The Krebs cycle takes place in which part of the cell?
- A.Ribosome
- B.Mitochondrial matrix
- C.Golgi apparatus
- D.Nucleus
Correct answer
Explanation
The correct answer is B, the mitochondrial matrix. Pyruvic acid formed in glycolysis enters the mitochondrion, is converted to acetyl coenzyme A and is oxidised completely in the matrix through the cycle named after Hans Krebs, who received the Nobel Prize for the discovery; the cycle releases carbon dioxide and reduced coenzymes. Option A is wrong because ribosomes are the sites of protein synthesis. Option C is wrong because the Golgi apparatus packages and secretes materials and is not involved in respiration. Option D is wrong because the nucleus stores genetic material and controls the cell. Remember that the mitochondrion is called the powerhouse of the cell because both the Krebs cycle in its matrix and the electron transport chain on its inner membrane are housed there.
Read the full article: Plant Physiology: Transpiration, Transport and Respiration
Practice Questions
View allThe ascent of sap to the top of a tall tree is explained mainly by which force?
- A.Root pressure
- B.Capillarity alone
- C.Transpiration pull under the cohesion tension theory
- D.Active transport by xylem vessels
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Dixon and Joly explained that water molecules cling to one another by cohesion and to the xylem walls by adhesion, forming an unbroken column; evaporation from the leaf surface creates a suction at the top that pulls this column upward.
Read the full explanation →The loss of water in liquid form from the margins of leaves through special pores is called
- A.transpiration
- B.guttation
- C.bleeding
- D.imbibition
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It occurs through pores called hydathodes at the leaf margin or tip, usually in the early morning when the soil is moist, the air is humid and transpiration is low, so root pressure forces out drops of water with dissolved salts; Colocasia, grasses and tomato show it well.
Read the full explanation →Which tissue is responsible for the transport of prepared food in a plant?
- A.Xylem
- B.Phloem
- C.Parenchyma
- D.Sclerenchyma
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Its sieve tubes, helped by companion cells, carry sucrose and other soluble food from a source such as a mature leaf to a sink such as a root, fruit or bud, and the movement can be upward or downward.
Read the full explanation →The opening of stomata is brought about by the movement of which ion into the guard cells?
- A.Sodium
- B.Calcium
- C.Potassium
- D.Magnesium
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In light, potassium ions are actively pumped into the guard cells, their solute concentration rises, water enters by osmosis, the cells swell and because their inner walls are thicker they bend apart, opening the pore; when potassium leaves, the cells lose water and the pore closes.
Read the full explanation →Which instrument is used to measure the rate of transpiration in a cut shoot?
- A.Potometer
- B.Auxanometer
- C.Clinostat
- D.Respirometer
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Ganong's potometer and the simpler bubble potometer measure the water absorbed by a cut shoot in a given time, and since almost all of that water is lost as vapour, the reading is taken as the rate of transpiration.
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