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biology chap 6 > 6.1 Photosynthesis > Flashcards

6.1 Photosynthesis Flashcards

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1
Q

what is photosynthesis

A

the process by which plants synthesise carbohydrates from raw materials using energy from light

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2
Q

what is the word equation for photosynthesis

A

carbon dioxide + water -> glucose + oxygen
*light and chlorophyll needed

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3
Q

chemical equation for photosynthesis

A

6CO2 + 6H20 -> C6H12O6 + 602

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4
Q

what is chlorophyll

A

a green pigment that is found in chloroplasts

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5
Q

function of chlorophyll

A

chlorophyll captures light energy which is transferred to proteins and enzymes to use in photosynthesis and converted to chemical energy when carbohydrates are synthesised

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6
Q

why is glucose converted to carbohydrates

A

it is too soluble to be transported around the plant on its own

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7
Q

use of carbohydrates

A

-the glucose may be used in respiration to release energy
-it can be converted to starch as an energy store
-the glucose may be converted to a complex carbohydrate called cellulose, which may be used to build cell walls
-the glucose may be converted into sucrose so that it can be transported around the plant in the phloem
-the glucose may be used as nectar to attract insects form pollination

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8
Q

two mineral requirement for plants

A

-nitrate ions to make amino acids
-magnesium ions for making chlorophyll

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9
Q

symptoms of deficiency of nitrate ions

A

-slow down the growth of the plant
-cause the leaves to turn yellow

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10
Q

symptoms of deficiency of magnesium ions

A

-cause the leaves to turn yellow between their veins, starting from the lower leaves
-slow down the growth of plant

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11
Q

factors needed for photosynthesis

A

-chlorophyll - helps absorb the light required
-light - provides the energy to drive the reaction
-carbon dioxide - is converted into sugars such as glucose

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12
Q

how to destarch a plant

A
  1. leave the plants in the dark for 48 hours
  2. during this period the plants will be unable to photosynthesise and therefore use up all its starch for respiration
  3. this means that in the beginning of our experiments, all plants (test and control) will have absolutely no starch in them
  4. so after the experiment, if we do a starch test (iodine test) and we find starch is present, it would indicate that photosynthesis has occurred
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13
Q

how to remove chlorophyll

A

-boil the leaf in water to break down cell membranes and denature enzymes to make it permeable
-boil the leaf in a test tube of ethanol that is in a water bath with the boiling water to remove the chlorophyll from the leaf and decolour it
-leaf removed and dipped in hot water once more to further soften it
-leaf is ready to test for starch with iodine solution

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14
Q

investigate need for chlorophyll

A

1.potted plant with variegated leaves is held in the dark for 48 hours to destarch leaves
2.leaf is detached and tested for starch
3.plant is then exposed to full sunlight for 8-12 hours
4.another leaf detached, outline drawn and areas with chlorophyll-free tissue are drawn on the diagram
4. the leaf is tested for starch
5.blue-black colour appears only in tissue with chlorophyll

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15
Q

investigate need for light

A

1.plant kept in dark for 48 hours to destarch
2.leaf detached and tested for starch
3.lightproof stencil fixed to 1 leaf and exposed to sunlight for 6 hours
4.stencil removed and leaf tested for starch
5.part of leaf that is not covered turns blue-black

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16
Q

investigate need for carbon dioxide

A
  1. 2 potted plants are put in the dark for 48 hours to destarch it
  2. a leaf from each plant is tested for starch
  3. 1 plant enclosed with a dish of sodium hydrogen carbonate solution which gives off carbon dioxide
  4. other plant enclosed with sodium hydroxide to absorb carbon dioxide
  5. both plants exposed to full sunlight for 8-12 hours
  6. a leaf from each plant is tested for starch
  7. leaf with carbon dioxide supplied turns blue-black
  8. leaf without carbon dioxide supplied remain brown
17
Q

what factors affect the rate of photosynthesis

A

-light intensity
-carbon dioxide concentration
-temperature

18
Q

investigate with varying light intensities

A
  1. an aquatic plant is cut diagonally at the end of the stem with a scalpel
  2. the plant is put under an inverted funnel which is inside an inverted boiling tube into a beaker containing water with sodium hydrogen carbonate. a thermometer is also put into the beaker with a clamp and retort stand without touching the beaker
  3. light source set up 10 cm away from apparatus
  4. number of bubbles appearing from cut end of stem is counted over fixed period of time and recorded
  5. repeat the counting 2 more times
  6. repeat steps 5-6 with distances of 20cm, 30cm, 40cm and 50cm away from light source
  7. plant left for 5 mins to adjust to new light intensity before counting
  8. calculate light intensity with formula: 1/(distance)^2
  9. graph plotted with rate of photosynthesis against light intensity
19
Q

varying light intensity graph

A

-steep increase at start as increasing light intensity increase rate of photosynthesis
-horizontal line as another factor becomes limiting so rate becomes constant

20
Q

investigate varying carbon dioxide concentration

A
  1. an aquatic plant is cut diagonally at the end of the stem with a scalpel
  2. the plant is put under an inverted funnel which is inside an inverted boiling tube into a beaker containing water with 1% sodium hydrogen carbonate. a thermometer is also put into the beaker with a clamp and retort stand without touching the beaker
  3. light source set up at a constant distance from apparatus
  4. number of bubbles appearing from cut end of stem is counted over fixed period of time and recorded
  5. repeat the counting 2 more times
  6. repeat steps 5-6 with 2.5%, 5%, 7.5% and 10% sodium hydrogen carbonate solution
  7. graph plotted with rate of photosynthesis against carbon dioxide concentration
21
Q

varying CO2 conc graph

A

-steep increase at the start as increasing CO2 conc increases rate of photosynthesis
-horizontal line as other factor becomes limiting so rate becomes constant

22
Q

investigate varying temperature

A
  1. an aquatic plant is cut diagonally at the end of the stem with a scalpel
  2. the plant is put under an inverted funnel which is inside an inverted boiling tube into a beaker containing water with sodium hydrogen carbonate. a thermometer is also put into the beaker with a clamp and retort stand without touching the beaker
  3. setup placed in a water bath at 0 degrees
  4. light source set up at a constant distance from apparatus
  5. number of bubbles appearing from cut end of stem is counted over fixed period of time and recorded
  6. repeat the counting 2 more times
  7. repeat steps 5-6 with water bath at temperatures 20, 25, 30 degrees
  8. plant left for 5 mins to adjust before counting
  9. graph plotted with rate of photosynthesis against temperature (degrees celsius)
23
Q

varying temp graph

A

-curve increase as number of collisions between enzymes and substrates increases
-reaches high temp - optimum temp
-decreasing curve as enzymes start to denature

24
Q

the effect of light conditions on gas exchange

A

-during the day especially when the sun is bright and the light intensity is high, plants photosynthesise at a faster rate than they are respiring
-so overall there is a higher intake of carbon dioxide and a higher output of oxygen
-if the light is bright enough the rate of carbon dioxide absorption becomes greater than the rate of carbon dioxide release

25
Q

how does hydrogencarbonate indicator work

A

yellow - high carbon dioxide level
red - equal to atmosphere
purple - low carbon dioxide level

26
Q

investigate effect of light with hydrogencarbonate indicator

A

-tube 1(has leaf in light) - purple because overall absorption of CO2 by the leaf is high in light conditions
-tube 2(has leaf in dark) - yellow because overall release of CO2 from the leaf is higher in dark condition
-tube 3(has no leaf in light) - red because this is the control, since there’s no leaf in it, the level of CO2 is the same as that of the atmosphere

27
Q

what is a limiting factor

A

something present in the environment in such short supply that it restricts life processes

biology chap 6 (2 decks)

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