Exercise and starvation Flashcards
What does creatine/phosphocreatine act as a source for for the heart and muscles?
- Source of phosphate groups
- Can donate to ADP -> ATP
- Reserve when ATP falls rapidly in exercise
What enzyme converts creatine to phsophocreatine?
Creatine kinase
What can creatine kinase be an important biomarker for identifying?
MI
What is creatinine?
Spontenously converesed from creatine
What is the amount of creatinine proportional to?
Muscle mass
What is creatinine excreted by?
Kidneys
When is ATP and creatinine consumed (what period of time)?
Within seconds of exercise
- Used for short intense exertion
- > Heavy lifting
- > Sprinting
Why does intensity of exercise diminish over time?`
Creatinine and ATP are consumed rapidly
- Other pathways are required for longer exercise (which have a slower metabolism)
What does calcium (released from muscles) activate (what pathways)?
- Glycogenolysis
- TCA cycle
What do Glucagon and epinephrine inhibit to stop fatty acid synthesis?
This occurs in intense aerobic exercise
Inhibit Acetyl-CoA Carboxylase (rate limiting step of fatty acid synthesis)
Acetyl CoA + CO2 -> Malonyl-CoA
What process does Malonyl-CoA inhibit?
B-oxidation
What vitamin is a cofactor for Acetyl-CoA carboxylase?
Biotin
Levels of what molecule fall in intense aerobic exercise, signalling a drop in fattyacid synthesis?
Malonyl-CoA
What molecule inhibits Carnitine Palmitoyl Transferase-1?
Malonyl-CoA
- Less fatty acid degraded
What molecule is consumed in exercise which subsequently leads to muscle cramps?
NAD+ consumed
- NAD+ generated in Pyruvate to lactate conversion
- Increased lactate causes low pH and cramps
What organelle is more abundant in the muscles of distance runners?
Mitochondria
The presence of what chemical will cause NAD levels to increase (NADH to decrease)?
O2
- NADH can be converted to NAD in the ETC
What are the effects of insulin?
- Glycogen synthesis
- Increases glycolysis
- Inhibits gluconeogenesis
- Promotes glucose -> adipose tissue (used to form triglycerides)
- Promotes uptake of amino acids by muscle
- Stimulates protein synthesis / inhibits breakdown
What enzyme found in the liver and pancreas is induced by insulin?
Glucokinase (Glu -> G6P)
- ATP -> ADP
What enzyme does insulin stimulate?
In regards to glucose/glycogen levels
Glycogen synthase
What enzyme does glucagon (+epinephrine) stimulate?
In regards to glucose/glycogen levels
Glycogen phsophorylase (breaks down glycogen)
What molecules/hormones stimulate acetyl-CoA carboxylase (fatty acid synthesis)?
- Insulin
- Citrate
What are the effects of glucagon?
- Glycogen breakdown in liver
- Inhibits fatty acid synthesis
- Stimulates release of fatty acids from adipose tissue
- Stimulates gluconeogenesis
After how much time fasting will glycogen stores be exhausted roughly?
~ 24 hours
What is glutamate and pyruvate converted into in the alanine cycle in muscles?
- Alanine
- alpha-KG
What substance does Glutmate require in the muscle cells to undergo the alanine cycle?
NH4+
Where does alanine travel to to create glutamate and pyruvate?
The liver
- Also requires a-KG
What is glutamate converted into in the liver?
NH4+
Where does the pyruvate and subsequently glucose travel to to renter the alanine cycle?
Muscle tissue
What molecule is involved in the cori cycle?
Lactate
What 2 cycles maintain plasma blood sugar levels during starvation?
- Cori cycle - Lactate
- Alanine cycle
Describe the steps involved in glycerol becoming Dihydroxyacetone Phosphate?
Glycerol
- > Glycerol-3-Phosphate (enzyme: Glycerol Kinase
- > Dihydroxyacetone Phosphate
enzyme: G-3-P Dehydrogenase)
What is the 3-carbon fatty acid that B-oxidation stops at?
Propionyl-CoA
What is propionyl-CoA converted into to join the TCA cycle?
Succinyl-CoA
What enzyme converts propionyl-CoA (3C FA) to Succinyl-CoA (TCA cycle or gluconeogenesis)?
Propionyl-CoA Carboxylase
What vitamin acts as a cofactor for Propionyl-CoA carboxylase?
Biotin
What causes oedema in Kwashiorkor?
Inadequate protein intake
- Hypoalbuminemia -> oedema
What is the other malnutrition disease that has normal protein but insufficient total calories?
Marasmus
- Muscle and fat wasting
- No oedema
Hypoglycemia and ketosis in a child, after an overnight fast is can be due to what group of diseases?
Glycogen storage diseases
What enzyme is deficient in hereditray fructose intolerance?
- Aldolase B
When does hereditray fructose intolerance usually present?
After weaning from breast milk
What is depleted and what can build-up in hereditray fructose intolerance?
- F1P builds up
- ATP depletes
- Glucose depleted
Disorders of what organelle create hypoketotic hypoglycemias?
Mitochondrial disorders
Explain how a disorder in the mitochondria can create a hypoketotic hypoglycemia?
- Loss of B-oxidation and gluconeogensis
- FFA -> B-oxidation -> ketones (B-oxidation), cannot happen as mitochondria not functional
- First step of gluconeogensis is pyruvate -> oxaloacetate, occurs in mitochondria also
- Leads to hypoglycemia
What are 2 disorders which cause hypoketotic hypoglycemia?
- Carnitine deficiency
- MCAS deficiecy
What are the findings in carnitine deficiency?
- Hypoketosis
- Hypoglycemia
- Low serum carnitine
- Low serum acylcarnitine
What are the findings in MCAD deficiency?
- Hypoketotic hypoglycemia
- Medium chain acyl-CoA dehydrogenase
- Dicarboxylic acids 6-10 carbons in urine
- High acylcarnitine levels
