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GCSE Biology (Advanced Specification 2022 ONLY) > B8 - Photosynthesis > Flashcards

B8 - Photosynthesis Flashcards

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1
Q

What is an endothermic reaction?

A

a reaction that requires a transfer of energy from the environment

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2
Q

What is glucose?

A

a simple sugar

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3
Q

What are limiting factors?

A

factors that limit the rate of a reaction

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4
Q

What is photosynthesis?

A

the process by which plants make food using carbon dioxide, water, and light

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5
Q

What is the word equation for Photosynthesis?

A

Carbon Dioxide + water —(light)—> glucose + oxygen

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6
Q

What is the balanced symbol equation for photosynthesis?

A

6H₂O + 6CO₂ —(light)—> C₆H₁₂O₆ + 6O₂

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7
Q

What part of the leaf absorbs the energy from the sun?

A

The chlorophyll in the chloroplasts

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8
Q

What type of reaction is photosynthesis and why?

A

Photosynthesis is an endothermic reaction, this is because energy is transferred from the environment when the light is absorbed by the chlorophyll

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9
Q

What is the formula of glucose?

A

C₆H₁₂O₆

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10
Q

What happens to the glucose produced during photosynthesis?

A

Some of the glucose is immediately used by the plant cells for respiration, however much of it is converted into insoluble starch and is stored.

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11
Q

Explain the process of photosynthesis

A

Photosynthesis is an endothermic reaction used by plants to make their own food. Energy is required in the form of light from the sun. Light energy is absorbed by the chlorophyll in the chloroplasts in the leaf. This energy is then used to convert Carbon Dioxide (absorbed from the air through the stomata) and water (absorbed from the ground through the roots) into glucose. This chemical reaction also produces oxygen as a by-product. The oxygen is released into the air

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12
Q

What leaf adaptations are there to make photosynthesis more efficient?

A
  • Most leaves are broad
  • Most leaves are thin
  • They contain chlorophyll within chloroplasts
  • They contain veins
  • They contain air spaces
  • They have guard cells
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13
Q

How does having broad leaves make photosynthesis more efficient?

A

Broader leaves means that there is more surface area for the light to fall on

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14
Q

How does having thin leaves make photosynthesis more efficient?

A

Thinner leaves means that the diffusion distances for the gases are short

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15
Q

How does containing chlorophyll in chloroplasts make photosynthesis more efficient?

A

Chlorophyll within the chloroplasts absorbs the light which is needed to provide energy for photosynthesis

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16
Q

How does having veins make photosynthesis more efficient?

A

Leaf veins contain xylem and phloem in vascular bundles. The xylem brings in plenty of water to the cells of the leaves and the phloem removes the products of photosynthesis (Glucose)

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17
Q

How does having air spaces make photosynthesis more efficient?

A

Having air spaces in a leaf means that carbon dioxide can diffuse into the cells, and oxygen can diffuse out of the cells

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18
Q

How does having guard cells make photosynthesis more efficient?

A

Guard cells open and close the stomata to regulate gas exchange

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19
Q

How is algae adapted for photosynthesis

A

Algae is aquatic so they have a large surface area and can absorb carbon dioxide dissolved in the water around them, they also release the oxygen that they produce which dissolves into the water

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20
Q

State 4 limiting factors of photosynthesis:

A
  • Light* Temperature* Carbon Dioxide Concentration* Chlorophyll levels in the leaf
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21
Q

Explain how light is a limiting factor

A

If there is plenty of light then lots of photosynthesis can take place, if there a lack of light, photosynthesis would slow down. If there is no light, photosynthesis would stop. This is because light transfers the energy needed for the process. Even on sunny days, light may be limited due to shade from other plants or buildings. For most plants, the brighter and more intense the light is, the faster the rate of photosynthesis

22
Q

Explain how temperature is a limiting factor

A

Temperature affects all chemical reactions, including photosynthesis. Photosynthesis is controlled by enzymes, if it is too cold the reactant particles will not have much kinetic energy, reducing the number of collisions, the enzymes will also not work as effectively. As temperature increases, the rate of photosynthesis speeds up as the particles gain more kinetic energy and there is more collision between reactants and enzymes. However, if the temperature continues to rise, the enzymes will become denatured at around 40-50*C, this will cause the rate of photosynthesis to fall eventually to 0.

23
Q

Explain how Carbon Dioxide concentration is a limiting factor

A

Plants need Carbon Dioxide to perform photosynthesis. However, the atmosphere is only about 0.04% carbon dioxide. This means that carbon dioxide often limits the rate of photosynthesis. Increasing the carbon dioxide concentration will increase the rate of photosynthesis

24
Q

Explain how Chlorophyll levels in the leaf is a limiting factor

A

If the amount of chlorophyll in a leaf is limited in any way, less photosynthesis will take place. The leaves on some ornamental plants have white, chlorophyll-free areas. This reduces the rate of photosynthesis, causing the plants to grow less vigorously than plants with all green leaves. This is because chlorophyll in chloroplasts absorb the light that transfers the energy needed for the process.

25
Q

Describe the method for how the rate of photosynthesis is effected by light intensity:

A

1) Cut a piece of pondweed 8-10cm long. Place it in a boiling tube of water with the cut end uppermost
2) Use the thermometer to measure the temperature of the water in the boiling tube
3) Place the boiling tube in the large beaker of water, making sure that the top of the boiling tube is floating above the surface of the water in the beakerPlace the lamp 15cm from the boiling tube. Place the large beaker of water between the lamp and the boiling tube
4) Wait until there is a steady flow of bubbles from the cut end of the pondweed. Count the number of bubbles in 2 minutes. Record this in your results table.
5) Measure the temperature of the water in the boiling tube to make sure it has not changed.
6) Repeat steps 1-5 four more times but in step 3 increase the distance between the lamp and boiling tube by 2cm each time
7) Repeat the whole investigation (steps 1-6) two more times and record your results
8) Calculate the mean number of bubbles for each distance, leaving out any anomalous results.
9) Record data in appropriate table/graph

26
Q

What is the equation for light intensity?

A

Light intensity = 1 / (distance²)

27
Q

How do plants use glucose produced during photosynthesis?

A
  • For respiration
  • To convert into insoluble starch
  • To produce fats and oils
  • To produce cellulose
  • To produce amino acids
28
Q

Why do plants use glucose produced in photosynthesis for respiration?

A

Plant and algal cells, like all other living cells, need to respire all the time. They use some of the glucose produced during photosynthesis as they respire. The glucose is broken down using oxygen to provide energy for the cells. Carbon dioxide and water are waste products of the reaction. Chemically, respiration is the reverse of photosynthesis

29
Q

Why do plants convert glucose produced in photosynthesis into insoluble starch?

A

Plants convert some glucose produced in photosynthesis into starch to be stored. Glucose is soluble in water. If it were stored in plant cells, it could affect the way water moved in and out of the cells by osmosis. Lots of glucose could affect the water balance of the whole plant. Starch is insoluble in water, this means that it has no effect on the water balance of the plant so plants can store large amounts of starch in their cells. Starch is the main energy store in plants and it is found in cells all over a plant:

  • Starch is often stored in the cells of the leaves. It provides an energy store for when it is dark or when light levels are low
  • Starch is also kept in special storage areas of a plant. For example, many plants produce tubers and bulbs that are full of stored starch to help them survive through the winter
30
Q

Why do plants use glucose produced in photosynthesis to produce lipids?

A

Plants and algae use some of the glucose from photosynthesis and energy transferred from respiration to build up fats and oils. These may be used in the cells as an energy store. They are sometimes used in the cell walls to make them stronger. In addition, plants often use fats or oils as an energy store in their seeds. Seeds provide food for the new plant to respire as it germinates.

31
Q

Why do plants use glucose produced in photosynthesis to produce cellulose?

A

Energy transferred in respiration may be used to build smaller molecules into bigger molecules. For example, plants build up glucose into complex carbohydrates such as cellulose. They use this to strengthen their cell wall.

32
Q

Why do plants use glucose produced in photosynthesis to produce amino acids?

A

Plants use some of the glucose from photosynthesis to make amino acids. They do this by combining sugars with nitrate ions and other mineral ions from the soil. These amino acids are then used for protein synthesis to make proteins. These proteins can then be used in the plant in many ways, including making enzymes. This uses energy from respiration. For this, the plant must be able to absorb nitrates and other minerals from the soil

33
Q

Can plants photosynthesise at night and why?

A

Plants cannot photosynthesise at night as there is no light, this means that photosynthesises stops

34
Q

Can plants respire at night and why?

A

Plants can respire 24 hours a day as they do not need light to respire, unlike photosynthesis

35
Q

What is the rate of photosynthesis compared to the rate of respiration of a plant in a completely dark room?

A

Photosynthesis stops but respiration continues

36
Q

What is the rate of photosynthesis compared to the rate of respiration of a plant in a dim light?

A

Photosynthesis rate = respiration rate

37
Q

What is the rate of photosynthesis compared to the rate of respiration of a plant in a bright light?

A

Photosynthesis rate > respiration rate

38
Q

What happens to the gas exchange in a plant at night and why?

A

Oxygen is taken in and Carbon Dioxide is given out, this is because respiration continues but photosynthesis stops

39
Q

What happens to the gas exchange in a plant under a dim light and why?

A

The net amount of oxygen in and out and Carbon dioxide in and out is 0, this is because the rate of photosynthesis is equal to the rate of respiration

40
Q

What happens to the gas exchange in a plant under a bright light and why?

A

More Carbon dioxide is taken in and more oxygen is given out, this is because the rate of photosynthesis is more than the rate of respiration.

41
Q

How are some carnivorous plants adapted to live in nitrate-poor soil such as bogs?

A

Some carnivorous plants, such as pitcher plants or Venus fly traps, are adapted to live in nitrate-poor soil. They can survive because they obtain most their nutrients from the animals, such as insects, that they catch. The plants produce enzymes to digest the insects they trap. They then use nitrates and other minerals from the digested bodies of their victims in place of nutrients they cannot get from the poor soil that they grow in

42
Q

What happens if a plant begins to photosynthesise faster?

A

It grows faster and creates more biomass

43
Q

How do farmers increase the yield of their crop?

A

They can use greenhouses or huge plastic polytunnels to try and remove limiting factors

44
Q

How do greenhouses or huge plastic polytunnels increase the yield of a crop?

A

The glass or plastic building means that the environment is much more controllable than in an ordinary garden or field. This means that farmers can try and eliminate limiting factors as much as possible:

  • The temperature is maintained at the optimum temperature for enzyme activity
  • Carbon dioxide levels are increased so they do not become a limiting factor
  • Artificial lighting can be used to extend the hours of the day, and months of the year when plants can photosynthesise
  • Plants can be grown in a mineral solution with a perfect balance of nutrients, such as nitrate ions, instead of soil to ensure optimum growth. This is called hydroponics

This increases the rate of photosynthesis and therefore the rate of growth of the plants.

45
Q

What is hydroponics?

A

Hydroponics is when soil is replaced by a mineral solution pumped around the plant roots instead of soil.

  • Removing the soil means there’s no risk of soil organisms causing disease.
  • Monitoring and adjusting the concentrations of minerals in the solution enable the farmer to optimise growth.
  • Hydroponics allows crops to be grown in regions where there’s infertile or poor soil.
  • Due to the costs involved, hydroponics is used only for high-value crops.
46
Q

Explain the economics of using a greenhouse to optimise photosynthesis:

A

Using a greenhouse and keeping the conditions just right can be very costly. Electricity and gas are used to maintain the lighting and temperatures and to control the carbon dioxide levels. Expensive monitoring systems are needed to maintain the conditions within the greenhouse. However, less staff are needed as much of it is automated, the time from seed to harvest is much shorter, and the final crop is larger and cleaner. The higher yields also help to increase profits

47
Q

In which cell organelle does photosynthesis take place?

A

Chloroplasts

48
Q

Which chemical in the leaves is required for photosynthesis?

A

Chlorophyll

49
Q

What is the compensation point in a plant?

A

When the rate of photosynthesis is equal to the rate of respiration

50
Q

In which layer of the leaf does the most photosynthesis take place?

A

Palisade mesophyll layer

51
Q

Where is starch stored in a plant?

A

Starch is the main energy store in plants and it is found in cells all over a plant:

  • Starch is often stored in the cells of the leaves. It provides an energy store for when it is dark or when light levels are low
  • Starch is also kept in special storage areas of a plant. For example, many plants produce tubers and bulbs that are full of stored starch to help them survive through the winter
52
Q

Why may plants have a difference in the rate of water loss?

A
  • One plant may have more stomata
  • One plant may have more leaves
  • One plant may have bigger leaves

GCSE Biology (Advanced Specification 2022 ONLY) (16 decks)

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