Photosynthesis Flashcards
What is the distribution of photosynthesis globally?
50% in oceans and 50% on land
What was the great oxygenation even which occurred 200 billion years ago?
involved the evolution of cyanobacteria which produces O2 via photosynthesis
Whats the difference between heterotrophs and autotrophs?
heterotrophs can’t produce their own food, can only consume whereas autotrophs cant produce their own food and consume
Name some components of cyanobacteria
- thylakoid membrane
- rubisco as a carbon fixer
- membrane and DNA
What is endosymbiosis?
when originally living bacteria engulfed by a new cell in a phagosome
What is the result of endosymbiosis?
- chloroplasts as the outer and inner membrane form a double membrane
What are photons?
small packages of energy
what is the equation for photon energy?
E= hc/y
What are pigments?
molecules that can absorb photons e.g chlorophyll
What is the role of photosystem 1?
it harnesses light to obtain and excite electrons from water
What is the chloroplast electron transport chain also known as?
non cyclic phosphorylation
What occurs during phosphorylation?
- split water using light (hydrolysis)
- creates an excited electron
- produces NADPH
What are the 2 different ways in which organisms harness energy?
- no cyclic route; protons pumped, NADPH
- cyclic route; more protons pumped
Name the 3 stages of light independent reactions?
- fixation
- reduction
- regeneration
role of teh stomata?
gas exchange
what is the problem that stomata causes for plants?
need to be open to take in CO2 and to remove O2
need to be closed to preserve H2O
What is the c4 pathway?
It is the first step in extracting carbon from carbon dioxide to be able to use it in sugar and other biomolecules
What is the c4 molecule?
the 4 carbon molecule which is the first product of this type of fixation
What is photorespiration like as a pathway?
it is a wasteful pathway that occurs when the calvin cycle enzyme rubisco acts on oxygen rather than CO2
What does CAM stand for when referring to a type of plant?
Crassulacean Acid metabolism
When does photorespiration occur?
when plants close their stomata (leaf pores) to reduce water loss.
Why are C4 and CAM pathways more beneficial than photorespiration?
they work by ensuring RUBISCO always encounters high concentrations of CO2, making it unlikely to bind to O2
How did the C4 and CAM pathways evolve?
natural selection
What are C4 plants?
plants in which light dependent reactions and calvin cycle are physically separated
Where does LDR occur in C4 plants?
mesophyll cells
Where does teh Calvin cycle occur in C4 plants?
in bundle-sheath cells
How do CAM plants separate LDR and CC?
between day and night
What occurs at night in CAM plants?
open stomata, allowing CO2 to diffuse into leaves, fixing CO2 by PEPC and then converted to malate
How do CAM plant photosynthesize in the daytime?
organic acids are transported out of the vacuole and broken down to release CO2 which enters the calvin cycle
Name 3 ways in which you can measure photosynthesis?
- measure co2 consumption
- measure increase in mass
- measure O2 production
What do photosynthetic rates depend on? (3)
light, temperature and CO2 levels
Name the 3 ways in which chloroplasts recharge ATP?
- electron transfer chain
- electrochemical gradient
- ATP synthase
