Lecture 9 - Glycolysis Flashcards
What organelle are most metabolic pathways connected to?
mitochondria
Anabolic vs catabolic pathways
anabolic = making large molecules
- requires energy
catabolic = breaking large molecules
- release energy
Different definitions of oxidation
With respect to hydrogen transfer
- oxidation is the loss of hydrogen
- reduction is the gain of hydrogen
With respect to oxygen transfer
- oxidation is the gain of oxygen
- reduction is the loss of oxygen
With respect to electron transfer
- oxidation is the loss of electrons
- reduction is the gain of electrons
What are coenzymes? What are the coenzymes of redox reactions and electron carriers?
coenzymes are organic molecules that bind to the active sites of certain enzymes
NAD and FAD are coenzymes
- they accept electrons (become reduced) during catabolic steps in the breakdown of organic molecules
- NADH and FADH2 donate these electrons to some other biochemical reaction normally involved in a process that is anabolic (like the synthesis of ATP)
Why is glucose such an important oxidizable substrate in energy metabolism?
- its oxidation is highly exergonic (releases lots of energy)
- many polysaccharides break into glucose
- starch, glycogen, cellulose
Why do enzymes catalyze oxidation in small steps?
enables free energy to be transferred in conveniently sized packets to carrier molecules - most often ATP and NADH
- if done in one big step, all energy would be lost as heat and none would be stored
What is glycolysis?
a metabolic pathway that entails the oxidation of glucose into 2 pyruvate molecules
Briefly, what are the 3 phases of glycolysis?
- preparation and cleavage of glucose molecule
- requires input of 2 ATP molecules
- oxidation and ATP generation
- some energy of this reaction is conserved as 2 ATP and 2 NADH molecules produced
- pyruvate formation and ATP generation
- produces 2 ATP molecules
- net gain of 2 ATP molecules per glucose molecule (4 produced but 2 were used in the break down of glucose)
What are the 3 monosaccharides produced in the break down of disaccharides?
glucose, galactose and fructose
Besides glucose, how are other monosaccharides used in glycolysis?
they are converted into glycolysis intermediates
What is the branch point between aerobic and anaerobic metabolism?
pyruvate:
if high [O2], PDH takes pyruvate
if low [O2], LDH makes lactate
Warburg effect
Tumour cells mainly metabolize glucose to lactate independent from intracellular oxygen levels (i.e., the cells might have oxygen, but they don’t care)
How does pyruvate get into the mitochondria?
through transport mediated by a mitochondrial pyruvate carrier
What molecule enters the TCA cycle?
Acetyl-CoA
How does pyruvate become Acetyl-CoA?
a pyruvate dehydrogenase converts pyruvate into acetyl-CoA by removing a carbon and adding a CoA
