Lecture 17--Starvation Flashcards
What are the body energy stores (the form)?
(1) Free glucose
(2) Glycogen (liver & muscle)
(3) Triacylglycerol (TG)
(4) Protein
What is the highest energy density energy store?
Triglycerides
What is the quantity of free energy contained in each storage form? How long would these stores each last?
(1) Free glucose: 12g = 0.2MJ = 30minute supply
(2) Glycogen: 450g =7.7 MJ = 18 hours
=> Muscle = 250g glycogen
=> Liver = 100g glycogen
(3) TG: 15kg = 550 MJ = 55 days
(4) Protein: 12.5kg = 210 MJ = 21 days
________ = largest energy store
ADIPOSE TISSUE
TGs are mobilised to non-esterified Fatty Acids (NEFA; aka FFA)
What is GLUCAGON
- Where is it synthesised?
- What stimulates secretion?
- What is it’s function?
Function: Prevent/minimise hypoglycaemia
Stimulated by: Decrease [glucose], increase in AAs
What pancreatic hormone is released during FASTING?
GLUCAGON = prevents hypoglycaemia
Why are Insulin AND Glucagon both stimulated by Amino Acids?
Insulin secretion is stimulated by Amino Acids but you haven’t taken in any new CHO… .: cells take up all the available glucose, leaving you hypoglycaemia (glucagon keeps glucose high to maintain glycemic level)
Plasma glucose during fasting is provided by glycogenolysis in the LIVER not muscle. Why?
b/c GLUCOSE-6-PHOSPHATASE (is absent in skeletal muscle) .: glucose cannot be liberated from muscle. & glycogen stores can only be utilised within the muscle itself.
Glycogen stores are gone in _________
1 day
What is the order of priority for energy store use
Glucose–>glycogen–>fat mobilisation–>protein
What tissues cannot used FFA for energy?
(1) Heart
(2) Red blood cells
(3) Renal Cortex
Gluconeogenesis
Make glucose from non-CHO sources (usually AAs)
____ carbon substrate is needed to synthesise glucose
3 carbon substrate is used as a skeleton for glucose synthesis.
- Lactate (byproduct of glycolysis)
- Pyruvate
- Amino Acids (deaminated and used for carbon skeleton)
- Glycerol (break down to FFAs)
KETONE BODIES aka _______
Include: (3)
KETONE BODIES aka KETOACIDS:
1) ACETOACETATE
2) B-HYDROXY BUTYRATE
3) ACETONE (minor)
ketone bodies are produced by _____ when ________.
Produced by the LIVER from FFA
…when OXALOACETATE stores are completely depleted
FFA–>acetyl CoA =gluconeogenesis=> Ketone bodies
What are blood ketone concentrations during STARVATION?
6-8mmol/L
What proportion of blood ketones are used by the brain during starvation?
2/3rds
What is the role of thyroid hormone (T3) in starvation?
General decrease in metabolism reduces energy requirements
For what reason (to do with physiological response to starvation) might crash diets be ineffective?
Because starvation leads to an increase in T3 secretion which can reduce overall metabolic energy requirements by up to 1/2
Where is the main target for glucagon?
The liver
What are the responses to insulin in the liver?
Promote glycogenesis
Inhibit glycogenolysis
Glucose stored as glycogen
Promote Lipogenesis
What are the responses to glucagon in the liver?
Inhibit glycogenesis
Promotes glycogenolysis
Promotes lipolysis & FA oxidation
Inhibits lipogenesis
What is the hormone of general metabolism that decreases during starvation?
Thyroid hormone (T3). Leptin may also signal to reduce metabolism.
What is the average daily energy expenditure?
9700kJ/day
