Module 1 Flashcards
(46 cards)
Compare a terrestrial environment to an aquatic environment for plant life
Aquatic environment:
- buoyancy
- abundant water
- moderate temperatures
- filtered light
Terrestrial environment:
- No buoyancy
- Scarce water
- Extreme temperatures
- Excess light
What stores chemical energy in plants?
Chemical emergy is stored in starch and is released when carbon in starch is oxidized
What is NADPH?
Energy currency - stored as reducing power and electrons
Fuels anabolic reactions (synthesizing amino acids)
Explain chloroplast anatomy
- Double membrane
- stroma is liquid inside
- Stacks of thylakoids called call grana - chlorophyll embedded here
- inside of thylakoid is called the lumen
Explain both reactions in CO2 during photosynthesis
- Light energy is used to split water (oxygen byproduct)
- Dark reaction where CO2 is fixed into organic carbon
Explain light reaction of photosynthesis
- Light is absorbed into PSII, splits water, releasing electrons
- New electron pushes electron out of PSII, which them moves down the ETC,
- Electrons in PSI, absorb more light energy and flow down - used to form NADPH
What is chemiosmosis?
Different ion concentrations and/or electric potentials across a semi-permeable membrane = potential source of energy
Uses proton motive force
Describe Calvin benson cycle
Light reaction produces ATP and NADPH - use them to fix C
- Use RuBisCo to stick RuBP to CO2, splitting it into two PGA
- Reduce PGA into sugars using ATP and NADPH
- Recycle the RuBP
Why does photorespiration happen?
RuBisCoo can bind to oxygen as well as CO2
- If it binds to oxygen, it only creates on PGA and a PGlycolate (toxic)
- Plant then has to use energy ATP to break down PGlycolate
How does temperature impact RuBisCo binding?
- High temperature means low CO2:O2 - high photorespiration
- Low temperature menas hgih CO2:O2 ratio - photosynthesis
What are the two main challenges in photosynthesis?
- How to take in CO2 while minimizing water loss?
- How to maximize carboxylation and minimize oxygenation by RuBisCo
Explain the mechanism of C4 plants
C4 is separate steps in space - CO2 is carboxylated twice
- CO2 is first bound by PEP (PEP can’t bind oxygen), then PEP moces into the bundle-sheath cell
- PEP releases CO2 here for RuBisCo
This is water efficient because stomata don’t need to be open as much
Dark reaction is far inside the leaf, far from the stomata
Where might we find C4 plants more frequently?
C4 in warmer areas - higher water stress areas
Is there a cost to using PEP?
PEP is an extra cost - uses an ATP for regeneration
Explain mechanism of CAM plants
Open stomata at night - less hot so won’t lose as much water
- PEP system still takes place, but at night time to uptake CO2
- Calvin cycle happens during the day, taking CO2 from PEP
What is the light compensation point? How does it differ in sun vs shade plants?
Point where rate of respiration is equal to rate of photosynthesis
It is much lower in shade plants
What are 4 morphological adaptations of shade leaves?
- thinner leaves
- more chlorophyll per reaction centre
- light focusing via convex epidermal cells
- solar tracking
What is photo-oxidation?
- Process that bleaches things in the sun
- Causes cell damage and death
How can excess energy be dissipated in high light environment?
Physiological adaptation - too dry to open stomata
‘non-photochemical quenching”
What are 4 adaptations for light avoidance?
- Chloroplast hiding
- Leaf folding
- Vertical orientation of plant minimizes light absoprtion at midday
- Production of photo-protective pigments
How does temperature impact RuBisCo - Carbon affinity?
With incresing temperature, RuBisCo-Carbon affinity declines
How do leaves cope with temperature in increase dissipation
Larger Surface Area - higher heat loss
As water leaves, heat is reduced
What are 4 “fates” of fixed carbon?
- energy
- growth
- storage
- exchange
How can we prove that the phloem is made of living cells?
“Girdle” tree - remove outside living layer
Roots die because they aren’t receiving any nutrients - there is also a bulge above the girdled area that is made of accumulated nutrients
