P1 - Bioenergetics (Done) Flashcards
What is photosynthesis ?
Creates food for a plant, takes place in chloroplasts, chloroplasts contain pigments like chlorophyll to absorb light, it’s an endothermic reaction - energy is transferred from the environment by light.
What is the word equation for photosynthesis ?
Carbon dioxide + water –> glucose + oxygen (light over the arrow)
What are the chemical symbols for the substances involved in photosynthesis ?
carbon dioxide: CO2, water: H2O, glucose: C6H12O6 and oxygen: O2.
How do plants use the glucose produced ?
For respiration, making cell walls - changed into cellulose for strong cell walls, making amino acids - glucose + nitrate ions = amino acids used to make proteins, stored as oils or fats in seeds and stored as starch - for use when photosynthesis isn’t happening.
What are the limiting factors of photosynthesis ?
Intensity of light, concentration of CO2, temperature and chlorophyll.
How can chlorophyll be a limiting factor of photosynthesis ?
Amount of chlorophyll can be affected by disease or changes in the environment - lack of nutrients, causing chloroplasts to become damaged or not have enough chlorophyll which means they can’t absorb as much light.
How can you measure the effect of light intensity on the rate of photosynthesis ?
Ruler used to measure set distance between pond-weed and light source, pond-weed left to photosynthesise for set amount of time - oxygen released will collect in capillary tube. Syringe used to draw gas bubble in tube up against ruler, length of bubble measured - tells you how much oxygen produced thus rate of photosynthesis. Repeat with light source different distances away.
How can you measure the effect of temperature or carbon dioxide on the rate of photosynthesis ?
The test tube of pondweed can be put in a water bath at a set temperature or a measure amount of sodium hydrogencarbonate can be dissolved in the water (gives off CO2) and then oxygen produce can be measured in the normal way.
What is the relationship between light intensity and distance ?
Light intensity decreases in proportion to the square of the distance. This is called the inverse square law.
How is the inverse square law written ?
light intensity ∝ 1 ÷ distance^2
What does the inverse square law mean ?
If you halve the distance, the light intensity will be four times greater.
How can you artificially create ideal conditions for farming ?
Grow plants in a greenhouse, making it easier to control the conditions and keep them free of pests and diseases.
How can you control the limiting factors of photosynthesis in a greenhouse ?
If it’s too hot they can use shades or ventilation to cool it down, if it’s too cold they can use a paraffin heater which heats the greenhouse, and as paraffin burns it also makes CO2 as a bi-product. Light is always needed so they can use artificial light when there’s not enough.
What is respiration ?
The process of transferring energy from glucose, which goes on in every cell. It’s not just breathing in and out. And it’s exothermic.
How might organisms use energy transferred from respiration ?
To build larger molecules, in animals it’s used to allow muscles to contract, in mammals and birds it’s used to keep their body temp. steady in colder surroundings.
