3.2 Photosynthesis Flashcards
What is the equation for photosynthesis ?
Carbon dioxide + Water = Glucose + Oxygen
Where does photosynthesis take place ?
In chloroplasts
What do chloroplasts contain that enable photosynthesis ?
Photosynthetic pigments which absorb light energy at different wavelengths
How can photosynthetic pigments be separated ?
Chromatography
How are pigments identified in chromatography ?
By calculating Rf values to compare to values of known pigments
How is Rf value calculated ?
Distance moved by pigment from origin % Distance moved by solvent front from origin
What is absorption spectrum ?
A graph that shows how much light is absorbed by a pigment at different wavelengths of light
What does a low absorbency of light mean ?
It has been reflected
What does a high light absorbency mean ?
High rate of photosynthesis
What is an action spectrum ?
Graph which shows the rate of photosynthesis at different wavelengths of light
What is the benefit of a plant containing more than 1 pigment ?
Able to absorb more wavelengths of light = More light energy for photosynthesis
What does Englemann’s experiment determine ?
Which wavelengths of light were used most for photosynthesis
How is Englemanns experiment carried out ?
Algae was placed in suspension of motile aerobic bacteria, the light was refracted using a prism into rainbow colours
What regions of the spectrum cause most photosynthetic activity ?
Blue and red
What is light harvesting ?
The process of photosynthetic pigments absorbing light energy
How is light harvesting achieved ?
By antenna complexes in the thylakoid membranes
What is the name of the cell in Englemann’s experiment ?
Spirogyra cell
What happens in light dependent cyclic photo phosphorylation ?
Light energy produces ATP
No splitting of water
Only product is ATP
Electrons keep travelling around
Where does non cyclic photo phosphorylation occur ?
Chloroplasts
Which photo system comes first in non cyclic photo phosphorylation?
2
What is photolysis of water ?
Splitting of H2O into 2 electros, 2 H+ and 1/2 O2
What are the products of non cyclic photo phosphorylation ?
NADPH2
ATP
Oxygen
Where does the light independent stage (Calvin cycle) occur ?
Stroma of chloroplast
What does the light independent stage use ?
Products of light dependent stage
What are the 2 main minerals required in photosynthesis and plants ?
Nitrogen and magnesium
What does nitrogen deficiency cause ?
Reduced growth and chlorosis
What does magnesium deficiency cause ?
Chlorosis
How is nitrogen processed in a plant ?
Taken up by roots as nitrates with are transported in the xylem and added to triose phosphate to produce amino acids which are transported in the phloem and used to make proteins and nucleic acids
What is magnesium required for ?
By all tissues and to produce chlorophyll and activate ATPase
Where is magnesium transported ?
Xylem
What are the 4 limiting factors of photosynthesis ?
Carbon dioxide concentration
Light intensity
Temperature
Water
What does extremely high light intensity cause ?
Damage to photosynthetic pigments which decreases rate of photosynthesis at different
What is the light compensation point ?
The light intensity at which a plant has no net gas exchange as the volume of gases used and produced in respiration and photosynthesis are equal.
What does a lack of water cause ?
Cell plasmolysis
Stomata closing
Wilting
Affected physical functions
Reduced carbohydrate production
What is the algal balls experiment measuring ?
The rate of photosynthesis by measuring the colour change of a pH indicator
What causes an increase in pH in algal balls experiment ?
CO2 absorption from the solution where aquatic organisms photosynthesise
What happens when CO2 dissolves in water ?
Carbonic acid produced disassociates releasing hydrogen ions, causing pH to lower
CO2+H20 = H2CO3= H+HCO3
What causes pH indicator to change colour in algal balls experiment ?
Photosynthesis removes CO2 from a solution so H+ ion concentration decreases and pH increases
What colour represents low pH/ acidic ?
Yellow
What colour represents high pH or alkaline ?
Blue
How is a leaves large flat surface an advantage for photosynthesis ?
Allows absorption of maximum light energy
How does a thin leaf (lamina) benefit photosynthesis ?
Allows CO2 and sunlight to reach mesophyll cells
How are stomata pores an advantage for photosynthesis ?
Allow CO2 to enter the leaf
How are air spaces in the spongy mesophyll layer an advantage for photosynthesis ?
They allow CO2 to diffuse through the leaf
What is the benefits of the cubical and epidermal layers being transparent with thin cell walls ?
Light can penetrate through to the mesophyll layer
What are the benefits of palisade cells being cylindrical and elongated to the surface of the leaf ?
Allows more cells to feet in the leaf and light only has to penetrate through cuticular and 1 epidermal cell before reaching the palisade cell
What are the advantages of a palisade cells large vacuole ?
Pushes chloroplast to the outer layer of the cell resulting in no shading so greater light intensity
Why do chloroplasts have a large surface area ?
To absorb maximum light intensity
Why do chloroplasts move within the palisade layer ?
To get optimum light intensity
