In which part of the cell, the glucose is converted into pyruvate?
- A.Mitochondria
- B.Nucleus
- C.Cytoplasm
- D.Endoplasmic reticulum
Correct answer
Explanation
The correct answer is C, Cytoplasm. The breakdown of glucose into pyruvate, called glycolysis, takes place in the cytoplasm (cytosol) of the cell.
Glycolysis is the first step of respiration in almost every living cell. One molecule of glucose, a six-carbon sugar, is split into two molecules of pyruvate, a three-carbon compound, with a small net gain of two ATP. It needs no oxygen, which is why it happens in both aerobic and anaerobic respiration. What happens to pyruvate next depends on oxygen: with oxygen it enters the mitochondria for the Krebs cycle; without it, yeast turns it into ethanol and our muscles turn it into lactic acid.
A is wrong: the mitochondria break pyruvate down further into carbon dioxide and water; they do not make pyruvate.
B is wrong: the nucleus holds DNA and controls the cell; it plays no part in glycolysis.
D is wrong: the endoplasmic reticulum makes and transports proteins and lipids.
Exam tip: Glycolysis in the cytoplasm (glucose to 2 pyruvate); Krebs cycle in the mitochondrial matrix.
Practice Questions
View allConsider the following animals :
1. Hedgehog
2. Marmot
3. Pangolin
To reduce the chance of being captured by predators, which of the above organisms rolls up/roll up and protects/protect its/their vulnerable parts?
- A.1 and 2
- B.2 only
- C.3 only
- D.1 and 3
Show answer
Hedgehogs and pangolins curl into a tight ball when threatened, covering the soft belly and face with spines or scales; marmots do not.
Read the full explanation →Which one of the following is used in preparing a natural mosquito repellent?
- A.Congress grass
- B.Elephant grass
- C.Lemongrass
- D.Nut grass
Show answer
Lemongrass and its close relative citronella grass yield aromatic oils that keep mosquitoes away, so they are the base of many natural repellents.
Read the full explanation →Which one of the following devices is non-ohmic ?
- A.Conducting copper coil
- B.Electric heating coil
- C.Semi conductor diode
- D.Rheostat
Show answer
A diode does not obey Ohm's law: the current through it is not proportional to the voltage across it. An ohmic conductor gives a straight-line graph of current against voltage, so its resistance stays constant at a fixed temperature.
Read the full explanation →What is the formula mass of anhydrous sodium carbonate? (Given that the atomic masses of sodium, carbon and oxygen are 23 u, 12 u and 16 u respectively)
- A.286 u
- B.106 u
- C.83 u
- D.53 u
Show answer
Anhydrous sodium carbonate is Na₂CO₃, and 2 × 23 + 12 + 3 × 16 = 106 u. Formula mass is the sum of the atomic masses of all the atoms in one formula unit of an ionic compound.
Read the full explanation →Which one of the following minerals is used as a fuel in nuclear power stations ?
- A.Bauxite
- B.Quartz
- C.Feldspar
- D.Pitchblende
Show answer
Pitchblende, or uraninite, is the chief ore of uranium, the fuel used in most nuclear power stations. Pitchblende is a heavy, black mineral made mostly of uranium oxide.
Read the full explanation →