Topic 4: Bioenergetics Flashcards
(71 cards)
Why are plants autotrophs?
Make their own food using light, water and carbon dioxide
What is photosynthesis?
Endothermic reaction in which energy is transferred from the environment to the chloroplast by light
Where does most photosynthesis take place?
Leaves of plant, in specialised mesophyll cells which are packed with chloroplasts containing chlorophyll to absorb as much light energy as possible
What is produced in photosynthesis?
Glucose, sugars, used to make all the substances a plant needs, as well as being used in respiration to release energy
What is the word equation for photosynthesis?
Carbon Dioxide + Water –> Glucose + Oxygen
(Arrow has light and chlorophyll)
What is the balanced symbol equation for photosynthesis?
6 CO₂ + 6 H₂O –> C₆H₁₂O₆ + 6O₂
How are the reactants of the photosynthesis equation obtained?
Carbon Dioxide - Diffuses into the leaf through the stomata
Water - Taken up by the roots and transported through the xylem to the leaves
How are the products of the photosynthesis equation used or released?
Glucose - Used to make substance needed by plant; used in respiration to release energy
Oxygen - Diffuses out of the leaf through the stomata; used in respiration
What does a plant need in order for photosynthesis to occur?
- Light
- Water
- Carbon Dioxide
Why is water not a limiting factor for photosynthesis?
Amount needed is relatively small compared to amount of water transpired from a plant so there is hardly a situation where there is not enough water for photosynthesis
How does temperature affect the rate of photosynthesis?
- Temp. of environment affects amount of kinetic energy particles have
- Affects speed at which CO₂ and H₂O move through plant
- Lower temp. , the less kinetic energy particles have, resulting in fewer successful collisions occurring
- High temp. , increase kinetic energy of particles, increasing likelihood of collision between reactants and enzymes which results in formation of products
- However, at high temp. enzyme that control photosynthesis can be denatured
How does light affect the rate of photosynthesis?
- Intensity of light available to the plant will depend on the amount of energy that it has to carry out photosynthesis
- More light a plant receives, the faster the rate of photosynthesis
- The trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
How does carbon dioxide concentration affect rate of photosynthesis?
- One of the raw materials required for photosynthesis
- More carbon dioxide, the faster the reaction can occur
- Trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
How does chlorophyll affect rate of photosynthesis?
- Number of chloroplasts
- More chloroplasts a plant has, the faster rate of photosynthesis
- Amount of chlorophyll can be affected by:
> Diseases
> Lack of nutrients
> Loss of leaves
What does the inverse square law describe in relation to light?
The inverse square law describes the relationship between light intensity and distance, showing they are inversely proportional to each other.
How does light intensity change as distance increases?
As distance increases, light intensity decreases. Specifically, when distance doubles, light intensity decreases by a factor of four.
What is the equation for the inverse square law relating to light intensity?
Light intensity = 1/d² (where d is the distance from the light source)
Calculate the light intensity when a plant is placed 30cm from a lamp.
Light intensity = 1/30² = 0.001 au (arbitrary units)
What does ‘au’ stand for when measuring light intensity?
‘au’ stands for arbitrary units.
Why do commercial horticulturists grow plants in greenhouses?
To control as many of the limiting factors of photosynthesis as possible.
What limiting factors can be controlled in a greenhouse?
Heat, light, water, carbon dioxide, and nutrients.
Why are limiting factors important in greenhouse economics?
They’re important for enhancing conditions to gain maximum photosynthesis rates while still maintaining profit.
How do greenhouses help farmers make more money despite their costs?
Through increased crop yield and more frequent harvests.
Why do farmers carefully control resource levels in greenhouses?
To use only the smallest amounts needed and avoid wasting money.
