/
Principles of Photosynthesis
Save to my account
Sign up
Principles of Photosynthesis
Principles of Photosynthesis
Study
1
Question
How do autotrophic organisms like plants and cyanobacteria convert light energy into chemical energy?
Page 1
Answer
These organisms use photosynthesis to transform light energy from the sun into the chemical energy stored in intracellular organic compounds.
2
Question
What distinguishes oxygenic photosynthesis from anoxygenic forms regarding its byproducts?
Page 1
Answer
Oxygenic photosynthesis releases oxygen as a byproduct of water splitting, whereas anoxygenic forms do not produce oxygen.
3
Question
Which organic compounds are typically used by photosynthetic organisms to store converted chemical energy?
Page 1
Answer
Converted chemical energy is stored within the bonds of carbohydrates such as sugars (glucose, fructose, sucrose) and starches.
4
Question
How do some bacteria like purple bacteria perform photosynthesis without producing oxygen?
Page 1
Answer
They use bacteriochlorophyll to split hydrogen sulfide as a reductant instead of water, releasing sulfur instead of oxygen.
5
Question
What unique method of energy production is utilized by Archaea such as Halobacterium?
Page 1
Answer
They use retinal and microbial rhodopsin to absorb light and create a proton gradient to directly synthesize adenosine triphosphate (ATP).
6
Question
Where are photosynthetic pigments specifically located in the cells of plants compared to cyanobacteria?
Page 1
Answer
In plants, pigments are held inside chloroplasts, while in cyanobacteria, they are embedded directly in the plasma membrane.
7
Question
How does photosynthesis fundamentally differ from cellular respiration in terms of carbon transformation?
Page 2
Answer
Photosynthesis reduces carbon dioxide to carbohydrates, while cellular respiration oxidizes carbohydrates back to carbon dioxide.
8
Question
What is the general chemical equation for photosynthesis as first proposed by Cornelis van Niel?
Page 3
Answer
\[\text{CO}_2 + 2\text{H}_2\text{A} + \text{photons} \rightarrow [\text{CH}_2\text{O}] + 2\text{A} + \text{H}_2\text{O}\]
9
Question
What are the two distinct stages of the photosynthetic process?
Page 3
Answer
Photosynthesis occurs in light-dependent reactions that capture energy and light-independent reactions that capture and reduce carbon dioxide.
10
Question
How do the photosynthetic membranes of bacteria differ from those in eukaryotic plants and algae?
Page 3
Answer
Bacterial membranes are often folded into thylakoids or vesicles within the cell, whereas eukaryotes possess specialized chloroplast organelles.
11
Question
What is the structure and function of the aqueous fluid known as stroma?
Page 3
Answer
The stroma is the aqueous fluid enclosed by the chloroplast membrane where the light-independent reactions take place.
12
Question
What are the stacks of thylakoids located within the chloroplast stroma called?
Page 3
Answer
The stacks of thylakoids are called grana, and they serve as the site for light-dependent reactions.
13
Question
Which pigments besides chlorophyll are used by plants and algae to absorb light?
Page 4
Answer
Plants and algae use accessory pigments such as carotenes, xanthophylls, phycocyanin, phycoerythrin, and fucoxanthin.
14
Question
Where in the leaf anatomy does the majority of photosynthesis take place?
Page 4
Answer
Most photosynthesis occurs in the palisade mesophyll cells, located beneath the transparent epidermis layer.
15
Question
What is the function of the waxy cuticle on the surface of a leaf?
Page 4
Answer
The cuticle is water-resistant to prevent excessive evaporation and decreases the absorption of harmful ultraviolet light.
16
Question
What occurs during the process of photolysis in light-dependent reactions?
Page 4
Answer
A water molecule is split to regain electrons lost by chlorophyll, which simultaneously releases oxygen as a waste product.
17
Question
What is the overall equation for the light-dependent reactions in green plants?
Page 4
Answer
\[2\text{H}_2\text{O} + 2\text{NADP}^+ + 3\text{ADP} + 3\text{P}_i + \text{light} \rightarrow 2\text{NADPH} + 2\text{H}^+ + 3\text{ATP} + \text{O}_2\]
18
Question
How do red algae adapt their photosynthetic action spectrum for deep water environments?
Page 4
Answer
They use pigments like phycoerythrin to absorb blue-green light, which penetrates deeper into the water than red light.
19
Question
What distinguishes the non-cyclic from the cyclic form of light-dependent reactions?
Page 5
Answer
The non-cyclic reaction produces both ATP and NADPH, while the cyclic reaction generates only ATP at Photosystem I.
20
Question
What role does the chemiosmotic potential play in the light-dependent reactions?
Page 5
Answer
It is a proton gradient generated across the membrane that powers ATP synthase to produce ATP through photophosphorylation.
21
Question
Which molecules replace the excited electrons lost from the reaction center (P700) of Photosystem I?
Page 5
Answer
The lost electrons are replaced by transfer from plastocyanin, which obtains its electrons from Photosystem II.
22
Question
What catalytic structure is responsible for the oxidation of water in Photosystem II?
Page 6
Answer
The oxygen-evolving complex, containing four manganese ions and one calcium ion, binds and oxidizes water molecules.
23
Question
What are the primary products of the light-independent reactions (Calvin cycle)?
Page 6
Answer
The Calvin cycle uses NADPH and ATP to produce three-carbon sugars, which are then combined into sucrose and starch.
24
Question
What is the role of the enzyme RuBisCO in carbon fixation?
Page 6
Answer
RuBisCO captures CO2 from the atmosphere and combines it with the five-carbon sugar ribulose 1,5-bisphosphate (RuBP).
25
Question
How is ribulose 1,5-bisphosphate (RuBP) regenerated in the Calvin cycle?
Page 6
Answer
Most (five out of six) of the glyceraldehyde 3-phosphate molecules produced are used to regenerate RuBP for the cycle to continue.
26
Question
Why do plants close their stomata in hot and dry conditions, and what is the consequence?
Page 7
Answer
Stomata close to prevent water loss, but this decreases CO2 and increases O2 levels, leading to wasteful photorespiration.
27
Question
How does the C4 carbon fixation process differ from the standard C3 process?
Page 7
Answer
C4 plants physically separate initial CO2 fixation in mesophyll cells from the Calvin cycle in bundle sheath cells.
28
Question
What is the primary carboxylation enzyme used in C4 and CAM plants?
Page 7
Answer
The enzyme phosphoenolpyruvate (PEP) carboxylase is used to fix carbon dioxide into four-carbon organic acids.
29
Question
How do CAM plants like cacti temporally separate the processes of carbon dioxide fixation?
Page 7
Answer
They fix CO2 at night when stomata are open and perform the Calvin cycle during the day with closed stomata.
30
Question
What is the mechanism of alarm photosynthesis in calcium-oxalate-accumulating plants?
Page 8
Answer
Calcium oxalate crystals function as dynamic carbon pools that release CO2 via an oxalate oxidase enzyme during stress.