PHOTOSYNTHESISPHOTOSYNTHESISChapter 6 Chapter 6

https://www.youtube.com/watch?v=uixA8ZXx0KU

The main form of energy from the sun is in the form of electromagnetic radiation

Visible radiation (white light) used for photosynthesis

Remember : Remember :

ROY G. BIV?ROY G. BIV?

pigment a compound that absorbs light different pigments absorb different wavelengths of white

light.

chlorophyll is a pigment that absorbs red & blue light so green is reflected or transmitted.

Chlorophyll is located in the Chlorophyll is located in the thylakoid thylakoid membranesmembranes

So, So, Plants are green because the green wavelength Plants are green because the green wavelength is reflected, not absorbed.is reflected, not absorbed.

Why are plants green?

2 types of chlorophyll2 types of chlorophyll Chlorophyll Chlorophyll aa – involved in – involved in light reactionslight reactions

Chlorophyll Chlorophyll bb – assists in capturing light – assists in capturing light energy – energy – accessory pigmentaccessory pigment

CarotenoidsCarotenoids – accessory pigments – – accessory pigments – captures more light energy captures more light energy RedRed,, orange orange & & yellowyellow

The electromagnetic wavelengths and the The electromagnetic wavelengths and the wavelengths that are absorbed by the wavelengths that are absorbed by the chlorophyllchlorophyll

Photosynthesis is - Photosynthesis is -

conversion of light energy into chemical conversion of light energy into chemical energy that is stored in organic compounds energy that is stored in organic compounds (carbohydrates > glucose)(carbohydrates > glucose)

Used by autotrophs such as:Used by autotrophs such as: PlantsPlants AlgaeAlgae Some bacteria (prokaryotes) Some bacteria (prokaryotes)

glucose - energy-rich chemical produced through photosynthesis C6H12O6

Biochemical pathwayBiochemical pathway – series of reactions – series of reactions where the product of one reaction is where the product of one reaction is consumed in the nextconsumed in the next

E.g. photosynthesis product is glucose which is E.g. photosynthesis product is glucose which is used in cellular respiration to make ATPused in cellular respiration to make ATP

(carbohydrate)

Photosynthesis equation

Light energy

6CO2 + 6H2O C6H12O6 + 6O2

Chlorophyll

Reactants: Carbon dioxide and water

Products: : glucose and oxygen which is a glucose and oxygen which is a byproductbyproduct

Where does Where does photosynthesis take photosynthesis take

place?place?Mainly occurs in the Mainly occurs in the leaves:leaves:

a.a.stoma - poresstoma - pores

b.b.mesophyll cellsmesophyll cells

StomaMesophyllCell

Chloroplast

Stomata (stoma)Stomata (stoma)Pores in a plant’s cuticle through Pores in a plant’s cuticle through

which which water vaporwater vapor and and gasesgases (CO(CO22 & O & O22)) are exchanged are exchanged between the plant and the between the plant and the atmosphere.atmosphere.

Guard CellGuard CellCarbon Dioxide (CO2)

Oxygen (O2)

Found on the underside of Found on the underside of leavesleaves

StomStomaa

ChloroplastChloroplast

OrganelleOrganelle where where photosynthesisphotosynthesis takes takes place.place.

GranumThylakoid

Stroma

Outer Membrane

Inner Membrane

Thylakoid stacks are connected Thylakoid stacks are connected togethertogether

PartsPartschloroplastschloroplasts – membrane organelle that absorbs – membrane organelle that absorbs

light energylight energyThylakoidsThylakoids – flattened sacs contain pigment - – flattened sacs contain pigment -

chlorophyllchlorophyllGranaGrana ( (pl: pl: granum) – layered thylakoids (like granum) – layered thylakoids (like

pancakes)pancakes)StromaStroma – solution around thylakoids – solution around thylakoidsStomataStomata – pore on underside of leaf where O – pore on underside of leaf where O22 is is

released and COreleased and CO22 enters enters

Energy for Life on EarthEnergy for Life on Earth

Sunlight Sunlight is the ULTIMATE is the ULTIMATE energy for all life on Earthenergy for all life on Earth

Plants store energy in the Plants store energy in the chemical bonds of sugarschemical bonds of sugars

Chemical energy is released Chemical energy is released as as ATPATP during during cellular cellular respirationrespiration

Structure of ATPStructure of ATP ATPATP stands for stands for adenosine adenosine

triphosphatetriphosphate It is composed of the nitrogen It is composed of the nitrogen

base base ADENINEADENINE, the pentose (5C) , the pentose (5C) sugar sugar RIBOSERIBOSE, and three , and three PHOSPHATEPHOSPHATE groups groups

The The LAST phosphate groupLAST phosphate group is is bonded with a bonded with a HIGH ENERGYHIGH ENERGY chemical bondchemical bond

This bond can be This bond can be BROKENBROKEN to to release ENERGY for CELLS to userelease ENERGY for CELLS to use

PhotosynthesisPhotosynthesisPhotosynthesis can be divided into Photosynthesis can be divided into

two stages: two stages:

1. 1. Light Reaction -Light Reaction -

Produces energy from solar power Produces energy from solar power (photons) in the form of ATP and (photons) in the form of ATP and NADPH.NADPH.

2. 2. Calvin CycleCalvin Cycle Also called Also called Carbon FixationCarbon Fixation,Uses ,Uses

Co2 & energy (Co2 & energy (ATP and NADPHATP and NADPH) ) from light reaction to make sugar from light reaction to make sugar (glucose).(glucose).

SUNSUN

2 stages of photosynthesis-2 stages of photosynthesis-

STAGE 1: Light Reaction STAGE 1: Light Reaction (Electron Flow)(Electron Flow)

Occurs in the Thylakoid Occurs in the Thylakoid membranesmembranes

Photosystem I and IIPhotosystem I and II Step 1Step 1 – light excites – light excites e-e- in photosystem II in photosystem II Step 2Step 2 – – e-e- move to primary e- acceptor move to primary e- acceptor

Step 3Step 3 – – e-e- move along electron transport move along electron transport chain (etc)chain (etc)

Step 4Step 4 – light excites – light excites e-e- in photosystem I in photosystem I Step 5Step 5 – – e-e- move along 2 move along 2ndnd (etc) (etc) End – NADP+ combine H+ to make NADPHEnd – NADP+ combine H+ to make NADPH

ChemiosmosisChemiosmosis – synthesis of ATP – synthesis of ATP

Powers Powers ATP synthesisATP synthesis Takes place across the Takes place across the

thylakoid membranethylakoid membrane Uses Uses ETCETC and and ATP ATP

synthase synthase H+H+ move down their move down their

concentration concentration gradient forming gradient forming ATP ATP from ADPfrom ADP

Concentration of protons is Concentration of protons is greater in thylakoid than greater in thylakoid than stromastroma

ELECTRON TRANSPORT CHAIN ELECTRON TRANSPORT CHAIN ANIMATION ANIMATION

STAGE 2: CALVIN CYCLESTAGE 2: CALVIN CYCLE Biochemical pathway in photosynthesis that Biochemical pathway in photosynthesis that

produces organic compounds (Glucose) using produces organic compounds (Glucose) using ATP & NADPH from the light reactions of ATP & NADPH from the light reactions of photosynthesisphotosynthesis

Carbon fixationCarbon fixation – carbon atoms from CO – carbon atoms from CO2 2 are are

bonded or ‘fixed’ into carbohydratesbonded or ‘fixed’ into carbohydrates

occurs in stromaoccurs in stroma