Topic 2.9: Photosynthesis Flashcards
Definition of photosynthesis
Process by which cells synthesize organic compounds from inorganic molecules using light energy
Chemical equation of photosynthesis
6CO2 + 12H2O + Light => C6H12O2 + 6O2
Definition of electromagnetic spectrum
Range of all possible frequencies of electromagnetic radiation
Relationship between wavelength and energy
The shorter the wavelength, the greater the energy
Wavelength range of visible light
400 – 700 nm
Function of chlorophyll
Pigment responsible for the absorption of light and its conversion into chemical energy (ATP)
Light absorption and reflection of chlorophyll
a) Absorption of blue and red light most effectively
b) Reflection of green light more than other colors
Photosynthesis => Type of reaction
a) Endothermic
b) Anabolic
Steps in photosynthesis
a) Light dependent reactions
b) Light independent reactions
Purpose of light dependent reactions
Light is converted into chemical energy
What happens in light dependent reactions?
a) Light is absorbed by chlorophyll to produce ATP
b) Photolysis of water forms oxygen and hydrogen
Purpose of light independent reactions
Carbon compounds are made from chemical energy
What happens in light independent reactions?
ATP and hydrogen are fixed with carbon dioxide
Definition of chromatography
Experimental technique by which mixtures can be separated
Procedure of chromatography
a) A mixture is dissolved in a fluid and passed through a static material
b) The different components of the mixture travel at different speeds, causing them to separate
c) A retardation factor is calculated
Consequences of photosynthesis on Earth in Oceans
a) Oxidation of dissolved iron in water
b) Precipitation of iron oxide, creating banded iron formations
Consequences of photosynthesis on Earth in Atmosphere
a) Rise in oxygen concentration to 20%
b) Formation of ozone layer, protecting Earth from UV radiation
Limiting factors of photosynthesis
a) CO2
b) Light intensity
c) Temperature
CO2 as a limiting factor
a) CO2 is involved in the fixation of carbon to form organic molecules
b) Increasing CO2 concentration increases the rate of photosynthesis, until the enzymes involved in the Calvin cycle reach their saturation point and can no longer increase reaction rates.
Temperature as a limiting factor
a) Photosynthesis is controlled by enzymes, which are sensitive to temperature fluctuations
b) As temperature increases reaction rate will increase, as reactants have greater kinetic energy and more collisions result
c) Above a certain temperature the rate of photosynthesis will decrease as essential enzymes begin to denature
Light intensity as a limiting factor
a) Light is absorbed by chlorophyll, which converts the radiant energy into chemical energy (ATP)
b) As light intensity increases, reaction rate will increase since more chlorophyll are being photoactivated
c) At a certain light intensity photosynthetic rate will plateau, as all available chlorophyll are saturated with light
Ways to measure rate of photosynthesis
a) Measuring CO2 uptake
b) Measuring O2 production
c) Measuring Biomass
Measuring CO2 uptake
a) CO2 uptake can be measured by placing leaf tissue in an enclosed space with water
b) Water free of dissolved CO2 can be produced by oiling and cooling water
c) CO2 interacts with H2O molecules, producing bicarbonate and H+, which changes the pH
d) Increased uptake of CO2 by the plant will lower the concentration in solution and increase the alkalinity
Measuring O2 production
a) O2 production can be measured by submerging a plant in an enclosed water filled space attached to a sealed gas syringe
b) Any oxygen gas produced will bubble out of solution and can be measured by a change in meniscus level on the syringe
Measuring biomass
a) Glucose production can be indirectly measured by a change in the plant’s biomass (weight)
b) This requires the plant tissue to be completely dehydrated prior to weighing to ensure the change in biomass represents organic matter and not water content
Pigments in plants
Chlorophyll
Carotene
Xanthophyll
Definition of limiting factor
Factor nearest its minimum/furthest from its optimum that increasing it while maintaining other factors constant increases reaction rate
