Module 5 ChatGPT Flashcards
(260 cards)
1
Q
Insulin
A
The major anabolic hormone in the body that promotes the storage of fuels and the use of fuels for growth
2
Q
Glucagon
A
The major hormone responsible for fuel mobilization, particularly during fasting or energy-demanding situations
3
Q
Epinephrine
A
A hormone released in response to stress, hypoglycemia, or exercise, increasing the availability of fuels for immediate use
4
Q
Hormones
A
Intravascular carriers of messages between their sites of synthesis and target tissues, crucial for metabolic regulation
5
Q
Fuel Homeostasis
A
The balance between fuel storage and fuel mobilization, regulated by hormones such as insulin and glucagon, in response to daily eating patterns
6
Q
Glucose and Metabolic Homeostasis
A
Glucose is critical for tissues like the brain, red blood cells, and muscle, which require continuous glucose supply to meet their energy needs
7
Q
Daily Glucose Requirement
A
An adult requires at least 190 g of glucose per day, with approximately 150 g needed for the brain and 40 g for other tissues
8
Q
Hypoglycemia
A
A condition where blood glucose drops below 60 mg/dL, limiting glucose metabolism in the brain and potentially leading to neurological symptoms
9
Q
Fuel efflux during exercise is
A
The continuous release of fuels from storage during exercise is essential to meet the high demand for ATP
10
Q
Hyperosmolar Effect
A
A potential metabolic derangement where high levels of circulating glucose and amino acids cause severe neurological deficits and other complications
11
Q
Renal Tubular Threshold
A
The maximum concentration of glucose and amino acids that can be reabsorbed by the kidneys, beyond which they are excreted in urine
12
Q
Nonenzymatic Glycosylation
A
The process by which elevated blood glucose levels cause glucose to bind to proteins nonenzymatically, altering their function and potentially damaging tissues
13
Q
Fatty Acids and Metabolism
A
The concentration of fatty acids in the blood determines whether skeletal muscles use fatty acids or glucose as a primary fuel source
14
Q
Ketone Body Formation
A
Ketone bodies are synthesized in the liver’s mitochondrial matrix from acetyl-CoA, which is generated from fatty acid oxidation when acetyl-CoA levels are high
15
Q
Acetoacetate
A
A ketone body that can enter the blood directly or be reduced to beta-hydroxybutyrate. It can also spontaneously decarboxylate into acetone, which is exhaled by the lungs
16
Q
beta-Hydroxybutyrate
A
A ketone body formed by the reduction of acetoacetate, with a blood ratio of approximately 3:1 compared to acetoacetate, determined by the mitochondrial NADH/NAD+ ratio
17
Q
Acetone
A
A volatile compound formed by the spontaneous decarboxylation of acetoacetate, giving the breath of individuals in ketosis a fruity smell
18
Q
Utilization of Ketone Bodies
A
Ketone bodies (acetoacetate and beta-hydroxybutyrate) are oxidized as fuels in tissues like skeletal muscle, brain, kidneys, and intestinal mucosa, but not in the liver
19
Q
beta-Hydroxybutyrate Dehydrogenase
A
An enzyme that interconverts beta-hydroxybutyrate and acetoacetate, producing NADH in the process, with the reaction direction influenced by the mitochondrial NADH/NAD+ ratio
20
Q
Acetoacetate Oxidation
A
Once transported into cells, acetoacetate is converted to acetyl-CoA, which enters the TCA cycle to produce energy
21
Q
Lack of Ketone Body Utilization in Liver
A
The liver cannot utilize ketone bodies because it lacks the enzyme beta-ketoacyl-CoA transferase, which is necessary for their oxidation
22
Q
Tissue Utilization of Ketone Bodies
A
Ketone bodies are utilized as a fuel source by the heart, brain, and muscles, but not by red blood cells (which lack mitochondria) or the liver
23
Q
NADH/NAD+ Ratio
A
The ratio in the mitochondrial matrix that determines the equilibrium between beta-hydroxybutyrate and acetoacetate
24
Q
Ketosis and Breath Odor
A
The fruity odor in the breath of individuals in ketosis is due to the volatile acetone, a byproduct of acetoacetate decarboxylation
25
Fuel Metabolism
The process by which macronutrients (carbohydrates, fats, proteins) from the diet are digested, absorbed, and oxidized to produce energy
26
Fuel Stores
Excess dietary fuel is stored as triacylglycerol (fat) in adipose tissue, glycogen in muscles and liver, and protein in muscles, which are used during fasting periods
27
Respiration
The oxidation of fuels to generate ATP, involving pathways like glycolysis, TCA cycle, and oxidative phosphorylation
28
ATPADP Cycle
The continuous conversion of ATP to ADP and inorganic phosphate (Pi) during energy-consuming processes, and the regeneration of ATP from ADP
29
Macronutrients
Carbohydrates, proteins, and fats from the diet that serve as the primary sources of energy for the body
30
TCA Cycle
A series of reactions in the mitochondrial matrix that oxidizes acetyl-CoA to CO2 and produces electrons for the electron transport chain, generating ATP
31
Glycolysis
The metabolic pathway that converts glucose to pyruvate, generating a small amount of ATP and NADH, and providing intermediates for other pathways
32
Oxidative Phosphorylation
The process by which ATP is generated from ADP and Pi in the mitochondria, driven by the transfer of electrons through the electron transport chain to oxygen
33
Fat Oxidation
The complete oxidation of triacylglycerols to CO2 and H2O, which releases approximately 9 kcal/g, making fats a dense energy source
34
Protein Oxidation
The oxidation of amino acids from proteins to CO2, H2O, and NH4+, yielding approximately 4 kcal/g of energy
35
Dietary Recommendations for Fats
Fats should account for 20%-35% of total calories, with saturated fatty acids being <10% and emphasis on unsaturated fats from fish, nuts, and vegetables
36
Alcohol Metabolism
Ethanol is oxidized to CO2 and H2O, yielding about 7 kcal/g, and should be consumed in moderation, with specific guidelines for men and women
37
Protein Intake
Adults should consume approximately 0 8 g/kg of body weight per day of high-quality protein, with attention to essential amino acids, particularly for vegans
38
Waste Disposal
Xenobiotic compounds and metabolic waste products from diet and air are excreted in urine and feces, maintaining metabolic balance and preventing toxicity
39
Energy Balance
Maintaining a balance between energy intake and expenditure is crucial for achieving and maintaining a healthy body weight and overall fitness
40
How does glucose enter the cells
Glucose enters cells via two main transport systems: Sodium- and ATP-independent (GLUT transporters) and Sodium- and ATP-dependent co-transport systems
41
What is the primary function of GLUT4 transporters
GLUT4 transporters facilitate glucose uptake in skeletal muscle, cardiac muscle, and adipocytes, and their expression is regulated by insulin
42
What are the main substrates and products of glycolysis
Glycolysis uses glucose as a substrate and produces pyruvate, ATP, and NADH
43
What is the net ATP gain from glycolysis
The net ATP gain from glycolysis is 2 ATP molecules per glucose molecule
44
What are the key enzymes of glycolysis, and why are they important
Key enzymes include hexokinase, phosphofructokinase, and pyruvate kinase They regulate glycolysis, controlling the flow of glucose through the pathway
45
What are the fates of pyruvate under aerobic and anaerobic conditions
Aerobically, pyruvate enters the TCA cycle to produce ATP Anaerobically, it is converted into lactate in humans or ethanol in yeast
46
What is the role of pyruvate dehydrogenase (PDH)
PDH converts pyruvate into acetyl-CoA in the mitochondria, linking glycolysis to the TCA cycle
47
What causes lactic acidosis, and what are its consequences
Lactic acidosis is caused by hypoxia, vigorous exercise, or mitochondrial dysfunction, leading to an accumulation of lactic acid, decreased blood pH, and potential metabolic complications
48
How is 2,3-Bisphosphoglycerate (2,3-BPG) produced, and what is its role in erythrocytes
2,3-BPG is produced via the Luebering-Rapoport shunt in glycolysis and reduces hemoglobin's affinity for oxygen, facilitating oxygen release to tissues
49
What is the relationship between erythrocyte structure, metabolism, and oxygen delivery
Erythrocytes, which lack organelles and are biconcave in shape, rely on glycolysis for ATP and use hemoglobin to deliver oxygen to tissues
50
What is the function of GLUT1 transporters
GLUT1 is responsible for high-affinity glucose transport in RBCs and the blood-brain barrier
51
What are the products of glycolysis
The end products of glycolysis are 2 pyruvate, 2 ATP, and 2 NADH per glucose molecule
52
How does insulin affect glucose uptake
Insulin increases glucose uptake by stimulating the translocation of GLUT4 to the cell membrane
53
How does pyruvate enter the mitochondria
Pyruvate enters the mitochondria via the pyruvate translocase protein
54
What is the function of hexokinase in glycolysis
Hexokinase phosphorylates glucose to form glucose-6-phosphate, trapping it inside the cell
55
What regulates phosphofructokinase-1 (PFK-1)
PFK-1 is allosterically activated by AMP and fructose-2,6-bisphosphate, and inhibited by ATP and citrate
56
What happens to pyruvate in the absence of oxygen
In the absence of oxygen, pyruvate is converted into lactate in humans or ethanol in yeast
57
What are the cofactors required by pyruvate dehydrogenase
Pyruvate dehydrogenase requires thiamine pyrophosphate, lipoamide, CoA, FAD, and NAD+ as cofactors
58
What is the role of lactate dehydrogenase
Lactate dehydrogenase converts pyruvate to lactate under anaerobic conditions
59
What are the two main shunts in erythrocyte glycolysis
The two main shunts are the pentose phosphate pathway (HMP shunt) and the Luebering-Rapoport shunt
60
What is the effect of 2,3-BPG on hemoglobin
2,3-BPG decreases hemoglobin's affinity for oxygen, facilitating oxygen release to tissues
61
What are the consequences of pyruvate dehydrogenase deficiency
PDH deficiency leads to lactic acidosis, neurological deficits, and various metabolic disorders
62
How is 2,3-BPG regulated in erythrocytes
2,3-BPG levels increase in response to chronic hypoxia and anemia to enhance oxygen delivery
63
What role does thiamine play in metabolism
Thiamine is a cofactor for pyruvate dehydrogenase and is essential for glucose metabolism
64
What is the Cori cycle
The Cori cycle involves the conversion of lactate from muscles into glucose in the liver
65
How does arsenic poisoning affect pyruvate dehydrogenase
Arsenic binds to lipoamide in PDH, inhibiting its activity and causing lactic acidosis
66
What is the function of GLUT2 in the liver
GLUT2 facilitates the uptake and release of glucose in the liver, playing a key role in glucose homeostasis
67
What enzyme deficiency can lead to methemoglobinemia
Deficiency in cytochrome b5 reductase can lead to methemoglobinemia
68
How does the pentose phosphate pathway relate to erythrocytes
The pentose phosphate pathway provides NADPH for maintaining reduced glutathione in erythrocytes
69
What is the primary source of lactate at rest
The primary sources of lactate at rest are red blood cells, brain, and skin
70
What is the role of pyruvate kinase in glycolysis
Pyruvate kinase catalyzes the final step in glycolysis, converting phosphoenolpyruvate to pyruvate and generating ATP
71
How does hypoxia affect lactic acid production
Hypoxia increases lactic acid production as cells rely more on anaerobic metabolism
72
What is hereditary spherocytosis
Hereditary spherocytosis is a condition where mutations in spectrin lead to abnormally shaped erythrocytes
73
How does insulin affect pyruvate dehydrogenase
Insulin activates pyruvate dehydrogenase by promoting its dephosphorylation
74
What is the effect of chronic anemia on 2,3-BPG levels
Chronic anemia increases 2,3-BPG levels to enhance oxygen unloading from hemoglobin
75
What is the significance of the Luebering-Rapoport shunt
The Luebering-Rapoport shunt allows for the production of 2,3-BPG in erythrocytes, affecting oxygen delivery
76
What are the symptoms of lactic acidosis
Symptoms include headaches, abdominal pain, nausea, rapid breathing, and fatigue
77
How is glucose transported in the brain
Glucose is transported in the brain primarily by GLUT1 and GLUT3 transporters
78
What are the metabolic products of anaerobic glycolysis
The primary product is lactate, which can lead to lactic acidosis if accumulated
79
What is the role of glucokinase in the liver
Glucokinase phosphorylates glucose, allowing it to enter glycolysis or glycogenesis in the liver
80
What is pyruvate carboxylase and where is it located
Pyruvate carboxylase is a mitochondrial enzyme that converts pyruvate to oxaloacetate, linking glycolysis to gluconeogenesis
81
What are the effects of metformin on lactic acidosis
Metformin can inhibit mitochondrial respiration, potentially leading to lactic acidosis in rare cases
82
How is 2,3-BPG involved in adaptation to high altitude
2,3-BPG levels increase at high altitude, enhancing oxygen delivery to tissues despite lower oxygen availability
83
What are the effects of a pyruvate kinase deficiency
Pyruvate kinase deficiency leads to hemolytic anemia due to impaired ATP production in erythrocytes
84
What is the function of NADPH in erythrocytes
NADPH helps maintain reduced glutathione levels, protecting erythrocytes from oxidative damage
85
What happens during the oxidative phase of the pentose phosphate pathway
NADPH is generated, which is crucial for antioxidant defense in erythrocytes
86
What is the role of phosphoglycerate kinase in glycolysis
Phosphoglycerate kinase catalyzes the transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP, producing ATP
87
What are the products of the TCA cycle per pyruvate molecule
The TCA cycle produces 3 NADH, 1 FADH2, 1 GTP (or ATP), and 2 CO2 per pyruvate
88
What is the role of lactate in gluconeogenesis
Lactate can be converted back to glucose in the liver via the Cori cycle
89
What enzyme catalyzes the conversion of pyruvate to acetyl-CoA
Pyruvate dehydrogenase catalyzes this conversion, linking glycolysis to the TCA cycle
90
What is the main cause of hereditary spherocytosis
Mutations in the spectrin protein lead to a loss of erythrocyte membrane integrity
91
What is the significance of fructose-2,6-bisphosphate in glycolysis
Fructose-2,6-bisphosphate is a potent activator of phosphofructokinase-1 (PFK-1), enhancing glycolysis
92
How does thiamine deficiency affect metabolism
Thiamine
93
What are the primary sources of acetyl-CoA for the TCA cycle
Primary sources of acetyl-CoA include pyruvate from glycolysis, fatty acid oxidation, and amino acid catabolism
94
What is the main function of the TCA cycle
The TCA cycle generates high-energy electron carriers (NADH, FADH2) and GTP/ATP, which are used for energy production in the ETC
95
Where are TCA cycle enzymes located
TCA cycle enzymes are located in the mitochondrial matrix
96
What is the significance of mitochondrial compartmentalization for TCA cycle enzymes
Compartmentalization ensures that enzymes and substrates are localized for efficient energy production and metabolic regulation
97
What is the role of citrate synthase in the TCA cycle
Citrate synthase catalyzes the first step of the TCA cycle, converting acetyl-CoA and oxaloacetate to citrate
98
Which enzyme catalyzes the conversion of isocitrate to alpha-ketoglutarate
Isocitrate dehydrogenase catalyzes the conversion of isocitrate to alpha-ketoglutarate, producing NADH and CO2
99
What are the products of the TCA cycle per acetyl-CoA molecule
Each acetyl-CoA produces 3 NADH, 1 FADH2, 1 GTP (or ATP), and 2 CO2
100
What is the role of succinate dehydrogenase in both the TCA cycle and ETC
Succinate dehydrogenase converts succinate to fumarate in the TCA cycle and also functions as Complex II in the ETC
101
How does NADH contribute to ATP production
NADH donates electrons to Complex I of the ETC, driving proton pumping and ATP synthesis via oxidative phosphorylation
102
What is the function of the electron transport chain (ETC)
The ETC transfers electrons from NADH and FADH2 to oxygen, generating a proton gradient used to synthesize ATP
103
What is the role of Complex IV in the ETC
Complex IV transfers electrons to oxygen, the final electron acceptor, forming water
104
What is the proton gradient, and how is it established
The proton gradient is established by the ETC pumping protons across the inner mitochondrial membrane, creating an electrochemical gradient
105
What is the significance of the proton motive force
The proton motive force drives ATP synthesis by allowing protons to flow back into the mitochondrial matrix through ATP synthase
106
What is oxidative phosphorylation
Oxidative phosphorylation is the process by which ATP is produced using the energy from electrons transferred through the ETC
107
What are the consequences of ETC uncoupling
ETC uncoupling dissipates the proton gradient as heat, reducing ATP production and increasing thermogenesis
108
What is the effect of cyanide on the ETC
Cyanide inhibits Complex IV, preventing electron transfer to oxygen, halting ATP production, and leading to cellular asphyxiation
109
What are common inhibitors of Complex I in the ETC
Common inhibitors of Complex I include rotenone and barbiturates
110
What is the role of ATP synthase in oxidative phosphorylation
ATP synthase uses the proton gradient to convert ADP and inorganic phosphate into ATP
111
What happens to oxygen consumption when the ETC is inhibited
Oxygen consumption decreases because electron transfer to oxygen is blocked, halting ATP production
112
How does the TCA cycle interact with the ETC
The TCA cycle generates NADH and FADH2, which donate electrons to the ETC for ATP production
113
What is the role of coenzyme Q in the ETC
Coenzyme Q (ubiquinone) transfers electrons from Complex I and II to Complex III in the ETC
114
How does Complex III contribute to the proton gradient
Complex III pumps protons into the intermembrane space while transferring electrons to cytochrome c
115
What is the role of cytochrome c in the ETC
Cytochrome c transfers electrons from Complex III to Complex IV in the ETC
116
What are the main components of the electron transport chain
The main components are Complex I, II, III, IV, coenzyme Q, and cytochrome c
117
What is the effect of dinitrophenol (DNP) on the ETC
DNP uncouples the ETC by allowing protons to cross the mitochondrial membrane without ATP synthesis, generating heat instead
118
What are the clinical signs of a deficiency in Complex I of the ETC
Signs include muscle weakness, neurodegeneration, and lactic acidosis due to impaired ATP production
119
What is MELAS syndrome, and which part of the ETC is affected
MELAS syndrome affects Complex I and leads to mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes
120
What is the consequence of fumarase deficiency in the TCA cycle
Fumarase deficiency leads to developmental delay, hypotonia, and severe metabolic acidosis
121
What is Leigh syndrome, and how is it related to the ETC
Leigh syndrome is a neurodegenerative disorder often caused by mutations in ETC complexes, particularly Complex I and IV
122
What is the role of biotin in the TCA cycle
Biotin is a cofactor for pyruvate carboxylase, which converts pyruvate to oxaloacetate, a TCA cycle intermediate
123
What is the impact of arsenic poisoning on the TCA cycle
Arsenic inhibits alpha-ketoglutarate dehydrogenase, leading to energy depletion and accumulation of toxic intermediates
124
What are the effects of succinate dehydrogenase deficiency
Deficiency can lead to muscle weakness, neurological defects, and an increased risk of tumors due to impaired TCA cycle and ETC function
125
What is the role of alpha-ketoglutarate dehydrogenase in the TCA cycle
Alpha-ketoglutarate dehydrogenase catalyzes the conversion of alpha-ketoglutarate to succinyl-CoA, producing NADH
126
What are the consequences of pyruvate dehydrogenase deficiency
Deficiency leads to lactic acidosis, neurodegeneration, and poor energy production due to impaired entry of pyruvate into the TCA cycle
127
What is the function of Complex II in the ETC
Complex II (succinate dehydrogenase) transfers electrons from FADH2 to coenzyme Q, linking the TCA cycle to the ETC
128
What is the role of NADH dehydrogenase in the ETC
NADH dehydrogenase (Complex I) transfers electrons from NADH to coenzyme Q, initiating the ETC
129
What are the products of one cycle of the TCA cycle
One cycle produces 3 NADH, 1 FADH2, 1 GTP (or ATP), and 2 CO2 molecules
130
What is the role of oxaloacetate in the TCA cycle
Oxaloacetate combines with acetyl-CoA to form citrate, initiating the TCA cycle
131
What is the impact of a succinyl-CoA synthetase deficiency
Deficiency can cause encephalomyopathy, developmental delay, and lactic acidosis
132
What is the effect of rotenone on cellular respiration
Rotenone inhibits Complex I of the ETC, reducing ATP production and leading to oxidative stress
133
What is the impact of vitamin B1 (thiamine) deficiency on the TCA cycle
Thiamine deficiency impairs pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, leading to lactic acidosis and energy deficits
134
What is the significance of cytochrome c oxidase (Complex IV) in the ETC
Complex IV catalyzes the final transfer of electrons to oxygen, a critical step for ATP production
135
What is the role of Complex III in the ETC
Complex III transfers electrons from coenzyme Q to cytochrome c, while pumping protons to contribute to the proton gradient
136
What are the consequences of fumarase deficiency
Fumarase deficiency can cause severe neurological deficits, developmental delay, and metabolic acidosis
137
What is the impact of malonate on the TCA cycle
Malonate inhibits succinate dehydrogenase, reducing ATP production and leading to metabolic disturbances
138
What are the effects of uncoupling proteins on the ETC
Uncoupling proteins dissipate the proton gradient as heat, reducing ATP production and increasing thermogenesis
139
What is the role of Complex I in the ETC
Complex I transfers electrons from NADH to coenzyme Q, initiating the proton gradient essential for ATP synthesis
140
What is the normal fasting blood glucose range in a healthy person
The normal fasting blood glucose range is approximately 80 to 100 mg/dL
141
What happens to blood glucose levels after a meal in a healthy individual
Blood glucose levels rise to approximately 120 to 140 mg/dL but do not exceed 140 mg/dL
142
What is glycogenolysis and when is it activated
Glycogenolysis is the breakdown of glycogen to glucose, activated during fasting to maintain blood glucose levels
143
What is the primary source of blood glucose during the first few hours of fasting
Liver glycogen is the primary source of blood glucose during the first few hours of fasting
144
Which metabolic process becomes more important during prolonged fasting
Gluconeogenesis becomes more important during prolonged fasting
145
What are the major substrates for gluconeogenesis
The major substrates for gluconeogenesis are glycerol, lactate, and amino acids
146
How is gluconeogenesis regulated during stress or prolonged exercise
Gluconeogenesis is stimulated by the availability of substrates and the activity of key enzymes, regulated by hormones like glucagon, cortisol, and epinephrine
147
What is the role of pyruvate carboxylase in gluconeogenesis
Pyruvate carboxylase converts pyruvate to oxaloacetate, a key step in gluconeogenesis
148
What activates pyruvate carboxylase during fasting
Acetyl-CoA activates pyruvate carboxylase during fasting
149
What happens to pyruvate dehydrogenase during fasting
Pyruvate dehydrogenase is inactivated during fasting, preventing pyruvate from being converted to acetyl-CoA
150
What is the role of PEPCK in gluconeogenesis
Phosphoenolpyruvate carboxykinase (PEPCK) converts oxaloacetate to phosphoenolpyruvate, a key step in gluconeogenesis
151
What is the effect of glucagon on PEPCK
Glucagon induces the expression of PEPCK, promoting gluconeogenesis
152
What is the function of glucose 6-phosphatase in gluconeogenesis
Glucose 6-phosphatase converts glucose 6-phosphate to glucose, allowing glucose to be released into the blood
153
Which hormone decreases the transcription of PEPCK
Insulin decreases the transcription of PEPCK, reducing gluconeogenesis
154
What is the role of glucokinase in glucose metabolism
Glucokinase phosphorylates glucose, trapping it in the cell for glycolysis or glycogen synthesis
155
What is the primary effect of insulin on blood glucose levels
Insulin lowers blood glucose levels by promoting glucose uptake and storage
156
What metabolic process is activated when blood glucose levels fall below the normal range
Gluconeogenesis and glycogenolysis are activated to raise blood glucose levels
157
What are the consequences of hyperglycemia if not regulated
Severe hyperglycemia can lead to dehydration of tissues, hyperosmolar coma, and organ dysfunction
158
What are the consequences of hypoglycemia if not regulated
Severe hypoglycemia can lead to brain dysfunction, coma, hemolysis, and potentially death
159
Which enzyme converts pyruvate to acetyl-CoA under normal conditions
Pyruvate dehydrogenase converts pyruvate to acetyl-CoA under normal conditions
160
Which enzymes are bypassed in gluconeogenesis compared to glycolysis
Gluconeogenesis bypasses pyruvate kinase, phosphofructokinase-1, and glucokinase/hexokinase
161
What are the effects of cortisol on gluconeogenesis
Cortisol induces the expression of gluconeogenic enzymes, promoting glucose production
162
How does lactate contribute to gluconeogenesis
Lactate, produced by muscles and red blood cells, is converted to pyruvate and then to glucose in the liver
163
What is the role of the liver in maintaining blood glucose levels
The liver maintains blood glucose levels by storing glycogen and performing gluconeogenesis
164
What happens to gluconeogenesis during a high-protein diet
Gluconeogenesis is stimulated during a high-protein diet due to the increased availability of amino acids as substrates
165
What are Glycogen Storage Diseases (GSDs)
Glycogen Storage Diseases are a group of inherited metabolic disorders caused by enzyme deficiencies that affect glycogen synthesis, breakdown, or regulation
166
What is the primary function of glycogen in the body
Glycogen serves as a storage form of glucose, primarily in the liver and muscles, to be used as an energy source during periods of fasting or intense activity
167
How is GSD classified
GSDs are classified based on the specific enzyme deficiency and the tissues affected, such as liver, muscle, or both
168
What enzyme is deficient in GSD Type I (Von Gierke disease)
GSD Type I is caused by a deficiency of glucose-6-phosphatase
169
What are the main clinical features of GSD Type I
Key features include severe hypoglycemia, hepatomegaly, lactic acidosis, and hyperuricemia
170
What is the primary treatment for GSD Type I
Treatment involves frequent feedings of glucose or cornstarch to maintain blood glucose levels and avoid hypoglycemia
171
What is the enzyme deficiency in GSD Type II (Pompe disease)
GSD Type II is caused by a deficiency in the enzyme acid alpha-glucosidase (GAA)
172
What tissues are primarily affected in GSD Type II
GSD Type II primarily affects the muscles, including the heart, leading to cardiomegaly, muscle weakness, and respiratory issues
173
What is the inheritance pattern of GSDs
Most GSDs are inherited in an autosomal recessive manner
174
What are the two main subtypes of GSD Type III
GSD Type III is divided into Type IIIa (affecting liver and muscle) and Type IIIb (affecting only the liver)
175
What is the enzyme deficiency in GSD Type IV (Andersen disease)
GSD Type IV is caused by a deficiency in the branching enzyme, leading to abnormal glycogen structure
176
What are the clinical features of GSD Type IV
Clinical features include hepatomegaly, muscle weakness, and progressive liver cirrhosis
177
What is the key difference between GSD Type III and GSD Type IV
GSD Type III involves a debranching enzyme deficiency, while GSD Type IV involves a branching enzyme deficiency
178
What is the prognosis for individuals with GSD Type IV
The prognosis for GSD Type IV is generally poor, often leading to liver failure and early mortality
179
What enzyme is deficient in GSD Type V (McArdle disease)
GSD Type V is caused by a deficiency in muscle phosphorylase
180
What are the main symptoms of GSD Type V
Symptoms include muscle cramps, exercise intolerance, and myoglobinuria following strenuous activity
181
What is the role of glycogen phosphorylase in muscle cells
Glycogen phosphorylase breaks down glycogen into glucose-1-phosphate during muscle activity
182
What dietary recommendations are made for individuals with GSD Type V
A high-protein diet with moderate carbohydrate intake is recommended to enhance muscle glycogen availability
183
What is the enzyme deficiency in GSD Type VI (Hers disease)
GSD Type VI is caused by a deficiency in liver glycogen phosphorylase
184
What are the clinical features of GSD Type VI
Features include mild hypoglycemia, hepatomegaly, and growth retardation, with symptoms often improving with age
185
What enzyme is deficient in GSD Type IX
GSD Type IX is caused by a deficiency in the phosphorylase kinase enzyme
186
What is unique about the inheritance pattern of GSD Type IX
GSD Type IX can be inherited in an X-linked recessive pattern, unlike most other GSDs
187
What are the effects of GSD on fasting tolerance
Individuals with GSD have reduced fasting tolerance due to impaired glycogen breakdown, leading to hypoglycemia
188
How is GSD typically diagnosed
GSD is diagnosed through a combination of clinical features, enzyme activity assays, and genetic testing
189
What are potential long-term complications of GSD
Long-term complications may include liver cirrhosis, cardiomyopathy, and progressive muscle weakness
190
What is the importance of early diagnosis and management in GSD
Early diagnosis and management are crucial to prevent severe hypoglycemia, organ damage, and improve overall quality of life
191
What are the symptoms of hypoglycemia in GSD
Symptoms include sweating, confusion, tremors, irritability, and in severe cases, seizures or unconsciousness
192
How does GSD Type III affect growth and development in children
Children with GSD Type III may experience growth retardation and delayed puberty due to chronic hypoglycemia
193
What is the role of liver biopsy in GSD diagnosis
Liver biopsy can help identify abnormal glycogen accumulation and assess enzyme activity
194
What is the relationship between GSD and exercise intolerance
GSD, particularly types affecting muscle (e g , Type V), often leads to exercise intolerance due to insufficient glycogen breakdown
195
What are the four types of hypoglycemia
The four types of hypoglycemia are insulin-induced, postprandial, fasting, and alcohol-related hypoglycemia
196
How is insulin-induced hypoglycemia treated
Mild cases are treated with oral carbohydrates, while severe cases may require subcutaneous or intramuscular glucagon
197
What causes postprandial hypoglycemia
Postprandial hypoglycemia is caused by an exaggerated insulin release following a meal
198
What is fasting hypoglycemia and its common causes
Fasting hypoglycemia occurs due to reduced hepatic glycogenolysis or gluconeogenesis, often seen in liver disease or adrenal insufficiency
199
What are the symptoms of alcohol-related hypoglycemia
Symptoms include agitation, impaired judgment, and combativeness due to decreased glucose synthesis caused by ethanol metabolism
200
What are the two types of hyperglycemia
The two types of hyperglycemia are fasting hyperglycemia and postprandial hyperglycemia
201
What role does insulin play in fuel metabolism
Insulin promotes glucose storage as glycogen, conversion to triglycerides, and protein synthesis while inhibiting fuel mobilization
202
What is the main action of glucagon during fasting
Glucagon stimulates glycogenolysis and gluconeogenesis to maintain blood glucose levels during fasting
203
What are the primary counterregulatory hormones to insulin
The primary counterregulatory hormones are glucagon, epinephrine, norepinephrine, cortisol, and growth hormone
204
What happens to insulin and glucagon levels after a high-carbohydrate meal
Insulin levels rise while glucagon levels decrease, promoting nutrient storage and inhibiting gluconeogenesis
205
What is the role of cortisol in metabolism during stress
Cortisol increases glucose production from amino acids, enhances lipolysis, and suppresses immune responses
206
How does epinephrine affect glucose metabolism
Epinephrine stimulates glycogenolysis, inhibits insulin secretion, and increases glucose availability during stress
207
What is the primary function of the ?1-adrenergic receptor
The ?1-adrenergic receptor increases heart rate and force of contraction in response to norepinephrine
208
Where are ?2-adrenergic receptors found, and what is their function
?2-adrenergic receptors are found in the liver, skeletal muscle, and smooth muscle, where they mediate glycogenolysis and muscle relaxation
209
What is the role of ?3-adrenergic receptors in adipose tissue
?3-adrenergic receptors stimulate fatty acid oxidation and thermogenesis in adipose tissue
210
How does cortisol influence gene transcription
Cortisol binds to intracellular receptors, influencing gene transcription by interacting with chromatin in the cell nucleus
211
What are the three basic types of hormone signal transduction
The three types are receptor coupling to adenylate cyclase, receptor kinase activity, and receptor coupling to PIP2 hydrolysis
212
What is the role of cAMP in glucagon signaling
cAMP acts as a second messenger, activating PKA, which phosphorylates key enzymes in carbohydrate and fat metabolism
213
What is the main function of insulin in the body
Insulin facilitates glucose uptake, promotes glycogen and fat storage, and stimulates protein synthesis
214
What is the role of glucagon in regulating blood glucose
Glucagon raises blood glucose by promoting glycogen breakdown and gluconeogenesis in the liver
215
How is insulin secretion regulated
Insulin secretion is primarily regulated by blood glucose levels, with additional modulation by amino acids and gastrointestinal hormones
216
What is the relationship between insulin and glucagon during fasting
During fasting, insulin levels decrease while glucagon levels rise, leading to glucose release from the liver and fatty acid mobilization
217
How do catecholamines like epinephrine and norepinephrine affect metabolism
They increase fuel mobilization, enhance cardiac output, and prepare the body for stress (fight-or-flight response)
218
What is the function of the insulin receptor
The insulin receptor, through its tyrosine kinase activity, initiates a signaling cascade that regulates glucose uptake and metabolism
219
What are the effects of insulin on protein synthesis
Insulin stimulates protein synthesis by promoting amino acid uptake and enhancing mRNA translation
220
What is the role of glucagon in lipid metabolism
Glucagon stimulates lipolysis in adipose tissue, releasing fatty acids as an alternative energy source
221
What is the effect of insulin on glycogen synthesis
Insulin promotes glycogen synthesis by activating glycogen synthase and inhibiting glycogen phosphorylase
222
What are the effects of hypoglycemia on the body
Hypoglycemia can cause symptoms like sweating, confusion, tremors, and in severe cases, seizures and loss of consciousness
223
How does cortisol impact glucose metabolism
Cortisol promotes gluconeogenesis and inhibits glucose uptake in tissues, contributing to elevated blood glucose levels during stress
224
What are the primary metabolic effects of fasting
Fasting leads to increased gluconeogenesis, lipolysis, and ketogenesis to maintain energy supply
225
What are the key hormones involved in the fed state
Insulin is the key hormone in the fed state, promoting nutrient storage and utilization
226
What is the effect of glucagon on hepatic fructose 2,6-bisphosphate
Glucagon decreases hepatic fructose 2,6-bisphosphate, inhibiting glycolysis and activating gluconeogenesis
227
What is the role of the hypothalamus in glucose regulation
The hypothalamus triggers the release of counterregulatory hormones like glucagon and epinephrine in response to low blood glucose
228
What is the significance of GLUT transporters in insulin secretion
GLUT transporters facilitate glucose entry into ?-cells, triggering insulin release through metabolic signaling pathways
229
How does alcohol consumption affect glucose metabolism
Alcohol metabolism increases NADH, diverting gluconeogenic precursors away from glucose production and potentially leading to hypoglycemia
230
What is the function of glucagon-like peptide 1 (GLP-1)
GLP-1 enhances insulin secretion in response to food intake and slows gastric emptying, contributing to blood glucose regulation
231
What is the relationship between cortisol and epinephrine during stress
Cortisol and epinephrine work synergistically to increase blood glucose levels and energy availability during stress
232
What is insulin resistance, and how does it affect metabolism
Insulin resistance is the reduced response of tissues to insulin, leading to elevated blood glucose and altered lipid metabolism
233
How does glucagon influence amino acid metabolism
Glucagon promotes the use of amino acids for gluconeogenesis, particularly during fasting or low-carbohydrate intake
234
What is the impact of epinephrine on muscle metabolism
Epinephrine stimulates glycogenolysis in muscle tissue, providing glucose for immediate energy during physical activity
235
What role does insulin play in lipid metabolism
Insulin inhibits lipolysis in adipose tissue and promotes the storage of triglycerides
236
What is the primary function of glucose in metabolism
Glucose serves as a primary energy source, providing ATP through glycolysis, the TCA cycle, and oxidative phosphorylation
237
What enzyme converts glucose to glucose 6-phosphate in the liver
Glucokinase converts glucose to glucose 6-phosphate in the liver, especially active in the fed state
238
What is the role of glycogen in the body
Glycogen acts as a storage form of glucose in the liver and muscles, providing a rapid source of energy during fasting or exercise
239
How is glycogen synthase regulated
Glycogen synthase is activated by dephosphorylation when insulin levels are high and glucagon levels are low
240
What is the key regulatory enzyme in glycolysis
Phosphofructokinase-1 (PFK-1) is the key regulatory enzyme in glycolysis, activated by fructose 2,6-bisphosphate and AMP
241
What happens to pyruvate in the presence of oxygen
Pyruvate is converted to acetyl-CoA by pyruvate dehydrogenase, entering the TCA cycle for further energy production
242
What is the role of acetyl-CoA in fatty acid synthesis
Acetyl-CoA provides the two-carbon units for fatty acid synthesis in the cytosol, following its conversion from pyruvate in the mitochondria
243
How does insulin affect acetyl-CoA carboxylase
Insulin activates acetyl-CoA carboxylase by dephosphorylation, promoting fatty acid synthesis
244
What is the significance of malonyl-CoA in lipid metabolism
Malonyl-CoA inhibits carnitine palmitoyltransferase I (CPTI), preventing fatty acid oxidation in the mitochondria during the fed state
245
How is glucose 6-phosphate used in lipogenesis
Glucose 6-phosphate enters glycolysis, where it is eventually converted to acetyl-CoA, a precursor for fatty acid synthesis
246
What happens to citrate in the cytosol during lipogenesis
Citrate is cleaved by citrate lyase into acetyl-CoA and oxaloacetate, providing substrates for fatty acid and cholesterol synthesis
247
How does fasting affect liver glycogen levels
During fasting, liver glycogen is degraded to maintain blood glucose levels, driven by the activation of glycogen phosphorylase
248
What triggers gluconeogenesis during prolonged fasting
Gluconeogenesis is triggered by increased availability of precursors and the induction of enzymes like PEPCK and glucose 6-phosphatase
249
What role does AMP play in regulating metabolism
AMP activates AMP-activated protein kinase (AMPK), which promotes glucose uptake and fatty acid oxidation, particularly during low energy states
250
What happens to fatty acids during fasting
Fatty acids are released from adipose tissue and oxidized in the liver, producing acetyl-CoA for ketone body synthesis
251
What is the role of pyruvate dehydrogenase (PDH) in energy metabolism
PDH converts pyruvate to acetyl-CoA, linking glycolysis to the TCA cycle for ATP production
252
What is the function of ketone bodies during fasting
Ketone bodies serve as an alternative energy source, particularly for the brain, during prolonged fasting when glucose is scarce
253
What is the effect of insulin on GLUT4 transporters in muscle cells
Insulin increases the number of GLUT4 transporters on the muscle cell membrane, enhancing glucose uptake
254
How is glycolysis inhibited during fasting
Glycolysis is inhibited by low levels of fructose 2,6-bisphosphate, which decreases PFK-1 activity, favoring gluconeogenesis
255
What enzyme is responsible for the final step of gluconeogenesis
Glucose 6-phosphatase catalyzes the conversion of glucose 6-phosphate to glucose, enabling its release into the bloodstream
256
What happens to pyruvate carboxylase activity during fasting
Pyruvate carboxylase activity increases during fasting, promoting gluconeogenesis by converting pyruvate to oxaloacetate
257
What is the relationship between citrate levels and fatty acid synthesis
High citrate levels in the cytosol promote fatty acid synthesis by providing acetyl-CoA and activating acetyl-CoA carboxylase
258
How does fasting influence ketone body production
Fasting increases ketone body production as fatty acids are oxidized in the liver, with acetyl-CoA being converted to ketone bodies
259
What is the effect of NADH on isocitrate dehydrogenase
High levels of NADH inhibit isocitrate dehydrogenase, leading to citrate accumulation and promoting fatty acid synthesis in the cytosol
260
How does glucagon influence liver metabolism during fasting
Glucagon activates glycogenolysis and gluconeogenesis in the liver, raising blood glucose levels
