In anaerobic respiration in yeast, glucose is finally converted into
- A.lactic acid and water
- B.ethanol and carbon dioxide
- C.pyruvic acid and oxygen
- D.acetic acid and hydrogen
Correct answer
Explanation
The correct answer is B, ethanol and carbon dioxide. In yeast the pyruvic acid formed by glycolysis is decarboxylated and then reduced to ethyl alcohol, a process called alcoholic fermentation, which is the basis of brewing and of the rising of dough. Option A is wrong because lactic acid fermentation happens in overworked muscle and in bacteria such as Lactobacillus, which sours milk into curd, and water is not its product. Option C is wrong because pyruvic acid is the intermediate at the end of glycolysis, not the final product, and oxygen is never released in respiration. Option D is wrong because acetic acid is produced by Acetobacter from alcohol in the presence of oxygen, which is vinegar making and not fermentation of glucose. Fermentation yields only two ATP per glucose.
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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