Bio 111 Photosynthesis

photoautotrophs

“light, self, feed;” use light and carbon dioxide to make sugar, they get energy into biological systems so the rest of us can use it

photosynthesis

photoautotrophs use light and carbon dioxide to make sugar; carbon dioxide is reduced to glucose and water is oxidized to oxygen

energy in photosynthesis equation

energy in glucose is high, energy in water is low (waste from respiration, is stable, holds energy molecules tightly) so needs input of energy (the sun)

respiration vs photosynthesis

reactants and products are opposite of respirationbut chemical pathways are not in reverse (photosynthesis biochem pathway is very different); plants do photosynthesis and respiration

photosynthesis- big picture

energy from sun is transferred into energy stored in NADPH and ATP, the stored energy is then used to synthesize sugar

NADPH

electron carrier

sugar

high energy molecule, can go into cellular respiration in mitochondrion so cells have usable energy in form of ATP

photosynthesis ETC

water is oxidized into oxygen by energy from the sun to boost the energy of electrons so they can enter photosynthetic ETC

Calvin Cycle

carbon dioxide reduced to glucose; products of ETC and used to fuel this reduction

chloroplast

powerhouse of plant, many layers and lots of surface area

outer membrane, inter membrane space, inner membrane, stroma, thylakoid, lumen

thylakoid

contain chlorophyll that absorb light 

light dependent reactions

convert light energy into chemical energy through pigments

chlorophyll

absorbs light energy through polar head, the nonpolar tail inserts into thylakoid membrane and anchors in thylakoid membrane to absorb light energy (done by exciting electrons)

electron excitement

light energy hits antenna pigments and excites electrons, this boost of energy pushes electrons from the gorund state to the excited state, the antenna pigments pass excitement to others, eventually get so excited they pass electrons into the ETC

transfer of energy

antenna pigments pass excitement to each other

photosystem

big complexes in thylakoid membrane that have lots of chlorophyll

reaction center

oxidized by light and the missing electron is replenished through reduction by water;

oxidation of reaction center

transferring energy between antenna chlorophylls to reaction center which passes the electrons to the ETC

reduction of reaction center

water is oxidized and passes a high energy electron (because hit with sunlight) which replenishes reaction center plate since missing electron

photosynthetic electron transport (PETC)

H2O is initial source of electrons (lower in energy than NADH/FADH2 which are initial source in RETC because holds electrons loosely), and the final electron acceptor is NADP+ which is higher in energy than the final product of RETC (H2O) because they are used to make sugar (which is high in energy so the carriers need to be high in energy too)

overall idea of PETC

electrons are passed from H2O to NADP+ and are energized by sunlight

PETC goal vs RETC goal

PETC- harness energy of sunlight and put into compounds (like sugar); makes sense that we start with something low in energy and end with something high in energy

RETC- suck energy out of organic molecules; makes sense that we start with something high in energy and end with something low

energy in PETC

moving electrons requires them to go to increasingly higher affinity molecules so they can snatch the electrons away, so at each step the electron energy decreases which is why they are zapped with sunligh

PSII- sunlight energy input to reduce H2O to O2

PSI- sunlight energy input #2 to give electrons energy boost so they can reduce NADP+ to make a high energy molecule (like sugar)

thylakoid membrane proton (H+) gradient

use energy of moving electrons to pump H+, so lots of H+ in thylakoid lumen → high H+ in lumen, low H+ in stroma, ATP synthase lets H+ go down the gradient to generate ATP thru oxidative phosphorylation

oxidative phosphorylation

transferring the energy stored in NADH/FADH2 gradients into a proton gradient, transferring the energy stored in the proton gradient into ATP, serves the second 2 energy goals

products required for Calvin Cycle

ATP and NADPH, both in stroma of chloroplast (Calvin Cycle is in chloroplast too)

initial source of electrons in respiration

NADH/FADH2

initial source of electrons in photosynthesis

H2O

initial source of energy in respiration

organic molecules

initial source of energy in photosynthesis

sun

electron donors in respiration

NADH/FADH2

electron donors in photosynthesis

H2O

moves electrons in respiration

complexes I, II, III, IV and coQ and cytoC

moves electrons in photosynthesis

PSII, PSII, and NADP+ reductase

electron acceptor in respiration

O2

electron acceptor in photosynthesis

NADP+

method of driving ATP synthesis in respiration

oxidative phosphorylation by ATP synthase

method of driving ATP synthesis in photosynthesis

oxidative phosphorylation by ATP synthesis

Calvin Cycle

inorganic carbon is reduced to carbohydrates

occurs in choroplast stroma, CO2, 3ATP, and 2NADHPH go in, Triose Phosphates, ADP, and NADP+ come out

basic idea of Calvin Cycle

energy of ATP and NADPH is used to make sugar (CO2 reduced to sugar)

is lowkey long and inefficient process to regenerate RuBP

3 steps of Calvin Cycle

carboxylation, reduction, and regeneration

carboxylation/fixation

CO2 from air is added to existing 5 C molecule, RuBP, by enzyme rubisco

rubisco

enzyme that adds CO2 to RuBP; most inefficient and mistake protein but also most common

RuBP

5 carbon molecule

reduction

energy of ATP and NADP+  used to make 3 carbon sugars “triose phosphates” because 5 carbon molecules are low in energy and need to be boosted

triose phosphates

high energy precursors that assemble to make glucose, only able to give up 1 of every 6 made each turn of cycle, and the remaining 5 are used to regenerate RuBP

regeneration

triose phosphate and ATP are used to regenerate RuBP (and then CO2 will be added to it)

how carbon flows among organisms

CO2 in air → turned into sugar by photosynthesis → goes thru biological systems:

1) stay in plant and become starch

2) plant makes starch and heterotrophs consume starch → glucose in cytoplasm → becomes exhaled CO2 by respiration

then cycle starts again

how electrons flows among organisms

water → NADPH by PETC → sugar by Calvin Cycle → NADH/FADH2 by stages I-III of respiration → back to H2O by RETC

how energy flows among organisms

sun → NADPH and ATP by PETC → sugar by Calvin cycle → NADH and FADH2 (ATP) by stages I-III of respiration → H+ gradient by RETC → ATP by ATP synthase

relationship between cellular respiration and photosynthesis

photosynthesis stores energy in organic molecules, and respiration releases it