Glycolysis Flashcards
how are carbohydrates broken down
- amylase in the salvia and pancreas
2. disaccharidases break down disaccharides in the small intestine
what are dextrins
smaller subunits of carbohydrates
name 4 disaccahridases
lactase, sucrase, pancreatic amylase, isomaltase
what is lactose intolerance
when you don’t have the enzyme lactase so cant break down lactose
what is primary lactase deficiency
absence of the lactase allele. Only occurs in adults
why is primary lactase deficiency only seen in adults
as children are born with lactase to break down breast milk, but they may not carry on expressing this gene into adult life
what is secondary lactase deficiency
deficiency caused by damage to the small intestine. Occurs in both adults and children
true or false: secondary lactase deficiency is reversible
true
what is congenital lactase deficiency
an extremely rare recessive defect in the lactase gene.
what are the symptoms of lactose intolerance
bloating, flatulence, diarrhoea, vomiting, rumbling stomach
how are monosaccharides absorbed into the intestinal epithelia cells
active transport by sodium dependant glucose transporter 1 (SGLT1)
which transporter do monosaccharides go through to enter the blood
GLUT2
how do monosaccharides enter cells from the blood
facilitated diffusion using GLUT1-GLUT5 transport proteins
where are GLUT 2 proteins found
kidney, liver, pancreatic beta cells, small intestine
where are GLUT 4 proteins found
adipose tissue, striated muscle
which cells have an absolute requirement of glucose (4)
- RBC- no mitochondria so can only get energy from glycolysis no other sources
- Neutrophils- use their mitochondria to produce free radicals so cant be used in energy production
- Kidney Medulla - cortex require lots of oxygen so little reaches medulla
- lens of the eye - no capillaries so no oxidative phosphorylation so relies on glycolysis
what does the uptake of glucose depend on
blood glucose concentration
what is stage 2 of energy release from carbohydrates
glycolysis
what occurs in phase 1 of glycolysis
2 ATP are used (investment)
why is phase 2 of glycolysis called the payback phase
4 ATP are produced
what is the net production of glycolysis from 1 molecule of glucose
2 NADH, 4 ATP, 2 Pyruvate
true or false: glycolysis is exergonic
true
what does hexokinase catalyse
conversion of glucose to glucose-6-Phosphate using energy from ATP. This makes the glucose negatively charged so prevents it passing out of membrane and makes the glucose more energetically favourable
what does phosphofructokinase catalyse
conversion of Fructose-6-P to Fructose-1,6-biphosphate using energy from ATP
what does pyruvate kinase catalyse
production of Pyruvate from Phosphoenolpyruvate which produces ATP
why are there so many steps and enzymes in glycolysis
allows parts to be reversed, allows for control, produces useful intermediates