Integration of Metabolism Flashcards
What is the % body weight of muscles and which energy sources do they use?
40% of total body weight
uses carbohydrates and FA
What is the % body weight of brain and which energy sources do they use?
2% of total body weight - uses 20% of resting metabolic rate
uses mainly carbohydrates, cannot use FA
What is the % body weight of adipose tissue and what do they store?
15% total body weight
Long-term storage of triacyl glycerols
What is the % body weight of heart and which energy sources do they use?
1% total body weight - uses 10% of resting metabolic rate
uses carbohydrates and FA
What is the % body weight of liver and what does it store?
2.5% of total body weight - uses 20% of resting metabolic rate
glycogen storage and source of blood glucose
Which energy source does the brain need continuously?
Glucose
What can partially substitute for glucose in the brain?
ketone bodies (e.g. β-hydroxybutyrate)
What are the terms called when there is not enough blood glucose or too high blood glucose?
Hypoglycaemia
Hyperglycaemia
How is the energy supplied for light contraction of skeletal muscle?
OxPhos
How is the energy supplied for vigorous contraction of skeletal muscle?
O2 becomes limiting factor → Glycogen breakdown in muscles → Lactate formation
Can heart muscle also rely on anaerobic metabolism?
No, it utilises only aerobic metabolism
Which energy sources can the heart use?
TCA cycle substrates (e.g. free fatty acids, ketone bodies)
Which organ/tissue can interconvert nutrient types?
Liver
What is the normal range for blood glucose?
4.0-5.5 mM
What happens to Acetyl CoA during fasting?
Rather than entering TCA cycle, most of it is converted into ketone bodies
Which enzyme is used to convert lactate back to pyruvate?
Lactate dehydrogenase (LDH)
What is glycerol converted into for gluconeogenesis?
DHAP
Which molecules can be derived from amino acids to start gluconeogenesis?
Oxaloacetate and Pyruvate
What is lactate converted into for gluconeogenesis?
Pyruvate
How is gluconeogenesis not just reverse glycolysis?
Irreversible steps in glycolysis need to be bypassed
What is the net change in ATP for gluconeogenesis?
net loss of 6 ATP
Gluconeogenesis
How is pyruvate kinase bypassed?
1st step: Pruvate converted into oxaloacetate by pyruvate carboxylase
2nd step: Oxaloacetate converted into phosphoenolpyruvate by phosphoenolpyruvate carboxykinase
Gluconeogenesis
Which enzyme bypasses phosphofructokinase?
Fructose 1-6 bisphosphatase
Gluconeogenesis
Which enzyme bypasses hexokinase?
Glucose-6-phosphatase
What happens to fatty acids during fasting?
Can’t enter gluconeogenesis, converted into ketone bodies
How does adrenalin help increase rate of glycolysis in muscles?
Increase gluconeogenesis in liver
Increase release of FA from adipose tissue
How is glycogen from liver used in anaerobic respiration of muscles?
Glycogen broken down to glucose in liver → Transported to muscles → Glycolysis and lactate formation → Lactate taken up by liver for gluconeogenesis
What does a high Km (Michaelis constant) indicate?
Enzyme active at high concentrations of substrate → Low substrate affinity
What does a low Km (Michaelis constant) indicate?
Enzyme active at low concentrations of substrate → High substrate affinity
Where is Hexokinase (Hk I) found?
Muscle cells
Where is Hk IV or Glucokinase found?
Liver
What are the differences between Hk I and Hk IV?
Hk I (Muscle) and Hk IV (Liver)
Which glucose metabolism enzyme is present in liver but not muscle?
GLucose-6-phosphatase
When is insulin secreted and what does it do?
secreted when glucose levels rise - it stimulates uptake and use of glucose and storage as glycogen and fat
When is glucagon secreted and what does it do?
secreted when glucose levels fall - it stimulates production of glucose by gluconeogenesis and breakdown of glycogen and fat
When is adrenaline (epinephrine) secreted and what does it do?
strong and fast metabolic effects to mobilise glucose for “flight or fight”
When are glucocorticoids secreted and what do they do?
secreted when glucose is less available - they are steroid hormones which increase the synthesis of metabolic enzymes concerned with glucose availability
What are the types of Diabetes Mellitus?
Type I - limited secretion of insulin
Type II - limited response to insulin
What are some complications of diabetes?
Hypo/hyperglycaemia - Coma
Cardiovascular (i.e. atherosclerosis)
Ketoacidosis
Retinal damage
What is ketoacidosis?
Excess ketone bodies in plasma lowering the pH as they are acidic
How can hyperglycaemia result in coma?
The high plasma glucose will disturb solute balance in the brain due to increased osmolarity of body fluids
