Photosynthesis Flashcards
Draw diagram of the chloroplast
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Define photosynthesis
Making food using light
What is the equation for photosynthesis?
6CO2+6H2O -> 6O2 + C6H12O6
What does the chlorophyll do in photosynthesis
It traps sunlight energy
What is the primary site of photosynthesis?
Leaf
Explain some adaptions of leafs for photosynthesis
- Stomata: pores for gaseous exchange. Mostly on lower epidermis. Open during day to allow carbon dioxide in for photosynthesis. Closed at night - reduces transpiration
- Air spaces: Between spongy mesophyll cells allow for diffusion of CO2 and H2O within the leaf
- Thin: For rapid diffusion of CO2 in and oxygen out. Also allows all cells to capture light
- Cuticle: Prevents excessive water loss, transparent - allows light through for photosynthesis. Waxy
- Leaf flattened: To give maximum surface area for maximum absorption of light and CO2
- Xylem vessels: To bring water for photosynthesis and phloem sieve tubes to translocate food eg. sucrose etc.
- Petiole: Places lamina in best position for light absorption
Explain some factors affecting photosynthesis
Carbon dioxide:
- Enters through stomata on lower epidermis and diffuses through the air in the atmosphere into spaces of the mesophyll (ground tissue).
- As CO2 increases, so does the rate of photosynthesis until it reaches a plateau (optimum=0.1%)
- Increase crop production in a greenhouse by pumping in CO2.
- CO2 may be a limiting factor when plants are overcrowded on a sunny day
Light:
- Light is necessary because it provides the energy needed to convert carbon dioxide into water and glucose
- With an increase in light intensity photosynthesis increases up to light saturation when a plateau is formed
- Light may be a limiting factor at dawn, dusk, in a wood or on a warm but dull day
Temperature:
- Optimum temperature for most plant enzymes is 25 degrees celsius. Minimum is 0 degrees celsius
- This is why plants grow better in warm climates, indoors, heated glasshouses or in summer
- Growth of plants is slower in colder months due to lower light intensity
- May be a limiting factor in early morning when it is bright
Water:
- Water is freely available
- Absorbed by plants root hairs and is conducted through the xylem by the transpiration stream
Where does photosynthesis occur?
Chloroplasts
When does photosynthesis occur?
In the presence of light
What is the input in photosynthesis?
Carbon dioxide and water
What is the output in photosynthesis?
Glucose and oxygen
What is the energy source for photosynthesis?
Light
What happens to energy in photosynthesis?
It is stored
What is the energy conversion in photosynthesis?
Light energy to chemical energy
Define limiting factor
Factor in short supply that determines rate of photosynthesis
Define compensation point
The light intensity at which the rate of photosynthesis equals the rate of respiration. No change in the amount of food in the plant or oxygen or carbon dioxide concentration of air around the plant
Define saturation point
When the plant cannot absorb any more light
What happens to the products of photosynthesis?
ATP - Supplies energy for the dark stage
NADPH: Supplies protons and energised electrons for the dark stage
Oxygen: Used for respiration or released into the atmosphere
Define photophosphorlyation
Addition of a phosphate group using light
Define phosphorylation
Addition of a phosphate group
How can you increase photosynthesis in greenhouses (artificially)?
- Pump in CO2 gas to supply for the dark stage
- Increase CO2 increases enzymes activity
What is the first stage of photosynthesis called?
Light dependent
Does the first stage of photosynthesis require light?
Yes
Where does the light dependent stage of photosynthesis take place?
Thylakoid membranes of chloroplast
