Metabolism and Fatigue Flashcards
What can creatine kinase tell you about muscle damage?
It’s presence can indicate muscle damage, but the amount does not relate to the amount of muscle damage
Why is energy not stored directly all as ATP?
too heavy and unstable of a molecule
Can you ever run out of ATP?
No. You always have atleast 50% of your ATP stores
How long does it take PCr to recover?
2 min for 80%,, 3-4 min for 100%
Why is glycogen more efficient to break down than glucose during glycolysis?
It is already partially oxidised.
- Conversion of glycogen to g6p via glycogen phosphatase does not require ATP
- Conversion of glucose to g6p via hexokinase does require ATP
What is the difference between lactate and lactic acid?
Lactic Acid does not accumulate, Lactate does. Lactate is made when Lactic acid dissociates from hydrogen ions
How may hydrogen ion accumulation associated with lactate accumulation contribute to fatigue?
- Metabolic acidosis, inhibiting glycogen phosphorylase and PFK and thus glycolysis (but only in vitro, not in vivo)
- Inhibition of calcium release and binding with troponin, impacting cross-bridge formation
How may inorganic phosphate contribute to fatigue?
-Accumulation impacts PCr breakdown by Creatine Kinase, also potential inhibition of calcium uptake to sarcoplasmic reticulum
What process can break down lipids for use in the Krebs Cycle and Oxidative phosphorylation to produce energy?
-Beta Oxidation
What is beta oxidation?
Conversion of fatty acids and glycerol into acetyl-CoA
What are the two ways lactate can be used as fuel?
- Transported to and oxidised by other tissues, via intercellular lactate shuttling
- Used as a gluconeogenic precursor by the liver
Explain intracellular lactate shuttling
Lactate Dehydrogenase converts lactic acid back into pyruvic acid, providing the necessary substrates to continue with aerobic glycolysis
What can we glean from high blood lactate concentration?
Either high lactate production, or poor lactate clearance, but not necessarily one or the other.
Summarise lipid oxidation briefly
- Triacylglycerol is broken down into glycerol and 3 NEFA. Glycerol and NEFA are then converted into Acetyl CoA
Where is Vitamin B1 used metabolically, and where can you find it in diet?
Involved in krebs cycle, found in brown rice and wheat
Where is Vitamin B5 used metabolically, and where can you find it in diet?
Part of Acetyl CoA, comes from eggs and wheat
Where is Vitamin B2 used metabolically, and where can you find it in diet?
Part of FAD, Comes from Green Leaves and Dairy
Where is Vitamin B6 used metabolically, and where can you find it in diet?
It is a coenzyme for glycogen phosphorylase. Found in Green Leaves, avocado, egg and banana
Where is Vitamin B12 used metabolically, and where can you find it in diet?
Used in Krebs Cycle, comes from microbacteria or synthetic fortification
What is the cause of fatigue in the oxidative system?
- Muscle glycogen depletion
- Liver Glycogen Depletion
- Hypoglycemia
What are the associated issues contributing to fatigue in the oxidative system?
- Dehydration
- Reduced Central Drive
Why does dehydration contribute to fatigue?
-Lower blood volume means heart has to work harder to deliver nutrients and oxygen to the muscle, and muscle does not receive them at a high enough rate
Is glycogenin necessary for glycogen synthesis?
-Testoni et al 2017 found that glycogen synthesis can occur without glycogenin and may actually be increased, though also reducing mitochondrial oxidation
DESCRIBE the steps of glycogen synthesis
Glucose to G6P to G1P to Uridine Disphosphate-Glucose (1 Glucosyl Unit).
Glycogenin makes a chain on itself, glycogen synthase continues it, glycogen branching enzyme makes branches. Initially made glycogen is called proglycogen, then gets converted to macroglycogen over time when enough glucosyl units have been added.
