lecture 10 glycolysis Flashcards
hexokinase reaction and what it does energetically
Traps Glucose in the Cell and Begins Glycolysis. phosphorylates any glucose that enters cell to create glucose-6-phosphate. ATP–> ADP
Phosphofructokinase (PFK) reaction
fructose 6-phosphate -> fruc 1,6 bisphosphate. turns ATP into ADP. part of stage 1 of glycolysis
pyruvate kinase reaction
last step of glycolysis. phosphoenolpyruvate –> pyruvate, generates 4 ATP’s as each of the ADP’s get phosphorylated
hexokinase phosphorylates glucose at what position?
c6
hexokinase is an example of ___ coupling
enzymatic
how does the hexokinase enzyme work?
brings both substrates together in the active site so that OH faces the gamma ATP and then wraps around them so tightly that no water molecule can get through
why would it be bad if water got into the active site?
premature hydrolyzing of atp before we can obtain our energy from it
is phosphofructokinase reaction reversible or irreversible
irreversible
what step in glycolysis involves NAD+
1,3 BPG
1,3-bisphosphoglycerate has a greater _____ than ATP, and thus can be used to power the synthesis of ATP from ADP and Pi
phosphoryl transfer potential
___ is material in the first step that involves ATP formation
1,3 BPG
metabolic coupling
happens on subsequent enzymes rather than same enzymes- pulls reaction forward through its negative delta G or le chat’s principle
how can you regenerate NAD+ to keep glycolysis going?
NAD+ can be regenerated by further oxidation of pyruvate to CO2, or by the formation of ethanol or lactate from pyruvate.
fermentation is a means of oxidizing __
NADH
The conversion of glucose into 2 molecules of lactate is called
lactic acid fermentation.
when oxygen is present, NADH does what?
When oxygen is present NADH donates electrons to another molecule to shuttle them into the mitochondrial matrix for use and gets reoxidized to NAD+ in the process.
When oxygen is not present, what happens?
animal cells transfer the electrons and two protons onto pyruvate to form lactate, and thereby reoxidizeing NAD+ in the process.
Yeast transfers electrons onto acetaldehyde to produce ethanol.
Generating energy in absence of oxygen is called fermentation. Glucose to lactate is called lactic acid fermentation.
____controls efflux from the pathway and is also inhibited by high energy charge.
pyruvate kinase
____ raises free energy level and traps hexose in ketose form to make next step of cleavage in half more possible. The cleavage remains + ΔGo value, however, and moves forward by metabolic coupling (Le Chatlier’s principle in play) since overall ΔGo is negative. reaction is irreversible.
Phosphofructokinase
stages of glycolysis: first stage
glucose –> fructose –> fructose 6 phosphate –> F6biphosphate–> chopped in half, to form glyceradlehyde 3-phosphate
second stage of glycolysis
the two glyceraldehyde 3-phosphates are oxidized to acids as NAD+ is reduced, and each gets another phosphate group- now they each have two
role of PFK
adds a phosphate group onto F6phosphate to turn it into fructose 1,6 biphosphate
stage 3 glycolysis
Stage 3 moves each of the four phosphates onto 4 molecules of ADP to form ATP. Net gain = 2 ATP
which reaction in glycolysis involves NAD+? aka the ‘money step’
glyceraldehyde 3-phosphate –> 1,3 bisphosphoglyerate.
we took a phosphate from the cytoplasm and plopped it on GAP. we get the energy to do this from the oxidiation of NAD+ . enables rxn to go. redox ‘electron acceptor’ is NAD+
an acid w/ high phosphoryl transfer potential, 1,3-bisphosphoglycerate, is generated by the oxidation of GAP in a reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase
T/F: 1,3-bisphosphoglycerate has a greater phosphoryl transfer potential than ATP
true - that is how we create ATP for the first time in glycolysis . powers the synthesis of ATP from ADP and P
the formation of ___ generates ATP in glycolysis
pyruvate
T/F: Phosphoenolpyruvate is a high phosphoryl-transfer compound
true, thats how we power ATP formation
how many atp’s are formed in glycolysis (net)
2
how can we regenerate NAD+ to continue glycolysis if we have used up all our NAD+?
make lactate , ethanol, or acetyl coA
fermentations are a means of oxidizing ___
NADH (so u can form NAD+)
T/F: other sugars, like fructose and galactose, can enter glycolytic pathway and be converted into intermediates
true!
