1. Glycolysis Flashcards
what is glycolysis
oxidation of 1 glucose to 2 pyruvate - catabolic/exergonic
what 4 components does glycolysis require
1) 1 glucose
2) 2 ATP
3) 2 NAD+
4) 4 ADP
what are the main products of glycolysis
1) 2 pyruvate
2) 4 ATP - net gain = 2 ATP
3) 2 NADH
what are the 3 main regulatory steps in glycolysis
1 - glucose to glucose-6-P by HEXOKINASE (or glucokinase)
2 - fructose-6-P to fructose-1,6-bisP by PHOSPHOFRUCTOKINASE (main regulatory step)
3 - phosphoenolpyruvate to pyruvate by PYRUVATE KINASE
what is the difference between hexokinase and glucokinase
hexokinase
- all tissues
- higher affinity to glucose: lower Km, always active
- regulated by product: inhibited by high [glucose-6-P]
glucokinase
- liver
- lower affinity to glucose: higher Km, only active after meal
- regulated by substrate availability: stimulated by high [glucose]
how is phosphofructokinase regulated
allosterically in muscle:
- inhibited by high ATP
- stimulated by high AMP
hormonal regulation in liver:
- inhibited by glucagon
- stimulated by insulin
how is pyruvate kinase regulated
- inhibited by glucagon
- stimulated by insulin
name 2 important intermediates of glycolysis
- DHAP
2. 2,3-BPG
in which cells is DHAP produced and why
- adipose and liver
- DHAP is converted to glycerol phosphate via GLYCEROL 3-PHOSPHATE DEHYDROGENASE, which is used for:
- phospholipid synthesis (polar head)
- triacylglycerol synthesis (= glycerol phosphate + fatty acids)
in which cells is 2,3-BPG produced and why
- RBCs
- regulation of haemoglobin O2 affinity (decreases affinity)
how is NAD+ required for glycolysis regenerated in different tissues
- most tissues with O2 supply: via oxidative phosphorylation (NADH to NAD+ at ETC)
- but in RBCs (lack MT) and in reduced O2 conditions (eg muscle and gut): via lactate dehydrogenase
which reaction does lactate dehydrogenase catalyse
pyruvate + NADH + H+ to lactate + NAD+
what are the 2 fates of lactate
travels via blood to:
1- heart… converted back to pyruvate via lactate dehydrogenase… oxidised for energy production
2- liver/kidney… converted back to pyruvate via lactate dehydrogenase… converted to glucose via gluconeogenesis… returns to tissues