B8 photosynthesis Flashcards
(18 cards)
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?
Light intensity: As light intensity increases, the rate of photosynthesis increases proportionally, up to a point. Beyond this point, increasing the light intensity further will not increase the rate of photosynthesis because other factors become limiting.
Carbon dioxide concentration: Similarly, as carbon dioxide concentration increases, the rate of photosynthesis increases until another factor becomes limiting.
Water availability: Water is essential for photosynthesis. A lack of water can cause stomata to close, limiting carbon dioxide uptake and thus slowing down the rate of photosynthesis.
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.
How are leaves adapted to photosynthesis?
Stomata: The lower epidermis of the leaf contains stomata, which are small pores that allow carbon dioxide to enter and oxygen to exit. Guard cells control the opening and closing of stomata to regulate gas exchange and water loss.
Veins: Leaves have a network of veins containing xylem and phloem. Xylem transports water to the leaf for photosynthesis, while phloem carries away the glucose produced during photosynthesis to other parts of the plant.
Cuticle: A waxy cuticle covers the upper epidermis of the leaf. This layer is transparent to allow light to pass through, but it also reduces water loss by evaporation.
Palisade Mesophyll: This layer is located beneath the upper epidermis and consists of tightly packed cells that are rich in chloroplasts. This is the primary site of photosynthesis in the leaf. The cells are elongated and arranged vertically to maximise light absorption.
Spongy Mesophyll: Located below the palisade layer, the spongy mesophyll has irregularly shaped cells with air spaces between them. These air spaces allow for efficient gas exchange of carbon dioxide and oxygen within the leaf.
Large Surface Area: Leaves are broad and flat to maximise the surface area exposed to sunlight. This allows them to capture as much light as possible.
Thinness: Leaves are thin, which reduces the distance that gases like carbon dioxide need to diffuse to reach the photosynthetic cells.
What is the inverse square law light intensity equation
light intensity = 1/distance²
Why is glucose converted to starch in plants?
Storage: Starch is a more compact and insoluble storage form of glucose. If plants stored glucose directly, it would lead to a high concentration of glucose within cells. This would cause water to enter the cells via osmosis, potentially damaging them. Starch, being insoluble, doesn’t have this effect.
Energy Reserve: Starch acts as a readily available energy reserve for plants. When the plant needs energy, it can break down starch back into glucose through hydrolysis. This glucose can then be used in cellular respiration to produce ATP
adenosinetriphosphate, the energy currency of the cell.
Osmotic Stability: As mentioned earlier, starch’s insolubility prevents it from affecting the osmotic balance of the cell. This is crucial for maintaining cell turgor and preventing water stress.
?How do greenhouses maximise photosynthesis
Light: Greenhouses use transparent materials like glass or plastic to allow maximum sunlight to reach the plants. Supplemental lighting, such as LED grow lights, can be used to extend the day length or increase light intensity, especially during winter months or in regions with low sunlight.
Temperature: Maintaining an optimal temperature range is crucial for photosynthesis. Greenhouses are equipped with heating and cooling systems to regulate temperature, ensuring that plants are not stressed by excessive heat or cold.
Carbon Dioxide: Photosynthesis uses carbon dioxide. Some greenhouses inject into the environment to increase its concentration, thereby boosting the rate of photosynthesis.
Water: Adequate water supply is essential. Greenhouses often use automated watering systems to provide plants with the necessary moisture, preventing water stress that can inhibit photosynthesis.
Nutrients: Plants require essential nutrients for healthy growth and efficient photosynthesis. Greenhouses often employ hydroponic systems or carefully controlled soil-based systems to deliver the right balance of nutrients.
