Redox reactions + glycolysis Flashcards
End-product inhibition
- metabolic pathways are nearly always down regulated by the final product to avoid overproduction
cooperativity
- occurs w/ two or more identical enzyme subunits forming enzyme complex
- first inhibitor molecules binds to allosteric site, induces conformation change in the subunit binds to, and partial conformation change in neighbouring units
- partial change is what facilitates binding of second inhibitor
- you now see curve w/ increasing inhibitor concentration leading to switch-like behaviour of multi-subunit enzymes - THIS CATALYZES the metabolic pathway!!!!
Metabolic pathway
- first step in path way is usually catalyzed by multi-subunit enzyme negatively regulated by cooperative allostay via end product of pathway
Catabolic pathways
- long and complex in order to release energy slowly
- burning glucose to carbon dioxide and water released all free energy in one reaction w/o capturing any energy for the cell
- better to do this in smaller steps, keep reaction going, half is ATP, other half is released as heat to drive reactions
Burning of glucose
- it is oxidation, a redox reaction, can be efficient (releases lots of energy) when oxygen is a electron acceptor
- or inefficient when there is absense of oxygen (fermentation)
Reduction
Gain of electrons
Oxidization
Loss of elections
Photosynthesis
- photosynthesis
- stored chemical energy
- glycolysis
- aerobic: CELLULAR RESPIRATION complete oxidation, water products: H20, C02, net energy trapped: 29 ATP
- anaerobic: FERMENTATION incomplete oxidation, waster product: organic compound, net energy trapped 2 ATP
How is oxidation stored?
- in intermediate NAD, it gets reduced to NADH, NADH is later oxidized and it releases energy
NADH
- temp. electron carrier (energy carrier)
- crucial for redox reactions
ATP
- crucial energy carrier for non-redox reactions
How do you know if NADH or NAD+ gets reduced?
- any two half reactions can be coupled in a redox reaction
- redox reactions are fully reversible
- direction of electron flow depends on which two half reactions get coupled (either flow to NAD+ or away from NADH)
Which way does it flow when couples w/ oxygen as electron acceptor?
- flow away from NADH
Which way does it flow when couples w/ glucose intermediates?
- electrons flow toward NAD+
How is electron flow measured? Which way does it flow?
- it is measured in Volts - redox potential
- when you couple two together, electrons always flow from more negative to more positive redox potential
Overview of cellular repsiration
1) Glycolysis: glucose goes in and create NADH and ATP
2) Pyruvate processing: Pyruvate turns into Acetyl CO A and makes C02, and NADH
3) Citric acid cycle: Acetyl Co A goes through citric acid cycle. Makes NADH, FADH, C02 and ATP.
4) Electron transport chain/ATP: Goes through electron transport chain and makes ATP, H20, 02
What is the energy consuming reaction/energy releasing one of glycolysis?
1) energy consuming reactions (investment of ATP to activate sugar followed by splitting of C6 to 2 C3)
2) energy releasing ones: oxidation of C3 giving NADH + H+ and ATP followed by recovery of initial ATP investment, coupled to high energy phosphate bond
Substrate-level phospholylation
- phosphate transferred from substrate directly to ADP
Visualize sequential coupling
- favourable reaction removes all the product of the unfavourable reaction, which just makes it favourable
Where does glycolysis occur?
- it occurs in cytosol
What is the end product of glycolysis?
Pyruvate
- further oxidized in mitochondrial matrix to acetyl-coenzyme A
What is Acetyl-coenzyme A?
- “high energy bond” - generated by large amount of free energy released by pyruvate/NAD+ of redox reaction
- energy carrier, allows transfer of 2-carbon group to another molecule at start of citric acid cycle
- key molecule in metabolism, everything broken down to it
- building block for making fats and other metabolites
