2.9 Photosynthesis Flashcards
What is photosynthesis?
The process where cells synthesise organic compounds from inorganic molecules in the presence of sunlight
What does photosynthesis require?
A photosynthetic pigment
What is an example of a photosynthetic pigment?
Chlorophyll
Where can photosynthesis occur?
Only in certain organisms eg plants and certain bacteria
What do photosynthetic organisms use to create chemical energy?
Light energy from the sun
What are the two ways that chemical energy can be used?
Directly by the organism
or
Used to synthesise organic compounds
How do animals consume the organic compounds?
As food
How do animals release the stored energy from organic compounds?
Via cell respiration
What is photosynthesis the reverse of?
Cell respiration
What type of synthesis is photosynthesis?
Anabolic
What is the electromagnetic spectrum?
The range of all possible frequencies of electromagnetic radiation
What are colours?
Different wavelengths of white light
What is the range of wavelengths of colours?
700nm - 400nm
Red to violet
What are the colours of the visible spectrum from longest to shortest wavelength?
Red
Orange
Yellow
Green
Blue
Indigo
Violet
Where does the sun emit its peak power?
In the visible region of the electromagnetic spectrum
What is the wavelength range of visible light?
400nm - 700nm
What is chlorophyll?
A green pigment found in photosynthetic organisms that is responsible for light absorption
What happens when chlorophyll absorbs light?
It releases electrons which are used to synthesise ATP
What does each different chlorophyll molecules have their own of?
Absorption spectra
Where does chlorophyll absorb light most strongly?
In the blue portion of the visible spectrum
Where does chlorophyll absorb light second most strongly?
By the red portion
Where does chlorophyll reflect light most strongly?
In the green portion of the visible spectrum
What are the two components of a typical chlorophyll molecule?
Chlorin ring and hydrocarbon tail
What does the absorption spectrum indicate?
The wavelengths of light absorbed by each pigment
What does the action spectrum indicate?
The overall rate of photosynthesis at each wavelength of light
What do pigments absorb as a source of energy for photosynthesis?
Light
There is a strong correlation between the cumulative absorption spectra of all pigments and what?
The action spectrum
Where are there two main peaks in the absorption and action spectra?
Large peak in the blue region
Smaller peak in the red region
Where does the absorption and action spectra display a trough?
In the green/yellow region
What are the two steps of the photosynthesis process?
Light dependent reactions and light independent reactions
What does the light dependent reaction convert light energy from the sun into?
Chemical energy (ATP)
What does the light independent reactions use the chemical energy to synthesise?
Organic compounds
During the light dependent reaction what results in the production of ATP?
Light being absorbed by chlorophyll
As well as chlorophyll what else absorbs light?
Water
During the light dependent reactions, what happens to the water that absorbs light?
It is split to produce oxygen and hydrogen
What is it called what light splits water?
Photolysis
What is released as a waste product during the light dependent reactions?
Oxygen
Where is oxygen released during the light dependent reaction?
From the stomata
What are used during the light dependent reactions?
Hydrogen and ATP
During the light independent reaction what is transferred to the site of the light independent reaction?
ATP and hydrogen
How is ATP and hydrogen carried to the site of the light independent reaction?
By NADPH
What combines with what to form complex organic compounds during light independent reactions?
Hydrogen combines with carbon dioxide
What does ATP do in light independent reactions?
Power anabolic reactions and fix carbon molecules together
What doe photosynthetic organisms benefit from to absorb light?
The combined action of many pigments
What is chromatography?
An experimental technique by which mixtures can be separated
What is the mobile phase of chromatography?
A mixture is dissolved in a fluid
What is the stationary phase of chromatography?
When the mixture is passed through a static material
What causes the mixture to separate in chromatography?
The different components of the mixture travel at different speeds
How do you calculate the Rf value?
distance component travels / distance solvent travels
What are the two most common techniques for separating photosynthetic pigments?
Paper chromatography and thin layer chromatography
What is paper chromatography?
Uses paper (cellulose) as the stationary bed
What is thin layer chromatography?
Uses a thin layer of absorbent which runs faster and has better separation
What does the law of limiting factors say about when a chemical process depends on more than one essential condition being favourable?
The rate of reaction will be limited by the factor that is nearest its minimum value
What are the three main favourable conditions photosynthesis is dependent on?
Temperature
Light intensity
Carbon dioxide concentration
What controls photosynthesis?
Enzymes
What are enzymes sensitive to?
Temperature fluctuations
Why does the reaction rate increase as temperature increases?
Reactants have greater kinetic energy and more collisions occur
What happens to the rate of photosynthesis when the experiment goes above a certain temperature and why?
It will decrease as enzymes begin to denature
What does chlorophyll absorb?
Light
What happens to the reaction rate as light intensity increases and why?
It will increase as more chlorophyll are being photo-activated
Why will photosynthetic rate plateau at a certain light intensity?
As all available chlorophyll are saturated with light
Does different wavelengths of light have different or the same effect on the rate of photosynthesis?
Different effects
What is the carbon dioxide involved in the fixation of in photosynthesis?
The fixation of carbon atoms to form organic molecules
What happens to the reaction rate when carbon dioxide concentration increases and why?
It increases as more organic molecules are being produced
Why will the photosynthetic reaction plateau at a certain concentration of CO2?
As the enzymes responsible for carbon fixation are saturated
How can photosynthesis be measured directly?
Via the uptake of CO2 or the production of O2?
How can photosynthesis be measured indirectly?
Via a change in biomass
What may influence levels of Co2 and O2?
The relative amount of cell respiration happening in the tissue
How can carbon dioxide uptake be measured?
By placing leaf tissue in an enclosed space with water
How can water free of dissolved carbon dioxide be produced?
By boiling and cooling water
What is produced when carbon dioxide interacts with water molecules and what is their impact?
Bicarbonate and hydrogen ions which changes the pH
What does increased uptake of CO2 by the plant do in the experiment with the leaf?
Reduce the amount in the solution and increase the alkalinity
What are the two instruments to measure carbon dioxide levels?
A probe and a data logger
How can oxygen production be measured?
By submerging a plant in an enclosed water filled space attached to a sealed gas syringe
What are the two ways an experiment can be measured when measuring O2 production?
A change in meniscus level on the syringe
or
the time takes for submerged leaf discs to surface
How can glucose production be measured?
By a change in the plants weight
What is required prior to measuring biomass and why?
The plant tissue to be completely dehydrated to ensure water content is not accounted for
What is an alternative method to measuring biomass that does not include measuring the weight?
To determine the change in starch levels
How can starch be identified?
Via iodine staining
How can starch be quantitated?
Using a colorimeter
What is the one significant source of oxygen gas in the known universe?
Biological photosynthesis
Before the evolution of photosynthetic organisms how was any free oxygen produced?
Chemically captured and stored
How long ago did photosynthetic organisms begin to saturate the environment with oxygen?
2.3 billion years ago
When photosynthetic prganisms began to produce oxygen where were there changes?
In the earth’s atmosphere
Oceans
Rock deposition
Biological life
What did earths oceans initially have?
High levels of dissolved iron
Why did earths oceans initially have high levels of dissolved iron?
Released from the crust by underwater volcanic vents
What happens when iron reacts with oxygen gas?
A chemical reaction to form an insoluble precipitate known as iron oxide
What happened when the iron in the ocean was completely consumed?
Oxygen gas started accumulating in the atmosphere
What was earths atmosphere like for the first 2 billion years?
Anoxic (oxygen free)
What is the current concentration of oxygen gas within the atmosphere?
Approximately 20%
What are the ocean deposits formed by dissolved iron and oxygen gas called?
Banded iron formations
What happens as banded iron formations deposition slowed in oceans?
Iron rich layers started to form on land due to the rise in atmospheric O2 levels
Why will you not find banded iron formations in sedimentary rock younger than 1.8 billion years old?
It reflects the the time when oxygen levels caused the near complete consumption of dissolved iron levels
What is free oxygen toxic to?
Obligate anaerobes
What may have wiped out obligate anaerobes?
Increase in O2 levels
What was a critical determinant to the evolution of aerobically respiring organisms?
Rising O2 levels
