36 Flashcards
You need to supply your brain with fuels - how much glucose per day?
Uses 120 g of glucose per day
What other fuel do other tissues (not brain) need?
Fatty acids mainly
We need to conserve _____ as much as possible to maintain ______ and ________
Protein
Strucuture
Function
What hormone is mainly involved during survauval while starving
glucagon is the main hormone involved - it is produced by pancreas a cells when blood glucose drops
What kind of hormone is glucagon? How many fatty acids?
Peptide hormone
29 amino acids
Triacylglycerol stored in adipose tissue amounts to at least…..
15kg of fat
Triacylglycerol stores in adipose tissue is enough energy to survive at least ___ days of starvation
40
What hormone stimulates lipolyis
Glucagon
What is used at fuel in aerobic tissues (except Brian?)
Fatty acids (via beta oxidation)
- not brain, brain used glucose
How much energy per frames of fat?
- 38-40kj
How long can we last without food? - calculation
Why can’t we just use glycerol to make glucose?
Brain needs ~120 g glucose per day
We get around 20 g of glucose from glycerol each day. Where do we get the extra glucose?
How many grams of glycogen in the liver?
90-120g
What happens to liver glycogen during starvation?
mobilised back to glucose
What hormone is mobilisation of liver glycogen stimulated by?
stimulated by the hormone, glucagon
Mobilisation of liver glycogen provides enough glucose for the brain for…
1 day
What breaks the 1-4 linkages in glucose
Glycogen phosphorylase
what breaks 1-6 linkages in glycogen
Debranching enzyme
Debranching enzyme
And Glycogen phosphorylase work together to..
Mobiles glucose for metabolism
- Glycogen phosphorlyse works with attaching an in-organic phosphate group onto a carbon of terminal glucose and cleaves the glycosidic bond between carbon 1 and 4 - producing glucose 1-P
- Glucose-1 phosphate is then converted by mutate to glucose-6P
- In the liver, NOT in muscle, only liver there is another enzymes called glucose-6-phosphatase
This glucose is for the Brian
Gluconeogenesis
- where does it mainly occur?
Liver (also kidney cortex)
Gluconeogenesis is the synthesis of glucose from:
lactate from muscle glycogen
alanine from muscle protein
glycerol from adipose tissue (TAG)
What hormone is Gluconeogenesis stimulated by?
stimulated by glucagon
Gluconeogenesis - what provides the energy required to do this?
fatty acid oxidation provides the energy required
What is most of the glucose produced from gluconeogeneis used towards?
Brain
What do lactate, Alanine and glycerol all have in common?
All 3 carbons in length
- used in gluconeiogenesis by the liver
Can Fatty acids (acetylCoA) be used to make glucose ?
Fatty acids (acetylCoA) cannot be used to make glucose B ut can via β-oxidation provide ATP and NADH for gluconeogenesis
Big diagram
Remember the NADH part
Where the liver gets heat it needs to make glucose form (gluconeogeneis)
Starvation metabolism
Burn ca. 200 g of TAG per day; - if we get 40 kJ g -1 then: = 200 x 40 or 8000 kJ per day
The glycerol released corresponds to about 20 g of glucose per day
Brain needs about 120 g of glucose per day
Proteolysis (alanine) to give 100 g of glucose per day corresponds to about 150 g of protein per day — this would deplete muscle reserves to critical in about 2 weeks!
How did James last 43 days?
How many kg of protein in our body? Where is it stored?
• 10 - 15 kg protein in body
• BUT no specific storage proteins
During starvation what happens to some protein?
must be degraded to amino acids to make glucose
loss of too much protein causes…
structural and functional damage
• protein must be conserved as much as possible
Protein conservation system in human is specific to only —-
Humans
Clinical Research at Harvard — Metabolic Ward
Experiment — 6 weeks starvation
New assays had been developed by the Krebb’s lab in Oxford
Obese patient: Ms B 5’ 8’’; 280 pounds (127 kg)
Measured Carotid artery entering and Jugular vein leaving and found 50 g ketone bodies used per day
Hence providing 50% of the brain’s requirement
What are Ketone Bodies synthesised from and where are they synthesised?
• synthesised in the liver from fatty acids
When are ketone bodies used?
• used by starving brain as energy source
/
Human only adaptation
Metabolic adaptations to starvation
• fatty acids can be used as a fuel by all aerobic tissues
(except brain); essentially unlimited supply from TAGs
• ketone bodies used by brain
- Therefore, brain needs less glucose; now only about 50 g/day
- Therefore, muscle degradation can slow down (not so many amino acids needed for gluconeogenesis)
- Therefore, body can survive longer
Glucose levels in blood over 40 days - Phases of starvation assessed from point of view of glucose metabolism
How are you able to starve for so long
Fuel stores, gluconeogenesis and ketogenesis
How does brain continue to function during starvation
Ketone bodies, glucose
What happens to fat stores during starvation
Mobilised to fatty acids and glycerol
What happens to muscle during starvation
Proteolysis to amino acids
Did the energy from the chocolate bar help him survive?
About 1 h
Process of ketone body synthesis
