Energy Production: Carbs 1+2 Flashcards
What occurs in stage 1 of metabolism?
Occurs extracellularly (GI tract), complex molecules are broken down to smaller molecules. Breakage of C-N and C-O bonds, and no energy is produced.
What occurs in stage 2 of metabolism?
Occurs intracellularly (cystolic and mitochondrial). Has many pathways, C-C bonds are broken and some energy is produced.
What occurs in stage 3 of metabolism
Occurs in mitochondria, a single pathway (TCA cycle), is oxidative and some energy is produced. Acetyl CoA is converted to 2CO2.
What occurs in stage 4 of metabolism?
Occurs in mitochondria. Electron transport and ATP synthesis. NADH and FAD2H re-oxidised and large amounts of energy carrier (ATP) generated.
What’s the general formula for carbohydrates?
(CH2O)n, may contain aldehyde (H-C=O) or keto (-C=O) group
Examples of dietary carbohydrates?
Sucrose (Glucose-Fructose disaccharide), Lactose (Glucose-Galactose disaccharide), Maltose (Glucose-glucose disaccharide)
Which tissues have an absolute requirement for glucose?
Red blood cells, neutrophils, innermost cells of kidney medulla, lens of eye
Describe primary lactase deficiency
Inability to digest lactose products due to an absence of lactase persistence allele. Only occurs in adults.
What causes secondary lactase deficiency?
Caused by injury to small intestine, e.g. gastroenteritis, coeliac disease, Crohn’s disease. Occurs in both infants/adults and is generally reversible.
Describe congenital lactase deficiency
An autosomal recessive defect in the lactase gene, meaning breast milk can’t be digested.
What does allosteric mean?
An activator or inhibitor that binds at ‘another’ site.
What are key features of glycolysis?
Oxidation of glucose, NADH production (2 per glucose), synthesis of ATP from ADP with a net gain of 2 ATP.
What are the allosteric and hormonal regulators of phosphofructokinase?
Allosteric: inhibited by high ATP and high citrate, stimulated by high AMP and high F2, 6BP. Hormonal: Stimulated by insulin, inhibited by glucagon.
When is pyruvate reduced to lactate?
When there is an inability to use NADH for oxidative phosphorylation
What’s the equation for lactate production
NADH + H+ + pyruvate <—> NAD+ + lactate
(Lactate dehydrogenase)
What is lactic acidosis
Occurs when plasma lactate concentration is above 5mM, above renal threshold and blood pH is lowered.
Diseases associated with fructose metabolism.
Essential fructosuria- where fructokinase is missing (fructose in urine). Fructose intolerance- aldolase missing so F1P accumulates in liver causing damage and possible death. Managed by removing fructose and sucrose from diet.
What enzymes are involved in galactose metabolism
Galactokinase, Galactose-1-P uridyl transferase, UDP-galactose 4’-epimerase.
Describe galactosaemia
Body unable to utilise galactose due to enzyme deficiencies. Problem here is that galactose enters other pathways. Accumulation of galactose-1-P affects liver, kidney and brain. Treatment- no lactose in diet.
