Biology · Respiration in Plants · NEET
The NET gain is 2 ATP. Glycolysis makes 4 ATP (by substrate-level phosphorylation in the pay-off phase) but spends 2 ATP earlier (in the investment phase). So net = 4 made minus 2 spent = 2 ATP. NEET often writes 4 as a trap option to check if you remember the 2 ATP that were invested.
Because glycolysis has two phases. In the preparatory (investment) phase, 1 ATP is used to make glucose-6-phosphate (hexokinase) and 1 ATP to make fructose-1,6-bisphosphate (phosphofructokinase) = 2 ATP spent. In the pay-off phase, 4 ATP are formed. The cell keeps only what is left over: 4 - 2 = 2 ATP net.
Exactly 2 molecules of pyruvic acid. Glucose has 6 carbons; it is split into two 3-carbon pyruvate molecules. So for N glucose molecules you get 2N pyruvate. Example: 206 glucose give 206 x 2 = 412 pyruvic acid (asked in ReNEET 2026).
Gross ATP = total ATP produced = 4 (it counts only the ATP made, not the ATP used). Net ATP = ATP the cell actually keeps = gross (4) minus ATP invested (2) = 2. If a question says 'produced' it may want 4; if it says 'net gain' the answer is always 2. Read the exact word.
2 molecules of NADH per glucose. NAD+ picks up hydrogen (2 redox equivalents) when PGAL (glyceraldehyde-3-phosphate) is oxidised. Since one glucose gives two 3-carbon molecules, this step happens twice, giving 2 NADH. These NADH are used later in the ETS (aerobic) or to reduce pyruvate (fermentation).
No. The glycolysis output is the same in both: 2 pyruvate + 2 NADH + net 2 ATP. Oxygen is NOT needed for glycolysis. What changes is the FATE of pyruvate and NADH afterwards. That is why fermentation gives a net of only 2 ATP for the whole glucose.
What is the net gain of ATP when each molecule of glucose is converted to two molecules of pyruvic acid?
How many molecules of pyruvic acid are produced at the end of glycolysis from 206 molecules of glucose?
Assertion A: ATP is used at two steps in glycolysis. Reason R: First ATP is used in converting glucose into glucose-6-phosphate and second ATP is used in conversion of fructose-6-phosphate into fructose-1,6-diphosphate.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Per one glucose: 2 pyruvic acid + 2 NADH + net 2 ATP. Remember this as the standard glycolysis balance line for NEET.
In the cytoplasm (cytosol). Glycolysis needs no membrane or oxygen, which is why it occurs in every living cell, aerobic or anaerobic.
Because it is a one-word discrimination test. Students who memorise '4 ATP' without recalling the 2 ATP invested pick the wrong option. Knowing net = 2 shows you understand the two-phase structure.
No, it is only partially oxidised to pyruvic acid. Most of the energy is still locked in pyruvate; full oxidation needs the Krebs cycle and ETS in aerobic respiration.
Yes. In aerobic respiration each glycolytic NADH is later used in the ETS, so they contribute to the total 36/38 ATP balance sheet, but they are not counted as ATP within glycolysis itself.
