2.6 Integration of metabolism Flashcards
What are the energy sources of the brain
ketone bodies and glucose
why can the brain not metabolise fatty acids
won’t pass the blood brain barrier
What does hypoglycemia cause for the brain
faintness and coma
what does hyperglycemia cause for the brain
‘irreversible damage ‘
what can the brain use a partial substitute for glucose
beta hydroxybutyrate and other ketone bodies
In light contraction how are the energy requirements of skeletal muscles met
by oxidative phosphorylation
In vigorous contraction how are the energy requirements of skeletal muscles met
by lactate production and glycogen formation
what percentage of body mass do skeletal muscles make up
40%
What can the heart metabolise
basically anything
fatty acids, ketone bodies, glucose
What are some metabolic processes that happens in the liver
gluconeogenesis
beta oxidation
fatty acid synthesis (also happens in lactating breast and adipose tissue and cancer cells )
ketone body production
What concentration does the liver keep blood glucose at
4 - 5.5 mM
What can excess glucose - 6 phosphate be used for
1) glycogen store
2) formation of pentose phosphates that can form nucleotides
How is NADPH produced and in what pathway is it used
from glucose 6 phosphate and used in the cholesterol pathway ( 3 HMG CoA )
What are the uses of acetyl CoA
1) combines with oxaolacetate to form citrate in the krebs cycle
2) combines with another acetyl CoA to form acetoacetyl CoA, which can be used to form ketone bodies ( acetoacetate, acetone, 3 hydroxybutyrate)
3) forms cholesterol by HMG CoA reductase of HMG which is formed from acetoacetyl CoA
What happens if glucose concentration falls below a certain amount
If falls below 3mM, enters hypoglycemic coma
What are the 4 ways that the body can prevent going into a hypoglycemic coma
1) release of Free fatty acids from adipose tissue
2) making ketone bodies
3) break down of glycogen in the liver
4) gluconeogenesis
Describe gluconeogenesis’ bypass reactions
formation of glucose in starving conditions
4 bypass reactions:
pyruvate forms oxaloacetate (enzyme: pyruvate carboxylase)
oxaloacetate forms phosphophenolpyruvate (enzyme: phosphophenolpyruvate carboxykinase)
Fructose 1,6 bisphosphate to fructose 1 phosphate (fructose 1,6 bisphospohatase)
glucose 6 phosphate to glucose (glucose 6 phosphatase)
why are bypass reactions required
to make a favourable negative gibbs free energy.
the straight reversal of this process would be +90kj/mol whereas witht the bypass reactions it is -38kj/mol
What non carbohydrate molecules can enter gluconeogenesis
1) glycerol forms dihydroxyacetone phosphate
2) amino acids form oxaloacetate (aspartate)
3) amino acids form pyruvate (alanine, serine, and cysteine)
4) lactate forms pyruvate
Deamination of all 20 amino acids lead to which products
1) acetyl CoA
2) Acetoacetyl CoA
3) fumerate
4) succinyl CoA
5) Alpha keto glutarate
6) oxaloacetate
7) pyruvate
Describe the metabolic processes that occur during exercise (aerobic)
1) contractions mean increased demand for ATP
2) contractions increase glucose transport
3) muscle glycolysis increases
4) gluconeogenesis in liver
5) fatty acids increase
3,4,5 happen as a result of adrenalin
Describe the metabolic processes that occur during exercise (anerobic)
1) muscle contractions increase demand for ATP
2) Muscle produces lactate
3) Lactate is transported to the liver, where it is converted to pyruvate and used in gluconeogenesis
4) glycogen is broken down in the muscles to glucose
outline the differences between hexokinase in the liver and the blood
The muscles have hexokinase 1 whereas the liver has hexokinase 4
hexokinase 1 has a lower Km and so has a greater affinity to glucose
hexokinase 1 can be more readily inhibited by glucose 6 phosphate
In anerobic conditions hexokinase 1 is inhibited
What does adrenalin do
strong and fast metabolic effects
to mobilise glucose for ‘fight or flight’
what do glucocorticoids do
steroid hormones that increase synthesis of of metabolic enzymes concerned with glucose availability
What does insulin do
secreted in high blood glucose levels
stimulates uptake of glucose by cells and
storage as glycogen and fat
What does glucagon do
production of glucose by gluconeogenesis
breakdown of glycogen and fat
What happens on having a meal
1) blood glucose levels rise
2) insulin secreted
3) triglycerides synthesized in adipose tissue
4) uptake of glucose by muscle cells
5) uptake of glucose by liver to be stored as glycogen or to undergo glycolysis (as acetyl CoA can be used to make fatty acids)
What happens after prolonged fasting
1) glucagon: insulin ratio increases
2) adipose tissue breaks down triglycerides to fatty acid and glycerol (used to form DHAP in glycolysis )
3) break down of proteins to substrates used in the TCA cycle
4) formation of ketone bodies to use as energy source for brain
What are the 2 types of diabetes
1) Type 1 DM - inability to secrete insulin
2) type 2 DM - insensitive to insulin
What are 4 complications of diabetes
1) hyperglycemia ( increased glucagon levels relative to insulin so more glucose in blood )
2) hypoglycemia ( if injects too much insulin )
3) ketoacidosis ( if makes too many ketone bodies in ‘starvation conditions’ )
4) increased levels of fatty acids + lipoproteins means cardiovascular implications
