photosynthesis Flashcards
general symbol equation photosynthesis
6CO2 + 6H20 -> C6H12O6 + 6O2
use of chlorophyll
define photosynthesis
transformation of light energy into chemical energy in the form of organic compounds
2 stages of photosynthesis
light dependent reaction
light independent reaction
explain in detail stages of photosynthesis
LDR-
photolysis of water, h2o reactant o2 is the waste product
photoactivation
and more, where their products are used in LIR
LIR-
co2 is also added and used in calvin cycle to make glucose
describe structure of leaf
waxy cuticle
upper epidermis
palisade mesohpyll- packed chloroplasts
vascular bundle= xylem on top and phloem on bottom
spongy layer
lower epidermis; stomata and guard cells
describe chloroplast strucutre
outer memebrane
inner membrane
stroma (like matrix)
circular DNA
lamelae= “bridge””
thylakoid- thylakoid lumen + thylakoid membrane, many thylakoids make up a grana (or granum plural)
70s ribosome
what is inside thylakoid membrane
PSII
ETC
PSI
describe overall LDR
occur on the thylakoid membranes
photolysis of water
photophosphoralation
in: H2O and NADP+
out: O2 NADPH
describe overall LIR
occur in the stroma of the chloroplast
carbon fixation
calvin cycle
synthesis of carbohydrate
in: co2 NADPH
out: glucose phosphate NADP+
describe steps in LDR
- photoactivation of PSII- chlorophyll in PSII absorbs light, light energy taises the energy level of electrons in chlorophyll= photoactivation electrons in photosystem 2 are activated by light
- photolysis of water- photoactivated electrons are passed along membrane by electron carriers, electrons replaced through photolysis of water
hydrogen ions accumulate in thylakoid lumen oxygen is waste product - electron transport chain- energy from photoactivated electron is used to pump protons across thylakoid membrane
- photoactivation of PSI= same as step 1
5.NADPH production- NADP+ id reduced into NADPH
electrons are received by ferrodoxin (NADP reductase) and used to reduce NADP with a H ion
NADPH carried to LIR, conc gradient of H protons is maintained
electrons are replaced by electrons lost by PSII, as electrons used for reduction
- formation of electrochemical gradient- hydrogen ions accumulate in thylakoid space, generate high H ions concentration gradient
- chemiosmosis and ATP production chemiosmosis= diffusion of ions accross selectively permeable membrane through ATP synthase
flow of H ions through ATP synthase couples ATP and Pi to make ATP
what enzyme is nvovled in photosynthesis
rubisco
plant pigments
proteins that absorb wavelengths of visible light
what are the 3 plant pigments
chlorophylls (green)- most abundant pigment
-darker
-lighters
castenoids (yellow,orange)
-xanothophyll- yellow
-carotenes- orange
protective pigments- attract pollinators protect DNA from UV light
eg. anthocyanins (red, purple, blue)
wavelength of blue light
440- 485 mm
wavelength of green light
510-565 mm
wavelength of yellow light
565-590 mm
wavelength of red light
625-740 mm
rf value
distance travelled pigment/ distance solvent travelled
anthocyanins
attract insects for pollination by abosrbing light in the UV spectrum, serve as a sunscreen to protect plants from sun damage and provide protection against predators because of their foul taste
carotenoids and chlorphyll
both serve as light harvesting pigments in the photosynthetic processes of plants
action spectrum
this shows the rate of photosynthesis for all the wavelengths of light as a % of the maximum possible rate
involves all photosynthetic pigments= chlorophyll and accessory pigments (caretnoids/ xanthophyll)
describe action spectrum graph
does not start at x=0, violet/ blue has highest peak then drops at green- yellow color wavelength and then increases a bit to organe-red
x-axis= wavelength of light (mm)
y-axis= % of the max rate of photosynthesis
absorption spectrum
shows the absorbance of light by photosynthetic pigments for all wavelengths of light
describe absorption spectrum graph for chlorophyll
peak at violet and blue (highest) then flat for green and yellow and then increase for orange/ red
x-axis= wavelength of light (mm)
y-axis= % absorption of light
what conclusions can be drawn by overlaping action and absorption spectrum
both have same pattern pf absorbance and reflection
action spectrum has a lower absorbance in the green yellow wavelength ( min point lower) due to xanophyll
majority of action spectrum is performed by chlorophyll
accessory pigments play smaller role on the action spectrum
what are the two types of LDR that can happen
cyclic or non cyclic
describe non cylicc LDR
non cyclic photoactivation
involves PSII and PSI
produces oxygen NADPH and ATP
happens during regular enviornmental conditions
follows Z diagram
electrons lost by each PS are replaced by a different pathway
PSII= photolysis of water
PSI=PSII
describe cyclic LDR
cyclic photoactivation
involves only PSI
produces ATP
happens in enviornments with reduction light and/ or CO2
follows A diagram
decrease in photosynthesis (low glucose and low o2) reduces aerobic respiration reduces ATP formation
electrons lost by PSI return to PSI
emergency reaction for plants under stressful environemental conditions enables plants to ease ATP to survive until enviornment returns optimum conditions
describe cyclic LDR diagram
photons absorbed by PSI, electrons raised to higher energy state electron carriers carries the 2 electrons to another electron carrier, which carries them to ETC where ATP is produced, remaining electrons return to PSI
compare simply non cyclic and cyclic LDR
non- cyclic
source of electrons:
PSI=PSII
PSII= photolysis of water
destination of electrons
PSII=PSI
PSI=NADP reductase
products= useful- ATP NADPH
waste- O2
photosystems involved= PSII, PSI
cyclic
source of electrons
PSI
destination of electrons
PSI
products- useful- ATP
photosystems involved
PSI
