Topic 6 Flashcards
What type of reaction is photosynthesis
Endothermic
Photosynthesis definition
The process by which plants manufacture carbohydrates from raw materials using energy from light
Autotrophs
They can make complex molecules from simple molecules
Producers
They can make their own food so are the first organism at the start of all food chains
Photosynthesis word equation
Carbon dioxide + water ———> glucose + oxygen
Balanced equation for photosynthesis
6Co2 + 6H20 ——> C6H12O6 + 6o2
Limiting factors of photosynthesis
Light
Temperature
Carbon Dioxide concentration
Temperature limiting factor
Effects how much kinetic energy the particles have, determines enzyme activity
Fewer successful collisions occurring between reactants and enzymes
Increased causes increased successful collisions over time
Too high - denature, active site changes shape
Light intensity limiting factor
The more light the faster the rate of photosynthesis
Will continue until some other factor prevents rate
Carbon dioxide concentration limiting factor
More carbon dioxide the faster the rate of photosynthesis
Trend will continue until other factor limits
What can the number of chloroplasts a plant has be affected by
Disease
Lack of nutrients
Loss of leaves
Light distance
The further away the light source the lower the rate of photosynthesis
As the distance increases teh light intensity reduces
Thus it is inversely proportional
Inverse square law
Inverse square law
Light intensity c— 1\distance 2
Light intensity practical
Change the distance of the light source from the plant
Root hair cells
Single cell extensions of epidermis cells in the root
Increased surface area to volume ratio
Increase rate of mineral ion absorption through active transport
High proportion of dissolved minerals gives it low water potential, causing a concentration gradient and allowing water to move in through osmosis
Phloem
Carry’s dissolved sugars (translocation )
Made of living cells
Has end walls
Has a two way flow
Xylem
Flow of water (transpiration)
No end walls
No living cells
One way flow
Walls thickened with lignin
Stomata
Stomata (specifically the guard cells ) control diffusion of gases in and out of leaves
They open and close in a daily rhythm
Opening stomata during the day
Maintains inwards diffusion of co2 and outward diffusion of oxygen
Allows outwards diffusion of water vapour
Closing during the night
Reduces rate if transpiration
Conserves water
Transpiration simple
The loss of water vapour from the parts of the plant that are above the ground
Occurs through evaporation of water at the surfaces of the springy mesophyll cells
Followed by diffusion of water vapour through the stomata
Large surface are means evaporation occurs rapidly
Transpiration in plants important
Water mover through xylem vessels in continuous transpiration stream via the stem in order to replace the water lost by transpiration
Due to cohesion the water in the xylem creates a continuous unbroken colum
This produces tension and pulls the water up into the xylem vessels
Factors affecting transpiration
Air movement
Humidity
Light intensity
Temperature
Air movement affecting rate of transpiration
High :
Airflow removes water vapour from the air surrounding the leaf which sets up a concentration gradient between the leaf and the air, increasing water loss
Humidity
When the air is humid it is saturated with more water meaning the concentration gradient is less, so less water is lost
Light intensity
When light intensity is high the stomata open allowing the water to be lost
Temperature
Particles have more kinetic energy so transpiration occurs at a faster rate as water molecules evaporate faster
Investigating transpiration
Bubble photometer
Rate of transpiration = distance moved by bubble divided by time
Limitations to potameter
Potometer has leak
The plant cutting has a blockage
The optometrist shows no change
