integration of metabolism Flashcards
where does the metabolism of fatty acids and carbohydrates occur
it occurs in different extents in different organs reflecting the metabolic needs and function of the tissue
What does the brain use as its source of energy
under normal conditions- glucose and aerobic metabolism
what does the brain use as a source of energy when the body is in resting state
When the body is the resting state, the brain has high respiratory rate, O2 consumption & uses about 60% of the available glucose
Cannot use fatty acids (fatty acids will not cross the blood brain barrier)
Therefore under conditions of starvation the brain will use Ketone bodies
what does the skeletal muscle use as fuel under resting conditions
fatty acids
what happens when the skeletal muscles start working
muscle will break down its own stores of glycogen to produce glucose-6-phosphate.
If the production of pyruvate exceeds the oxygen capacity of the muscle cell, then pyruvate is converted Into lactate.
what is the purpose of the liver
ensures adequate supply of blood glucose for the brain, muscle and RBCs
it also converts excess fuel into fatty acids- fatty acids are transported from the liver for storage in adipose tissue
during fasting what will the liver convert fatty acids into
acetoacetate and other ketone bodies
what is the ratio in a well fed state
insulin : glucagon ratio is higher
what is the ratio in a fasting state
glucagon : insulin ratio is higher
what does adipose tissue rely on
Does not have a high energy requirement but
does rely on a supply of glucose for glycolysis.
how is TAG produced in adipose tissue
Glycolysis will produce glycerol-3-phosphate
+ fatty acids to produce triacylglycerol (TAG)
what is TAG production regulated by
hormonal signals
where are GLUT proteins found
in the plasma membranes of various cells and are responsible for glucose uptake from blood stream
where is GLUT 1 found
RBCs
where is GLUT 2 found
liver
where is GLUT 3 found
brain
where is GLUT 4 found
adipose and muscle- mobilised to cell membrane by insulin
what type of hormone is insulin
anabolic hormone and works to lower blood glucose concentration
it boosts protein synthesis, promotes glycolysis, increases the conversion of carbohydrates to fatty acid
When are insulin levels high
when there is high blood glucose, amino acids, glucagon and gastrointestinal hormone levels
when is insulin decreased
by fasting, exercise and adrenergic activity
what is glucagon
a peptide hormone- 29 amino acids produced by the a-cells of the pancreas
Secreted in response to low blood glucose and high circulatory levels of gluconeogenic amino acids
Secretion inhibited by insulin and by high blood glucose conc
what type of hormone is glucagon
a catabolic hormone - works to raise blood glucose concentration, Promotes glycogen breakdown
Stimulates fat breakdown - lipolysis.
when is glucagon released
when there is low blood glucose & adrenaline
what tissues does glucagon target
liver, fat cells, heart muscle
what type of hormone is cortisol
a steroid hormone produced by the adrenal cortex and has increased secretion during stress and works to raise blood glucose concentration
what does cortisol do when insulin concentration falls
it increases protein mobilisation via proteolysis
what does the insulin : glucagon ratio determine
levels of circulating glucose
what does the insulin : glucocorticoid ratio determine
determines the net protein turnover and availability of circulating amino acids
what occurs in early starvation
Fatty acids cannot penetrate the Blood Brain Barrier
Brain and RBC use glucose derived mainly
from Amino Acids
The switching by Peripheral tissues to use fats as a source of energy conserves glucose for use by the brain and RBC’s
what occurs in prolonged starvation
there is Excess Acetyl CoA and this produces ketone bodies
Ketone bodies are used as a fuel source by the brain to help preserve glucose for use by the RBC’s and suppress the loss of skeletal muscle protein
when fat stores depleted - No acetyl CoA, Gluconeogenesis ceases, Blood glucose rapidly drops, No fuel in blood (coma and death)
