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LGS Biology > B1.4 Photosynthesis > Flashcards

B1.4 Photosynthesis Flashcards

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1
Q

Define photosynthesis

A

The process by which plants harness the energy from the sun and transfer this energy into a useable food source in the form of glucose that can be stored as starch

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2
Q

State the reactants of photosynthesis

A

Carbon dioxide & water

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3
Q

State the products of photosynthesis

A

glucose + oxgygen

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4
Q

Photosynthesis is an ‘……..’thermic reaction.

A

Endothermic

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5
Q

Endothermic means

A

a chemical reaction in which energy is transferred from the surrounding to the reacting mixture

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6
Q

State the word equation for photosynthesis?

A

carbon dioxide + water (+ light) ——> oxgyen + glucose

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7
Q

State the chemical equation for photosynthesis?

A

6CO2 + 6H20 ( + light) ———> C6H12O2 + 6O2

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8
Q

Why are plants and some algae termed ‘producers’?

A

They are organisms that make their own food through the process of photosynthesis

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9
Q

Name the two main stages of photosynthesis?

A
  1. Light dependent
  2. Light independent
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10
Q

State what happens in the first stage of photosynthesis?

A

The first stage is the light dependent stage of photosynthesis where energy transferred from light is used to split water molecules into oxygen gas and hydrogen ions

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11
Q

State what happens in the second stage of photosynthesis?

A

The second stage is the light independent stage of photosynthesis where carbon dioxide gas combines with the hydrogen ions produced in stage 1 of photosynthesis to make glucose

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12
Q

What happens to the glucose produced in photosynthesis?

A
  1. Stored as starch - food store
  2. Used for respiration
  3. Stored in fruit as sucrose
  4. Used to build cellulose cell walls
  5. Combined with nitrogen to build protiens for grow and repair
  6. Biosynthesis into fats and oils for food and growth
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13
Q

How can you test for starch to prove photosynthesis has taken place?

A
  1. Place leaf in boiling water for 1 minute to kill it
  2. Place in boiling tube with ethanol
  3. Place boiling tube in a water bath an boil until white (chlorophyll removed)
  4. Wash leaf with water to remove ethanol and soften
  5. Place on white tile and add 1-2 iodine drops
  6. Watch for colour change in iodine.
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14
Q

How can a leaf be ‘destarched’ before a photosynthesis experiement?

A

Keep it in the dark for a minimum of 24 hours - starch present will be used up in respiration and without light no further glucose can be produced by photosynthesis to be converted to starch.

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15
Q

How do you prove chlorophyll is needed for photosynthesis?

A
  1. Take a variagated plant and destarch
  2. Place the destarched plant in sunlight for several hours
  3. Test oneof the leave with iodine for the presence of starch
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16
Q

How do you prove light is needed for photosynthesis?

A
  • Take a destarched plant and cover part of one of its leaves with black card or tin foil
  • Place the destarched plant in sunlight for several hours
  • Remove and uncover the partially covered leaf
  • Test the leaf that was partially covered with iodine for the presence of starch
17
Q

How do you prove carbon dioxide is needed for photosynthesis?

A
  • Take a destarched plant cover part of one of its leaves/stems with a conical flask or polythene bag containing soda lime
  • Place the destarched plant in sunlight for several hours
  • Remove one of the covered leaves and test with iodine for the presence of starch
18
Q

How do you prove oxygen is given of during photosynthesis?

A
  1. Place an upturned funnel and test tube over an aquatic plant in a beaker of water
  2. Put the apparatus in the light for maximum photosynthesis
  3. Collect a full test tube of gas
  4. Place a glowing splint into the test tube to test for oxygen
  5. Relights = oxygen present
19
Q

What is meant by a ‘limiting factor’?

A

Factors which can prevent an increase in the rate of photosynthesis

20
Q

State the main limiting factors which affect the rate of photosynthesis?

A
  • Light intensity
  • Carbon dioxide availability
  • Temperature
21
Q

Which of the following is NOT a limiting factor of photosynthesis:

  1. Temperature
  2. Light intensity
  3. Amount of chlorophyll
  4. Carbon dioxide concentration
  5. volume of rain
A

volume of rain

22
Q

Describes the effect of light intensity on the rate of photosynthesis

A

As light intensity increases, the rate of photosynthesis increases until another limiting factor has an effect.

23
Q

Describes the effect of temperature on the rate of photosynthesis?

A

As temperature increases, the rate of photosynthesis increases, up to a point and then any further increase in temperature decreases the rate of photosynthesis

24
Q

Why does the rate of photosynthesis drop if the temperature gets too high?

A

The enzymes involved in photosynthesis have denatured

25
Q

Describe the effect of carbon dioxide concentration on the rate of photosynthesis

A

As carbon dioxide concentration increases, the rate of photosynthesis increases until another limiting factor has an effect

26
Q

What is happening at point B on the graph?

A

Another limiting factor is preventing an increase in rate of photosynthesis.

27
Q

Based on the graph, predict where the rate of photosynthesis would plateau if the temperature was 10 degrees Celcius and the carbon dioxide concentration was 0.04%.

A

Below the 0.04% line

28
Q

Why should a farmer keep careful control of the limiting factors for photosynthesis in their greenhouse? Choose the best answer

  • To maximise the rate photosynthesis to get the biggest plants
  • To maximise the rate of photosynthesis in the most efficient way possible
  • To maximise the light intensity for photosynthesis
  • To keep the greenhouse warm for their plants
A

To maximise the rate of photosynthesis in the most efficient way possible

29
Q

Explain why commercial growers increase the carbon dioxide concentration in a greenhouse?

A

A Greenhouse is warm and light so temperature and light intensity are therefore not limiting factors.

As CO2 concentration is the limiting factor in this situation therefore increasing CO2 concentration with increase photosynthesis and therefore plant growth/yield

30
Q

State the inverse square law

A

relative light intensity = 1

(distance from light source)2

The law states that when you double the distance from the light source, the light intensity fall by a factor of four.

31
Q

State the limiting factor for line B

A

Temperature

32
Q

Explain why, for line A, increasing the temperature does not increase the rate of photosynthesis.

A

The carbon dioxide concentration has limited the rate of photosynthesis.

LGS Biology (21 decks)

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