Energy Balance in Exercise Flashcards
It is recommended that all adults exercise at least
30 minutes per day
Studies show that individuals with type 2 DM show increased insulin sensitivity and better blood glucose control after
Exercising
Has also been shown to improve with moderate exercise in comparison to being sedentary
Immune function
However, too much exercise can also lead to a
Depressed immune system
Requires a lot of energy, which is used through ATP, leading to its consumption and increased quantity of ADP and AMP
Exercise
This combination of decreased ATP and increased AMP leads to activation of
AMPK
Activation of AMPK stimulates
-Leads to more energy production
Catabolism
AMPK activates?
-Increases glucose transport into the cell and skeletal muscle FA oxidation
GLUT 4
Inhibits ATP-consuming processes including TAG, glycogen, and protein synthesis
AMPK
In the liver, energy requirements dictate whether glycolysis or gluconeogenesis will take over via the enzyme
PFK-2
In glucose abundant conditions, release of insulin leaves PFK-2 in an unphosphorylated state, and thus it is able to produce
Fructose 2,6-BP
This then further stimulates
-continues glycolysis
PFK-1
On the other hand, a glucose scarce state leads to glucagon secretion which results in
Phosphorylation and inactivation of PFK-2
In this case, PFK-1 is not stimulated and instead FBP-1,6-ase is allowed to continue with
Gluconeogenesis
Accelerates glycolysis in muscle and inhibits glycolysis in the liver
Epinephrine
Leads to glycogen breakdown in muscl and increased F-6-P substrate for PFK-1 to use in glycolysis
Epinephrine
Lacks the regulatory serine residue, which is phosphorylated in the liver, thus allowing glycolysis to continue in the muscle
Skeletal muscle isozyme of PFK-2
During long periods of exercise, the liver maintains blood glucose levels through hepatic
Glycogenolysis and gluconeogenesis
Initially, we will see predominance of
Glycogenolysis
However, after several hours we will slowly see a switch to reliance on
Gluconeogenesis
Returned from BCAAs to the liver via alanine in the
Alanine cycle (no net production of glucose)
When β-‐oxidation of fatty acids is required as an energy source, there is a tight regulatory system in place to control the entrance of
Fatty Acyl CoA into mitochondria
There is no fatty acid synthesis in the
Muscle tissue
An isozyme of the enzyme for the committed step of fatty acid synthesis
-found in muscle
Acetyl CoA carboxylase-2 (ACC-2)
ACC-2 inhibits
Carnitine palmitoyl transferase (CPT-I)
ACC-2 inhibits CPT-I through
Malonyl CoA
ACC-2 inhibits CPT-I through malonyl CoA, thereby blocking fatty acyl CoA entry into the
Mitochondria
As energy levels drop, AMP activates
AMPK
Phosphorylates and inactivates ACC-2
AMPK
Phosphorylates and activates malonyl CoA Decarboxylase (MCoADC)
AMPK
Converts malonyl CoA to acetyl CoA, thereby relieving the inhibition of CPT-I and allowing fatty acyl CoA entry into the mitochondria
MCoADC
This allows muscle to generate ATP via the oxidation of
Fatty Acids
During lipolytic conditions, when fuel must be provided by adipose tissue, FA release from the stored TAGs is accelerated by
Hormone sensitive lipase
However, FAs are released in excess. So the liver continues to recycle the excess FA via
VLDL
Although this cycling process has a cost, it requires only
5% of energy stored in FAs
Necessary for TAG formation
Glycerol-3-phosphate
During lipolysis, glycolysis is inhibited and thus, does not have a readily available supply of
DHAP
Makes DHAP in the adipose tissue for glycerol-3-Phosphate generation
Glyceroneogenesis
A shortened version of gluconeogenesis in the adipose tissue and it contains some of the same steps as gluconeogenesis
Glyceroneogenesis
Explains wht adipose cells express pyruvate carboxylase and PEPCK even though fat cells don’t make glucose
Glyceroneogenesis
GLyceroneogenesis converts pyruvate to
DHAP
Activates glycolysis in muscle
Epinephrine
Results in a net transport of nitrogen from BCAAs to the liver, but results in no net production of glucose
Alanine Cycle
Made by ACC-2 to regulate beta-oxidation in muscle
Malonyl CoA
How many biological energy systems are used by muscle?
Three
Anaerobic, and provides ATP primarily for short-term, high-intensity activities
Phosphagen system
The key energy generator of the phosphagen system
Creatine Phosphate
Active at the start of all exercise regardless of intensity
Phosphagen system
Serves as a small reservoir of high-energy phosphate that can readily regenerate ATP from ADP
Creatine Phosphate
Creatine phosphate carries high-energy phosphate from the mitochondira and to
Myosin filaments
Where ATP is used for muscle contraction
Myosin filaments
Requires ATP and only occurs during recovery from exercise
Creatine phosphate reformation
What are the three biological energy systems for muscle?
- ) Phosphagen system
- ) Glycolysis
- ) Oxidative system
The breakdown of carbohydrates to either be stored in glycogen or delivered in the blood to produce ATP
Glycolysis
The primary source of ATP at rest and low-intensity
-uses primarily carbohydrates and fats as substrates
Oxidative system
After the phosphagen system is used up, what does the body decide to do next?
Anaerobic glycolysis
How much faster is the rate of ATP production from glycolysis (anaerobic) than from oxidative phosphorylation?
100 times faster
During fast glycolysis, pyruvate is converted into
-provides ATP at a fast rate
Lactic acid
During exertion, muscle cells do not need to energize
Anabolic reaction pathways
Slow-twitch fibers with high capacity to store O2 via myoglobin, leading to their red color
Type I Fibers
Use the oxidative system and are typically more prominent in marathon runners
Type I muscle fibers
Fast twitch fibers that appear white due to low myoglobin
Type IIb fibers
Use the fast glycolytic system and are seen more in sprinters
Type IIb fibers
As intensity increases (i.e. sprinting) what happens to
- ) Carbohydrate use
- ) Fat use
- ) Increases
2. ) Decreases
As duration increases (i.e. a marathon), what happens to
- ) Carbohydrate use
- ) Fat use
- ) Decreases
2. ) Increases
Plasma FFA (fat from fat cells) is the primary fuel source for
Low intensity exercise
As intensity increases, the source shifts to
Muscle glycogen
Decreases 50-70% during high intensity exercise and can be almost eliminated by exercise to exhaustion
Creatine Phosphate
However, even during intense exercise, muscle ATP concentrations do not decrease by more than
60%
Post exercise repletion of phosphagen occurs via resynthesis of ATP in
3-5 minutes
The whole repletion process is so quick that complete creatine phosphate resynthesis can occur in
8 minutes
Resistance training can result in an increase in the resting concentration of
Phosphagens
A likely cause of fatigue during prolonged exercise
Glycogen depletion
Repletion of muscle glycogen during recovery is related to post exercise
Carbohydrate consumption
With adequate carbohydrate intake, muscle glycogen may be completely replenished within
24 hours
Anaerobic training can increase
Glycogen stores
Muscle glycogen is more important than liver glycogen during
Moderate/high intensity exercise
More important in low intensity exercise and its contribution increases with duration
Liver glycogen
