51 Questions
What is the primary function of photosynthesis in plants?
Building sugars
What is the main purpose of cellular respiration in plants?
Extracting energy stored in sugars
What type of work does ATP primarily perform in living cells?
Chemical Work
Why are plants green?
Chlorophyll reflects green wavelength of light
What happens to the free energy in a closed system?
Reactions eventually reach equilibrium
What is the main reason why living systems do not reach equilibrium?
Energy still comes in, matter can't enter or exit
What is the primary reason for plants to use light energy to build organic molecules?
Stores energy in chemical bonds
What is the critical process in both respiration and photosynthesis involving electron transfer?
Redox Reactions
What is the water potential of pure water in an open beaker at room temperature?
Zero
What does the solute potential of a solution depend on?
Number of dissolved molecules
What supports plant cells and tissues, especially young, non-woody tissues?
Turgor pressure
What is the main driving force for the transport of water and minerals from roots to shoots via the xylem?
Transpiration
What is the function of Casparian strip in the endodermis?
Blocks apoplastic transfer of minerals
What allows water to withstand transpiration according to the Cohesion-Tension Hypothesis?
Hydrogen bonding of water molecules
What is the main mechanism for the transport of xylem sap from roots to leaves?
Bulk flow
What is the result of increased surface tension during transpiration according to the Cohesion-Tension Hypothesis?
Pulls water from surrounding cells and air spaces
What is the driving force for the movement of xylem sap against gravity?
Cohesion-tension mechanism
Which structural adaptation helps reduce evaporative water loss in plants adapted to arid climates?
Thicker waxy cuticle
What is the primary component of phloem sap in flowering plants?
Sucrose
What is the function of companion cells in the phloem?
Provide needed proteins to sieve tube cells
What triggers the opening and closing of stomata?
Changes in turgor pressure
What drives the movement of phloem sap from source to sink?
Positive pressure flow
What is the primary cause of guttation in plants?
Continued water uptake in roots
What prevents vessel elements and tracheids from collapsing under negative pressure in the xylem?
Thick secondary walls
What is the main factor determining the rate of transpiration in plants?
Relative humidity
What is the primary mechanism for sugar loading into sieve-tube elements in the phloem?
Active transport with protons via cotransport
What is the driving force for the movement of water in the xylem?
Cohesion and adhesion
What is the primary pathway for water loss in plants?
Stomata
What did W. Engelmann experiment with in 1883?
Filamentous algae and different light wavelengths
Who discovered purple sulfur bacteria using H2S in photosynthesis?
C.B van Neil (1930)
What are the two stages of photosynthesis?
Light-dependent reactions and light-independent reactions
Why does chlorophyll appear green?
It absorbs light mainly in the red and blue part of the visible spectrum
Which molecules are included in photosynthetic pigments?
Reaction center chlorophyll a, chlorophyll b, and carotenoids
Where does light energy transduction occur?
In photosystems I and II, consisting of chlorophyll and pigment molecules
What does cyclic phosphorylation in PSI produce?
Additional ATP for the Calvin cycle
What is the practical application of blocking photosynthetic reactions?
To prevent weed growth
What does the Calvin Cycle involve?
Carbon fixation reactions producing a 3-carbon sugar called PGAL
What happens to triose phosphate in the Calvin Cycle?
Converted to starch, exported from chloroplast, and used in cellular respiration
Who identified the carbon flow in the Calvin cycle and its three stages?
Melvin Calvin
What is the consequence of low CO2 levels in plants?
Increase in photorespiration
Under what condition do mutant Arabidopsis plants without photorespiration survive?
High CO2 levels
What are the characteristics of CAM photosynthesis?
Fixes CO2 at night and conserves water
What are the adaptations to reduce losses to photorespiration?
Carbon dioxide concentrating mechanisms and spatial/temporal segregation
What is the key factor in plant distribution and transport in vascular plants?
Water
What is the consequence of stomata closing due to water stress?
O2 build up and depletion of CO2
What is the process of photorespiration?
Consuming O2 while producing CO2
What is the main characteristic of incomplete/facultative CAM plants?
Recycling CO2 from respiration under drought stress
What is the involvement of C4 photosynthesis?
CO2 concentrating mechanisms and spatial segregation of photosynthetic cells
What is the consequence of shoot and root architecture in resource acquisition and transport in vascular plants?
Enhanced resource acquisition and transport
What are the characteristics of CAM photosynthesis in extremely arid environments?
High water use efficiency rates
What is the consequence of chloroplast avoidance and chemiosmosis in C4 photosynthesis?
Increased cost
Study Notes
Photosynthesis and Resource Acquisition in Plants
- Rubisco enzyme catalyzes the reaction between RUBP and CO2, fixing CO2 80x faster than O2 and can also react with oxygen
- Low CO2 levels lead to photorespiration, consuming O2 while producing CO2, and occurring in light
- Stomata closing due to water stress causes O2 build up, depleting CO2 and favoring photorespiration
- Mutant Arabidopsis plants without photorespiration can only survive under high CO2
- Adaptations to reduce losses to photorespiration include carbon dioxide concentrating mechanisms and spatial/temporal segregation
- C4 photosynthesis involves CO2 concentrating mechanisms and spatial segregation of photosynthetic cells
- CAM photosynthesis fixes CO2 at night, conserves water, and is simple, with morphological features minimizing water loss
- Incomplete/Facultative CAM plants can recycle CO2 from respiration and occur only under drought stress
- CAM has high water use efficiency rates in extremely arid environments
- C4 is more costly than C3 and CAM, involving chloroplast avoidance and chemiosmosis
- Shoot and root architecture, as well as microbial mutualists, are key in resource acquisition and transport in vascular plants
- Water is a major factor in plant distribution, with important properties including cohesion, adhesion, and surface tension, and transport routes including apoplastic, symplastic, and transmembrane routes
Test your knowledge of photosynthesis and resource acquisition in plants with this informative quiz. Explore the role of enzymes like Rubisco, the impact of low CO2 levels on photorespiration, and the adaptations plants use to reduce losses. Dive into the different types of photosynthesis, such as C4 and CAM, and their unique mechanisms. Gain insights into the importance of water in plant distribution and the role of shoot and root architecture in resource acquisition.
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