B8 photosynthesis Flashcards
How do plants and algae make food
By photosynthesis
What happens during photosynthesis?
plants produce
glucose from simple
inorganic molecules –
carbon dioxide and water using light energy.
What are the formulas for photosynthesis?
6CO2 + 6H2O → C6H12O6 + 6O2 (the arrow also has light and the word chlorophyll under it)
light carbon dioxide + water-->
chlorophyll --->glucose + oxygen
Photosynthesis is an ____ reaction?
Endothermic(it brings in energy)
How is the light energy absorbed during photosynthesis?
The light energy required is absorbed by a green
pigment called
chlorophyll in the leaves. Chlorophyll is located in
chloroplasts in plant cells, particularly the
palisade and spongy
mesophyll cells.
How is there more oxygen in the day?
Oxygen is formed as the waste product. Some is used for the plant’s respiration, and also released which makes it available for respiration to animals and many microorganisms. During the day, provided the rate of photosynthesis is sufficiently high, plant leaves, and water plants, give out oxygen.
What is glucose used for in the plant
making fats and amino acids
most importantly respiration
building cellulose for cell walls
making starch for storage of glucose as glucose can dissolve and affect osmosis
What factors affect photosynthesis?
Several factors can affect the rate of photosynthesis:
light intensity
carbon dioxide concentration
temperature
How does the amount of chlorophyll affect photosynthesis?
The amount of
chlorophyll
also affects the rate of photosynthesis:
plants in lighting conditions unfavourable for photosynthesis synthesise more chlorophyll, to absorb the light required
the effects of some plant diseases affect the amount of chlorophyll, and therefore the ability of a plant to photosynthesize
Explain the curve in the graph that links temperature with rate of photosynthesis
The chemical reactions that combine carbon dioxide and water to produce glucose are controlled by
enzymes. As with any other enzyme-controlled reaction, the rate of photosynthesis is affected by temperature.
At low temperatures, the rate of photosynthesis is limited by the number of molecular collisions between enzymes and substrates. At high temperatures, enzymes are denatured.
Why does the light intensity graph and co2 concentration graph plateau
a limiting factor which is another factor needed for photosynthesis.
– becomes in short supply.
How factors interact limiting the rate of photosynthesis?
With the law of limiting factors, each factor does not work in isolation. Several factors may interact, and it may be any one of them that is limiting photosynthesis.
One example of how factors might interact:
The graph shows how carbon dioxide concentration and temperature interact with the effect of light intensity on photosynthesis:
the rate of photosynthesis increases until factors becoming limiting
if carbon dioxide concentration is increased, the rate increases further, and then another factor becomes limiting
the rate can be increased further if the temperature is increased
the rate increases again until another factor becomes limiting
required practical for effect on photosynthesis
The leaf of a variegated Pelargonium is dropped in boiling water to kill and preserve it
The leaf is left for 10 minutes in hot ethanol in a boiling tube. This removes the chlorophyll
The leaf is dipped in boiling water to soften it
The leaf is spread out in a Petri dish and covered with iodine solution
The areas that had the chlorophyll stain blue-black. The areas that had no chlorophyll remain pale.
Care must be taken when using boiling ethanol. Make sure that no Bunsen burners are turned on as the ethanol is highly flammable.
Photosynthesis Required Practical:
The effect of light intensity on photosynthesis can be investigated in water plants. Use Cabomba or Elodea, which are sold in aquarium shops.
The plants will release bubbles of oxygen – a product of photosynthesis – which can be counted.
A lamp with an LED bulb is set up at different distances from the plant in a beaker of water:
an LED bulb is best as this will not raise the temperature of the water
sodium hydrogencarbonate – formula NaHCO3 – is added to the water to supply carbon dioxide – a reactant in photosynthesis – to the plant
the light intensity is proportional to distance – it will decrease as the distance away from the bulb increases – so light intensity for the investigation can be varied by changing the distance from the lamp to the plant.
Set up a boiling tube containing 45 cm3 of sodium hydrogencarbonate solution (1%). Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form.
Cut a piece of the pondweed, Cabomba. The pondweed should be 8 cm long.
Use forcepts to place the pondweed in the boiling tube carefully. Make sure that you don’t damage the pondweed, or cause the liquid to overflow.
Position the boiling tube so that the pondweed is 10 cm away from the light source. Allow the boiling tube to stand for five minutes. Count the number of bubbles emerging from the cut end of the stems in one minute. Repeat the count five times and record your results.Calculate the average number of bubbles produced per minute. Repeat the experiment at different distances away from the light source.
Variables
Independent variable – distance from the light source/light intensity.
Dependent variable – the number of bubbles produced per minute.
Control variables – concentration of sodium hydrogen carbonate solution, temperature, using the same piece of Cabomba pondweed each time.
