Photosynthesis - Bio 102

where energy comes from

the sun

where photosynthesis occurs

the chloroplasts in the green parts of the plants

where the chloroplasts live

mesophyll

structure of a chloroplast

• outer and inner membrane

• contain chlorophyll

stack of membrane in chloroplasts

granum

multiple stacks of membranes in a chloroplast

grana

individual membrane in a stack

thylakoid

space in between the grana

stroma

equation for photosynthesis

6CO2 + 6H2O → (light energy) 6O2 + C6H12O6

equation for cellular respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O + chemical energy

photo

light

synthesis

to put together

why we need activated carriers

to store the light energy for times when the sun is not out

activated carriers in photosynthesis

• ATP

• NADPH

two major stages of photosynthesis

• light reactions

• dark (light independent) reactions

why chlorophyll is green

• they absorb every color except for green

• absorbs blue and red, but not green and yellow - they reflect it instead

photosystems

protein complex in the thylakoid membrane that contains chlorophyll

• allow light energy absorbed by chlorophyll to be harnessed rather than wasted

characteristic of chlorophyll

• amphipathic

• polar head - porphyrin ring with Mg atom in the center

• hydrophobic tail - this helps anchor chlorophyll in the thylakoid membrane

reaction center

place where the special pair resides

first step of light reaction

light hits chlorophyll in photosystem II and bounces around until it hits a special pair of chlorophyll molecules and releases an electron

how we replace the electron in photosystem II

break apart 2H2O molecules and transform it into O2 and 4H+ to release electrons

goal of photosystem II

generate ATP

where the electron goes after it leaves photosystem II

plastoquinone

where plastoquinone takes the electron

cytochrome b6-f complex

process that takes place in cytochrome b6-f complex

cytochrome attempts to balance out the charge of the electron by passing protons through it

• charge difference drives these protons against their gradient into the thylakoid space

ATP synthase

takes the abundance of protons in the thylakoid space and uses the energy they produce going down their gradient (into the stroma) to transform ADP into ATP

where the original electron goes after it goes through cytochrome b6-f complex

plastocyanin

where plastocyanin takes the electron

photosystem I

what occurs in photosystem I

gathers light and goes through the same process as photosystem II, except it gains the electron from the pathway rather than breaking down H2O

where photosystem I passes the electron

ferredoxin

where ferredoxin transfers the electron

ferredoxin NADP reductase

ferredoxin NADP reductase

uses the power from the electron to turn NADP into NADPH

end goal of photosystem I

produces NADPH

inputs of light reaction

• water

• light

• NADP+

• ADP

outputs of light reaction

• ATP

• NADPH

• O2

stomata

how plants take in carbon dioxide

when stomata are open

they open at night because this allows less water to evaporate

• this means that the light reaction and dark reaction occurs at different times which is why we need activated carriers, to keep the energy

calvin cycle

another name for the dark reaction

3 stages of the calvin cycle

• carbon fixation

• reduction

• regeneration of RuBP

inputs of the dark reaction

• ATP

• NADPH

• CO2

outputs of dark reaction

• 3 carbon sugar

• ADP

• NADP+

carbon fixation

• takes 3 RuBP

• breaks apart 3 CO2 to add the carbons to RuBP

• creates 3 6-carbon molecules each with 2 phosphates (using rubisco)

• this immediately breaks into 6 3-carbon molecules each with one phosphate

  • called 3-phosphoglycerate (3PG)

reduction

• start with 6 3PG molecules

• uses 6 ATP to phosphorylate the 3PG and turn it into 6 1,3-biphosphoglycerate molecules (these each have 3 carbons and 2 phosphates)

  • releases 6 ADP

• then uses 6 NADPH to transform the 6 1,3-biphosphoglycerate molecules into 6 glyceraldehyde 3-phosphate molecules (G3P)

  • releases 6 NADP+ and 6 phosphates

regeneration of RuBP

• 5 G3P (one left to be turned into sugar) gets reorganized with the help of 3 ATP molecules to get turned into 3 RuBP molecules

  • releases 3 ADP

when rubisco is most active

when pH of stroma is high

affects of the presence of protons

more acidic, low pH

affects of lack of protons

more basic, higher pH

when the pH of the stroma is high

when cytochrome pumps protons from the stroma to the thylakoid space

• in the daytime