White And Brown Adipose Tissue Flashcards
During exercise, what happens to the glycogen level in the liver, the glucose level in the blood, the free fatty acids level in the blood, and the level of ketone bodies?
Glycogen level in the liver decreases to almost zero, glucose level in the blood decreases, plasma free fatty acids increases, level of ketone bodies increases from almost zero.
Why does the glucose level in the blood never drop to zero?
Glucose is used by all tissues, it is needed by the central nervous system, and it is used for aerobic glycolysis by erythrocytes and cells in the retina.
Fatty acids can’t cross the blood-brain barrier, and they need to be respites in mitochondria so can’t be used for aerobic glycolysis.
During starvation, what is triacylglycerol converted to in the white adipose tissue, and then what happens to the products?
TAG converted to non-esterified fatty acids.
NEFA carried by albumin in the blood to the liver.
In the liver there is beta oxidation of NEFA to acetyl coA, which can then either enter the krebs cycle or undergo ketogenesis to produce ketone bodies to fuel the CNS.
What happens to plasma fatty acids if blood glucose level decreases?
Fatty acids are released so level increases.
What happens to plasma fatty acids if blood glucose level increases?
Insulin is released so fatty acids are taken up for lipogenesis and the plasma level decreases.
What hormones does white adipose tissue secrete?
Inflammatory factors and leptin (which controls appetite).
Given that TAG is constantly broken down in white adipose tissue as part of the glucose-fatty acid cycle, what factors mean fatty acids are released, and what factors mean TAG is built up again?
In white adipose tissue there is no glycerol kinase, which means glycerol can’t be used for gluconeogensis inside the white adipose tissue and will instead form TAG. In the presence of adrenaline, noradrenaline and glucagon, TAG is broken down, the glycerol is exported for gluconeogensis, and the fatty acids are released to be carried to the liver by albumin.
In the presence of insulin, glucose enters the White adipose tissue and forms glycerol which combines with fatty acids to form TAG.
What controls brown adipose tissue?
Brown adipose tissue is under nervous rather stimulation.
Where is brown adipose tissue found?
Inter scapula region of neonates.
What is the purpose of brown adipose tissue?
Neonates can’t shiver, so they use brown adipose tissue to generate heat.
Why does brown adipose tissue appear brown?
It contains LOADS of mitochondria, and there’s lots of iron in the cytochromes in the mitochondria.
What is the name of the specific protein channel in brown adipose tissue which opens to uncouple ATP synthesis from the proton gradient?
Thermogenin
How does heat generation occur in brown adipose tissue?
Noradrenaline stimulates the breakdown of TAG to release fatty acids.
This triggers the thermogenin channel to open.
This destroys the proton gradient - protons can just move back into the matrix through thermogenin so circle round and round instead of accumulating.
ATP is not produced, but the fatty acids are still oxidised, which produces energy as heat.
ADP accumulates and a high enough level of ADP will stimulate thermogenin to close.
What is the major function of white adipose tissue?
To release fatty acids for use for energy during exercise and starvation.
