Trace glycolysis from glucose to pyruvate
Outline glucose phosphorylation, splitting and oxidation to pyruvate, including ATP and reduced NAD production.
A Level; Cambridge International Biology 9700, 2028–2030. Written practice is self-checked; practical investigations need supervised work and human subject-teacher review remains pending.
Before you begin
- ATP transfers energy for cellular work, and enzymes control metabolic reactions.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What six-carbon phosphorylated intermediate is split during glycolysis?
What you will learn
- Describe phosphorylation and splitting of glucose
- Trace oxidation of triose phosphate to pyruvate and identify products
Build the explanation
During glycolysis, glucose is phosphorylated and converted to fructose 1,6-bisphosphate (6C). It splits into two triose phosphate molecules (3C each). These are oxidised through a series of enzyme-controlled steps to two pyruvate molecules. ATP is used early and produced later; the net gain per glucose is two ATP, and reduced NAD is also produced. Glycolysis occurs in the cytoplasm and does not require oxygen directly.
Apply it carefully
Track carbon numbers: one 6C glucose-derived intermediate becomes two 3C molecules and then two 3C pyruvate molecules. Do not say the six-carbon molecule splits into one triose phosphate, or that oxygen is used during glycolysis. ATP is produced overall even though some ATP is invested at the start.
Pause and explain
What reduced coenzyme is produced when triose phosphate is oxidised?
Worked example
How many pyruvate molecules form from one glucose molecule in glycolysis?
Show the worked solution
- Track the two 3-carbon products from the 6-carbon intermediate.
- Two 3-carbon pyruvate molecules form.
Answer Two pyruvate molecules, each with three carbon atoms.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Outline glycolysis from glucose to pyruvate, including carbon numbers and energy carriers.
Give me a hint
Start with a 6C molecule and follow the two 3C products.
Compare my reasoning
- Glucose is phosphorylated; fructose 1,6-bisphosphate (6C) splits into two triose phosphate (3C) molecules.
- Triose phosphate is oxidised to pyruvate, producing ATP and reduced NAD; net ATP gain is two per glucose.
Glucose is phosphorylated and converted to fructose 1,6-bisphosphate (6C), which splits into two triose phosphate molecules (3C). These are oxidised to two pyruvate molecules (3C), producing reduced NAD and ATP; glycolysis has a net gain of two ATP per glucose.
Look for these in your work
- Correct intermediate and split
- Carbon numbers correct
- Pyruvate and reduced NAD stated
- ATP gain qualified as net
A learner says glycolysis consumes oxygen to make pyruvate. Correct the statement.
Give me a hint
Separate oxygen requirement from the products of cytoplasmic glycolysis.
Compare my reasoning
- Glycolysis occurs in the cytoplasm and does not directly use oxygen.
- It converts glucose-derived intermediates to pyruvate and produces ATP and reduced NAD.
Glycolysis occurs in the cytoplasm and does not directly use oxygen. It converts glucose through phosphorylated intermediates to pyruvate, with ATP produced overall and NAD reduced.
Look for these in your work
- Oxygen claim corrected
- Location stated
- Products stated
A labelled pathway shows one 6C compound becoming two 3C triose phosphate molecules, followed by oxidation. State the likely pathway and one product of oxidation.
Give me a hint
Use carbon conservation and the reduced coenzyme.
Compare my reasoning
- The pathway is glycolysis.
- Oxidation leads to pyruvate and reduced NAD, with ATP produced.
The pathway is glycolysis. Triose phosphate is oxidised to pyruvate, producing reduced NAD and ATP.
Look for these in your work
- Pathway identified
- Oxidation product included
- Energy carrier included
Common mistakes
- Losing track of 6C and 3C molecules
- Saying glycolysis requires oxygen
- Forgetting ATP investment when describing net yield
What can you explain now?
What six-carbon phosphorylated intermediate is split during glycolysis?
Compare with the explanation
Fructose 1,6-bisphosphate
It is split into two three-carbon triose phosphate molecules.
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Make it stick
What are the carbon and energy-carrier changes from glucose through glycolysis?
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