Integration of Full Body Metabolism Flashcards
how many grams of glucose does the brain use per day?
100-120g
what is half the energy supplied to the brain used for?
→Na-K transports to maintain membrane potential
→ synthesis of neurotransmitter
What does the brain lack and how is glucose transported in cardiac muscle?
Comment on the km of the transporter
→ Lacks energy stores
→ glucose is transported by GLUT3
→ has a low Km
→ meaning the transporter is active at most times
At what level of glucose is it deemed dangerous?
→ glucose levels drop below 2.2mM.
What are fatty acids usually used for and not usually used for?
→ Fatty acids not usually used for energy
→ used for membrane biosynthesis
comment on the glycogen stores in cardiac muscle
Little or no glycogen stores
what is the main energy source for cardiac muscle and what is that followed by?
→Fatty acid main source of energy
→followed by lactate and ketone bodies.
what is adipose tissue a store for?
Store for fatty acids
What do adipose tissue act as and in the form of what?
→ reservoir of metabolic energy
→ form of triglycerides
What are fatty acids synthesised by when a person is starved?
→person starved, FA synthesised by chylomicrons
How is glucose transported in adipose tissue?
Glucose is transported by GLUT 4
What is GLUT 4 sensitive to?
GLUT 4 is insulin sensitive
What do kidneys produce and how many times a day is it filtered?
Produces urine and plasma is filtered up to 60 times a day
Why is only a small volume of urine produced?
Only small volume of urine produced because water soluble material is largely reabsorbed to prevent loss
What do kidneys contribute during starvation?
kidney may contribute half of the blood glucose through gluconeogenesis
What does the liver regulate?
Regulates metabolism: carbs, fatty acids and amino acids
Where do most compounds absorbed by the gut pass through?
Most compounds absorbed by gut pass through the liver
What does the liver provide?
Provides fuel for brain muscle and other peripheral organs
Where does the liver take its energy from?
alpha ketoacids
What is glucose absorbed by hepatocytes used for more than the other?
→glucose absorbed by hepatocytes used for production of fat synthesis
→ more than the production of energy
How is blood glucose controlled by liver metabolism?
→glucose transported into hepatocytes by GLUT2 and immediately phosphorylated by glucokinase
→G6P from glycogen breakdown converted to glucose by the action of G6P and transported out the cell into the blood by GLUT-2
What is GLUT2 not sensitive to?
GLUT-2 is not insulin sensitive
What is GLUT2 driven by?
GLUT2 is driven by concentration gradient and is a means of regulating low blood glucose levels
what is glucose uptake by GLUT4 in muscles dependent on?
Glucose uptake by GLUT-4 is insulin dependent
what is glucose converted by into G6P in muscles?
Glucose converted to G6P by hexokinase
comment on the free glucose concentration in muscle cells
low free glucose concentration in cell
How is glucose mobilised in muscles during exercise?
Glucose is mobilised from glycogen in exercise
What is a rapid source of ATP in muscle cells?
Glycolysis of the G6P is a rapid source of ATP
What does ATP directly power?
ATP directly powers myosin
What are the sources of energy in 100m sprint?
→ATP stores → Glycolysis →Glycogen stores →Creatine phosphate -Small store of ATP
How many seconds of reserve does creatine phosphate provide?
5-6 seconds
What does anaerobic breakdown of glycogen stores give and the effect on pH?
Anaerobic respiration gives lactate and a fall in pH
How many moles of ATP required roughly in a marathon?
150 moles of ATP needed
How many moles will body glycogen provide in a marathon?
Body glycogen will provide only 103 moles
What type of respiration is more efficient in marathons?
Aerobic respiration more efficient in marathons
What cooperation is required in marathons and why?
→Co-operation between muscle, liver and adipose tissue required
→Because ATP required exceeds that stored by muscles
What is a large source of ATP and comment on the metabolism of this source compared to others?
→Fats are a large source of ATP, metabolism even slower than glycogen
→x10 slower than creatine phosphate
What is energy sources are more efficient to use in marathons?
More efficient to use both fat and glycogen
How much glycogen is left at the end of a marathon?
At end of marathon, 1/2 glycogen left
What are the interactions between the liver and muscle during exercise?
→During exercise, glycolysis exceeds the capacity of TCA,
→pyruvate converted to lactate in muscles and transported to livers cori cycle
What happens to muscle proteins during exercise and the interactions between liver and muscle?
→Muscle protein also broken down into amino acids
→majority is converted to alanine and transported to liver.
→Used for gluconeogenesis
What happens to amino acids in a fed state?
Amino acids used for protein synthesis
What happens to excess amino acids in a fed state?
Made into keto acids
In a fed state, where are fats delivered and with the aid of what?
Fats also delivered to muscle via the aid of VLDLs
What do resting muscles use in a fed state?
Resting muscle use FA as source of energy
What is excess glucose stored as in adipocytes and muscles in a fed state?
Excess glucose stored as FA in adipocytes or as glycogen in muscle
What happens to blood glucose, insulin levels and glucagon levels in post absorptive phase?
Blood glucose falls, insulin level falls and glucagon levels rise
Activity of what enzyme increases in post absorptive phase as well as what breakdown?
Phosphorylase a activity increases as does glycogen breakdown
In post absorptive phase, what does a drop in insulin do?
Drop in insulin reduces glucose uptake by muscle and adipose tissue
In early starvation(4-24hrs), where is glucose released from and due to what reason?
Glucose released from liver due to gluconeogenesis and glycogenolysis
In early starvation, what is there a mobilisation of?
Mobilisation of FA from adipose tissue
What happens to the glucose use in early starvation and due to what reason?
Glucose use falls as muscle switches to FA oxidation
What does insulin drop cause in early starvation?
Insulin drops causing GLUT4 expression by muscle to fall reducing glucose uptake
What happens after 12 hrs of starvation in terms of percentage of energy?
After 12hrs 45% of resting energy from FA and 40% from glucose
What happens to glycogen stores after intermediate starvation(1-20 days)?
Glycogen stores almost completely depleted
What process increase is there in intermediate starvation?
Increased lipolysis and ketogenesis and gluconeogenesis
Why is there an increase in gluconeogenesis in intermediate starvation?
Increased gluconeogenesis to maintain blood glucose
What does 60hrs of FA account for?
60hrs FA account for 3/4 energy provision
What happens after 8 days in intermediate starvation?
After 8 days, beta-hydroxybutyrate is raised 50 fold
What do you see in further starvation?
Further starvation sees kidney take over gluconeogenesis from liver
In prolonged starvation(>3weeks)what plateaus at 20 day?
Βeta hydroxybutyrate plateaus at 20 days
In prolonged starvation, what does the brain start to use and what amount of glucose needed in grams falls to?
As brain starts to move to using ketone bodies, the need for glucose falls from 100g to 40g/day
What other sources are there for gluconeogenic precursors?
Other sources of gluconeogenic precursors are lactate and glycerol
What is lactate recycled by in prolonged starvation?
Lactate recycled by the cori cycle
What is oxidised in prolonged starvation?
Glycerol and amino acids are oxidized
What are the proteins? from what precursors in prolonged starvation?
Proteins are broken down muscle forming amino acid precursors
How else is alanine formed in skeletal muscles?
Alanine also formed by transamination of pyruvate
What happens to the alanine formed in skeletal muscles?
released into blood where it is taken up by liver and converted to glucose
Why does the liver release pyruvate from alanine?
Because muscle can use amino acids for carbon skeleton but cannot form urea therefore the liver removes nitrogen and release pyruvate
