Photosynthesis & Adaptations of Leaves - Bioenergetics Flashcards
What type of reaction is photosynthesis?
Endothermic
What is the word equation for photosynthesis?
Carbon dioxide + water → Glucose + Oxygen
What is the symbol equation for photosynthesis?
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
What are the 5 uses of glucose?
- To make cellulose for the cell wall
- To make starch - stored in the cells to break down when photosynthesis doesn’t happen, insoluble, compact
- Cellular respiration
- Make amino acids by glucose combining with nitrate ions from soil
- Make lipids - store for energy for later
What adaptations do leaves have to maximise photosynthesis?
- Large surface area
- Thin shape
- Lots of stomata
- Xylem and Phloem
- Long, narrow upper mesophyll cells with chloroplasts
- Waxy, waterproof cuticle
What does a large surface area do?
Allows them to absorb as much light as possible
What does having a thin shape do?
Short distance for carbon dioxide and oxygen to diffuse + most light is absorbed within the first few milimetres of the leaf
What does having lots of stomata do?
Allow more gas exchange
What does having a xylem an phloem do?
- Xylem brings water to the leaf for photosynthesis
- Phloem transports sugars produced in photosynthesis
What does having a long, narrow upper mesophyll cells with chloroplasts do?
More chloroplasts means more sunlight absorbed
What does having a waxy, waterproof cuticle do?
Cuts down water lost by evaporation and protects against parisitic fungi
Order of the leaf structure top to bottom
- Upper epidermis
- Palisade mesophyll
- Spongy mesophyll
- Gaurd cells
- Stomata
- Lower epidermis
Required Practical 6: Rate of Photosynthesis, why is an LED light used as the light source? What can we do if we want to use normal light?
- LED doesn’t change the temperature which is a factor that affects photosynthesis
- If you want to use normal light, have a beaker of water in front of the light so it absorbs the heat
Required Practical Method
- Fill boiling tube with with sodium hydrogen carbonate solution (will encourage pondweed to photosynthesise)
- Put pondweed, cut end of pondweed in water
3.Put boiling tube 10cm away (using ruler) - Let the pondweed adjust to lighting
- Count number of bubbles from the cut end
- Repeat and calculate the mean
- Increase distance by 10 cm and make a graph
Required Practical variables
Independant: Light intensity/Distance between boiling tube and light
Dependant: How light intensity affects the rate of photosynthesis
Controlled: Age of pondweed/ Volume of sodium hydrogen carbonate
What is the inverse square law formula?
light intensity∝ 1/distance(d)²
∝ = proportional
What is the inverse square law?
Light intensity decreases in proportion to the square of the distance
Inverse Square Law = What would the light intensity be if you halved the distance?
4 times greater
Inverse Square Law = What would the light intensity be if you third the distance?
9 times greater
Inverse Square Law = What would the light intensity be if you double the distance?
4 times smaller
Inverse Square Law = What would the light intensity be if you treble the distance?
9 times smaller
What do greenhouses do?
Trap the Sun’s heat to make sure temp doesnt become limiting
What if the temp gets too hot in greenhouses?
Use shades and ventiliation
How to increase CO2 in greenhouse?
Paraffin heaters burn paraffin, it makes co2 as a by-product
Why should greenhouses be enclosed?
Keeps pests away, diseases
What can the farmer do to provide minerals for healthy growth?
Add fertiliser
Factors that affect photosynthesis
CO2, temperature, light intensity, conc of chlorophyll
Invserse law formula
intensity of light decreases proportionally to the square of the distance from its source.
