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Biology yey > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

Define Photosynthesis

A

It is the process by which living plant cells containing chlorophyll produce food substances (glucose and starch) from carbon dioxide and water by using light energy. Oxygen is released as a product.

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2
Q

Importance of Photosynthesis

A
  • Food for all
  • Oxygen to breathe in: Photosynthesis is the only biological process which releases oxygen into the atmosphere
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3
Q

G.R: Leaves appear green

A

Chlorophylls absorb blue and red light and reflect away the green light due to which the chlorophyll appears green. The absorbed red and blue light are most effective for photosynthesis.

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4
Q

G.R: Too little light reduces rate of photosynthesis.
OR
G.R: Grass growing under shade turns yellowish

A

Due to no formation of new chlorophyll and disintegration of the old ones.

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5
Q

G.R: Photosynthesis stops above 40 degrees celcius

A

Temperature above 40 degrees c destroys chlorophyll as it it highly sensitive to light.

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6
Q

Transpiration is the price for photosynthesis. Justify.

A
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7
Q

What is the k+ ion theory?

A
  • Stomatal opening and closing depends on the generation of k+ ion gradient.

During day:
- more photosynthesis = more k+ ions/ more ATP = hypertonic guard cells = endosmosis = turgid vacuole = stoma opens

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8
Q

_____ is responsible for synthesis of chlorophyll.

A

Magnesium

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9
Q

What is the chemical equation for the process of photosynthesis

A

6C02 + 12H2O → C6H12O6 + 6H20 + 6O2

in the presence of light energy and chlorophyll

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10
Q

What are the steps in the photochemical phase

A

— Activation of chlorophyll
— Photolysis

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11
Q

What is activation of chlorophyll?

A

Chlorophyll absorbs photons on exposure to light and gets activated

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12
Q

What is photolysis?

A

The process of splitting of water molecules as h+ ion and o2 molecule in the presence of light in the thylakoid / grana

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13
Q

What is photophosphorylation?

A

The addition of inorganic phosphates to ADP to form ATP in the presence of light

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14
Q

Expand: NADP

A

Nicotinamide Adenine Dinucleotide Phosphate

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15
Q

What are the end products of photolysis

A
  • H+ ions given out during photolysis are picked up by NADP to form NADPH
  • O2 is given out as molecular O2
  • The electrons are used in converting ADP to ATP by adding one phosphate group. (Photophosphorylation)
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16
Q

State the site of occurrence of:
1. Light dependent phase
2. Light Independent phase

A
  1. Thylakoids
  2. Stroma
17
Q

What is the biosynthetic phase? When does it take place?

A

It is the conversion of glucose into starch and other chemicals. It takes place immediately after light reaction

18
Q

What is polymerisation?

A

The conversion of several glucose molecules to starch.

19
Q

What happens to starch at night?

A

The starch is reconverted back to glucose and is translocated to various parts of the plant from the leaves through the phloem.

20
Q

How is glucose formed in light independent phase?

A

CO2 is reduced to glucose by NADPH.

21
Q

G.R: Biosynthetic phase is also called dark reaction.

A

It is not dependent on light for the reactions to take place.

22
Q

What are the adaptions in a leaf to perform photosynthesis?

A

— Large surface area: Maximum light abs
— Leaf arrangement at the right angle to the light to obtain max light
— Transparent and water proof cuticle and upper epidermis to allow light to enter
— Numerous stomata to allow rapid exchange of gases.

23
Q

What is the fate of the end result of the products of photosynthesis?

A

— Glucose: is immediately consumed by plant, stored as insol. starch, converted to sucrose, used to synthesize fats and proteins
— Water: Reused in continuance of photosynthesis
— O2 : Used for photorespiration (Respiration of plants) Major part is diffused out through stomata

24
Q

What are the four external factors affecting photosynthesis?

A
  1. Light intensity
  2. CO2 conc.
  3. Temp
  4. Water content
25
Q

How does temperature affect rate of photosynthesis?

A

With increase in temperature up to 35 degrees, rate of photosynthesis increases after which it starts decreasing and stops above 40 degrees.

26
Q

How does water content affect rate of photosynthesis?

A

Reduced rate of water abs by roots and increased rate of transpiration decreases the rate of photosynthesis by decreasing diffusive capacity due to closure of stomata to prevent transpiration

27
Q

What are internal factors affection photosynthesis?

A
  1. Chlorophyll
  2. Protoplasm
  3. Structure of the leaf
28
Q

How does the content of protoplasm affect rate of photosynthesis?

A

Dehydration of protoplasm and accumulation of carbohydrates decreases rate of transpiration

29
Q

Plants like aloe vera, tulsi, neem and peepal release oxygen even during the night as they perform photosynthesis using a diff pathway called __________

A

CAM Pathway

30
Q

How is a leaf destarched?

A

It is left in the dark of 1-2 days. During this part the starch will be removed from the leaves and get stored in the storage organs.

31
Q

In test of starch using iodine, what is the leaf boiled in?

A

Methylated spirit or Alcohol

32
Q

Give examples of plants with variegated leaves

A

Coleus, Geranium, Croton

33
Q

What is the carbon cycle?

A

series of chem reactions in which co2 as a chemical element in removed from air, used by living organisms in their body processes and is finally returned to the air.

34
Q

What are the essential steps in carbon cycle

A
  1. Photosynthesis uses co2 to produce carbs
  2. Food chain: Food containing carbs passes from plants to consumers.
  3. Respiration: plants and animals respire by oxidising carbs to produce energy and five out co2 into the atmosphere
  4. Organic matter of dead plant animal remains are broken down by bacteria and fungi releasing co2 back into the atmosphere
  5. Combustion
  6. Heating lime stone in lime kilns

Biology yey (10 decks)

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