Photosynthesis

photosynthesis

plants do this by converting raw materials of carbon dioxide and water to glucose. takes place in the green part of the plants, mainly leaves.the green pigment is chlorophyll and it traps the light energy from the sun that is needed to drive the process.

what type of reaction is photosynthesis

endothermic

what to animals feed on

material ( plants, animals or both)

what do plants feed on

able to use sunlight to make their own food

word equation for photosynthesis

water + carbon dioxide → light → oxygen + glucose

symbol equation

6CO2 + 6H2O → C6H126O2

carbon dioxide

from the air

water

from the soil

glucose

used for energy, growth and making cellulose

oxygen

released into the air

how is a plant de starched

by keeping it in complete darkness for up to 48 hours, which uses up its stored starch for energy

why is a plant de starched

to ensure that any starch detected at the end of the experiment was produced during the experiment and not before

testing a leaf for starch

1) leave the leaf in the dark for up to 48 hours

2) place the lead in the boiling water for 30 seconds to kill the leaf

3) the lead is then placed in boiling ethanol ( use water bath as ethanol is flammable) to remove chlorophyll

4) dip the leaf in the water again to soften it

5) spread the leaf on the white tile and add 2-3 drops of iodine

If starch is present the yellow/brown iodine solution will change to blue/black

why is the test using sodium hydroxide to absorb carbon dioxide done

to confirm that carbon dioxide is an essential raw material required for photosynthesis

how is the sodium hydroxide test carried out

by removing carbon dioxide from the environment of one lead and comparing starch production to a leaf with carbon dioxide, usually proving that carbon dioxide is necessary for plants to produce starch

the sodium hydroxide absorbs carbon dioxide, allowing a comparison to a control leaf tjay has access to carbon dioxide

results of the sodium hydroxide test

a lead exposed to carbon dioxide will test positive for starch meanwhile the other wont, as carbon dioxide is essential for photosynthesis

variegated leaf to illustrate the role of chlorophyll

1) destarch the plant

2) test a leaf from the destarched plant for starch; if negative continue

3) cover one part of the leaf with light proof foil

4) place the plant in bright light for several hours

5) test the leaf for starch by adding iodine

what are the results for the variegated leaf test

the test shows that only the green parts of the leaf, which contain chlorophyll can produce starch

measuring the rate of photosynthesis

to find the production of oxygen, you measure the volume of oxygen instead of counting the bubbles as its more accurate, which is done by using an oxygen electrode

measuring the rate of photosynthesis results

if the rate of photosynthesis increases (e.g by increasing light intensity) the number of of oxygen bubbles or volume of oxygen produced will also increase. the more chlorophyll a plant has means the more light it can absorb meaning the rate of photosynthesis will also increase

Limiting factors light intensity

as light intensity increases, the rate of photosynthesis gets faster due to more successful reactions, but then gradually levels off because carbon dioxide or temperature has became the limiting factor, slowing the rate of photosynthesis

limiting factors carbon dioxide

as carbon dioxide concentration gets higher, so does the rate of photosynthesis. It then gradually levels off as the limiting factors like. light intensity and temp slow the rate of photosynthesis so it levels off

limiting factor temperature

as temperature increases, particles collide with more energy resulting in faster rate of reaction. this is only up to the optimum temperature, and at a temperature any higher than the optimum the enzymes denature which reduces the rate of photosynthesis

gas exchange test

each boiling tube is filled with hydrogen carbonate indicator and are placed in a bright light for one hour. This is the balance between photosynthesis and respiration using hydrogencarbonate

results tube A colours

red to yellow

tube A reason for change

the foil strip stops light energy entering and photosynthesis does not occur. respiration increase carbon dioxide concentration

tube B colours

red to purple

tube B reason for colour change

both photosynthesis and respiration take place in the pondweed. as the rate of photosynthesis is faster than the rate of respiration more carbon dioxide enters the plant

tube c colours

red to yellow

reason for tube c colour change

the water beetles produce for carbon dioxide in respiration than the pondweed takes in photosynthesis

epidermis

with cell walls as a physical defence that are transparent to allow light through

waxy cuticle

a physical defence that us transparent to allow light through and waterproof to reduce water loss

palisade mesophyll cells

tightly packed, end on to the upper surface with many chloroplasts to increase photosynthesis

spongy mesophyll

with few chloroplasts and a large surface area which allow diffusion of gases through the leaf

guard cells and stomata

allow gases to diffuse into and out of the leaf