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Life Processes Test - 46

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Life Processes Test - 46
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  • Question 1
    1 / -0
    The correct sequence of anaerobic reactions in yeast is
    Solution
    Hint: It involves the incomplete oxidation of glucose in the absence of oxygen

    Part 1 -  Definition - Anaerobic respiration
    • Fermentation is a type of anaerobic respiration in which pyruvic acid converts into ethanol and carbon dioxide. 
    • Fermentation follows glycolysis (responsible for the production of two pyruvic acid molecules from hexose sugar molecules such as glucose) during anaerobic respiration instead of Krebs cycle.

    Part 2 - Chemical Process of Fermentation
    • In this process, glucose is partially oxidized to form acids and alcohol.
    • In organisms like yeast, the pyruvic acid is converted to ethanol and carbon dioxide ($$CO_2$$).
    • However, in animal cells during muscle exercise, pyruvic acid reduces to lactic acid in case of inadequacy of oxygen for cellular respiration.
    • Two enzymes, alcohol dehydrogenase and acid-decarboxylase, catalyze the reactions of alcohol fermentation in yeast.
    • The reaction proceeds as follows:-
         $$Pyruvic$$ $$acid$$  $$\rightarrow$$  $$Acetaldehyde$$ + $$CO_2$$  $$\rightarrow$$  $$Ethanol$$

    Part 3 - Location
    • Both glycolysis and alcohol fermentation occur in the cytoplasm of yeast cell.

    Part 4 - Conclusion
    • From the above discussion, we are able to conclude that alcohol fermentation in yeast occurs only in the absence of oxygen during which glucose is partially oxidized to ethanol and $$CO_2$$.

    Final step : The correct sequence of anaerobic reactions in yeast is
    $$Glucose$$  $$\overset{cytoplasm}{\rightarrow}$$ $$Pyruvate$$ $$ \overset{cytoplasm}{\rightarrow}$$ $$Ethanol$$ + $$Carbon$$ $$dioxide$$
  • Question 2
    1 / -0
    Organisms that can prepare their own food are known as- 
    Solution
    • Green plants are autotrophic organisms because they can synthesize their own food by photosynthesis. 
    • During photosynthesis energy from sunlight is converted into chemical energy in the form of organic compounds and oxygen is released as a by-product.
    •  Animals, fungi and several bacteria are heterotrophic organisms and depend on organic compounds synthesized by autotrophs for their nutrition.
    • So, the correct answer is 'Autotrophs'
  • Question 3
    1 / -0
    Choose the correct statement that describes arteries.
    Solution
    Arteries are thick walled blood vessels which pump blood at high pressure away from the heart. They do not have valves as their walls are highly muscular. 
  • Question 4
    1 / -0
    The blood leaving the tissues becomes richer in :
    Solution
    Hint - Tissues perform cellular respiration and produce energy and releases some gas in the form of by-product.

    Part 1 - Cellular Respiration
    • Cells in our body perform cellular respiration to produce energy using glucose and oxygen as a precursor. In this process, carbon dioxide is produced as a by-product.
    • Chemical reaction - $$Glucose + O_2 \rightarrow ATP + CO_2$$

    Part 2 - Gaseous exchange
    • At tissue, the oxygen for the respiration comes from the haemoglobin present in the blood cells.
    • After the cellular respiration, the cells of the tissue releases carbon dioxide.

    Part 3 - Conclusion
    • The blood entering the tissue has a higher concentration of oxygen as compared to carbon dioxide.
    • Thus, the blood leaving the tissues has a higher concentration of carbon dioxide.

    Final step - The blood leaving the tissues becomes richer in carbon dioxide.
    So, the correct answer is option A.
  • Question 5
    1 / -0
    Which part of alimentary canal receives bile from the liver?
    Solution
    Hint:  Alimentary canal is a long hollow tube through which food is ingested from one end and egested from the opposite end after digestion.

    Part 1 - Definition- Alimentary canal
    • The Human Digestive system includes the alimentary canal and other accessory organs like the liver, salivary glands, and pancreas.
    • The alimentary canal is a continuous muscular tube that runs from mouth to anus and is approximately 9 meters in length.
    • It includes all the organs through which food and liquids travel during swallowing, digestion, absorption, and leave the body as feces.

    Part 2 - Digestive juices 
    • There are different digestive secretions secreted by organs of the digestive system that helps in the chemical breakdown of food. 
    • In the course of a day, the digestive system secretes around 7 liters of fluids.
    • Digestive secretion includes saliva, gastric juice, intestinal juice, pancreatic juice, and bile.

    Part 3 - Bile 
    • Bile is a digestive fluid produced by the liver and stored in the gallbladder.
    • Bile is composed of bile acids and salts, phospholipids, cholesterol, pigments (bilirubin and biliverdin), 95% water, and electrolytes.
    • Bile does not contain any digestive enzymes.
    • The pH of bile is slightly alkaline (with a pH of about 7 to 8).
    • Bile is transported into the duodenum through the hepato-pancreatic duct.

    Part 4 - Role of bile in digestion
    • Bile converts large fat globules into small fat droplets through a process called emulsification. 
    • Fat emulsification aims to increase the surface area of fats by grouping them into small clusters. 
    • Actual digestion of the fats is then accomplished by lipase, an enzyme from the pancreas.

    Part 5- Conclusion
    • We can conclude from the above discussion, that bile after secretion by the liver is stored in the gall bladder.
    • When food enters the small intestine, bile simultaneously is transported to the small intestine through the hepatopancreatic duct along with pancreatic juice.

    Final step - Small intestine of the alimentary canal receives bile from the liver.
  • Question 6
    1 / -0
    Organisms which cannot prepare their own food are called ________.
    Solution
    • Organisms that cannot synthesize their own food are called heterotrophs. Heterotrophs depend directly or indirectly on autotrophs for their food.
    • Autotrophs are the organism that can produce their own food using light, water, carbon dioxide, or other chemicals.
    • Algae are autotrophs.
    So, the correct answer is option B.
  • Question 7
    1 / -0
    What are the characteristic features of an artery?
    Solution
    ArteryVein
    Have thick elastic, muscular walls.

    Have thin, non-elastic walls.

    Lumen is narrow.Lumen is wide.
    Carry blood from the heart to all body parts.
    		Carry blood from all body parts to the heart.
    Carry oxygenated blood (except pulmonary artery).Carry deoxygenated blood (except pulmonary vein).
    The characteristic feature of an artery can be understood better when we compare the characters of the artery with the vein, which is shown in the above table.
    The correct answer is option D.
  • Question 8
    1 / -0
    Oxygen liberated during photosynthesis comes from
    Solution
    Hint: Water is the source of electrons and hydrogen ions during photosynthesis.

    Part 1 - Definition - Photosynthesis
    • Photosynthesis is the process of preparing food in the presence of sunlight and chlorophyll. 
    • In this process, the plant uses water from the soil, carbon dioxide from the air and energy from sunlight to prepare glucose.
      $$Carbon$$ $$dioxide$$ + $$Water$$ + $$light$$ $$energy$$ $$\rightarrow$$ $$Glucose$$ + $$Oxygen$$

    Part 2 - Role of water as Electron Feeder
    • During the light reaction of photosynthesis, when chlorophyll molecules absorb light their electrons get excited and leave the chlorophyll molecule to enter an electron transport system. In the end, these electrons are absorbed by $$NADPH^+$$.
    • To replace those electrons lost from chlorophyll, water molecule undergo photolysis.
    • The reaction proceeds as follows:
     $$H_2O$$  $$\rightarrow$$  $$2H^+$$   +  $$2e^-$$   +  $$1/2O_2$$
    • So, water provides electrons to replace those removed from chlorophyll.

    Part 3 - Role of water as Oxygen Provider
    • During the photolysis of water, oxygen is released as a side product.
    • This oxygen is released into the environment through stomata.

    Part 4 - Conclusion
    • From the above discussion, we can conclude that water serves as a source of protons and electrons during photosynthesis, while oxygen is released as a waste product.

    Final step- Oxygen liberated during photosynthesis comes from water.
  • Question 9
    1 / -0
    A destarched leaf of a potted plant is partially covered with black strip of paper on the upper
    and lower surfaces as shown in the figure and kept in sunlight. The starch test was
    performed after this. What will be the colour of the regions marked as A and B in the leaf ?

    Solution
    • Light is essential for photosynthesis to take place. As the partially covered part doesn't get light to carry out photosynthesis, no starch is produced in them. This part when tested with Iodine solution gives pale colour, which indicates absence of starch. 
    • The rest part of the Leaf which is not covered absorbs light and can perform photosynthesis. This part when tested with Iodine solution gives blue black colour, which indicates presence of starch.
    Thus, "A" part is pale colour and "B" part is blue black colour. 

    Option "C" is correct.
  • Question 10
    1 / -0
    A student covered a leaf from a destarched potted plant with a black paper strip and kept the plant in the garden in the morning hours. In the evening he tested the covered portion of the leaf to test the presence of starch. In this case, the student was trying to show that:
    Solution
    • The covered leaf part with a black paper strip, when tested for presence of starch gives negative test i.e. there is no starch produced in them. 
    • This case shows that light and water are essential for production of food (photosynthesis) in the plant. And as the covered part doesn't get any proper light, no starch is produced in that region of the plant.
    • Hence, light is necessary for photosynthesis. Option "D" is correct.
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