questions Flashcards
photosynthesis traps light energy and uses it to convert CO2 and water into another substance, what is this substance?
carbohydrates
Light energy from the sun is converted into chemical energy. Which process uses this chemical energy to synthesize organic compounds?
photosynthesis
which molecule acts as a catalyst for the reaction that incorporates CO2 into organic compounds in the calvin cycle.
Rubisco
which molecule oxidized water in photosystem 2
water
how do CAM plants avoid photorespiration
Fixing carbon in the form of malic acid in the night
which statement about photorespiration is true: It slows the calvin cycle, it catlyzes O2 instead of CO2, it uses ATP
It slows the calvin cycle
which organelle is the site of photorespiration
chloroplast
what is light used for in light reactions of photosynthesis
- Excite electrons
- To synthesize NADPH and ATP.
- Split water molecules (photolysis)
Spatial separation (C4) vs temporal separation (CAM)
- C4 Plants (Spatial Separation): C4 plants, like corn, keep their stomata closed during the day to reduce water loss. They capture CO₂ in one cell (mesophyll), convert it into malate, and then transport it to another cell (bundle-sheath) where it’s used in the Calvin cycle to make sugars. This separation of steps across different cell locations is called spatial separation.
- CAM Plants (Temporal Separation): CAM plants, like cacti, open their stomata at night to save water. They capture CO₂ at night and store it until the daytime, when it’s used in photosynthesis with the stomata closed. This separation of steps based on time is called temporal separation.
Certain marine algae are able to live in low light, at depths of more than 100 m. These algae appear almost black deep under water, but usually appear red when brought back to the surface.
a. Would you expect these species to contain more or less chlorophyll than green algae? Why?
These deep-water algae would have more chlorophyll than green algae because they need to absorb more light in low light conditions to produce energy. More chlorophyll helps them capture as much light as possible.
Certain marine algae are able to live in low light, at depths of more than 100 m. These algae appear almost black deep under water, but usually appear red when brought back to the surface.
b. Would you expect these species to perform photosynthesis more efficiently under a green light source or a red light source? Explain your reasoning.
These algae would perform photosynthesis better under a green light source. Since they live deep underwater where red light is absorbed by water, their pigments are not adapted to using red light for energy. They reflect red light, which means it can’t be used for photosynthesis. However, their pigments are more suited to using green light, even though they receive less of it underwater.
Certain marine algae are able to live in low light, at depths of more than 100 m. These algae appear almost black deep under water, but usually appear red when brought back to the surface.
c. things tend to look bluish underwater because water absorbs red light more effectively than blue light. How might this fact help account for the characteristics of the deep-water species of algae?
Deep-sea algae can use blue light better than red light for photosynthesis because water absorbs red light more. They may appear red because they reflect red light, which they aren’t adapted to use for photosynthesis.
How would these processes be affected if the enzyme NADP+ reductase was inhibited?
a. Non-cyclic ATP synthesis
- Non-cyclic ATP synthesis (ATP production) wouldn’t be much affected.
- But, NADP+ wouldn’t be reduced to NADPH, so the production of this important electron carrier would stop.
How would these processes be affected if the enzyme NADP+ reductase was inhibited?
b. Cyclic ATP synthesis
No electrons enter NADP reductase during cyclic ATP synthesis so it would have no affect
How would these processes be affected if the enzyme NADP+ reductase was inhibited?
c. Calvin cycle
The calvin cycle requires NADPH to supply energy for reactions, without NADPH reductase in light dependent reaction no NADPH will enter the calvin cycle impeding this process.
Diuron is a herbicide that inhibits photosystem 2, what does this mean for a plant?
If Diuron blocks Photosystem 2:
- Photosystem 2 can’t split water, so no oxygen is released.
- Fewer electrons enter the electron transport chain (ETC), and there are fewer protons in the lumen.
- This slows down the light-dependent reactions, producing less ATP.
- Less NADP+ is reduced to NADPH, which slows the Calvin cycle and reduces glucose and ATP production.
Define C4 plants, where are they found, why do they exist?
C4 plants are plants that have adapted to hot environments by using a special method to maintain CO2 levels while saving water.
- They keep their stomata closed more often to prevent water loss in the heat.
- They convert oxaloacetate to malate, which releases CO2 to enter the Calvin cycle and produce sugars.
Define photorespiration
Photorespiration is an unwanted process that reduces sugar production in photosynthesis.
- In hot conditions, guard cells close to conserve water, which increases O2 levels and decreases CO2 intake.
- In the Calvin cycle, the enzyme Rubisco binds with O2 instead of CO2, causing RuBP to be oxidized instead of carboxylated.
- This slows down the Calvin cycle and reduces sugar production because O2 competes with CO2 for Rubisco’s active site.
Can autotrophs live without heterotrophs
Yes, autotrophs can live without heterotrophs. They make their own food and energy through processes like photosynthesis. Even without other organisms, they can decompose to return nutrients to the soil, staying independent.
Do plants need cell respiration to function?
Yes, plants need cellular respiration to function. They constantly grow and repair, which requires energy. Through cellular respiration, plants convert glucose (from photosynthesis) into ATP, providing the energy they need.
BONUS
Who invented light independent reactions CALVIN CYCLE
Melvin Ellis Calvin
What is the full name for RuBp
Ribulose 1,5- bisphosphate
What is the pigemtns that makes leaves oranges
Carotenoids
True or false:
The reactions of the Calvin cycle take place in the thylakoid membranes of chloroplasts
Corrected: The reactions of the Calvin cycle take place in the stroma of chloroplasts.
False
True or false
Some processes of photosynthesis can occur without sunlight
True
True or false
Light-dependent reactions take place in the thylakoid membranes of chloroplasts
True
True or false
The splitting of water into electrons, protons, and oxygen gas involves photosystem I
The splitting of water into electrons, protons, and oxygen gas involves photosystem II.
False
True or false
Melvin Calvin found that PGA and starch were produced within the first 5 s of photosynthesis in Chlorella
True
True or false
In a Cy plant, the Calvin cycle usually takes place in the bundle-sheath cells, which are found in the leaves of the plant.
True
True or false
Rubisco is highly efficient at fixing CO2
Rubisco is not highly efficient at fixing CO2 due to its tendency to also fix oxygen.
False
True or false
Photosynthesis can occur only in the chloroplasts of eukaryotic cells.
Photosynthesis can occur in the chloroplasts of eukaryotic cells and in some prokaryotic cells like cyanobacteria
False
