Topic 2.9: Photosynthesis Flashcards Preview

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Flashcards in Topic 2.9: Photosynthesis Deck (27)
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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



Definition of limiting factor

Factor nearest its minimum/furthest from its optimum that increasing it while maintaining other factors constant increases reaction rate