Intro To Metabolism Flashcards
Fasted refers to
Overnight fast
Big picture of metabolism
Chemical energy contained in macronutrients needs to be converted into energy cell can use to do work
Primary organ of metabolic regulation
How?
Liver
Maintains blood glucose and amino acid homeostasis
Liver insulin transporter’s Km
High Km –> can always bring in glucose especially after a meal
Transporters function like
Enzymes
Metabolism involves (3)
- Homeostasis
- Redistribution of chemical energy between compounds
- Integration of metabolic pathways
Homeostasis
2 types?
Maintaining a constant internal environment
- changes do occur but mechanisms are in place that compensate for those changes to bring back to “normal”
Metabolic homeostasis and pH homeostasis
How are metabolic and pH homeostasis connected?
Metabolism releases weak organic acids and CO2
Need to maintain constant level of blood glucose
Fuel availability
stored energy in form of glycogen or fat
Metabolic homeostasis is the balance between
Fuel availability and what tissues need
Metabolic homeostasis is determined by (3)
- nutrient levels
- hormone signals
- nerve signals
What region of hypothalamus controls feeding?
ARC region
Orexigenic neurons
Promote feeding behavior
Anorexigenic neurons
Inhibit feeding behavior
When you take in nutrients, ______ levels rise and 2 things occur:
Insulin levels rise
- Metabolize some energy to maintain body function
- The excess calories are stored for breakdown during times of fasting
Importance of maintain blood glucose
Brain needs ~75% of daily need for glucose
Fiber
Restricts how rapidly glucose levels (thus insulin levels) rise in the blood
What happens to blood glucose, insulin, and glucagon levels after a meal?
- Blood glucose levels rise
- Insulin levels follow blood glucose and rise too
- Glucagon levels stay relatively constant
Insulin
Made by?
Responds to?
Corresponds to?
Insulin = FED STATE
- Made by beta cells of pancreas
- Responds to elevated blood glucose
Type 1 vs. Type 2 diabetic
Type 1: beta cells have been destroyed therefore do not produce insulin
Type 2: produce insulin, but no response because signal transduction cascade is affected
Insulin = “______ hormone”
Why?
Anabolic hormone
Promotes synthesis of macromolecules
Insulin stimulates
Glucose transport into skeletal muscle and adipose tissue
Once glucose is in skeletal muscle –>
- Metabolized for energy
- Stored as glycogen
Once glucose is in adipose tissue –>
Converted to fatty acids which are then esterified to glycerol backbone to yield triglycerides
In liver, glucose is
Made into glycogen and energy
Any excess can go into fatty acids
Glucagon
Made by?
Responds to?
Corresponds to?
Glucagon = FASTED STATE
- Made by alpha cells of pancreas
- Signals that current supply of glucose is low for the cell’s needs
Glucagon = “______ hormone”
Why?
Catabolic
It promotes the breakdown of stored fuels (glycogen and fat) to provide energy when it is not coming from the diet
Glucagon signal transduction is the same as
Epinephrine
Glucagon has no effect on ________ because ________
Skeletal muscle because no receptors
_______ and _________ respond to glucagon
Liver and fatty acids
In response to glucagon, in liver ____
Glycogen is broken down to glucose –> exits liver and enter blood
In response to glucagon, in adipocytes ______
Triglycerides broken down to fatty acids –> exit liver and enter blood to provide alternative source of energy
2 major fuel stores
- Glycogen - limited
2. Triglycerides/fatty acids- longer period of time; more nrg when oxidized
High insulin : glucagon ratio =
FED
What happens when high insulin: glucagon ratio?
Brain senses blood glucose is high –> CNS sends signal to pancreas to release insulin –> stimulates transport of glucose into skeleton muscle and adipose tissue –> synthesis of glycogen or fatty acids which are eventually converted into triglycerides
Low insulin: glucagon ratio =
FAST
What happens when low insulin:glucagon ratio?
Brain senses blood glucose is low –> CNS sends signal to pancreas to release glucagon –> promotes breakdown of liver glycogen and release of glucose into blood
(Gluconeogenesis in liver)
Glycogen breakdown can be stimulated by
Glucagon or epinephrine
In fasted state, most of the glucose generated is _________. Why?
Is selectively saved for the brain and RBC because brain and RBC cannot oxidize fatty acids for energy
NOT metabolized for energy
Catabolism =
Breakdown
Oxidative, exergonic
Paired to making ATP which is consumed in anabolic reactions
Anabolism =
Reductive, endergonic
Synthesis requiring reducing equivalents
Coupled to splitting ATP
What makes ATP an efficient energy currency?
“High phosphoryl transfer potential”
Why is ATP hydrolysis favorable? (3)
- It reduces the electrostatic repulsion of the 3 negative charged phosphate groups
- The inorganic phosphate has resonance stabilization, therefore entropy is increased
- Stabilization due to hydration with H2O molecules
Energy is ATP is contained in
The 3 phosphate bonds
Other molecules with high phosphoryl transfer potential (3)
- Phosphoenolpyruvate
- glycolytic intermediate - Creatine phosphate
- 1,3- Biphosphoglycerate (1,3-BPG)
- glycolytic intermediate
high phosphoryl transfer potential requirements (3)
- Have a phosphate
- Can transfer the phosphate to another molecule with lower energy
- Usually a lot of energy released when phosphate is transferred
ATP levels are maintained in equilibrium by
Adenylate cyclase
2 ADP ATP + AMP
If ATP levels decrease:
ADP levels increase by ~50%
AMP levels increase by several hundred fold
_____ is signal for low energy state
AMP
Small drop in ATP concentration is magnified by
Changes in AMP and ADP
How are ATP-generating and ATP-utilizing (biosynthesis) pathways related?
They function inversely based on ATP availability
Energy charge:
0 =
1 =
Cellular range =
0 = no ATP, all AMP 1 = all ATP, no AMP
Cellular range = 0.8-0.95
- Always trying to get back here (point of intersection)
If have all ATP, rate of ATP generation is ______.
If have no ATP, rate of ATP utilizing is ______.
Low
Low (b/c no availability)
If decrease ATP –> energy charge ______ and _________
Energy charge drops and rate of ATP generation increase
If have ATP, _______
Rate of biosynthesis increases
