Photosynthesis Flashcards
Statement 1: Joseph Priestley (1733-1804) in 1770 performed a series of experiments that revealed the essential role of air in the growth of green plants.
Statement 2: Priestley discovered oxygen in 1774.
Both are correct statements
Using a similar setup as the one used by……….. but by placing it once in the dark and once in the sunlight………….. (1730-1799) showed that………..is essential for photosynthesis
Priestley
Jan Ingenhousz
Sunlight
Assertion: it is only the green part of the plants that could release oxygen.
Reason: small bubbles were formed around the green parts while in the dark they did not
Both are correct and R is correct explanation of A
Statement 1: 1854 Julius von Sachs provided evidence for production of glucose when plants grow.
Statement 2: He found that the green parts in plants is where glucose is made, and that the glucose is usually stored as starch.
Both statements are correct
Statement 1: T.W Engelmann (1843 – 1909). Using a prism he split light into its spectral components and then illuminated a green alga, Cladophora, placed in a suspension of anaerobic bacteria.
Statement 2: bacteria accumulated mainly in the region of blue and red light of the split spectrum.
Statement 1 is incorrect and 2 is correct
Aerobic bacteria were used
The empirical equation representing the total process of photosynthesis for oxygen evolving organisms was then understood as:
CO2+ H2O + Light —————> [ CH2O] + O2
A microbiologist, Cornelius van Niel (1897-1985), who, based on his studies of purple (chromatium) and green(chlorobium) bacteria, demonstrated
2H2A +CO2 + light ———————> 2A + CH2O + H2O
O2 evolved by the green plant comes from H2 O, not from carbon dioxide.
True or false
True
Statement 1: There is a clear division of labour within the chloroplast.
Statement 2: The membrane system is responsible for trapping the light energy but not for the synthesis of ATP and NADPH.
Statement 1 is correct but statement 2 is incorrect
The membrane system is responsible for trapping the light energy and also for the synthesis of ATP and NADPH.
In stroma, enzymatic reactions synthesise sugar, which in turn forms………
starch
Colour
Chlorophyll a
chlorophyll b
xanthophylls
carotenoids
bright or blue green in the chromatogram
yellow green
yellow
yellow to yellow-orange
Statement 1: Light reactions or the ‘Photochemical’ phase include light absorption, water splitting, oxygen release but not the formation of high-energy chemical intermediates, ATP and NADPH.
Statement 2: Photosystem I (PS I) and Photosystem II (PS II). These are named in the sequence of their discovery, and not in the sequence in which they function
Statement 1 is incorrect and statement 2 is correct
Light reactions or the ‘Photochemical’ phase include light absorption, water splitting, oxygen release and the formation of high-energy chemical intermediates, ATP and NADPH.
PS I the reaction centre chlorophyll a has an absorption peak at……….hence is called……….while in PS II it has absorption maxima at………and is called……….
700 nm P700
680 nm P680
In photosystem II the reaction centre chlorophyll a absorbs 680 nm wavelength of …….. light causing electrons to become excited and jump into an orbit farther from the atomic nucleus.
red
This movement of electrons is uphill in terms of an oxidation-reduction or redox potential scale.
True or false
False
Downhill
Statement 1: lamellae of the grana have both PS I and PS II
Statement 2: stroma lamellae membranes lack PS II as well as NADP reductase enzyme.
Both are correct
Cyclic photophosphorylation also occurs when only light of wavelengths beyond………..are available for excitation.
680 nm
primary accepter of electron which is located towards the outer side of the membrane transfers its electron…………..
not to an electron carrier but to an H carrier.
Chemiosmosis requires
4 items
membrane, a proton pump, a proton gradient and ATP synthase.
Statement 1: immediately after light becomes unavailable, the biosynthetic process continues for some time, and then stops.
Statement 2: If then, light is made available, the synthesis starts again.
Both statements are correct
The use of radioactive………… by………… in algal photosynthesis studies led to the discovery that the first CO2 fixation product was a 3-carbon organic acid known as……..
14C
Melvin Calvin
3 phosphoglyceric acid
The studies very unexpectedly showed that the acceptor molecule was a 5-carbon ketose sugar –………..
ribulose bisphosphate (RuBP).
………….. is the most crucial step of the Calvin cycle where CO2 is utilised for the carboxylation of RuBP.
Carboxylation
Statement 1:Reduction involve utilisation of 2 molecules of ATP for phosphorylation and two of NADPH for reduction per CO2 molecule fixed.
Statement 2: 6 turns of the cycle are required for the formation of one molecule of glucose from the pathway.
Both statements are correct
The regeneration steps require………. ATP for phosphorylation to form RuBP
one
Hence for every CO2 molecule entering the Calvin cycle, 3 molecules of…….. and 2 of……..are required.
ATP NADPH
Statement 1: Plants that are adapted to dry tropical regions have the C4 pathway.
Statement 2: Though these plants have the C4 oxaloacetic acid as the first CO2 fixation product they use the C3 pathway or the Calvin cycle as the main biosynthetic pathway.
Both statements are correct
The bundle sheath cells may form several layers around the vascular bundles;
they are characterised by having(3 characters)
large number of chloroplasts
thick walls impervious to gaseous exchange
no intercellular spaces.
Statement 1: RuBisCO has a much greater affinity for CO2 when the CO2 : O2 is nearly equal. Statement 2: This binding is competitive. It is the relative concentration of O2 and CO2 that determines which of the two will bind to the enzyme.
Both statements are correct
RuBP instead of being converted to 2 molecules of PGA binds with O2 to form one molecule of……….. and……………… (2 Carbon) in a pathway called photorespiration
phosphoglycerate
phosphoglycolate
Green plants carry out ‘photosynthesis’, a………….process by which they use light energy to drive the synthesis of…….compounds.
physico-chemical
organic
Verigated leaf experiment is way to prove the importance of……… in photosynthesis
Light
Moll’s half leaf experiment is helpful in proving the importance of……… in photosynthesis
CO2
When H2S is used as hydrogen donor the what is observed
the ‘oxidation’ product is sulphur (green bacteria) or sulphate (purple bacteria) and not O2
Hence, he inferred that the O2 evolved by the green plant comes from H2O, not from carbon dioxide
Chloroplasts will be aligned with their flat surfaces parallel to the walls
At low light intensities or stressful situations
Chloroplasts would be aligned perpendicular to the incident light when
High light intensities
Statement 1: Grana lamella on its appressed membrane have both PS I and PS II
Statement 2: Non a pressed membrane of grana lamella have only PS II
Statement 1 is correct but 2 is incorrect
Non a press membrane has only PS I
Most abundant plant pigment in the world is
Chlorophyll A
Absorption is maximum at which wavelength
Blue
Blue is greater than Red
Action spectrum is maximum at which wavelength
Red
Red is greater than Blue
Wavelength (colour of light) at which chlorophyll a shows the maximum absorption
430nm
Another peak is at 660nm
Is there complete one-to-one overlap between the absorption spectrum of chlorophyll a and the action spectrum of photosynthesis
No
Since action spectrum is broader than the absorption spectrum. As the absorption spectrum is of chlorophyll an only and the action spectra includes all the other pigments as they also play role in photosynthesis.
If other pigments had no role then there would have been complete one to one overlap
Red drop effect
The quantum yield of oxygen evolution for ‘’far red’’ light of wavelengths greater than 680nm, indicating that far-red light alone is not efficient in driving photosynthesis
That means photosynthesis decreases as the wavelength goes beyond 680nm or red region
Emmerson enhancement effect
If we give a plant lights from two different monochromatic light simultaneously then the photosynthesis rate is enhanced as compared to giving those lights independently
Assertion: Though chlorophyll is the major pigment responsible for trapping light, other thylakoid pigments like chlorophyll b, xanthophylls and carotenoids, which are called accessory pigments are very essential
Reason: These absorb light and transfer the energy to chlorophyll a Thus enable a wider range of wavelength of incoming light to be utilised for photosyntesis and also protect chlorophyll a from photo-oxidation.
Both are correct and correct explanation
Statement 1: Photosynthesis is under the influence of several factors, both internal (plant) and external.
Statement 2: The plant factors include the number, size, age and orientation of leaves, mesophyll cells and chloroplasts, internal CO2 concentration and the amount of chlorophyll which are dependent on the genetic predisposition and the growth of the plant.
Both are correct
Statement 1: When several factors affect any [bio] chemical process, Blackman’s (1905) Law of Limiting Factors comes into effect. This states
Statement 2: If a chemical process is affected by more than one factor, then its rate will be determined by the factor which is nearest to its minimal value: it is the factor which directly affects the process if its quantity is changed.
Both are correct
There is a……….. relationship between incident light and CO2 fixation rates at low light intensities
linear
Light saturation occurs at……per cent of the full sunlight.
10
…………… is the major limiting factor for photosynthesis
Carbon dioxide
The concentration of CO2 is very low in the atmosphere between……..per cent
0.03 and 0.04
Increase in concentration of CO2 upto………. per cent can cause an increase in CO2 fixation rates; beyond this the levels can become damaging over longer periods.
0.05
Statement 1: At low light conditions C3 group responds to high CO2 conditions
Statement 2: At high light intensities C4 plants show increase in the rates of photosynthesis
Both are incorrect
At low light neither group responds to high CO2 conditions and at high light intensities both the C3 and C4 show increase in rates of photosynthesis
C4 plants show saturation at about………… while C3 responds to increased CO2 concentration and saturation is seen only beyond……….
360 µlL-1
450 µlL-1
Current availability of CO2 is limiting for the ……… plants
C3
Statement 1: The fact that C3 plants respond to higher CO2 concentration by showing increased rates of photosynthesis leading to higher productivity has been used for some greenhouse crops such as tomatoes and bell pepper.
Statement 2: They are allowed to grow in carbon dioxide enriched atmosphere that leads to higher yields.
Both are correct
Statement 1: The dark reactions being enzymatic are thus temperature controlled
Statement 2: Light reactions are not affected by the temperature
Statement 1 is correct and 2 is incorrect
Light reactions are also temperature sensitive but they are affected to a much lesser extent
Tropical plants have a lower temperature optimum than the plants adapted to temperate climates.
False
Tropical plants have a higher temperature optimum than the plants adapted to temperate climates.
List effects of water stress
Causes the stomata to close hence reducing the CO2 availability.
Makes leaves wilt, thus, reducing the surface area of the leaves and their metabolic activity as well.
