Carbohydrates Flashcards
Carbohydrate
Oxygen, carbon and hydrogen macromolecules being an important energy source, regulator of blood glucose and insulin metabolism, cholesterol and triglyceride metabolism and assist in fermentation.
Monosaccharide`
Most basic fundamental sugar like glucose, galactose and fructose.
Disaccharides
Compound of two monosaccharides in dehydration synthesis like sucrose and lactose
Polysaccharides
Long chain polymers of polysaccharides connected by glycosidic bonds like amylose and cellulose.
Oligosaccharides
A polymer of about 3-10 monosaccharides connected by glycosidic bonds, like amylose.
Simple Carbohydrate
Mono/Disaccharides easily utilised for energy where consumption results in rapid rise in blood sugar and insulin secretion.
Complex Carbohydrates
Oligo/Polysaccharides forming more complex chemical structures with longer digestion rates and more gradual effects on blood sugar increase.
What by and where is fructose absorbed?
GLUT5 in the intestinal lumen on enterocytes.
What is the function of Fructose as a substrate for bacterial fermentation?
It leads to gas and bacterial metabolite formation, affecting intestinal motility causing abdominal pain and bloating.
What does increased fructose consumption lead to?
Increased adaptability to it, inducing TXNIP which binds/regulates GLUT5-mediated intestinal fructose transport.
TXNIP
Intestinal thioredoxin-interacting protein is a powerful inhibitor of tumour growth and angiogenesis
How does fructose affect lipid metabolism and contribute to steatosis?
Activation of the lipogenic program, increasing VLDL triglyceride secretion and additionally supresses hepatic fatty acid oxidation, a process responsible for adipocyte lipolysis, where fats are hydrolysed.
De Novo Lipogenesis
A process converting excess carbohydrates into fatty acids which are esterfied to storage triacylglycerols that can provide energy for beta oxidation.
Acetyl-Coa
A protein begingin the final common pathway of the three major myocardium substrates; free fatty acids, glucose and lactate.
What does Acettyl-COA do in hepatic de novo lipogenesis?
Acetyl-COA are what fatty acids are synthesised from
Where is de novo lipogenesis contained and why?
Contained in the liver, where due to difference in fructose/glucose metabolism, has a higher fraction of diet-derived fructose available for conversion to fat via DNL.
What is the metabolic pathway of fructose in hepatocytes?
Fructose is phosphorylated into F1P, then cleaved into dihydroxyacetone phosphate and glyceraldehyde, where GAH is phosphorylated by triose-kinase to form G3P, both fructose-derivatives entering glycolytic and gluconeogenic pathways.
Why is DNL’s generation of malonyl-CoA important?
Malonyl-CoA is a metabolite limiting FA oxidation through inhibition of CPT1A enzymes, this inhibition increasing fatty acid availability for production.
How does chronic fructose consumption affect DNL regulaton?
It increases trans-reg of DNL by activation of TF’s promoting lip-syn.
SREPB1c
A gene required for glucose metabolism and fatty acid/lipid production
Why is the sweetness of fructose bad?
It increases food palatability, worsening food behaviour and overconsumption, which additional addiction inducing behaviours like dependance and binding by stimulation of dopaminergic pathways, and leading to leptin resistance, an appeptie supressor.
What is the mechanism fructolysis in relation to glucose metabolism?
It has most the same enzymes and metabolic intermediates, differing in that fructose predominantly synthesises in the liver for liver replenishment of glycogen/triglyceride synthesis.
What is the movement pathway for fructose upon consumption?
It absorbs passively via GLUT5 in the small intestine with high binding affinity for fructose, where entry into the bloodstream is done so by GLUT2.
How is fructose metabolised in adipose tissue/muscle
Hexokinase forms fructose-6-phosphate, of which enters glycolysis
