BIBIO301 Class 10 Flashcards
what is glycolysis
- breaking down of glucose molecules
- happens when glucose is high
- favored when insulin in high, glucagon is low
where does glycolysis occur
- cytoplasm
where does the citric acid cycle occur
- mitochondria
which are the steps in glycolysis that are not easily reversible? why?
- glucose phosporylation
- fructose 6-phosphate phosphorylation
- conversion of PEP to pyruvate
- these have a very negative delta G so reversing it would make it energetically unfavorable
what are the two phases of glycolysis?
1) preparatory phase: sets up glucose as a higher energy substamce prepped for lysis and eventual extraction of energy: an up front investment of 2 ATP
3) payoff phase: rearranges carbons to form strong phosphate donors to phosphorylate ADP; reap a 100% return on ATP investment with some NADH as a bonus
how many ATPs can be formed from 1 NADH
2.5 ATPs
why is the hexokinase step important?
- raises energy level of glucose
- traps glucose in the cell
how? - adds a phosphate using a kinase
- adding a phosphate increases its energy
- adding a phosphate ensures that glucose is not recognized by the glucose transporters
which hexokinase is used for high glucose levels? why?
- hexokinase IV/glycokinase is used as it has a high Km for glucose (low affinity) so it only works when there is a lot of glucose
- one possible location is liver cells
what is the commitment step of glycolysis?
phosphofructokinasse-1
what direction does G3P to 1.3 biphosphoglycerate go in high NADH conditions?
- reverse!
- so the reaction in glycolysis needs oxidized NAD: NAD+
what is the pentose phosphate pathway?
another essential fate for glucose that is important for anabolism
how do you decide between glycolysis and pentose phosphate pathways?
- build up of NADPH
