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AQA Biology [Paper 1] > B8- Photosynthesis ☀️🍀 > Flashcards

B8- Photosynthesis ☀️🍀 Flashcards

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1
Q

What do plants use for their source of energy ?

A
  • plants use [sun]light for their source of energy
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2
Q

What is photosynthesis?

A
  • photosynthesis, is an endothermic reaction which plants use to trap light energy.
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3
Q

Where does photosynthesis take place ?

A
  • photosynthesis takes place in the chloroplasts of a plant.
  • this is because, the chloroplasts contain a chemical known as chlorophyll, which can trap light energy.
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4
Q

What are chloroplasts ?

Hint: organelles

A
  • chloroplasts, are large organelles found inside plant cells
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5
Q

What is chlorophyll ?

A
  • chlorophyll is a green pigment within chloroplasts, that trap light energy.
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6
Q

What is the difference between chlorophyll 🆚 chloroplasts ?

A
  • chloroplasts, are large organelles found inside plant cells
  • ; chlorophyll is a green pigment within chloroplasts, that trap light energy.
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7
Q

What is the word equation for photosynthesis ?

A
  • carbon dioxide + water——> glucose + oxygen.
  • [light is on the top of the arrow; chlorophyll is on the bottom of the arrow]
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8
Q

What are the stages of photosynthesis ?

Hint: the plant takes…

A
  • the plant takes carbon dioxide and water into the leaf, then light energy is absorbed by chlorophyll.
  • the light energy [absorbed/trapped by chlorophyll] is then used to convert the carbon dioxide and water, into the sugar glucose.
  • and in this reaction, oxygen is also produced.
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9
Q

What is the chemical equation for photosynthesis ?

A
  • 6CO2 + 6H20—-> C6 H12 O6 + 6O2
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10
Q

What can you tell me about a graph that measures the rate of photosynthesis, at each level of light intensity? [5]

A
  • when the light intensity is zero, the rate of photosynthesis is zero. This is because plants need light to carry out photosynthesis.
  • as we increase the light energy, the rate of photosynthesis decreases.
  • since the plant now has more light energy to carry out photosynthesis, therefore the reaction gets faster.
  • ; if we increase the light intensity, and the rate of photosynthesis also increases, this means the light intensity was limiting.
  • and at this point, light intensity is a limiting factor.
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11
Q

if we increase the light intensity, and the rate of photosynthesis also increases, this means the light intensity was limiting. Why?

Hint: as fast

A
  • photosynthesis wasn’t as fast as it could have been, as there wasn’t enough light.
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12
Q

What happens if we keep increasing the light intensity, after light intensity is a limiting factor ?

Hint: no longer, limiting factor

A
  • if we keep increasing the light intensity, there comes a point where the rate of photosynthesis no longer increases.
  • at this point, light intensity is no longer the limiting factor and something else is now of short supply- [e.g- level of carbon dioxide in the air]
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13
Q

What can you tell me about a graph that measures the rate of photosynthesis, at each level of carbon dioxide ?

Hints: zero

A
  • when the level of carbon dioxide is zero, the rate of photosynthesis is zero. This is because plants need light to carry out photosynthesis.
  • as we increase the carbon dioixide level, the rate of photosynthesis increases.
  • ; if we increase the carbon dioxide level, and the rate of photosynthesis also increases, this means the light intensity was limiting.
  • and at this point, carbon dioxide is the limiting factor.
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14
Q

What happens if we keep increasing the carbon dioxide level, after light intensity is a limiting factor ?

A
  • if we keep increasing the carbon dioxide level, there comes a point where the rate of photosynthesis no longer increases.
  • at this point, carbon dioxide level is no longer the limiting factor and something else is now of short supply.
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15
Q

Explain how the amount of chlorophyll [in a leaf], can be a limiting factor.

A
  • For example, a leaf might have patches of chlorophyll.
  • and since these leaves can trap less light energy than normal leaves, they’ll have a lower rate of photosynthesis.
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16
Q

What are the four limiting factors of photosynthesis ?

A
  • the four limiting factors are:
  • temperature
  • light intensity
  • level of carbon dioxide
  • [amount of chlorophyll]
17
Q

How can temperature be a limiting factor?

Hint: enzymes

A
  • as we increase the temperature, the enzymes involved in photosynthesis work faster, meaning the rate of photosynthesis increases.
  • ; if we keep increasing the temperature, the enzymes will denature and the rate of photosynthesis falls.
18
Q

Describe how the leaf is adapted for photosynthesis

Hint: allow carbon dioxide

A
  • leaves are adapted for photosynthesis since:
  • they have: a large surface area, and contain openings, called stomata to allow carbon dioxide into the leaf and oxygen out.
19
Q

Explain how adaptations of the leaf make photosynthesis efficient. [2]

Hint: epidermis, prevents water loss

A
  • The internal structure of the leaf is also adapted to promote efficient photosynthesis since:
  • the Epidermis is thin and transparent, allowing more light to reach the palisade cells.
  • Thin cuticle made of wax [thin waxy cuticle], protects the leaf from infection and prevents water loss without blocking out light
21
Q

Explain how adaptations of the leaf make photosynthesis efficient. [1]

Hint: cell layer

A
  • the palisade cell layer at top of leaf is adapted to make photosynthesis efficient, to absorb more light and increase the rate of photosynthesis
21
Q

Further explain how adaptations of the leaf, make photosynthesis efficient. [2]

Hint: spongy layer, palisade

A
  • the spongy layer, has air spaces allowing gases to diffuse through the leaf
  • the palisade cells contain many chloroplasts, to absorb all the available light
22
Q

How do plants use glucose ? [2]

A
  • to release energy in respiration [which takes places in the mitochondria]
  • to produce the insoluble storage molecule starch, which can be converted back to glucose by the plant if needed.
23
Q

What are some other ways that plants can use glucose ? [2]

Hint: cellulose, storage form

A
  • in most plants, the glucose produced by photosynthesis, is converted to fats and oils, which are used by the plants as a storage form of energy.
  • cellulose is also made from the glucose produced by photosynthesis, to strengthen the cell walls [of a plant]
24
Q

How can plants use amino acids, from glucose ?

A
  • to produce amino acids- amino acids are used by the plant to synthesise proteins.
  • To make amino acids from glucose, as plants need to absorb nitrate ions from the soil.
25
Q

Explain why plants convert glucose to starch for storage.

A
  • Plants convert glucose to starch in photosynthesis for storage and long-term energy usage.
  • ; since glucose is soluble it can affect how water moves in and out of the cell by osmosis [as it would affect the concentration gradient]
  • so its converted to starch [which is soluble] so it’s more suitable for long-term storage.
26
Q

How do plants convert glucose to starch, for storage ? [2]

A
  • Glucose is converted into starch by the process called polymerization.
  • In polymerization, several simple and soluble molecules of glucose are put together to form a complex, insoluble molecule of starch.
27
Q

In simple terms, how can polymerisation be explained ? [2]

A
  • Polymerisation is similar to constructing a large building out of the same type of small blocks.
  • The blocks can be connected in various ways to create a larger, more intricately shaped structure.
28
Q

Why is photosynthesis an endothermic reaction ?

A
  • photosynthesis is an endothermic reaction because:
  • photosynthesis takes in energy, which is transferred from the environment, to the chloroplasts by light.

AQA Biology [Paper 1] (31 decks)

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