B1.4 Photosynthesis Flashcards

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1
Q

What is photosynthesis?

A

Photosynthesis is a chemical reaction in which producers make food by carbon dioxide reacting with water in the presence of sunlight to form glucose and oxygen

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2
Q

How do plants take in carbon dioxide?

A

It comes from the air, and then diffuses into the plant through the stomata(tiny pores in the underside of leaves)

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3
Q

How do plants take in water?

A

Water enters the roots through root hair cells by osmosis, from the soil

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4
Q

What is the oxygen produced in photosynthesis used for?

A

Some is used for respiration, the rest is waste product, so it is released back into the environment

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5
Q

Where does photosynthesis occur?

A

Photosynthesis takes place in the chloroplast, so mainly in The leaves

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6
Q

Why does photosynthesis occur in the chloroplasts

A

Because light transfers the energy from the sun to chlorophyll in the chloroplasts , and light energy is needed in the reaction to make glucose

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7
Q

Why are leaves and stems green?

A

Because the contain the green pigment chlorophyll in their chloroplasts

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8
Q

What is the first stage of photosynthesis?

A

Light dependent stage is when energy transferred form light splits water molecules into oxygen and hydrogen ions

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9
Q

What is the second stage of photosynthesis?

A

Carbon dioxide gas combines with hydrogen ions to make glucose

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10
Q

What kind of reaction is photosynthesis ?

A

It is an example of an endothermic reaction, this means that energy must be transferred from the surroundings to keep it going.
It absorbs sun light

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11
Q

What is a phototropism?

A

Growing towards the light

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12
Q

What is a photometer ?

A

An instrument for measuring light intensity

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13
Q

Photoconductive =

A

A material whose resistance decreases when it absorbs light

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14
Q

What happens to glucose produced?

A
  • when it’s not needed straight away it is converted into starch (store of energy)
  • converted into sucrose and fructose
    -cellulose to form cell walls
    -plus nitrogen,
    proteins for growth+ repair
    and fats and oils(food store and growth)
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15
Q

What are the steps to test for starch in a leaf?

A
  • place leaf in boiling water to kill it
  • then place it in a boiling tube of boiling ethanol to remove the chlorophyll (so you can see colour change )
  • add a few drops of iodine solution
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16
Q

What colour does the iodine solution Turn if starch is present?

A

Blue/black

17
Q

Formula

A

Carbon dioxide+ water —> glucose+ oxygen

6Co2 + 6H20 —-> C6h12O6 +6O2

18
Q

Prove carbon dioxide needed for photosynthesis

A

Destarched plant and place inside polythene bag,
Add pot of soda lime (absorbs CO2 and water vapour)
Seal bag
Place in sunlight before testing leaves for starch

19
Q

How to prove sunlight needed for photosynthesis

A

Destarched plant and cover one of leaves w black card/ tin foil
Place in sun for hours and test for presence of starch in leaf

20
Q

Prove oxygen given off during photosynthesis

A

Place upturned test tube above aquatic plant (pondweed)
Put apparatus in sunlight
Collected tube full of gas glowing splint test

21
Q

Limiting factors affecting rate of photosynthesis

A

Light intensity, carbon dioxide, temperature

22
Q

How does light intensity effect rate of photosynthesis

A

Higher light intensity, faster rate of photosynthesis

Until reaches maximum rate

23
Q

Carbon dioxide

A

Greater concentration of carbon dioxide, faster rate of reaction
Until reaches maximum rate of reaction
Most common limiting factor due to atmosphere 0.04%

24
Q

Temperature

A

Higher temperature, faster reaction as enzyme controlled reaction
Temp too high = enzymes denature and reaction stops

25
Q

How to measure rate of photosynthesis

A

Elodea/pondweed count number of oxygen bubbles produced per minute

26
Q

Inverse square law

A

Double distance from light source, light intensity falls by factor 4
Relative light intensity= 1/distance from light source^2