B8-Photosynthesis Flashcards
(15 cards)
What is the symbol equation for photosynthesis?
6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
Why do plants need light to carry out photosynthesis?
it provides the energy needed to convert carbon dioxide and water into glucose (a form of sugar) and oxygen
How are leaves adapted for photosynthesis?
a large surface area for maximizing light absorption, thin and flat structure for efficient gas exchange, and the presence of chloroplasts for capturing light energy
Describe an experiment to prove that photosynthesis occurs when plants are exposed to light:
-set up boiling tube with fixed volume of sodium hydrogen carbonate solution
-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, elodea.
-Use forceps to place the pondweed in the boiling tube carefully.
-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.
what is the independent, dependent and control variables of the experiment?
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
What factors affect the rate of photosynthesis?
-carbon dioxide concentration
-light intensity
-temperature (enzyme controlled reaction)
What does the inverse square law describe in the context of photosynthesis?
The inverse square law describes how light intensity decreases as the distance from the light source increases; light intensity is inversely proportional to the square of the distance from the light source
light intensity= 1/distance^2
Can you list some ways in which plants use glucose?
Used for respiration (both aerobic and anaerobic)
Converted into insoluble starch for storage in the stems, leaves and roots.
Used to produce fat or oil for storage (especially in seeds)
Used to produce cellulose, which strengthens the cell wall.
Describe an experiment testing a leaf for the presence of starch:
heat a plant leaf in boiling water for 30 seconds (this kills the leaf, stopping any chemical reactions)
add the leaf to boiling
ethanol
in a water bath for a few minutes (the boiling ethanol dissolves the chlorophyll and removes the green colour from the leaf - it turns white so it is easy to see the change in colour)
wash with water to rehydrate and soften the leaf and spread onto a white tile
add iodine solution from a dropping pipette
What are some hazards associated with this experiment?
hazard: Ethanol is flammable.
risk: It may ignite when heating to boiling point if using a naked flame.
control: Do not heat over a Bunsen burner. Use a beaker of hot water as a water bath.
How does a plant use the glucose from photosynthesis to create proteins?
Plants convert glucose, produced during photosynthesis, into proteins by combining it with nitrates absorbed from the soil to form amino acids, which are then linked together to create proteins. This process, called protein synthesis, occurs within the plant’s cells, specifically in the ribosomes.
Why do plants convert glucose to starch for storage?
Glucose is a soluble sugar, and its presence in high concentrations can affect water balance in the plant, leading to osmotic issues whereas starch is insoluble
Why do greenhouses increase plant growth?
Greenhouses can remove limiting factors which increase yield and maximises profit
How are greenhouses adapted for optimising conditions for plant growth?
-they naturally trap heat
-paraffin heaters release C02 and increase temp
-artificial light extends length of time plants can photosynthesise
What are the advantages of using hydroponics compared to soil-based farming?
-can be set up indoors where a farmer can optimise conditions
-Hydroponics replaces soil with a mineral solution pumped around the plant roots.
Removing the soil means there’s no risk of soil organisms causing disease but the plants have to be supported
-used for high value crops
-receive constant supply of water and nutrients- higher yield
-nutrient solution is recirculated meaning minimal water loss
