photosynthesis Flashcards
What phase of photosynthesis is more affected by temperature?
The light-independent phase is more affected by temperature than the light-dependent phase.
This is because it is controlled by enzymes such as rubisco, which can be denatured at high temperatures.
Where are photosynthetic pigments located?
Photosynthetic pigments are located in the photosystems within the thylakoid membranes.
Why are pigments important in photosynthesis?
Pigments absorb light/photons, exciting electrons to higher energy levels.
Accessory pigments pass energy to primary pigments in the reaction centre.
How do water-dwelling plants differ in light absorption compared to land plants?
Water-dwelling plants absorb shorter wavelengths of light because some wavelengths do not reach their depths.
What structures do plant chloroplasts contain?
Plant chloroplasts have many thylakoids with intergranal lamellae between them, and they also contain starch grains.
What is hydrolysis?
Hydrolysis is the process of using water to break bonds in molecules, breaking them down into smaller molecules.
What should you always identify in respiration or photosynthesis?
Always identify where in respiration or photosynthesis the process occurs (e.g., in the Calvin cycle).
What is an autotroph?
An autotroph can make organic molecules from inorganic molecules like carbon dioxide.
What is a heterotroph?
A heterotroph relies on and digests organic molecules made by another organism.
How is light harvested in chloroplast membranes?
Light is harvested by primary and accessory pigments in a photosystem/antenna complex, where a photon of light energy is absorbed, exciting an electron.
The photon is passed from one pigment to another and then to chlorophyll a in the reaction centre.
What do chloroplasts contain for membrane formation?
Chloroplasts contain fat droplets for membrane formation and pigment synthesis.
What is the pH difference between the thylakoid space and the stroma during the light-dependent stage?
The thylakoid space has a lower pH than the stroma due to a higher concentration of hydrogen ions.
This occurs as hydrogen ions are moved into the thylakoid space by electron carriers.
H+ ions produced in lumen +diffuse down the conc gradient across the thylakoid memebrane through ATP synthas , which generate ATP via proton motive force
What happens if substances interfere with the electron transport chain?
Plants may die as –> no cyclic/non cyclic photophosphorylation–> no ATP or reduced NADP produced–>halting the Calvin cycle–>no GP to TP–> no TP to RuBP–>no fixation of CO2 –>no production of substrates like glucose for respiration –> autotropic nutrition stops –> no repiratory substrate to respire
What should be ensured when using leaf discs to measure photosynthesis rates?
Ensure discs are the same size, cut w/ same cutter so that they have the same SA, cut from the same part of the leaf, leaves used are from the same part of the plant so same amount of pigment, test tubes same distance from light , and that conditions like light intensity (carry experiment in a dark room , only 1 light source)and CO2 levels are controlled(in excess so not limiting) , same vol of indicator, repeats + identify anomalies
Why do chlorophyll pigments not absorb green light?
Chlorophyll pigments reflect green light, which cannot be used in photosynthesis.
In a sample exposed to green light, there would be no photosynthesis as –> no light dependednt reaction –> no photolysis –>no CO fixation –>some CO2 producing during respiration –> which would decr pH of the sample
Where does the Calvin cycle take place?
The Calvin cycle takes place in the stroma of the chloroplast.
What does TP regenerate in the Calvin cycle?
TP regenerates ribulose bisphosphate (RuBP) to continue CO2 fixation for forming hexose sugars and other organic molecules.
What occurs during photorespiration?
In photorespiration, oxygen is used and carbon dioxide is produced, involving the Calvin cycle and Rubisco.
