Lecture 24 - Glucose as a fuel molecule 2 Flashcards
What is the main purpose of glycolysis
A conversion of one molecule of glucose into two molecules of pyruvate, captain energy in the form of ATP and NADH
What are the two phases of glycolysis
- Energy investment phase
- Energy payoff phase
Net gain from glycolysis
is 2 ATP and 2 NADH
How is glucose activated during glycolysis
Through two ATP consuming reactions catalysed by 1. hexokinase and 3. phosphofructokinase
What reaction does hexokinase catalyse in glycolysis
The phosphorylation of glucose to glucose-6-phosphate using ATP. ATP turns into ADP by giving away its phosphate and releasing energy
Why is energy input required in the first steps if glycolysis
To activate glucose, making it easier to split and capture energy in later steps
What happens to glucose-6-phosphate in the second step of glycolysis
It is isomerised to fructose-6-phosphate by glucose phosphate isomerase
What does photofructokinase do in glucose
It catalyses the phosphorylation of fructose-6-phostphate to fructose-1,6-biphosphate using ATP
Key enzyme that is responsible for splitting fructose
Aldose - splitting fructose into DHAP and G3P
What is the significance of G3P
It enters the energy payoff phase of glycolysis, where ATP and NADH are produce
How is NADH generated in glycolysis
Through the oxidation of G3P to 1,3-BPG by G3P dehydrogenase, with NAD+ being reduced to NADH
What is substrate level phosphorylation
A direct transfer of a phosphate group from a high-energy substrate to ADP to form ATP
what reactions in glycolysis involve substrate level phosphorylation
- Conversion of 1,3-BPG to 3-phospholglycerate
- Conversion of phosphoenolpyruvate ti pyruvate
what happens to pyruvate under aerobic conditions
It is converted into acetyl CoA, which enters the citric acid cycle
What happens to pyruvet under anaerobic conditions
It is converted in into lactate to regenerate NAD+
Why is lactate produce under anaerobic conditions
To regenerate NAD+ so that glycolysis can continue in the absence of oxygen
How does the chemical arsenic affect glycolysis
Arsenate can replace phosphate in the glycolyic pathway, preventing ATP synthesis and poisoning the pathway
What coenzyme is essential for glycolysis and other redox reactions
NAD+ derived from vitamin B3
What is Gibbs energy and its relevance in glycolysis
In glycolysis unfavourable reactions are coupled with ATP hydrolysis to make them favourable
What are the two main types of reactions involved in ATP synthesis
- substrate level phosphorylation
- Oxidative phosphorylation
what happens during pyruvate dehydrogenase reaction
Pyruvate us oxidised to acetate CoA - aerobic and NADH is produced as well well as CO2 is released
What is the significance of PEP in glycolysis
PEP is high energy compound that donates phosphate to ADP, forming ATP and pyruvate
