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GCSE Biology > Topic 4 - Bioenergetics (photosynthesis) > Flashcards

Topic 4 - Bioenergetics (photosynthesis) Flashcards

Pages 57 58 59 60

1
Q

What happens in photosynthesis?

A

energy is used to change carbon dioxide and water into glucose and oxygen

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2
Q

Where does photosynthesis take place and why?

A
  • In the chloroplasts of green plant cells
  • contain pigments like chlorophyl that absorb light
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3
Q

How is energy transferred to the chloroplasts?

A

from the environment by light

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4
Q

Is photosynthesis exothermic or endothermic?

A
  • endothermic (energy is transferred from the environment)
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5
Q

What is the word equation for photosynthesis?

A

carbon dioxide + water —light—> glucose and oxygen

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6
Q

What is the balanced symbol equation for photosynthesis?

A

6CO2 + 6H2O —–> C6H12O6 + 6O2

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7
Q

State the 5 main ways plants use glucose?

A

1) for respiration
2) making cellulose
3) making amino acids
4) stored as oils or fats
5) stored as starch

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8
Q

Why do plants use glucose for respiration?

A
  • this transfers energy from glucose
  • enables the plant to convert the rest of the glucose into other useful substances
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9
Q

Why do plants use glucose to make cellulose?

A

cellulose makes strong plant cell walls

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10
Q

Why do plants use glucose to make amino acids?

A

-glucose is combined with nitrate ions (absorbed from the soil) to make amino acids, which are then made into proteins

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11
Q

Why do plants store glucose as fats and oils?

A

glucose is turned into lipids for storage in seeds

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12
Q

Why do plants store glucose as starch?

A
  • glucose is turned into starch and stored in roots, stems and leaves, ready for use when photosynthesis isn’t happening, like in the winter
  • starch is insoluble which makes it better for storing than glucose - a cell with lots of glucose would draw in loads of water and swell up
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13
Q

What three factors can limit the rate of photosynthesis?

A
  • intensity of light
  • concentration of CO2
  • temperature
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14
Q

What is a limiting factor?

A

a factor that is stopping photosynthesis from happening any faster

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15
Q

What effects what is the limiting factor?

A

environmental conditions

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16
Q

What is often the limiting factor at night?

A

light

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17
Q

What is often the limiting factor in the winter?

A

temperature

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18
Q

What is often the limiting factor in warm and bright conditions?

A

amount of carbon dioxide

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19
Q

REMEMBER:

A

all environmental factors have a combined effect on the rate of photosynthesis

20
Q

What non-environmental factor can effect the rate of photosynthesis?

A

the amount of chlorophyl in a plant

21
Q

What can effect the amount of chlorophyl in a plant?
What are the effects of these?

A
  • disease (e.g. infection with tobacco mosaic virus)
  • environmental stress (like lack of nutrients)
  • chloroplasts become damages and not able to make enough chlorophyl
  • rate of photosynthesis is reduced because they can’t absorb as much light
22
Q

Why is light intensity important to photosynthesis?

A

light provides the energy needed for photosynthesis

23
Q

What happens to the rate of photosynthesis as the light intensity is raised?

A
  • the rate of photosynthesis increases steadily - but only up to a certain point
24
Q

Why will increasing light intensity only increase the rate up to a certain point?

A
  • the rate will no longer increase because either temperature or CO2 level has become the limiting factor, not light
25
Q

How can you change light intensity in a lab?

A

by moving a lamp closer or further away from your plant (see required practical)

26
Q

When you plot a graph with “distance of lamp from the plant”, you get a weird shape. How do you overcome this?

A
  • either measure the light intensity at the plant using a light meter
  • or calculate the light intensity
27
Q

Why does % level of CO2 effect the rate of photosynthesis?

A

carbon dioxide is one of the raw materials needed for photosynthesis

28
Q

What effects does increasing levels of CO2 have on the rate of photosynthesis?

A
  • the rate will increase up to a certain point
29
Q

Why can increasing levels of CO2 only effect the rate up to a certain point?

A
  • the graph will flatten out even if the amount of CO2 continues to increase because CO2 is no longer a limiting factor
30
Q

If light and CO2 are in plentiful supply, what is likely to be the limiting factor for photosynthesis?

A

temperature

31
Q

Why is temperature usually a limiting factor?

A
  • because it is too low
  • enzymes needed for photosynthesis work more slowly at lower temperatures (collision theory)
32
Q

What happens when the plant gets too hot?

A

enzymes needed for reactions in the plant like photosynthesis become damaged (or denatured)

33
Q

At what temperature are enzymes in plants usually denatured?

A
  • about 45 degrees C
    (this is pretty hot for outdoors, although greenhouses can get that hot if you’re not careful)
34
Q

REQUIRED PRACTICAL 5 - Effect of light intensity of photosynthesis:
What can be given off to show the rate of photosynthesis?

A

Oxygen production

35
Q

REQUIRED PRACTICAL 5 - Effect of light intensity of photosynthesis:
What plant may you use in this reaction?

A

Canadian pondweed (particularly an aquatic plant)

36
Q

REQUIRED PRACTICAL 5 - Effect of light intensity of photosynthesis:
The rate at which the plant produces oxygen corresponds to what?

A

The rate at which its photosynthesising

37
Q

REQUIRED PRACTICAL 5 - Effect of light intensity of photosynthesis:
The faster the rate of oxygen production, the faster …

A

the rate of photosynthesis

38
Q

REQUIRED PRACTICAL 5 - Effect of light intensity of photosynthesis:
What are two control variables?

A
  • temperature
  • time that the pondweed is allowed to photosynthesise
39
Q

REQUIRED PRACTICAL 5 - Effect of light intensity of photosynthesis:
What is the independent variable?

A
  • the distance between the pondweed and the light source (light intensity)
40
Q

REQUIRED PRACTICAL 5 - Effect of light intensity of photosynthesis:
What is the dependent variable?

A
  • the volume of oxygen produced
41
Q

What is the purpose of a greenhouse?

A

to artificially create the ideal environment for plants to grow

42
Q

How do greenhouses create the best conditions for plants to grow?

A

They trap the sun’s heat to make sure temperature doesn’t become the limiting factor

43
Q

How can the temperature of a greenhouse be prevented from getting too hot or cold?

A

In the winter- a farmer may use a heater as well to keep the temperature at the ideal level
In the summer- it could get too hot, they might use shades and ventilation to cool hings down

44
Q

What do commercial farmers often do to control the level of light intensity on their plants?

A

They often supply artificial light especially after the sun goes down to give their plant more quality photosynthesis time

45
Q

How can farmers and gardeners increase the level of carbon dioxide in their greenhouse?

A

They may use a paraffin heater to heat the greenhouse
As the paraffin burns, it makes carbon dioxide as a by-product

46
Q

What are two other benefits of a greenhouse?

A
  • easier to keep plants free from pests and diseases
  • fertilisers can also be added to the soil, to provide all the minerals needed for healthy grown
47
Q

Why is it important that a farmer supplies their plants with everything in the right amount?

A
  • changing the conditions cost money
  • just right conditions will lead to a faster-growing, better crop which can be sold and harvested more often
  • supplying the plants with more light or heat than they need would be wasting money

GCSE Biology (4 decks)

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