What is the starting molecule and the end product of glycolysis?

A hexose such as glucose (6C) is converted to two molecules of pyruvate (3C).

How many ATP are used at the start of glycolysis?

Two, to phosphorylate the hexose.

Why is the hexose phosphorylated?

It makes it more reactive so that it can be split into two 3-carbon molecules.

What happens to hexose bisphosphate?

It is split into two 3-carbon molecules (triose phosphate).

What does NAD do in glycolysis?

It accepts hydrogen removed from the intermediates, forming reduced NAD (NADH).

Glycerate 3-phosphate, a 3-carbon intermediate on the way to pyruvate.

What is the net gain of ATP in glycolysis?

Two ATP per glucose (4 made, 2 used).

What happens to the pyruvate and NADH from glycolysis?

Pyruvate enters the mitochondria for the link reaction, and NADH goes to oxidative phosphorylation.

GlycolysisEdexcel A-Level Biology B: Flashcards

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Where does glycolysis take place?

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Where does glycolysis take place?: In the cytoplasm of the cell.
What is the starting molecule and the end product of glycolysis?: A hexose such as glucose (6C) is converted to two molecules of pyruvate (3C).
How many ATP are used at the start of glycolysis?: Two, to phosphorylate the hexose.
What is formed when hexose is phosphorylated?: Hexose bisphosphate.
Why is the hexose phosphorylated?: It makes it more reactive so that it can be split into two 3-carbon molecules.
What happens to hexose bisphosphate?: It is split into two 3-carbon molecules (triose phosphate).
What does NAD do in glycolysis?: It accepts hydrogen removed from the intermediates, forming reduced NAD (NADH).
What is GP?: Glycerate 3-phosphate, a 3-carbon intermediate on the way to pyruvate.
How many ATP are made per glucose in glycolysis?: Four in total.
What is the net gain of ATP in glycolysis?: Two ATP per glucose (4 made, 2 used).
Does glycolysis need oxygen?: No.
What is made per glucose in glycolysis (net)?: 2 ATP, 2 NADH and 2 pyruvate.
What happens to the pyruvate and NADH from glycolysis?: Pyruvate enters the mitochondria for the link reaction, and NADH goes to oxidative phosphorylation.

Exam questions on Glycolysis

A biochemist adds glucose to an extract of yeast cytoplasm that contains all the enzymes of glycolysis, together with NAD, ADP and phosphate, but no ATP. No reaction takes place. When a small amount of ATP is added, glycolysis begins and pyruvate is soon detected.
Explain why glycolysis does not begin in this extract unless ATP is added.2 marks
A student supplies a cytoplasm extract with 2.0 mmol of glucose, with excess ATP, ADP, NAD and phosphate. After incubation she finds that all of the glucose has been converted to pyruvate.
Calculate the net amount of ATP gained by the extract. Show your working.2 marks
A researcher adds an inhibitor to a yeast cytoplasm extract. The inhibitor blocks the enzyme that converts glycerate 3-phosphate (GP) to pyruvate. She supplies glucose and a limited amount of ATP, and measures the concentrations of ATP, GP and pyruvate every minute for 10 minutes.
Explain why the concentration of ATP in the inhibited extract falls and stays low.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).