Click image to open full size
Glycolysis Step-by-Step Reference Cheat Sheet
A printable reference covering glycolysis steps, enzymes, ATP investment, NADH production, and net pyruvate yield for grades 11-12.
Related Labs
Related Worksheets
Glycolysis is the metabolic pathway that breaks one glucose molecule into two pyruvate molecules. Students need this cheat sheet because glycolysis includes many steps, enzymes, energy changes, and carbon changes that are easy to mix up. A step-by-step reference helps connect the names of intermediates to the overall purpose of cellular respiration. It also supports understanding of fermentation and aerobic respiration because both begin with glycolysis. The pathway has two main phases: an energy investment phase and an energy payoff phase. The overall net reaction is glucose + 2 NAD+ + 2 ADP + 2 Pi -> 2 pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O. ATP is spent in steps 1 and 3, while ATP is produced in steps 7 and 10 by substrate-level phosphorylation. NADH is produced in step 6 when glyceraldehyde-3-phosphate is oxidized.
Key Facts
- Glycolysis occurs in the cytosol and does not require oxygen directly.
- The net reaction of glycolysis is glucose + 2 NAD+ + 2 ADP + 2 Pi -> 2 pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O.
- The energy investment phase uses 2 ATP to phosphorylate glucose and fructose-6-phosphate.
- The energy payoff phase produces 4 ATP total, giving a net gain of 2 ATP per glucose.
- One glucose molecule with 6 carbons is split into two 3-carbon molecules that become pyruvate.
- NAD+ is reduced to NADH in step 6 when glyceraldehyde-3-phosphate is converted to 1,3-bisphosphoglycerate.
- Substrate-level phosphorylation makes ATP in glycolysis when a phosphate group is transferred directly to ADP.
- The key regulatory enzymes of glycolysis include hexokinase, phosphofructokinase-1, and pyruvate kinase.
Vocabulary
- Glycolysis
- Glycolysis is a ten-step pathway that breaks glucose into two pyruvate molecules while producing a small amount of ATP and NADH.
- Pyruvate
- Pyruvate is a 3-carbon molecule produced at the end of glycolysis.
- ATP
- ATP is the main energy-carrying molecule that stores usable energy in phosphate bonds.
- NAD+
- NAD+ is an electron carrier that accepts electrons and hydrogen during glycolysis to form NADH.
- Substrate-level phosphorylation
- Substrate-level phosphorylation is the direct transfer of a phosphate group from a metabolic intermediate to ADP to make ATP.
- Phosphofructokinase-1
- Phosphofructokinase-1 is a major regulatory enzyme that converts fructose-6-phosphate into fructose-1,6-bisphosphate.
Common Mistakes to Avoid
- Counting the gross ATP instead of the net ATP is wrong because glycolysis produces 4 ATP but spends 2 ATP, so the net gain is 2 ATP.
- Forgetting that each glucose forms two pyruvate is wrong because the 6-carbon glucose is split into two 3-carbon products.
- Saying glycolysis happens in the mitochondria is wrong because glycolysis occurs in the cytosol before pyruvate enters mitochondrial pathways in aerobic respiration.
- Assuming oxygen is required for glycolysis is wrong because glycolysis can run without oxygen as long as NAD+ is available.
- Mixing up NADH and NAD+ is wrong because NAD+ is the oxidized electron acceptor and NADH is the reduced electron carrier produced during glycolysis.
Practice Questions
- 1 One glucose molecule enters glycolysis. How many ATP are used, how many ATP are produced gross, and what is the net ATP gain?
- 2 If 3 glucose molecules go through glycolysis, how many pyruvate molecules and NADH molecules are produced?
- 3 A cell runs glycolysis for 10 glucose molecules. What is the net number of ATP molecules gained?
- 4 Why must cells regenerate NAD+ for glycolysis to continue when oxygen is not available?