Metabolism Flashcards
What is the Warburg effect?
The Warburg effect (also known as aerobic glycolysis) is where in cancer cells, even in the presence of 02, pyruvate metabolises into lactate.
Why do cancer undergo aerobic respiration (Warburg effect)? (3 reasons)
It is advantageous to them as it:
1) acidifies the tumour’s environment, which facilitates tumour invasion and inhibits the immune system.
2) provides a substrate for the pentose pathway, which produces precursors such as nucleotides that are required for growth.
3) reduces the dependence of cell growth on oxygen.
What facilities the switch to aerobic glycolysis?
Changes in the gene expression of hexokinase and pyruvate kinase facilitate the switch to aerobic glycolysis.
What is Leptin?
Leptin is a hormone secreted by adipocytes that binds to receptors in the brain to inhibit the release of appetite-stimulating neuropeptides.
How does Leptin bring about an increase in food intake?
1) A decrease in fat cell mass will lead to a decrease in leptin expression.
2) This will result in activation of NPY and AgRP-producing neurons, and inhibition of POMC-producing neurones.
3) As a result, NPY and AgRP expression and release will increase, and MSH expression will reduce.
4) Overall, food intake will then increase.
The activation and inhibition of which neurons will bring about an increase in food intake?
Activation of NPY and AgRP producing neurons.
Inhibition of POMC-producing neurones.
If leptin is produced in proportion to body-fat
mass and leptin inhibits eating, why do people
become obese?
It is suggested people still become obese due to Leptin resistance. This happen due to alteration in the transport of leptin across the Blood-brain-barrier.
What is Dyslipidemia?
Dyslipidemia is where there are high levels of cholesterol and LDL in the blood.
What is Metabolic syndrome?
Metabolic syndrome is a clustering of insulin resistance, hyperglycaemia and dyslipidemia.
How is insulin resistance brought about in muscle cells?
1) Enlarged adipocytes produce macrophage chemotaxis protein (MCP-1)
2) This causes macrophages to infiltrate the adipose and produce TNFa.
3) TNFa favours the export of fatty acids to muscle, where ectopic lipid deposits form.
4) Ectopic lipid interferes with GLUT4 movements to the myocyte surface, producing insulin resistance.
Why does exercise increase insulin sensitivity in type II diabetes?
Exercise causes an increased release of Ca2+, which stimulates Ca-dependent enzymes that function to activate transcription factors that increases mitochondrial biogenesis.
It also enhances the oxidising capability of fatty acids.
What are the changes that occur in the blood plasma during starvation?
1) The plasma levels of fatty acids and ketone bodies increases as become the main source of fuel.
2) The levels of glucose also decreases.
How does ethanol consumption lead to Hypoglycemia, Lactic acidosis and “Fatty Liver”?
As a by-product of the break down of ethanol, NADH is produced an accumulates in the cytoplasm. Consequently, this leads to lactate accumulation and triacylglycerol accumulation in the liver. Accumulation of these molecules leads to hypoglycaemia, lactic acidosis and fatty acid.
How is ethanol broken down in the liver?
Ethanol is converted to acetaldehyde by alcohol dehydrogenase. Then it is converted to acetic acid, also by alcohol dehydrogenase.
How does ethanol consumption lead to foetal alcohol syndrome?
Ethanol is a competitive inhibitor of Vitamin A and distrupts’ the retinoic acid signalling pathway. This is important because as part of the pathway, vitamin A (retinol) is converted to retinoic acid, which is an important signal molecule for growth and development.
