Question

glycolysis: fill-in-the-blank review

1. glycolysis takes place in the _________ of the cell.
2. the word glycolysis means splitting of _________.
3. glycolysis does not require _________ to occur.
4. one molecule of glucose contains _________ carbon atoms.
5. during glycolysis, glucose is broken down into two molecules of _________.
6. the first step of glycolysis requires an input of _________ atp molecules.
7. the enzyme that catalyzes the first step of glycolysis is _________.
8. energy is temporarily stored in molecules of _________ during glycolysis.
9. _________ is reduced to form nadh during glycolysis.
10. a total of _________ atp molecules are produced during glycolysis.
11. the net gain of atp from glycolysis is _________ atp molecules per glucose.
12. substrate - level phosphorylation is responsible for the production of _________ in glycolysis.
13. the final products of glycolysis include atp, nadh, and _________.
14. glycolysis is the first stage of both _________ respiration and anaerobic respiration.
15. if oxygen is not present, pyruvate will enter _________ pathways such as fermentation.

Explanation:

Each answer is based on core biological facts about glycolysis, the initial stage of cellular respiration.

1. Glycolysis occurs in the cell's cytoplasm, outside organelles.
2. The term "glycolysis" derives from Greek roots meaning "splitting of sugar".
3. Glycolysis is an anaerobic process, needing no oxygen.
4. Glucose is a 6-carbon sugar molecule, with the formula $C_6H_{12}O_6$.
5. Glucose is split into two 3-carbon pyruvate molecules.
6. The energy investment phase uses 2 ATP to start glycolysis.
7. Hexokinase is the enzyme that phosphorylates glucose to begin glycolysis.
8. ATP temporarily stores energy released during glycolysis.
9. $NAD^+$ (nicotinamide adenine dinucleotide) is reduced to form NADH.
10. A total of 4 ATP molecules are produced in the energy payoff phase.
11. Subtracting the 2 ATP invested, the net ATP gain is 2 per glucose.
12. Substrate-level phosphorylation directly generates ATP in glycolysis.
13. The three main end products are ATP, NADH, and pyruvate.
14. Glycolysis is the first step for both aerobic and anaerobic respiration.
15. Without oxygen, pyruvate enters anaerobic pathways like fermentation.

Answer:

1. cytoplasm
2. sugar
3. oxygen
4. 6
5. pyruvate
6. 2
7. hexokinase
8. ATP
9. $NAD^+$
10. 4
11. 2
12. ATP
13. pyruvate
14. aerobic
15. anaerobic