Cellular Energetics Notes Part 3 PDF

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TOPIC: CELL ENERGETICS NOTES—PART 3 Chapter 10: Photosynthesis Aim: How Do Plants Utilize Light Energy for Photosynthesis? I. Overview of Photosynthesis A. Energy Transformation: Light energy into chemical energy B. Chemical equation 1. Overall reaction light 6 CO2 + 12H2O → C6H12O6 + 6 O2 + 6H2O chlorophyll 2. Net reaction/equation light 6CO2 + 6H2O → C6H12O6 + 6 O2 chlorophyll it’s the reverse of respiration allows organic material to be turned into inorganic material light energy drives chem bonds-> excites electrons to form bonds -> make glucose molecules 6 oxygens produced as waste products all organisms carry out respiration all eukaryotic organisms carry out respiration plants carry it out too plants are self sufficient recycling oxygen and carbon dioxide base of energy pyramid highest biomass the glucose is either used by plant to make atp or oxygen is released into atmosphere which animals take in when plants r eaten, the glucose is taken in if plant lost this ability, they are able to take light energy and turn it into chem energy tp drive cellular activity C. Occurs in the chloroplast originated by endosymbiosis features that explain it: double membrane , own dna, own ribosomes, divide on own, make own proteins they're independent cells within a larger cell

double membrane can produce the conc gradient differences can produce this which drives and fuels atp production chloroplast manipulate aspects of membrane to do the same thing they carry out chemiosmosis to make atp needed to store in glucose bonds photosynthesis is 2 main reactions

Two sets of reactions 1. Light dependent reactions require light, water,chlorophyll occur in thylakoids release oxygen produce ATP, NADPH occur in window of sunlight availability reverse of krebs aka calvin cycle starting material: water, light (absorbed by chlorophyll which is a molecule embedded in the inner chloroplast membrane) it's the green pigment that absorbs light and it's found within chloroplasts the inner membrane of the chloroplasts is called thylakoid membrane light dependent membrane occur in it water is oxidized into oxygen and hydrogen oxygen produced immediately water is the electron donor electrons are extracted from water to fuel the electron transport chain to make more glucose water is oxidized into oxygen ‘products; atp and electron carrier used to help form bonds in glucose later on aka NADPH p stands for photosynthesis these coenzymes are use to donate hydrogens to form essential bonds once starting material is there and sufficient amt gets converted into atp and nadph, it can

proceed w calvin cycle which needs the products of the light dependent reaction which is energy and electrons cALVin cycle turns, nadph and atp get oxidized difference: calvin cycle occurs in stroma which is empty space between thylakoid and outer membrane chloroplast membrane thylakoid membrane is the folding ins sacks of pancakes the grana stacks: increase surface area so max atp and nadph can be made to fuel the most calvin cycle reactions and make most glucose

2. Light independent reactions (Calvin Cycle or Carbon Fixation Phase) require ATP, NADPH, CO2 occur in the stroma produce organic molecules *******occur 24/7

D. The Leaf - Adaptation for Photosynthesis structure of plant allows photos to occur the leaves absorb the sunlight chloroplasts are not in all plant cells, only in leaf structure influences function dif layer of cells

mesophyll layer- where the photosynthetic cells are photosynthetic portion of the leaf 2 dif layers in it: 1. palisades layer: high photo layer. most amt is happening here 2. spongy layer: photo cells are spread out which allows for air spaces. oxygen is produced and there needs to be space for diffusion into and out o plant cell one major transport factor that influences water moving is transpiration rate (water exiting leaves) this occurs on very hot days at high rates the pores open and water escapes so the plant can take in carbon dioxide through the pores (stoma) of the leaf they open and close because of guard cells depending on potassium ion concentration and water, the guard cells get turgid or placid so the stoma open or close they are on the underside of a leaf this is for a typical leafy plant not all plants have this structure the vascular tissues are the xylem and phloem the vascular bundle is those tubes which allow for water to keep moving up towards leaf so photosynthesis can occur the dermal layer is the epidermis it’s like skin layer provides protection for the plant through the cuticle layer (waxy layer on leaf surface) it’s waxy bc the wax prevents the plant from desiccating (letting excess water be released) normal diffusion and osmosis will not occur all over the cells because the wax has lipids in it. that is why water cannot escape plant adaptation occurred over time. first the photo organisms were the algae or simple single celled organisms in water aquatic organisms gave rise to terrestrial organisms and the plant structure is the #1 group of species that have the most adaptations to combat land factors for plant to move from water to terrestrial environments, they have the most adaptations that enable this (like roots, root hairs, wax, strict rigid plant cell walls to grow against gravity)

every body system in plant is example of adaptation bc its on land. same for plant reproduction

Shape of leaf - broad, thin for light absorption Cuticle- waxy layer - prevents water from evaporation Epidermis- protection, not photosynthetic Mesophyll- photosynthetic tissues = palisades & spongy layers -------palisades layer - most photosynthetic - top, many long cells ------spongy layer - air spaces for diffusion of O2, CO2, H2O Vascular bundle= xylem (water) and phloem (sugar) Bundle sheath- covers the vascular bundle- not photosynthetic Stoma- openings for CO2 to enter, O2 and water to be released Guard cells -regulate opening/closing of stoma

scientists over time had many hypotheses about why plants can sustain life all on their own how do they get their nutrients?

II. Experimental Evidence A. van Helmont (1600)--substance of plants came from water not soil something from soil is being removed and taken in it wasn't food from soil though plants were potted in soil and as time went off, they noticed plant was growing larger and bigger the soil’s mass never changed so the plants were not absorbing nutrients directly from soil and taking it in

sp the only thing they noticed that wasn't there anymore was the water wasn't there day after day B. Joseph Priestly (1771)--plants restored air damaged by animals if an insect or normal organism that wasnt photo would die in airtight jar they polluted the air in the jar and it wasn't useful but in same setup, the plant continued to survive and so did the organism C. T.W. Engelmann (1882)--used spirogyra (green algae) and aerobic bacteria to demonstrate the role of wavelengths of light depending on what wavelengths of light, not all wavelengths were utilized by the bacteria D. F.F. Blackman (1905)--role of light and 2 sets of reactions (light dependent and independent) 2 defined sets of reactions and certain stages of what was happening where E. C.B. Niel (1930)--used purple sulfur bacteria to discover water is split, oxygen is released, and Hydrogen fixes with carbon dioxide to form organic compounds water is being split and that's how oxygen was released into environment

III. Nature of Light A. Radiant energy, part of the electromagnetic spectrum

green isn't used by plants. plants don't absorb it so they reflect it, that's why they look green light is emitted from sun. theres the visible light spectrum (only light energy that's utilized by plants as energy that they can harvest and convert into chemically stored energy)

outside that range, there's other light

B. Two components 1. Wavelength (inverse to frequency) how long that exposure is of the full turn of the light it’s inversely proportional to frequency the shorter the wavelength, the quicker they are received the longer the wave, the slower they are received the violets are short wavelength but high frequency they get received quicker by cells/chemicals, etc reds have longer wavelengths so don't get received as quickly 2. Energy Particles - photons, inversely proportional to wavelength (ie. longer the wavelength, less energy) wavelength have photons which are energy particles. they are inversely prop to wavelength the longer the wave, the less the energy bc the exposure takes longer to be received not all photons are absorbed by pigments in plants that can receive them light energy is important bc electrons within the pigment molecules, when photons are received, they excite those electrons they are used to fuel energy production UV rays are cancerous. they cause skin cancer bc the skin cells are exposed to the uv rays and absorb them this is esp bad bc of the hole in the ozone layer which allows other light such as uv to enter they hve v short wavelengths of light = high frequency =high energy photons it’s like pinball machines against dna in cells that receive them dna gets damaged and broken -> cells start dividing out of control and can’t regulate how they grow and repair little cancer cells form

even x rays are bad high photon of energy

C. Only the visible wavelengths of spectrum are useful to life to excite electrons to higher level without destroying molecules. they have the perf energized amt to excite electrons IV. Nature of pigments A. Pigment - molecule that absorbs a specific wavelength of light equal to the energy needed to raise its outer electron to next higher level of energy = excited state/electron each pigment molecule is dif plants have several pigment molecules - good adaptation each pigment has its own wavelength/frequency it utilizes best more pigments -> more of visible light spectrum is can absorb the pigment contains the electrons that will get excited ****the freq & wavelength that pigment likes best is directly proportional to energy required to excite electron **when elec are excited, they become unstable and jump , causing electron transport chain which starts chemiosmosis -> proton gradient

B. Each pigment has a unique absorption spectrum= absorption pattern of a pigment to various wavelengths of light using a spectrophotometer if u took out all of pigments of plants u can summarize the colors of light it uses the most green is underutilized

C. Action Spectrum = Defines the relative effectiveness of different wavelengths of light on a light requiring process When used with an absorption spectrum, identifies which pigments are most effective. when is the most active within the plant

D. Chlorophyll a 1. Chlorophyll a - reaction center of photosynthesis the main one chlorophyll b to 2. Part of complex of proteins and antennae pigments called a photosystem embedded in the thylakoid membrane 3. Absorbs light of blue and red wavelengths, which excites its outer electron to higher, less stable level, and transfers it to ETC, i.e. light energy converted into chemical energy 4. Antennae pigments absorb other wavelengths of light and transfer energy to chlorophyll a (resonance transfer) green bc it reflects green light carotenoids are other pigments the carotenoids are the longer dashed line primary ranges of absorption are blue and red plants tend to change colors during year orange, red, brown, die changes in fall-days are shorter, temp changes chlorophyll and other pigments are proteins -the temp changes manipulates prot structure slightly and the decrease in temp causes pigments to become more rigid and not be able to utilize light energy the first ones to break down and become too rigid to absorb light energy of chlorophylls the various carotenoids are left they really absorb the blues if chlorophyll breaks down then that whole spectrum isn't absorbed and is reflected, so leaves turn into yellows, oranges, and reds then temps decrease more and the pigments are being slightly altered and not enough light energy is absorbed to create enough glucose to keep leaf cells living and they break off

chlorophyll a has the direct electron that has to get excited to start ETC which is the light dependent reaction the system that absorbs light energy is the photosystems in etc there's 2 systems: a complex of proteins w their embedded pigments in them the inner membrane of chloroplasts so this system is a protein embedded in the thylakoid membrane it’s the first and midway protein complex

reaction center is chlorophyll a antenna pigments absorb energy but it isn't the electron in their pigment that gets donated they absorb light energy and move it over to reaction center or chlorophyll a gets excited and donates its electron the reaction center is chlorophyll a which is the first primary electron donor an acceptor picks it up and takes it thru thylakoid membrane the photons of light energy are absorbed by antenna pigments the reds and blues provide sufficient photon energy excite the outer electron of chlorophyll a once it donates electron due to being excited, the electron must be replaced it's replaced by the electron donor in the chemical reaction which is water water is oxidized

Aim: How is the Light Dependent Stage of Photosynthesis Accomplished? I. Two Stages of Photosynthesis A. Light Reactions = Light Dependent Reactions 1. Absorption of light energy by chlorophyll a (making materials needed to fuel bonds made between carbon dioxides) 2. Conversion of light energy into chemical energy by electron transfer 3. Chemiosmosis and Photophosphorylation of ATP 4. Photolysis = 2 H 2O splits into 4 H+ + 4 e- + O2 (waste product) 5. Products that are used in next stage: ATP and NADPH 6. Occur in thylakoids/grana the transferring of electrons causes the proton gradient to be formed chemiosmosis and photophosphorylation are used in photosynthesis

water provides more electrons for light to excite more and fuel more atp light energy -> stored (chem) energy

B. Light Independent Reactions = Carbon Fixation Reactions = "Dark" Reactions 1. Use ATP for energy from light reactions 2. Temperature dependent because of enzymes used 3. Calvin Cycle to produce organic compounds 4. Occurs in stroma cyclic process of creating organic compounds calvin cycle is the reverse of krebs cycle take carbon dioxide and turn them into organic compounds temp is very important bc of the enzymes used. they are v sensitive to temp changes

II. Light Dependent Reactions A. Involve 2 Photosystems in thylakoid membranes = Photosynthetic Unit 1. Each consists of chlorophyll a molecule = reaction center, and antennae pigments (carotenoids, chlorophyll b) 2. Photosystem II (P680) occurs first (absorbs average wavelength 680nm) 3. Photosystem I (P700) (absorbs average wavelength 700nm) located second. 4. Each photosystem is associated with short ETC which transfers electrons. it is 2 etc-electron transport chains few dif proteins involved 2 sep photosystems (complex of proteins, and the proteins are pigments) they are absorbing photons of light they differ om avg wavelength of light they are absorbing electron carriers carry electrons past proton pumps so we can make atp this is important bc the energy is required to make a glucose molecule an additional enzyme is attached to the first of the 2 photosystems and the enzyme is a watersplitting enzyme and water’s electrons are harvested and replaced @ reaction center there's 2 photosystems found in etc but photosystem 2 occurs before photosystem 1 sometimes the light dependent reactions are also called non-cyclic photophosphorylation phosphorylation is adding on a phosphate group the energy required to add the phos comes from photons the adp gets phosphorylated and that show atp is made

photosystem 2, proton pump, photosystem 1, special protein embedded in thylakoid membrane (atp reductase)

ss electrons get excited by light energy, they're sos unstable that they quickly get moved to mobile carrier which moves it to etc between p2 and p1, it goes thru proton pump which allows for proton gradient to b e formed halfway thru the light dependent reaction, the proton gradient was made chemiosmosis is occurring only halfway thru this reaction the protons are being pumped from stroma to thylakoid space since the membrane is selectively permeable, thats why pump must be used -> established gradient which fuels atp synthase atp synthesis is considered to occur between p2 and p1 as electron moves thru the fist etc, it lost some of its enery when picked up by p1. it gets reexcited by absorbibgm ore photons of light energy a t thi new phase , it gets picked by by 2nd electron mobil ecarrier and compeletes etc an light deepdenent reactions at completion , the electorns get accepted by NADP+ it also accepts the excess h ydrogen ions bc those electrons associated w the hydrogens r usedin calvin cycle to add to the C and O of CO2 NADP turned into NADPH

B. How Photosystems Convert Light to Chemical Energy 1. Plants use PII (P680) then PI (P700) to produce ATP and NADPH 2. Process is called Non-Cyclic Photophosphorylation bc electron does not come back to where they originally started the ancestral photosynthetic bacteria did not utilize this noncyclic process but the original process was cyclic as organisms evolved, the noncyclic became the more complex and efficient way of harvesting energy from light universal trend in life a. Path of electron ends up in NADPH b. Electrons are replaced from photolysis (splitting of water) (water is the electron DONOR) 3. Reaction center chlorophyll a donates light-energized electrons to primary acceptor in ETC chlorophyll a is reaction center which donates 1st electron series of redox reactions once chlorophyll a becomes oxidized and released its electron, it is short 1 electron water is then the electron donor for the rest of the photosynthetic reactions water gets lysed (split) so electrons can be harvest and replace chlorophyll a’s reaction center waer provides more electrons-> it becomes oxidied into oxygen oxygen is teh oxidized form of water oxygen is a waste prodcut oxygen isnt a full waste produc for plants. they use some of it for cellular respiration and release the excess

4. Electrons from electron donor (ex. water for PII) replaces electron transferred. C. Chemiosmosis occurs in the ETC between P680 & P700 1. Proton gradient formed inside thylakoid space 2. ATP synthetase channels allow H+ back into stroma 3. Energy released is captured in ATP in stroma 4. This is photophosphorylation the atp synthase isnt embedded in middle of etc, embedded a little further down

the electrons dont move thru it even thqwo atp synthesis is associated between p2 and p1, atp synthase protein isnt embedded in there the proton gradient gets established which fuels atp synthesis D. Electrons excited in P700 transferred to short ETC 1. No chemiosmosis, no H+ pumps 2. Electrons transferred to NADP+, which picks up H+ to form NADPH 3. NADPH is used in the Calvin Cycle materials needed to fuel calvin cycle aremade atp and nadhp

Chemiosmosis in a chloroplast - Non-cyclic photophosphorylation even thoough atp synthase isnt emeddded between p2 and p1, its assumed atp has still been synthesixed due to proton gradient p2 is associated w short etc that makes atp p1 is associated w short etc that makes nadph cakvin cycle islight independent

Aim: How is the Light Independent Stage of Photosynthesis Accomplished? I. Light Independent Reactions aka (Carbon Fixation Reactions) (Calvin Cycle) ("Dark" reactions) fxing carbon to hydrogens A. Occurs in stroma of chloroplast the empty space between outer membrane and thylakoid membrane B. Requires ATP and NADPH produced from light reactions or else no hydrogen or electorn or energy available C. Cyclic, because it regenerates starting compound, RuBP (ribulose bisphosphate) the enzyme that s used is RuBisCo adds carbons to rubp

D. Reductive - ADDS H (NADPH is oxidized) to CO2 to form organic cmpds E. Ca...