L13 Flashcards
(203 cards)
1
Q
What is the overall definition of metabolism?
A
The sum of all chemical reactions in the body
2
Q
What is an anabolic process?
A
Building large molecules from smaller ones
3
Q
What is a catabolic process?
A
Breaking down large molecules into smaller ones
4
Q
Which metabolic state occurs just after a meal?
A
The fed (absorptive) state
5
Q
What is primarily used for energy in the fed state?
A
Glucose
6
Q
Which metabolic state occurs after fasting for at least 3-4 hours?
A
The fasted (postabsorptive) state
7
Q
What is used for energy in the fasted state?
A
Glucose and fat
8
Q
What is Basal Metabolic Rate?
A
Energy expenditure at rest, comfortable temperature, and fasted
9
Q
What factors control energy balance?
A
Caloric intake and exercise
10
Q
What is glycogenesis?
A
The making of glycogen from glucose
11
Q
What is glycogenolysis?
A
The breakdown of glycogen into glucose
12
Q
What process breaks down glucose to produce ATP?
A
Glycolysis, TCA, and oxidative phosphorylation
13
Q
What is lipogenesis?
A
The making of fat (triglycerides) from fatty acids and glycerol
14
Q
What is lipolysis?
A
The breakdown of triglycerides into fatty acids and glycerol
15
Q
What is beta oxidation?
A
The breakdown of fatty acids to produce ATP
16
Q
What is gluconeogenesis?
A
Synthesis of glucose from non-carbohydrate substrates
17
Q
Where is the pancreas located?
A
Under the stomach, near the small intestine and liver
18
Q
What does the exocrine pancreas produce?
A
Bicarbonate and proenzymes for digestion
19
Q
How does the exocrine pancreas release its secretions?
A
Directly into ducts
20
Q
How does the endocrine pancreas release its secretions?
A
Directly into the bloodstream
21
Q
What are the specialized cells of the endocrine pancreas called?
A
Islets of Langerhans
22
Q
What hormone do Beta cells secrete?
A
Insulin
23
Q
What hormone do Alpha cells secrete?
A
Glucagon
24
Q
What hormone do Delta cells secrete?
A
Somatostatin
25
What is proinsulin?
The precursor that Beta cells produce, cleaved to insulin
26
What is the main relationship between insulin and glucagon?
They are antagonistic
27
What type of receptor does insulin bind to?
A receptor tyrosine kinase
28
What type of receptor does glucagon bind to?
A G protein-coupled receptor
29
Do insulin and glucagon use the same signaling pathways inside the cell?
No, they initiate different cascades
30
What is the ultimate goal of their signaling in target cells?
To switch between feeding and fasting metabolism
31
Do they act on the same target cells?
Yes, they often share target cells
32
What happens after the receptor is bound?
Signaling occurs inside the cell
33
What is one step in the signaling cascade mentioned for insulin?
Phosphorylating proteins
34
How many transmembrane regions does the glucagon receptor have?
7
35
What is the final outcome of the cellular response?
Changes in cellular activity/metabolism
36
What is the primary substrate for regulating blood sugar levels?
Glucose
37
What does the insulin: glucagon ratio control?
Organ response and metabolism
38
In the fasted state, are insulin levels high or low?
Low
39
In the fasted state, are glucagon levels high or low?
High
40
What happens to plasma glucose levels after a meal?
They rise significantly
41
What happens to plasma insulin levels after a meal?
They spike
42
What happens to plasma glucagon levels after a meal?
They drop
43
What does insulin do to blood glucose levels?
It lowers them by pushing glucose into cells
44
Approximately how long after a meal does glucagon start to rise again?
About 4 hours
45
What is the goal of glucose homeostasis?
To maintain a stable blood glucose level
46
What metabolic state is insulin dominant in?
The fed state
47
Is insulin considered an anabolic or catabolic hormone?
Anabolic
48
How is insulin synthesized?
As a typical peptide
49
What type of receptor does insulin bind to?
A receptor tyrosine kinase
50
What is one major effect of insulin on blood glucose?
It reduces blood glucose
51
What does insulin promote the formation of?
Glycogen, fat, and protein
52
Does insulin encourage storing or breaking down glucose?
Storing glucose
53
What process does insulin activate related to glycogen?
Glycogenesis (making glycogen)
54
What process does insulin inhibit related to glycogen?
Glycogenolysis (breaking down glycogen)
55
Does insulin promote or inhibit lipolysis and protein synthesis?
Inhibits both
56
What is a main effect of insulin on glucose transport?
Increases glucose transport into insulin-sensitive cells
57
Which process does insulin activate to store glucose as glycogen?
Glycogenesis
58
Does insulin promote or inhibit glycogen breakdown?
Inhibits glycogenolysis
59
What effect does insulin have on fat synthesis?
Activates enzymes for lipogenesis
60
How does insulin impact protein synthesis in muscle?
Increases amino acid uptake and protein synthesis
61
Does insulin encourage or prevent the creation of new glucose from non-carbs?
Inhibits gluconeogenesis
62
What fat breakdown process does insulin inhibit?
Lipolysis and beta oxidation
63
Insulin promotes the formation of which large molecules?
Glycogen, fat, and protein
64
What happens to amino acid uptake in muscle cells when insulin is present?
It increases
65
Beyond metabolism, what general cell activity does insulin boost?
Enhances cell proliferation
66
What kind of receptor does insulin bind to?
Receptor tyrosine kinase
67
What molecule gets phosphorylated by the insulin receptor?
IRS (Insulin Receptor Substrate)
68
What do the activated second messenger pathways do?
Alter protein synthesis and existing proteins
69
How does insulin change membrane transport for glucose?
It modifies it to increase glucose uptake
70
Which specific glucose transporters are key to insulin's action in muscle/fat?
GLUT4 transporters
71
Where do GLUT4 transporters move when insulin signals?
To the cell membrane
72
What is the main outcome of these mechanisms for glucose?
Glucose enters the cell
73
Does insulin binding start a chain reaction inside the cell?
Yes, a signaling cascade
74
In which tissues are GLUT4 transporters mainly found?
Muscle and adipose tissue
75
Where are GLUT4 transporters located in the fasted state?
Inside the cell
76
Describe the insulin/glucagon ratio in the fed state.
High insulin, low glucagon
77
What process moves GLUT4 to the membrane in the fed state?
Exocytosis
78
What starts the signaling cascade in muscle and fat cells?
Insulin binding
79
What happens to glucose in muscle and fat cells during the fed state?
Glucose enters the cell
80
Which metabolic state has a low insulin/glucagon ratio?
Fasted state
81
Is there a lot of glucose available for storage in muscle/fat during the fasted state?
No
82
What experimental method showed GLUT4 moving to the cell surface?
GFP tagging
83
What type of tissue are GLUT4 transporters found in?
Muscle and adipose tissue
84
What protein was used to tag the GLUT4 transporters in the experiment?
Green fluorescent protein (GFP)
85
Where are GLUT4 transporters located in a fasted cell?
Inside the cell
86
What hormone causes GLUT4 transporters to move to the cell membrane?
Insulin
87
What state is the cell in when insulin is added?
Fed state
88
What process moves GLUT4 to the cell membrane?
Exocytosis
89
What is the purpose of moving GLUT4 to the cell membrane?
To increase glucose uptake into the cell
90
What glucose transporter is found in liver cells?
GLUT2 transporter
91
What enzyme does insulin activate in liver cells?
Hexokinase
92
What does hexokinase convert free glucose into?
Glucose-6-phosphate
93
Why is converting glucose to glucose-6-phosphate important for uptake?
It maintains a high glucose concentration gradient
94
Does maintaining the gradient increase or decrease glucose uptake by the liver?
Increases glucose uptake
95
What state is the liver in when insulin is around?
Fed state
96
What does the liver want to do with glucose in the fed state?
Store glucose
97
Does converting free glucose slow down the gradient of diffusion?
No, it helps maintain it
98
What is the primary stimulus for insulin secretion?
Increased plasma glucose
99
What cells in the pancreas secrete insulin?
Beta cells
100
What process in beta cells leads to a rise in ATP?
Glycolysis and the Citric Acid Cycle
101
What do increased ATP levels cause to close in beta cells?
K+ channels
102
What happens to the beta cell membrane when K+ channels close?
It depolarizes
103
What channels open when the beta cell depolarizes?
Ca2+ channels
104
What triggers insulin release from vesicles?
Influx of Ca2+ into the cell
105
What is being compared in the graph on the left?
Blood glucose levels after intravenous vs. intrajujunal glucose infusion
106
What is being measured in the graph on the right?
Plasma insulin levels
107
Which method of glucose administration resulted in a higher plasma insulin spike?
Intrajujunal (into the small intestine)
108
What is the term for the enhanced insulin response to oral glucose compared to intravenous glucose?
The Incretin effect
109
Where was the intravenous glucose injected?
Directly into the bloodstream
110
Where was the intrajujunal glucose injected?
Into a part of the small intestine (the jejunum)
111
How did the insulin spike compare to the glucose levels in the intravenous case?
The insulin spike mirrored the glucose levels
112
Does the small intestine have a bigger or smaller effect on insulin release compared to direct IV glucose?
Bigger effect
113
What happens to plasma glucose levels over time after a meal?
They rise initially and then go down
114
What happens to plasma insulin levels over time after a meal?
They spike and then drop as glucose levels decrease
115
What explains the enhanced effect of intrajujunal glucose on insulin?
Gastrointestinal hormones
116
Name two key gastrointestinal hormones mentioned that secrete insulin.
Gastric Inhibitory Peptide (GIP) and Glucagon-Like Peptide-1 (GLP-1)
117
What stimulates the release of GIP?
Glucose, fatty acids, and amino acids (nutrients)
118
What stimulates the release of GLP-1?
Nutrients and parasympathetic activity
119
What is one effect of GIP on insulin?
It increases insulin secretion
120
What is one effect of GLP-1 on insulin?
It increases insulin secretion
121
What effect does GLP-1 have on glucagon?
It decreases glucagon secretion
122
Besides insulin and glucagon, what is another effect of GLP-1 mentioned?
Increases beta cell growth, decreases gastric acid/emptying, or feeling of satiety
123
What is one effect of GIP on gastric activity?
It decreases gastric emptying/acid
124
Do these hormones support or inhibit insulin action?
They support insulin action
125
What is the primary stimulus for insulin secretion?
Increased plasma glucose
126
What type of regulation is it when GI hormones promote insulin secretion in response to nutrient ingestion?
Feedforward regulation
127
Does increased plasma amino acids stimulate or inhibit insulin secretion?
Stimulate
128
Which part of the nervous system stimulates insulin secretion?
Parasympathetic nervous system
129
Which part of the nervous system inhibits insulin secretion?
Sympathetic nervous system
130
Why does the sympathetic nervous system inhibit insulin?
To mobilize fuels and have excess glucose available (fight or flight)
131
What cells secrete glucagon?
Alpha cells secrete glucagon
132
What is glucagon's main target organ?
The liver is glucagon's main target
133
How does glucagon relate to insulin?
Glucagon antagonizes, or opposes, insulin's effects
134
What metabolic state does glucagon dominate?
Glucagon dominates in the fasted state
135
What process does glucagon increase to break down stored glucose?
Glucagon increases glycogenolysis
136
What process does glucagon increase to create new glucose?
Glucagon increases gluconeogenesis
137
What other process does glucagon increase, related to fat breakdown?
Glucagon increases ketogenesis
138
What does glucagon do to glucose stores in the liver?
It releases the glucose stored in the liver
139
What is glucagon's main goal?
Glucagon's goal is to prevent hypoglycemia
140
What is hypoglycemia?
Hypoglycemia is low blood glucose levels
141
What type of receptor does glucagon bind to in the liver?
Glucagon binds to a Gs protein-coupled receptor
142
What molecule is activated downstream of the Gs protein signaling cascade?
Adenylyl cyclase is activated
143
What second messenger is produced by adenylyl cyclase?
cAMP is produced
144
What enzyme does cAMP activate in the glucagon signaling pathway?
cAMP activates Protein kinase A
145
What is the main stored form of glucose in the liver that glucagon acts on?
Glycogen is the main stored form
146
How does glucagon promote glucose transport out of liver cells?
It does so indirectly by increasing intracellular glucose
147
What transporter is found in liver cells for glucose?
Liver cells express the GLUT2 transporter
148
Does glucagon increase or decrease the breakdown of glycogen stores?
Glucagon increases the breakdown of glycogen stores
149
Does glucagon increase or decrease gluconeogenesis?
Glucagon increases gluconeogenesis
150
Where does glucose accumulate before being transported out?
Glucose accumulates inside the liver cells (hepatocytes)
151
What happens to the accumulated glucose in liver cells?
It is transported out of the cells via transporters
152
Which hormone needs cortisol for its full activity?
Glucagon needs cortisol
153
What does cortisol work with glucagon to do?
To build up glucose in the body
154
How long does it take for the combined effect of epinephrine, glucagon, and cortisol to significantly raise blood glucose in the graph?
Around 2-3 hours
155
What stimulates glucagon secretion?
- Decreased plasma glucose
- Increased plasma amino acids
- The sympathetic nervous system
156
What hormone inhibits glucagon secretion?
Glucagon-like peptide-1 (GLP-1)
157
How does glucagon help prevent hypoglycemia in the low-carb scenario?
It's co-secreted to stimulate the liver to release more glucose
158
What is proglucagon?
A large gene that contains multiple active hormones
159
Which active hormones are contained within proglucagon?
Glucagon, GLP-1, and GLP-2
160
Where is proglucagon expressed?
In alpha cells, L cells of the intestine, and the brain
161
What is the main product of proglucagon in alpha cells?
Glucagon
162
What are the main products of proglucagon in L cells of the intestine and brain?
GLP-1 and GLP-2
163
Are the enzymes that cleave proglucagon the same in all tissues?
No, they differ, leading to different main products
164
What metabolic pathways does glucagon promote?
Catabolic pathways (like gluconeogenesis and glycogenolysis)
165
Where is GLP-1 released from?
The intestine
166
What effect does GLP-1 have on insulin and glucagon?
Stimulates insulin and decreases glucagon
167
What is Type 1 diabetes also known as?
Insulin-dependent or juvenile diabetes
168
What percentage of diabetics have Type 1?
About 10%
169
What is the main issue in Type 1 diabetes?
Insulin secretion is reduced or absent
170
How is Type 1 diabetes typically treated?
Insulin injections or pumps
171
What is Type 2 diabetes also known as?
Non-insulin-dependent or mature onset diabetes
172
What percentage of diabetics have Type 2?
About 90%
173
What are the main issues in Type 2 diabetes?
Defect in insulin secretion and reduced target cell responsiveness
174
What are some treatments for Type 2 diabetes?
Diet, exercise, oral hypoglycemics, or sometimes insulin injections
175
What effect does exercise have on GLUT4 transporters in Type 2 diabetes?
Causes translocation of GLUT4 to the membrane
176
What is a common characteristic of both types of uncontrolled diabetes?
High blood glucose levels (hyperglycemia)
177
What type of diabetes are Sulfonylureas used to treat?
Type 2 diabetes
178
What channels do Sulfonylureas close in beta cells?
KATP channels
179
What is needed to produce ATP in beta cells for insulin release?
Glucose metabolism (glycolysis and citric acid cycle)
180
What happens when K+ channels close in beta cells?
Less K+ leaves the cell
181
What does less K+ leaving the cell cause?
Cell depolarization
182
What opens when the beta cell depolarizes?
Ca2+ channels and they enter the cell
183
How do Sulfonylureas stimulate insulin release?
By blocking K+ ATP channels
184
What type of hormone is GLP-1?
It's an incretin hormone
185
What does GLP-1 do to gastric emptying?
It delays gastric emptying
186
Where is GLP-1 released from?
From the intestine
187
How does GLP-1 relate to the incretin effect?
It's one of the hormones responsible for the enhanced insulin response to oral glucose
188
What does GLP-1 do in the heart?
- increase cardioprotection
- increase cardiac output
189
What does GLP-1 do in the liver?
- decrease glucose production
190
What does GLP-1 do in the brain?
- increase neuroprotection
- decrease appetite
191
What does GLP-1 do in the pancreas?
- increase insulin biosynthesis
- increase beta cell proliferation
- decrease beta cell apoptosis
192
What happens to protein and fat in uncontrolled type 1 diabetes?
- no insulin is released
- increase in protein and fat being broken down for energy
- Leading to tissue loss and weight loss
193
What happens to plasma glucose in uncontrolled type 1 diabetes?
- no insulin is released
- decrease in glucose up in muscle and fat tissues
- hyperglycemia
- also a decrease in glucose utilization
- Leading to the brain thinking its starving - polyphagia (person wants to eat)
194
What is the primary cause of no insulin production in Type 1 Diabetes?
Autoimmune destruction of beta cells
195
Why does hyperglycemia occur in uncontrolled T1DM?
No insulin means GLUT4 transporters don't move to the cell membrane, so glucose can't enter muscle/fat cells
196
What happens when high blood sugar is filtered by the kidneys?
The kidneys can't reabsorb all the glucose, leading to glucose in the urine (glucosuria)
197
How does glucosuria lead to polyuria?
Water follows the glucose into the urine, causing increased urination
198
What is the consequence of polyuria on blood volume?
It leads to low blood volume
199
How does low blood volume affect ADH secretion?
It activates carotid baroreceptors, increasing ADH
200
Why does osmolarity increase despite lots of water being urinated?
Total body sodium remains the same while volume decreases, increasing osmolarity
201
What alternative fuels does the body use when it can't use glucose due to lack of insulin?
Fat and protein
202
What byproduct of fat use leads to acidosis in uncontrolled T1DM?
Ketones, which are acidic
203
How does the body try to compensate for acidosis?
By hyperventilating to breathe off CO2
