Glycolysis Flashcards
What is the molecule that forms the starting point for glycolysis?
glucose
What molecule is produced from the first step in stage 1 of glycolysis?
glucose 6-phosphate
What are the two main purposes of the production of glucose 6-phosphate from glucose during the first step of glycolysis?
- glucose 6-phosphate cannot pass through the cell membrane so is trapped in the cell
- the phosphory group addition destabilises glucose, facilitating its further metabolism
What enzyme catalyses the conversion of glucose to glucose 6-phosphate during the first step of glycolysis?
hexokinase
What molecule is produced from glucose 6-phosphate during the second step os stage 1 of glycolysis?
fructose 6-phosphate
What is the importance of the conversion of glucose 6-phosphate into fructose 6-phosphate for the later stages of glycolysis?
Unlike glucose 6-phosphate, fructose 6-phosphate is readily split into two three-carbon fragments. This is important as in the later stages of glycolysis only three-carbon molecules are metabolised.
What enzyme catalyses the conversion of glucose 6-phosephate to fructose 6-phosphate during the second step of glycolysis?
phosphoglucose isomerase
What is produced from fructose 6-phosphate during the third step of stage 1 of glycolysis?
fructose 1,6-bisphosphate
What enzyme catalyses the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate during the third step of stage 1 of glycolysis?
phosphofructokinase
What is the key regulatory step that sets the pace in glygolysis? What enzyme is involved? What are two reasons that this step is important?
Phosphofructokinase (PFK) catalyses the phosphorylation of fructose 6-phosphate by ATP to fructose 1,6-bisphosphate.
- stabilizes the fructose isomer
- prepares the way for the generation of two phosphorylated three-carbon fragments (the actual substrates for the ATP-generation phase of glycolysis)
In the second stage of glycolysis, fructose 1,6-bisphosphate is split into two triose phosphates. What are their names and which of them is on the direct pathway of glycolysis?
- glyceraldehyde 3-phosphate (GAP)
- dihydroxyacetone phosphate (DHAP)
Glyceraldahyde 3-phosphate is on the direct pathway of glycolysis.
What enzyme catalyses the cleaving of fructose 1,6-bisphosphate into two three-carbon units during the second stage of glycolysis?
aldolase
Only glyceraldehyde 3-phosphate is on the direct pathway of glycolysis. What is the enzyme that catylyses the interconversion between dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP)?
Why is this interconversion important?
- triose phosphate isomerase
- so that the three-carbon fragment that would be lost if dihydroxyacetone remained in this form, unusable, is not wasted
How many molecules of ATP are invested in stage 1 of glycolysis?
How many are generated during the final stage 3?
Net ATP yield per glucose?
2 are invested initially.
Stage 3 runs through twice so 4 are generated.
Net yield = 2
What product is generated from glyceraldehyde 3-phosphate after the first step of stage 3 of glycolysis?
1,3-bisphosphaglycerate
What enzyme catalyses the conversion of glyceraldehyde 3-phosphate into 1,3-bisphosphoglycerate in the first step of stage 3 of gluconeogenesis?
glyceraldehyde 3-phosphate dehydrogenase
What makes 1,3-bisphosphoglygerate so important during this stage of glycolosis?
Energy-rich molecule with greater phosphorylation potential than ATP - can be used for ATP synthesis.
What is the term used to describe the process of ATP synthesis from ADP and orthophosphate?
Substrate-level phosphorylation.
This occurs when ATP or GTP is generated by the transfer of a phosphate group from a substrate directly to ADP or GDP. Transferring from a higher energy (whether phosphate group attached or not) into a lower energy product (*wiki)