Question 1

Glycolysis (the EMP pathway) occurs in the ______ of the cell:

Accepted Answer

Cytoplasm. Glycolysis takes place in the cytoplasm and is common to both aerobic and anaerobic respiration.

Question 2

The end product of glycolysis is:

Accepted Answer

Pyruvic acid (pyruvate). One glucose (6-C) is split into two molecules of pyruvate (3-C) during glycolysis.

Question 3

The net gain of ATP and NADH per glucose in glycolysis is:

Accepted Answer

2 ATP and 2 NADH. Glycolysis uses 2 ATP and makes 4 (net 2 ATP) plus 2 NADH per glucose molecule.

Question 4

The enzyme-catalysed first committed step where glucose is phosphorylated uses:

Accepted Answer

ATP (converting glucose to glucose-6-phosphate). Glucose is phosphorylated to glucose-6-phosphate using ATP — one of two priming (investment) steps.

Question 5

Substrate-level phosphorylation in glycolysis refers to:

Accepted Answer

Direct transfer of a phosphate from a substrate to ADP forming ATP. In glycolysis, ATP is produced directly from high-energy intermediates (e.g. 1,3-BPG, PEP), not via the ETS.

Question 6

In glycolysis, the oxidation of glyceraldehyde-3-phosphate reduces:

Accepted Answer

NAD⁺ to NADH. The dehydrogenation of G3P (to 1,3-BPG) reduces NAD⁺ to NADH + H⁺.

Question 7

In glycolysis, two molecules of ATP are consumed in the preparatory phase before any ATP is generated. At which two steps is this ATP invested?

Accepted Answer

Phosphorylation of glucose (by hexokinase) and of fructose-6-phosphate (by phosphofructokinase). ATP is spent to make glucose-6-phosphate (hexokinase) and fructose-1,6-bisphosphate (phosphofructokinase, PFK). Thus 2 ATP are used and 4 are made, giving a net of 2 ATP.

Question 8

A key feature of glycolysis is that it does NOT directly require oxygen. Which statement best explains why glycolysis can proceed under anaerobic conditions only if a further reaction follows?

Accepted Answer

The NAD⁺ consumed during glucose oxidation must be regenerated, so a downstream reaction must reoxidise the NADH. Glycolysis reduces NAD⁺ to NADH at the glyceraldehyde-3-phosphate step. Because the cell has limited NAD⁺, it must be regenerated (by fermentation anaerobically, or the ETS aerobically) for glycolysis to continue.

Question 9

Glucose entering a cell may come from sources other than free glucose. In plants, which of the following can be broken down to yield glucose (or glucose-phosphate) that then feeds into glycolysis?

Accepted Answer

Sucrose and starch. Stored/transported carbohydrates such as sucrose (via invertase) and starch are broken down to glucose units that enter glycolysis. Structural lignin and pigments are not respiratory substrates in this way.

Question 10

Phosphofructokinase (PFK) is regarded as the key regulatory (rate-limiting) enzyme of glycolysis. This is chiefly because it catalyses:

Accepted Answer

The first irreversible, committed step that channels the sugar specifically into glycolysis. PFK converts fructose-6-phosphate to fructose-1,6-bisphosphate — the committed, essentially irreversible step that commits the molecule to glycolysis, making it the principal control point.

Question 11

Consider the following intermediates of glycolysis: (i) fructose-1,6-bisphosphate (ii) 3-phosphoglycerate (iii) glyceraldehyde-3-phosphate (iv) phosphoenolpyruvate. What is the correct sequence in which they appear?

Accepted Answer

(i) → (iii) → (ii) → (iv). Fructose-1,6-bisphosphate is split into two 3-carbon sugars (glyceraldehyde-3-phosphate), which is oxidised to 1,3-BPG then 3-phosphoglycerate, then 2-PG, then phosphoenolpyruvate, then pyruvate.

Question 12

Which two glycolytic steps are directly responsible for the substrate-level synthesis of ATP?

Accepted Answer

1,3-bisphosphoglycerate → 3-phosphoglycerate, and phosphoenolpyruvate → pyruvate. ATP is produced when 1,3-BPG transfers a phosphate to ADP (phosphoglycerate kinase) and when PEP transfers a phosphate to ADP (pyruvate kinase). Each occurs twice per glucose, giving 4 ATP gross.

Question 13

The six-carbon fructose-1,6-bisphosphate is cleaved into two three-carbon molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (PGAL). Why does DHAP not represent a dead end?

Accepted Answer

DHAP is isomerised to glyceraldehyde-3-phosphate, so effectively two PGAL molecules proceed per glucose. Triose phosphate isomerase interconverts DHAP and PGAL. Because only PGAL continues, DHAP is isomerised to PGAL, so both trioses ultimately proceed — this is why yields are counted per two trioses.

Question 14

Assertion (A): The complete oxidation of glucose does not occur during glycolysis. Reason (R): Glycolysis ends with pyruvate, which still contains a large amount of chemical energy in its bonds.

Accepted Answer

Both A and R are true and R is the correct explanation of A. Glycolysis only partially oxidises glucose to pyruvate; most of the energy is still locked in pyruvate and is released only when it is fully oxidised in the Krebs cycle and ETS.

Question 15

In the glyceraldehyde-3-phosphate dehydrogenase reaction, inorganic phosphate (Pi) is incorporated along with the oxidation of the aldehyde. What is the direct outcome of this single reaction?

Accepted Answer

Formation of 1,3-bisphosphoglycerate together with the reduction of NAD⁺ to NADH. This step oxidises PGAL and adds Pi to give the high-energy 1,3-bisphosphoglycerate while reducing NAD⁺ to NADH; no CO₂ or ATP is produced at this particular step.

Question 16

If a plant cell metabolises one molecule of sucrose completely through glycolysis, how many molecules of pyruvate are ultimately produced?

Accepted Answer

Four. Sucrose is a disaccharide of glucose and fructose. Each hexose yields 2 pyruvate through glycolysis, so one sucrose gives 2 hexoses × 2 = 4 pyruvate.

Question 17

Compounds that are oxidised during the process of respiration are called

Accepted Answer

Respiratory substrate. The organic compounds (carbohydrates, fats, proteins) broken down/oxidised during respiration are called respiratory substrates.

Question 18

Statement I: Only green plants and cyanobacteria can prepare their own food by photosynthesis. Statement II: Only green plants and cyanobacteria can prepare their own food by converting chemical energy to light energy. Which of the statements is/are true?

Accepted Answer

Only I. Statement I is correct; Statement II is wrong because photosynthesis converts light energy to chemical energy, not chemical to light.

Question 19

"Ultimately all the food that is respired for life processes comes from photosynthesis." This statement is

Accepted Answer

Correct. Photosynthesis is the ultimate source of all organic food later oxidised in respiration, so the statement is correct.

Question 20

Which of the following cannot be used as a respiratory substrate in plants under any conditions?

Accepted Answer

None of these. Carbohydrates, fats and proteins can all serve as respiratory substrates, so none of them is excluded.

Cellular Respiration & Glycolysis — NEET Biology MCQs with Solutions

Questions with solutions