acid oxidation, and citric acid cycle.
266
What is ATP known as?
The "energy currency" of the cell.
267
How is ATP produced in catabolism?
From ADP and phosphate (Pi) during the electron transport chain.
268
Why is ATP a high-energy molecule?
Due to the phosphoric acid anhydride bonds.
269
What drives unfavorable reactions in cells?
Coupling with energetically favorable reactions.
270
Example of a coupled reaction involving ATP?
Glucose + ATP → Glucose-6-phosphate + ADP.
271
What ion stabilizes ATP's phosphate groups?
Mg²⁺.
272
What are the end products of catabolism?
CO₂, H₂O, and ATP.
273
What bonds are broken in digestion?
Ester, acetal, and peptide bonds.
274
What does digestion produce?
Fatty acids, sugars, and amino acids.
275
What is the first step of glycolysis?
Conversion of glucose to glucose-6-phosphate.
276
What enzyme catalyzes the first step of glycolysis?
Hexokinase.
277
What are the products of glycolysis?
2 pyruvate, 2 NADH, and net 2 ATP.
278
What is the link between glycolysis and the citric acid cycle?
Pyruvate dehydrogenase complex.
279
What is produced by pyruvate dehydrogenase?
Acetyl CoA and CO₂.
280
What happens in the citric acid cycle?
Acetyl CoA is oxidized, releasing CO₂ and generating NADH, FADH₂, and GTP (or ATP).
281
Where does the citric acid cycle occur?
Mitochondrial matrix.
282
What enzyme catalyzes citrate formation in the citric acid cycle?
Citrate synthase.
283
What are the key products of the citric acid cycle?
CO₂, NADH, FADH₂, and GTP (or ATP).
284
What are NADH and FADH₂ used for?
Electron carriers in the electron transport chain.
285
Where does the electron transport chain occur?
Inner mitochondrial membrane.
286
What is the final electron acceptor in the electron transport chain?
Oxygen (O₂).
287
What is oxidative phosphorylation?
ATP production using energy from the electron transport chain.
288
How many ATP are produced from one glucose molecule?
~30–32 ATP.
289
What is substrate-level phosphorylation?
Direct ATP formation during a metabolic reaction.
290
What enzyme catalyzes ATP formation in the electron transport chain?
ATP synthase.
291
What drives ATP synthase?
Proton gradient across the inner mitochondrial membrane.
292
What are the products of β-oxidation of fatty acids?
Acetyl CoA, NADH, and FADH₂.
293
What happens to acetyl CoA from β-oxidation?
Enters the citric acid cycle.
294
What is the purpose of gluconeogenesis?
Formation of glucose from non-carbohydrate sources.
295
What is the Cori cycle?
Recycling of lactate from muscles to liver for glucose production.
296
What is the main storage form of glucose?
Glycogen.
297
What enzyme breaks down glycogen?
Glycogen phosphorylase.
298
What is the main regulatory point of glycolysis?
Phosphofructokinase (PFK-1).
299
What inhibits phosphofructokinase?
High ATP and citrate levels.
300
What activates phosphofructokinase?
High AMP and fructose-2,6-bisphosphate levels.
301
What regulates the citric acid cycle?
ATP, NADH, and product levels.
302
What molecule regulates pyruvate dehydrogenase?
Acetyl CoA and NADH (inhibit); Ca²⁺ (activates).
303
What is fatty acid synthesis regulated by?
Acetyl CoA carboxylase (inhibited by palmitoyl-CoA).
304
What is the primary regulator of cholesterol synthesis?
HMG-CoA reductase.
305
What molecule inhibits HMG-CoA reductase?
Cholesterol.
306
What is the role of AMP-activated protein kinase (AMPK)?
Activates catabolism and inhibits anabolism during low energy states.
307
What is the role of insulin in metabolism?
Promotes glucose uptake and anabolic pathways.
308
What is the role of glucagon?
Promotes gluconeogenesis and glycogenolysis during fasting.
309
What is the effect of epinephrine on metabolism?
Increases glycogen breakdown and glucose release.
310
What is the Warburg effect?
Cancer cells preferentially use glycolysis for energy even in the presence of oxygen.
311
What enzyme converts glucose to glucose-6-phosphate?
Hexokinase.
312
What enzyme converts pyruvate to lactate?
Lactate dehydrogenase.
313
What molecule serves as a redox carrier?
NAD+ and FAD.
314
What is the function of NADPH?
Reducing power for biosynthesis and detoxification.
315
What pathway produces NADPH?
Pentose phosphate pathway.
316
What is the role of glucose-6-phosphate dehydrogenase?
Catalyzes the first step of the pentose phosphate pathway.
317
What is glycogenesis?
Synthesis of glycogen from glucose.
318
What enzyme regulates glycogenesis?
Glycogen synthase.
319
What is glycogenolysis?
Breakdown of glycogen into glucose.
320
What molecule activates glycogen phosphorylase?
AMP and phosphorylation.
321
What enzyme removes the phosphate group from glucose-6-phosphate?
Glucose-6-phosphatase.
322
What is the primary site of gluconeogenesis?
Liver.
323
What enzyme converts pyruvate to oxaloacetate?
Pyruvate carboxylase.
324
What is the malate-aspartate shuttle?
Transports electrons from NADH into mitochondria.
325
What is the glycerol phosphate shuttle?
Transfers electrons from cytosolic NADH to FADH₂ in mitochondria.
326
What is the committed step of fatty acid synthesis?
Formation of malonyl-CoA by acetyl-CoA carboxylase.
327
What inhibits fatty acid synthesis?
Palmitoyl-CoA and AMPK.
328
What stimulates fatty acid oxidation?
High levels of AMP.
329
What molecule inhibits β-oxidation?
Malonyl-CoA.
330
What is ketogenesis?
Formation of ketone bodies from acetyl-CoA during fasting.
331
What are the three main ketone bodies?
Acetoacetate, β-hydroxybutyrate, and acetone.
332
What are the products of amino acid catabolism?
Ammonia (NH₃) and carbon skeletons.
333
What happens to ammonia from amino acid catabolism?
Converted to urea in the liver.
334
What is transamination?
Transfer of an amino group to α-ketoglutarate.
335
What is the role of glutamate dehydrogenase?
Converts glutamate to α-ketoglutarate and NH₃.
336
What is the rate-limiting step of the urea cycle?
Carbamoyl phosphate synthetase I.
337
What molecule is a key regulator of the urea cycle?
N-acetylglutamate.
338
What molecule links glycolysis to the citric acid cycle?
Acetyl CoA
339
What enzyme complex converts pyruvate to acetyl CoA?
Pyruvate dehydrogenase complex
340
How many enzymes are involved in the pyruvate dehydrogenase complex?
Three (E1, E2, E3)
341
What is the coenzyme required by pyruvate dehydrogenase for decarboxylation?
Thiamine pyrophosphate (TPP)
342
What coenzyme is required for acyl group transfer in the pyruvate dehydrogenase complex?
Lipoamide
343
What coenzyme accepts electrons in the pyruvate dehydrogenase reaction?
NAD⁺
344
What molecule carries acetyl groups to the citric acid cycle?
Coenzyme A (CoA)
345
What reaction is catalyzed by the E1 enzyme in the pyruvate dehydrogenase complex?
Decarboxylation of pyruvate
346
What reaction is catalyzed by the E2 enzyme in the pyruvate dehydrogenase complex?
Transfer of acetyl group to CoA
347
What reaction is catalyzed by the E3 enzyme in the pyruvate dehydrogenase complex?
Regeneration of oxidized lipoamide
348
What is the overall reaction of the pyruvate dehydrogenase complex?
Pyruvate + NAD⁺ + CoA → Acetyl CoA + NADH + CO₂
349
Where does the citric acid cycle take place?
Mitochondrial matrix
350
What molecule combines with acetyl CoA to form citrate in the citric acid cycle?
Oxaloacetate
351
What enzyme catalyzes the formation of citrate?
Citrate synthase
352
What is the first product of the citric acid cycle?
Citrate
353
What enzyme converts citrate to isocitrate?
Aconitase
354
What is the intermediate in the conversion of citrate to isocitrate?
Cis-aconitate
355
What enzyme catalyzes the oxidative decarboxylation of isocitrate?
Isocitrate dehydrogenase
356
What are the products of the isocitrate dehydrogenase reaction?
α-Ketoglutarate, NADH, CO₂
357
What enzyme catalyzes the conversion of α-ketoglutarate to succinyl-CoA?
α-Ketoglutarate dehydrogenase
358
What are the products of the α-ketoglutarate dehydrogenase reaction?
Succinyl-CoA, NADH, CO₂
359
What enzyme catalyzes the conversion of succinyl-CoA to succinate?
Succinyl-CoA synthetase
360
What high-energy molecule is produced during the conversion of succinyl-CoA to succinate?
GTP
361
What enzyme catalyzes the conversion of succinate to fumarate?
Succinate dehydrogenase
362
What coenzyme accepts electrons in the succinate dehydrogenase reaction?
FAD
363
What enzyme catalyzes the conversion of fumarate to malate?
Fumarase
364
What enzyme catalyzes the conversion of malate to oxaloacetate?
Malate dehydrogenase
365
What coenzyme is reduced in the malate dehydrogenase reaction?
NAD⁺
366
How many NADH molecules are produced per turn of the citric acid cycle?
Three
367
How many FADH₂ molecules are produced per turn of the citric acid cycle?
One
368
How many GTP molecules are produced per turn of the citric acid cycle?
One
369
What is the total ATP yield from one turn of the citric acid cycle (including NADH and FADH₂)?
10 ATP
370
What is the net reaction of the citric acid cycle?
Acetyl CoA + 3 NAD⁺ + FAD + GDP + Pi + 2 H₂O → 2 CO₂ + 3 NADH + FADH₂ + GTP + CoA
371
How is citrate synthase regulated?
Inhibited by ATP, NADH, and succinyl-CoA
372
How is isocitrate dehydrogenase regulated?
Activated by ADP, inhibited by ATP and NADH
373
How is α-ketoglutarate dehydrogenase regulated?
Inhibited by NADH and succinyl-CoA
374
What molecule serves as a feedback inhibitor for the citric acid cycle?
NADH
375
What molecules provide the main source of energy for ATP synthesis during oxidative phosphorylation?
NADH and FADH₂
376
What are the two electron carriers in the citric acid cycle?
NAD⁺ and FAD
377
What is the purpose of the citric acid cycle?
To generate high-energy electron carriers (NADH, FADH₂) for oxidative phosphorylation
378
How many carbons are lost as CO₂ per turn of the citric acid cycle?
Two
379
How many total ATP molecules are generated from one molecule of glucose via glycolysis, citric acid cycle, and oxidative phosphorylation?
Approximately 30–32 ATP
380
What enzyme complex links the citric acid cycle to the electron transport chain?
Succinate dehydrogenase
381
What molecule is regenerated at the end of the citric acid cycle to continue the cycle?
Oxaloacetate
382
What metabolic pathway follows the citric acid cycle in aerobic respiration?
Electron transport chain
383
What metabolic pathway occurs when oxygen is limited after glycolysis?
Fermentation
384
How does the citric acid cycle contribute to biosynthesis?
Provides intermediates for amino acid, nucleotide, and fatty acid synthesis
385
What molecule provides the reducing power for fatty acid and cholesterol biosynthesis?
NADPH
386
What reaction generates oxaloacetate for gluconeogenesis?
Pyruvate carboxylation
387
What is the effect of low ATP on the citric acid cycle?
Increases flux through the cycle
388
What happens to NADH and FADH₂ produced in the citric acid cycle?
They donate electrons to the electron transport chain
389
What type of reaction generates CO₂ in the citric acid cycle?
Oxidative decarboxylation
390
What is the rate-limiting step of the citric acid cycle?
Isocitrate dehydrogenase reaction
391
What is the primary fuel for the body when food is plentiful?
Glucose
392
What is the brain’s primary source of energy?
Glucose
393
What happens when glucose supply fails to the brain?
Irreversible damage
394
What are the three-carbon precursors for gluconeogenesis?
Lactate, glycerol, alanine
395
What is the starting molecule for gluconeogenesis?
Pyruvate
396
How many steps are involved in gluconeogenesis?
11
397
What enzyme catalyzes the carboxylation of pyruvate?
Pyruvate carboxylase
398
What cofactors are required for pyruvate carboxylase activity?
ATP, bicarbonate ion, biotin
399
What is the product of pyruvate carboxylation in gluconeogenesis?
Oxaloacetate
400
What enzyme catalyzes the decarboxylation and phosphorylation of oxaloacetate?
Phosphoenolpyruvate carboxykinase
401
What molecule is produced from oxaloacetate decarboxylation and phosphorylation?
Phosphoenolpyruvate
402
What is the product of hydration of phosphoenolpyruvate?
2-phosphoglycerate
403
What is the product of phosphorylation and dephosphorylation in gluconeogenesis?
3-phosphoglycerate
404
What enzyme catalyzes the reaction of 3-phosphoglycerate with ATP?
Glyceraldehyde 3-phosphate dehydrogenase
405
What is the product of reduction of 1,3-bisphosphoglycerate?
Glyceraldehyde 3-phosphate
406
What reaction combines dihydroxyacetone phosphate and glyceraldehyde 3-phosphate?
Aldol reaction
407
What is the product of the aldol reaction in gluconeogenesis?
Fructose 1,6-bisphosphate
408
What enzyme catalyzes the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate?
Fructose 1,6-bisphosphatase
409
What is the final product of gluconeogenesis?
Glucose
410
What enzyme catalyzes the conversion of glucose 6-phosphate to glucose?
Glucose 6-phosphatase
411
What is the overall equation for gluconeogenesis?
2 Pyruvate + 4 ATP + 2 GTP + 2 NADH + 6 H2O → Glucose + 4 ADP + 2 GDP + 6 Pi + 2 NAD+
412
What type of reaction is step 8 of gluconeogenesis?
Aldol reaction
413
What is the role of histidine in glucose 6-phosphate hydrolysis?
Forms phosphoryl enzyme intermediate
414
What is the main conclusion about biological chemistry from metabolic pathways?
Similarity between biological and laboratory reactions
415
What are examples of common biological reaction mechanisms?
Nucleophilic substitutions, eliminations, aldol reactions
416
What is the significance of understanding biosynthetic pathways?
Basis for drug development
417
What is the importance of pyruvate carboxylase in gluconeogenesis?
Catalyzes the first step
418
Why is gluconeogenesis not the reverse of glycolysis?
Different enzymes and mechanisms involved
419
Why can't higher organisms synthesize glucose from acetyl CoA?
Metabolic pathway limitation
420
What metabolic intermediate is formed in the reduction of 3-phosphoglycerate?
1,3-bisphosphoglycerate
421
What enzyme converts oxaloacetate to malate for transport into the cytosol?
Malate dehydrogenase
422
What molecule acts as the main reducing agent in gluconeogenesis?
NADH
423
What metabolic pathway directly competes with gluconeogenesis?
Glycolysis
424
How does glucagon influence gluconeogenesis?
Increases activity
425
What hormone inhibits gluconeogenesis?
Insulin
426
What is the rate-limiting enzyme in gluconeogenesis?
Fructose 1,6-bisphosphatase
427
What enzyme converts phosphoenolpyruvate to pyruvate in glycolysis?
Pyruvate kinase
428
What metabolic cycle is linked to gluconeogenesis through oxaloacetate?
Citric acid cycle
429
What is the primary purpose of gluconeogenesis?
Maintain blood glucose levels during fasting
430
How many ATP and GTP are consumed in gluconeogenesis per glucose molecule?
4 ATP, 2 GTP
431
What molecule is a key allosteric activator of pyruvate carboxylase?
Acetyl CoA
432
What step in gluconeogenesis requires biotin as a cofactor?
Pyruvate to oxaloacetate conversion
433
How is oxaloacetate transported from the mitochondria to the cytosol?
Converted to malate
434
What metabolic state favors gluconeogenesis?
Fasting or low-carbohydrate intake
435
What enzyme catalyzes the irreversible reaction in gluconeogenesis?
Glucose 6-phosphatase
436
What enzyme catalyzes the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate?
Fructose 1,6-bisphosphatase
437
What molecule inhibits fructose 1,6-bisphosphatase?
Fructose 2,6-bisphosphate
438
What molecule activates fructose 1,6-bisphosphatase?
Citrate
439
What two enzymes are involved in the phosphorylation and dephosphorylation of pyruvate kinase?
Protein kinase A and protein phosphatase
440
What is the Cori cycle?
Cycle of lactate and glucose between muscles and liver
441
What metabolic pathway supplies precursors for gluconeogenesis?
Amino acid catabolism
442
What are the two main energy currencies used in gluconeogenesis?
ATP and GTP
443
Why is gluconeogenesis energetically expensive?
High ATP and GTP consumption
444
What molecule is produced in the oxidation of glycerol?
Dihydroxyacetone phosphate (DHAP)
445
What enzyme catalyzes the oxidation of glycerol?
Glycerol kinase
446
What molecule inhibits pyruvate carboxylase?
ADP
447
What molecule activates pyruvate carboxylase?
Acetyl CoA
448
What are the key regulated steps in gluconeogenesis?
Pyruvate carboxylase, fructose 1,6-bisphosphatase, glucose 6-phosphatase
449
What are two amino acids that can be directly converted into pyruvate?
Alanine, serine
450
What molecule inhibits glucose 6-phosphatase?
Glucose 6-phosphate
451
What molecule activates glucose 6-phosphatase?
Glucagon
452
What metabolic condition stimulates gluconeogenesis?
Low blood glucose
453
What are the two sources of glycerol for gluconeogenesis?
Adipose tissue triglycerides, dietary fats
454
What is the enzyme that converts glycerol to glycerol-3-phosphate?
Glycerol kinase
455
What molecule links gluconeogenesis and the citric acid cycle?
Oxaloacetate
456
What is the main metabolic fate of lactate in gluconeogenesis?
Conversion to pyruvate
457
What enzyme converts lactate to pyruvate?
Lactate dehydrogenase
458
What is the first committed step of gluconeogenesis?
Pyruvate carboxylation
459
What is the source of NADH in gluconeogenesis?
Malate dehydrogenase reaction
460
What molecule is transported from the cytosol to the mitochondria during gluconeogenesis?
Pyruvate
461
What metabolic intermediate accumulates during gluconeogenesis?
Fructose 1,6-bisphosphate
462
What enzyme converts glucose 6-phosphate to glucose in the ER?
Glucose 6-phosphatase
463
What is the final step in gluconeogenesis?
Conversion of glucose 6-phosphate to glucose
464
What metabolic condition favors gluconeogenesis?
Low carbohydrate intake
465
What is the role of glucagon in gluconeogenesis?
Activates key enzymes
466
What is glycolysis?
The breakdown of glucose into two pyruvate molecules.
467
Where does glycolysis occur?
Cytoplasm.
468
Does glycolysis require oxygen?
No, it is an anaerobic process.
469
What are the main dietary sources of glucose?
Starch (plants) and glycogen (animals).
470
Why can't polysaccharides be transported in the blood?
They are too large for cell uptake.
471
What enzymes break down polysaccharides into glucose?
Amylases, maltase, α-glucosidase, α-dextrinase, sucrase, lactase.
472
What does salivary α-amylase do?
Begins cleavage of α-1,4-glycosidic linkages in the mouth.
473
What is the function of pancreatic α-amylase?
Breaks polysaccharides into maltose and maltotriose in the small intestine.
474
What is the role of maltase?
Converts maltose into glucose.
475
What is α-glucosidase responsible for?
Digestion of maltotriose and other glucose-based oligosugars.
476
What is the function of α-dextrinase?
Breaks down limit dextrin with α-1,6-linkages.
477
What do sucrase and lactase do?
Digest sucrose and lactose into monosaccharides.
478
What is the first stage of glycolysis?
Trapping glucose and destabilizing its structure.
479
What enzyme phosphorylates glucose?
Hexokinase.
480
Why does hexokinase undergo an induced fit upon glucose binding?
To seal off glucose and prevent ATP hydrolysis by water.
481
What ion is required for hexokinase activity?
Mg²⁺ or Mn²⁺.
482
What is the product of glucose phosphorylation?
Glucose 6-phosphate.
483
Why is glucose phosphorylation important?
It traps glucose in the cell and makes it more reactive.
484
What enzyme converts glucose 6-phosphate into fructose 6-phosphate?
Phosphoglucose isomerase.
485
What enzyme catalyzes the second phosphorylation in glycolysis?
Phosphofructokinase-1 (PFK-1).
486
What is the product of the second phosphorylation in glycolysis?
Fructose 1,6-bisphosphate.
487
Why is the second phosphorylation a key regulatory step?
It commits the sugar to glycolysis.
488
What is the second stage of glycolysis?
Cleaving fructose 1,6-bisphosphate into two three-carbon molecules.
489
What enzyme cleaves fructose 1,6-bisphosphate?
Aldolase.
490
What are the products of aldolase activity?
Glyceraldehyde 3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP).
491
What enzyme interconverts DHAP and GAP?
Triose phosphate isomerase (TPI).
492
Why must DHAP be converted to GAP?
Only GAP continues through glycolysis.
493
What is the third stage of glycolysis?
Harvesting energy to form ATP and pyruvate.
494
What enzyme converts GAP to 1,3-bisphosphoglycerate?
Glyceraldehyde 3-phosphate dehydrogenase.
495
What cofactor is reduced in this step?
NAD⁺ → NADH.
496
What enzyme catalyzes the first ATP-producing step in glycolysis?
Phosphoglycerate kinase.
497
What type of phosphorylation occurs in glycolysis?
Substrate-level phosphorylation.
498
What enzyme converts 3-phosphoglycerate to 2-phosphoglycerate?
Phosphoglycerate mutase.
499
What enzyme dehydrates 2-phosphoglycerate to phosphoenolpyruvate (PEP)?
Enolase.
500
What enzyme catalyzes the final step of glycolysis?
Pyruvate kinase.
501
What is the net ATP gain in glycolysis?
2 ATP per glucose molecule.
502
What is the overall equation for glycolysis?
Glucose + 2 ADP + 2 NAD⁺ + 2 Pi → 2 Pyruvate + 2 ATP + 2 NADH + 2 H₂O.
503
What happens to pyruvate under anaerobic conditions?
It undergoes fermentation.
504
What is the purpose of fermentation?
To regenerate NAD⁺ for glycolysis.
505
What enzyme catalyzes lactic acid fermentation?
Lactate dehydrogenase.
506
What is the reaction for lactic acid fermentation?
Pyruvate + NADH + H⁺ → Lactate + NAD⁺.
507
Why does lactic acid fermentation occur in muscles?
To generate ATP when oxygen is limited.
508
What is the net equation for lactic acid fermentation?
Glucose + 2 ADP + 2 Pi → 2 Lactate + 2 ATP + 2 H₂O.
509
What are the two steps of ethanol fermentation?
Pyruvate decarboxylation and acetaldehyde reduction.
510
What enzyme catalyzes pyruvate decarboxylation in ethanol fermentation?
Pyruvate decarboxylase.
511
What coenzyme is required for pyruvate decarboxylation?
Thiamine pyrophosphate (TPP).
512
What enzyme reduces acetaldehyde to ethanol?
Alcohol dehydrogenase.
513
What is the net equation for ethanol fermentation?
Glucose + 2 ADP + 2 Pi + 2 H⁺ → 2 Ethanol + 2 ATP + 2 H₂O + 2 CO₂.
514
What are the three major regulatory enzymes of glycolysis?
Hexokinase, phosphofructokinase, pyruvate kinase.
515
What is the main regulatory enzyme of glycolysis?
Phosphofructokinase (PFK).
516
How does ATP regulate PFK?
High ATP inhibits PFK.
517
What molecule activates PFK?
AMP.
518
What metabolite is a strong activator of PFK?
Fructose 2,6-bisphosphate.
519
What inhibits PFK at low pH?
High H⁺ concentration (lactic acid accumulation).
520
What is an allosteric inhibitor of pyruvate kinase?
ATP.
521
What molecule activates pyruvate kinase?
Fructose 1,6-bisphosphate.
522
How is glycolysis regulated in the liver?
By glucokinase, PFK-1, and pyruvate kinase.
523
What is the function of glucokinase in the liver?
Uptakes glucose only at high blood glucose levels.
524
How does glucagon regulate glycolysis?
It inhibits glycolysis by phosphorylating PFK-2, decreasing F2,6-BP levels.
525
How does insulin regulate glycolysis?
It increases glycolysis by activating PFK-2, increasing F2,6-BP levels.
526
What is gluconeogenesis?
The synthesis of glucose from non-carbohydrate sources.
527
Where does gluconeogenesis primarily occur?
Liver and kidneys.
528
What are the three irreversible steps bypassed in gluconeogenesis?
Hexokinase, phosphofructokinase, pyruvate kinase.
529
What enzyme converts pyruvate to oxaloacetate?
Pyruvate carboxylase.
530
What coenzyme does pyruvate carboxylase require?
Biotin.
531
What enzyme converts oxaloacetate to phosphoenolpyruvate?
PEP carboxykinase.
532
What enzyme hydrolyzes fructose 1,6-bisphosphate in gluconeogenesis?
Fructose 1,6-bisphosphatase.
533
What enzyme hydrolyzes glucose 6-phosphate to free glucose?
Glucose 6-phosphatase.
534
Why is gluconeogenesis necessary?
To maintain blood glucose levels during fasting.
535
How is gluconeogenesis regulated?
By ATP, AMP, fructose 2,6-bisphosphate, and hormones.
536
What molecule inhibits fructose 1,6-bisphosphatase?
AMP.
537
What hormone stimulates gluconeogenesis?
Glucagon.
538
What hormone inhibits gluconeogenesis?
Insulin.
539
What is the Cori cycle?
The recycling of lactate from muscles to liver for glucose production.
540
What metabolic pathway follows glycolysis under aerobic conditions?
The citric acid cycle.
541
What enzyme complex links glycolysis and the citric acid cycle?
Pyruvate dehydrogenase complex.
542
What is the product of pyruvate oxidation?
Acetyl-CoA.
543
What is the net ATP production from complete oxidation of glucose?
~30-32 ATP.
544
What is the function of epinephrine?
Triggers the fight or flight response.
545
What is another name for epinephrine?
Adrenaline.
546
What type of molecule is epinephrine?
Amino acid derivative.
547
Which amino acid is epinephrine derived from?
Tyrosine.
548
Is epinephrine polar or nonpolar?
Polar.
549
Why does epinephrine bind to surface receptors instead of entering the cell?
Because it is polar and cannot cross the cell membrane.
550
What type of receptor does epinephrine bind to?
G protein-coupled receptor (GPCR).
551
Where is epinephrine released from?
Adrenal medulla.
552
Why is it called "epinephrine"?
"Epi" means "on top of," and "nephron" refers to the kidney.
553
What is the primary function of epinephrine in the liver?
Increases blood glucose levels.
554
How does epinephrine increase blood glucose levels in the liver?
By stimulating glycogen breakdown and gluconeogenesis.
555
What is the primary function of epinephrine in muscle cells?
Increases ATP production.
556
How does epinephrine increase ATP in muscle cells?
By stimulating glycolysis, glycogen breakdown, and beta-oxidation.
557
What is the common function of epinephrine in liver and muscle cells?
Increases glycogen breakdown (glycogenolysis).
558
What initiates the epinephrine signaling cascade?
Epinephrine binding to GPCR.
559
What happens after epinephrine binds to its receptor?
The G protein is activated.
560
What type of G protein is activated by epinephrine?
Stimulatory G protein (Gs).
561
What is the inactive form of the G protein?
G protein bound to GDP.
562
How does the G protein become active?
GDP is exchanged for GTP.
563
What enzyme is activated by the G protein in epinephrine signaling?
Adenylyl cyclase.
564
What does adenylyl cyclase do?
Converts ATP into cyclic AMP (cAMP).
565
What is cAMP’s role in the epinephrine pathway?
It acts as a second messenger.
566
Which enzyme is activated by cAMP?
Protein kinase A (PKA).
567
What type of enzyme is PKA?
A kinase that phosphorylates proteins.
568
Which enzymes does PKA phosphorylate in glycogen metabolism?
Glycogen synthase, phosphorylase kinase, glycogen phosphorylase.
569
How does PKA affect glycogen synthase?
Inhibits it by phosphorylation.
570
How does PKA affect phosphorylase kinase?
Activates it by phosphorylation.
571
What is the function of phosphorylase kinase?
Phosphorylates glycogen phosphorylase, activating it.
572
How does PKA affect glycogen phosphorylase?
Activates it by phosphorylation.
573
What is the result of glycogen phosphorylase activation?
Increased glycogen breakdown.
574
Why is glycogen synthesis inhibited while glycogen breakdown is activated?
To prevent opposing processes from occurring simultaneously.
575
What is signal amplification in the epinephrine pathway?
A single epinephrine molecule leads to a large cellular response.
576
How is the epinephrine signal amplified?
Each step activates multiple downstream molecules.
577
What enzyme breaks down cAMP to terminate the signal?
Cyclic nucleotide phosphodiesterase.
578
How does caffeine affect the epinephrine pathway?
Inhibits phosphodiesterase, prolonging cAMP activity.
579
How does the G protein deactivate itself?
GTP is hydrolyzed to GDP.
580
What enzyme removes phosphate groups to terminate the signal?
Protein phosphatases.
581
What effect does protein phosphatase have on glycogen synthase?
Activates it by dephosphorylation.
582
What effect does protein phosphatase have on phosphorylase kinase?
Inactivates it by dephosphorylation.
583
What effect does protein phosphatase have on glycogen phosphorylase?
Inactivates it by dephosphorylation.
584
How does the epinephrine pathway ensure rapid glucose mobilization?
Through a cascade effect that amplifies the signal.
585
Why is epinephrine signaling essential for survival?
Provides quick energy for fight or flight responses.
